JP3236049B2 - Fuel injection control method for engine with variable valve timing control mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel injection control method for an engine having a variable valve timing (VVT) control mechanism.

[0002]

2. Description of the Related Art In recent years, variable valve timing control for improving engine output and reducing fuel consumption by changing the opening and closing timing of intake and exhaust valves of each cylinder of an engine according to the load state of the engine has been performed.

In this timing control, if the overlap time during which the intake valve and the exhaust valve are simultaneously opened becomes long, the intake air drawn into the combustion chamber via the intake valve directly reaches the exhaust pipe via the exhaust valve. A so-called blow-by occurs. Therefore, when fuel is injected into the intake pipe during such a period, the fuel also passes through the combustion chamber and reaches the exhaust pipe without being burned, resulting in damage to the exhaust gas purification catalyst and deterioration of emission.

Accordingly, for example, Japanese Patent Application Laid-Open No. 61-185628
JP-A-61-187543,
There has been proposed an apparatus in which fuel injection is performed after an exhaust valve is closed to prevent a problem caused by blow-by.

[0005]

When the throttle valve is greatly depressed in order to improve the acceleration performance of the electronic fuel injection, a separate injection from the injection synchronized with the engine crank rotation angle in the steady state is required. When the required amount of fuel injection is performed immediately and asynchronously, and this is performed immediately before the overlap operation or during the overlap operation, the above-described problem may also occur due to the blow-by.

Accordingly, the present invention has been made to solve the above-mentioned problem, and provides a fuel injection control method for an engine with a variable valve timing control mechanism which does not cause a problem of blow-through of injected fuel even in any operating state of an internal combustion engine. The purpose is to:

[0007]

To explain the structure of the present invention, a variable valve timing for changing at least one of an intake valve and an exhaust valve of an engine according to an operating state of the engine. In an engine having a control mechanism, a required amount of fuel is injected in synchronization with the crank rotation angle of the engine, and when an asynchronous fuel injection is requested in accordance with an operation state, the asynchronous fuel injection is performed.
Is performed at the same timing as the intake valve and the exhaust valve.
The exhaust valve from the intake valve to the exhaust valve
If it is determined that the vehicle is in the driving range where
The asynchronous fuel injection is not performed. Asynchronous
The fuel injection request specifically detects a vehicle acceleration request.
Occurs when When not performing the asynchronous fuel injection
Increases the synchronous fuel injection amount based on the asynchronous fuel injection request.
Injection can be performed after correcting the amount.
It is preferable to execute for injection of all cylinders of gin
No. In addition, the operating range in which the intake air blows through depends on the engine.
The determination can be made based on the rotation speed and the intake air amount.

[0008]

In this configuration, the intake air blows from the intake valve to the exhaust valve due to the overlap of the intake valve and the exhaust valve.
If it is determined that the vehicle is in the operating range, the asynchronous fuel injection is stopped. Therefore, there is no problem caused by blow-by.

[0009]

FIG. 1 shows the configuration of an engine control system to which the method of the present invention is applied. An intake pipe 2 of the engine 1 is provided with a throttle valve 3 at an upstream position, and a manifold 22 branched to each cylinder of the engine 1 downstream of a surge tank 21 is provided with an electromagnetic fuel injection valve 4.

The engine 1 is provided with a step motor 5 for driving a camshaft (not shown) for changing the opening timing of each cylinder intake valve to advance or delay. The rotation of the step motor 5 and the fuel injection valve 4 Is controlled by the output of the I / O port 61 of the control device 6.

The I / O port 61 has an oxygen sensor 7
1. Signals from a throttle opening sensor 72, an intake air amount sensor 73, an engine rotation sensor 74, a coolant temperature sensor 75, an intake air temperature sensor 76, and the like are input to the controller 6.
The microcomputer 62 controls the operation of the step motor 5 and the fuel injection valve 4 on the basis of the signals of the above sensors as described later. Hereinafter, the microcomputer 62
2 to 5 are shown in FIG.

FIG. 2 shows a variable valve timing control routine which is started every 32 ms by interruption. In step 101, the throttle opening degree TA and the engine speed Ne are fetched, and the intake valve is determined from a map value determined in advance in accordance with these. The target advance position θT is determined (step 102).

In step 103, the target advance position .theta.T is compared with the actual advance position .theta.R. If they do not match, the step motor 5 is rotated one step toward the advance side or the retard side according to the comparison result (step 103). 104, 105, 10
7) The actual advance position θR is counted up or down (steps 106 and 108).

FIG. 3 shows an asynchronous fuel injection control routine at the time of vehicle acceleration, which is interrupted every 64 ms. Step 20
In step 1, the throttle opening TA is fetched, and it is checked whether the difference from the previous throttle opening TAo is larger than a predetermined value ΔTA. If it is larger, it is determined that an acceleration request has been made and the process proceeds to step 203 and subsequent steps. In step 203, the engine speed Ne, the intake air amount Q, and the actual advance position θR are fetched, and the pulse width T 'of the asynchronous pulse is obtained from these values and the magnitude of (TA-TAo) (step 204).

In the following step 205, it is determined whether or not the area is a blow-by area. The determination of the blow-by area is described in, for example,
As described in Japanese Patent Application Laid-Open No. 297746/1989, in view of the fact that the overlap time between the intake valve and the exhaust valve is determined by the engine speed Ne and the intake air amount Q, the operating state of the engine becomes
It is determined in advance whether or not the engine is in the operating range where
Find it experimentally. And Ne and Q indicating the blow-by area
Prepare the area of the map in advance and use the microcomputer
This is performed by referring to this stored in the memory 62 .

If it is not determined in step 205 that the area is the blow-by area, an asynchronous pulse is immediately output to open the fuel injection valve 4 for a time corresponding to the pulse width T 'to perform asynchronous fuel injection ( Step 206). On the other hand, if it is determined that the area is the blow-by area, asynchronous injection is not performed, the injection correction flag fA is set (step 207), and the current throttle opening TA is set to TAo (step 208).

FIG. 4 shows an injection amount calculation routine that is activated every 16 ms. In step 301, the intake air amount Q, the engine speed Ne, the cooling water temperature THW, and the intake air temperature THA are taken in. In step 302, the basic injection time TD according to Q / Ne is calculated, and then the THW, THA and signals from the oxygen sensor 71 are calculated. The effective injection time Ti is calculated by obtaining the correction coefficients K1, K2, K3 based on
3).

In step 304, the injection correction flag fA is checked. If the flag is set, the asynchronous pulse width T 'calculated in step 204 in FIG. 3 is added to the effective injection time Ti calculated in step 303. In addition, the final effective injection time Ti is set (step 305).

FIG. 5 shows an injection output routine which is started in synchronization with the crankshaft rotation angle, and is started at every predetermined angle after the top dead center TDC in each cylinder (for example, at an angular position at which the exhaust valve closes). In step 401, the pulse width Tout of the output pulse is determined by adding the invalid injection pulse width TV corresponding to the battery voltage to the effective injection time Ti.

In step 402, an output pulse is given to the fuel injection valve 4 of the cylinder in the intake stroke to open the cylinder, and a predetermined amount of fuel is injected. In step 403, the state of the injection correction flag fA is determined, and if it is set, the counter K is counted up in step 404. When the counter K is counted up to a value equal to the number of cylinders (4 in this embodiment), the injection correction flag fA is reset (steps 405 and 406), and the counter K is reset (step 407).

In this manner, in the blow-by area, the asynchronous injection is stopped and the unburned fuel is prevented from being discharged to the exhaust pipe. Further, since the fuel increase based on the asynchronous injection request is injected in addition to the synchronous injection amount, the vehicle acceleration performance is not reduced.

In the variable valve timing control shown in FIG. 2, the actual rotation angle of the step motor 5 may be fed back using a potentiometer or the like.

In step 305 of FIG. 4, the asynchronous pulse width T
May be multiplied by a correction coefficient K4 corresponding to (TA-TAo), for example, to obtain the final effective injection time Ti.

To compensate for insufficient atomization caused by delaying asynchronous injection until the point of synchronous injection, (T ′ + α) obtained by adding an appropriate compensation time α to the pulse width T ′ is Ti
May be added.

Further, when the decrease in the vehicle acceleration performance is not so problematic, the synchronous injection is not increased,
Only the suspension of the asynchronous injection may be performed.

[0026]

As described above, according to the engine fuel injection control method of the present invention, it is possible to reliably prevent a problem that the increased amount of fuel accompanying the vehicle acceleration reaches the exhaust pipe unburned due to blow-by.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a control device to which a method of the present invention is applied.

FIG. 2 is a flowchart illustrating a control method.

FIG. 3 is a flowchart illustrating a control method.

FIG. 4 is a flowchart illustrating a control method.

FIG. 5 is a flowchart illustrating a control method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Engine 2 Intake pipe 22 Manifold 3 Throttle valve 4 Fuel injection valve 5 Step motor 6 Control device

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Keiichi Osawa 1-1-1, Showa-cho, Kariya-shi, Aichi Japan Inside Denso Co., Ltd. (56) References JP-A-61-252849 (JP, A)

Claims (6)

(57) [Claims] 1. An engine provided with a variable valve timing control mechanism for changing at least one of an intake valve and an exhaust valve of an engine according to an operation state of the engine. performs fuel injection required amount in synchronism with the rotation angle, when there is an asynchronous fuel injection request in accordance with the operating state, this inhomogeneous
The timing of executing the first fuel injection is determined by the intake valve and the exhaust valve.
The air valve and the air valve open at the same time.
It is determined that the engine is in the operating range where the intake air flows through the exhaust valve.
A method for controlling fuel injection of an engine with a variable valve timing control mechanism , wherein the asynchronous fuel injection is not performed. 2. The vehicle according to claim 2, wherein the asynchronous fuel injection request is for accelerating the vehicle.
Claims that occur when a request is detected
1. Engine fuel with variable valve timing control mechanism
Injection control method. 3. The engine according to the operating state of the engine.
If at least one of the intake valve and the exhaust valve is open,
Or variable valve timing control mechanism to change valve opening timing
In the engine provided with, the crank rotation of the engine
The required amount of fuel is injected in synchronization with the turning angle,
When an asynchronous fuel injection request is made according to the
The timing of executing the first fuel injection is determined by the intake valve and the exhaust valve.
The air valve and the air valve open at the same time.
It is determined that the engine is in the operating range where the intake air flows through the exhaust valve.
In the case, without performing the asynchronous fuel injection,
Increase the synchronous fuel injection amount based on the fuel injection request
Variable valve timing control characterized by firing
A fuel injection control method for an engine with a mechanism. 4. The request for asynchronous fuel injection includes:
Claims that occur when a request is detected
3. Engine fuel with variable valve timing control mechanism
Injection control method. 5. The method is executed when the asynchronous fuel injection is not performed.
Correction of the synchronous fuel injection amount to be performed
The method is executed for injection into a cylinder.
3. An engine with a variable valve timing control mechanism according to 3 or 4.
A gin fuel injection control method. 6. An operating area in which the intake air flows through is defined by an engine.
Speed and intake air volume Is characterized by making decisions based on
A variable valve timing according to any one of claims 1 to 5, wherein
A fuel injection control method for an engine with a steering control mechanism.