JPH06117297A - Fuel injection control device for four-cycle engine - Google Patents

Abstract

PURPOSE:To secure combustion stability, and eliminate an over-rich condition by arranging a fuel injection control means to carry out fuel injection by a fuel injection valve at least when an air intake valve is opened in the case where an intake air control valve is closed and is put under a low load. CONSTITUTION:A valve hole 17c is formed penetratingly in a cam shaft direction in downstream side straight line parts 17b of respective air intake passages 17. An intake air control valve 25 is inserted and arranged in this valve hole 17c so as to change a passage cross-sectional area and a cross-sectional shape of the respective air intake passages 17. A fuel injection valve 26 is installed respectively in the top wall parts of the respective air intake passages 17. When being put under a low load, the intake air control valve 25 is rotated in a fully closed position by a control device 40. In this case, the injection timing of the fuel injection valve 26 is controlled by a control signal A from the control device 40, and fuel is injected in an air intake valve 11 opened condition. In this way, fuel stability can be secured in a low load area, and an over rich condition can be eliminated in a high load area.

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 system for a four-cycle engine, and more particularly to a system capable of ensuring combustion stability in a low load range and eliminating overrich in a high load range.

[0002]

2. Description of the Related Art A fuel injection valve for injecting fuel into a combustion chamber,
4 with an intake control valve that variably controls the intake passage cross-sectional area
A cycle engine has been proposed. In this type of engine, the fuel is normally injected by the fuel injection valve once toward the back surface of the valve head of the intake valve in each exhaust stroke in which the intake valve is closed. The fuel injected into the intake valve in the exhaust stroke is vaporized, and the air-fuel mixture is introduced into the combustion chamber in the intake stroke. On the other hand, when the intake air amount is small, such as during low speed rotation, the intake control valve reduces the intake passage cross-sectional area. As a result, the flow velocity of intake air is increased, and directionality is created in intake air, resulting in lean combustion (lean air-fuel ratio combustion).
Can be stabilized.

[0003]

However, in the above engine, when the engine is running at a low speed and under a low load, the amount of fuel injection is reduced, which may result in an unstable combustion state.
Therefore, the present inventor is considering stabilizing the lean combustion by stratifying the fuel in the vicinity of the spark plug when the load is low.

On the other hand, if the fuel concentration is continued as it is even at low speed rotation and high load, the stratification is further promoted by the increase of the air flow velocity and the increase of the fuel amount, and as a result, a part of the combustion chamber is obtained. Is too rich, and black smoke may be generated in extreme cases.

The present invention has been made in view of the above problems, and provides a fuel injection control device for a four-cycle engine capable of ensuring combustion stability in a low load range and eliminating overrich in a high load range. It is intended to be provided.

[0006]

The present invention provides a four-cycle engine equipped with a fuel injection valve for injecting fuel into a combustion chamber and an intake control valve for variably controlling an intake passage cross-sectional area.
When the intake control valve is closed and the load is low, fuel injection by the fuel injection valve is performed at least when the intake valve is open, and when the intake control valve is closed and the load is high, Fuel injection control means for driving and controlling the fuel injection valve is provided so that the fuel injection by the fuel injection valve is performed both when the intake valve is open and when it is closed in the preceding stroke. I am trying.

[0007]

According to the present invention, at the time of low load and low speed rotation, the intake control valve reduces the cross-sectional area of the intake passage, and at the same time, at least the intake valve is opened by the fuel injection control means by the drive control. Sometimes done. As a result, it is possible to create a state in which fuel is present in the vicinity of the spark plug while setting the fuel supply amount to a low level in response to lean combustion, which facilitates ignition of the fuel. As a result, stratified combustion can be performed, and combustion stability during lean combustion can be ensured.

Further, at the time of high load and low speed rotation, the intake control valve reduces the cross-sectional area of the intake passage, and the drive control of the fuel injection control means controls the fuel injection by the fuel injection valve when the intake valve is open and It is performed both when the engine is closed in the previous stroke (exhaust stroke). That is, a part of the fuel is injected in the exhaust stroke when the intake valve is closed to form a uniform mixture, and the remaining fuel is injected when the intake valve is open, so that it is near the spark plug. Supplied centrally. As a result, it is possible to avoid excessive concentration of fuel that occurs when all fuel is injected in the intake stroke, improve the air utilization rate, eliminate overrich, and generate black smoke due to excessive concentration that is likely to occur during stratification. Can be suppressed and high horsepower can be obtained.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 and 2 are views for explaining a fuel injection control device for a 4-cycle engine according to an embodiment of the present invention.

In the figure, 1 is a water-cooled 4-cycle parallel 4
This is a four-cylinder cylinder engine, which has a structure in which a cylinder block 3 and a cylinder head 4 are stacked on a crankcase 2, fastened with head bolts, and a head cover 5 is attached to an upper mating surface of the cylinder head 4. is there. A piston 7 is slidably inserted in a cylinder bore 3a formed in the cylinder block 3, and the piston 7 is connected to a crankshaft (not shown) by a connecting rod 8.

A combustion recess 4b forming a combustion chamber is formed on the lower mating surface 4a of the cylinder head 4 on the cylinder block 3 side.
Is recessed. A spark plug 9 is screwed into the center of the combustion recess 4b, and two intake valve openings 4c and two exhaust valve openings 4d are opened around the spark plug 9. The openings 4c and 4d are provided with the substantially ring-shaped valve seats 28 and 2 attached to these portions.
9 openings. Further, the valve head 10a of the exhaust valve 10 is provided in each exhaust valve opening 4d.
However, the valve head 1 of the intake valve 11 is provided in each intake valve opening 4c.
1a is arranged so that each opening can be opened and closed, that is, it can contact each seat surface of the valve seats 28 and 29. This exhaust, intake valve 10, 11 valve stem 1
0b and 11b extend obliquely upward in the cylinder axis direction so as to form a predetermined included angle when viewed in the cam axis direction, and exhaust and intake lifters 12 and 13 are attached to the upper ends thereof. Further, exhaust and intake cam shafts 14 and 15 for pressing and driving the lifters 12 and 13 are arranged in a direction perpendicular to the cylinder axis and parallel to each other.

The two exhaust valve openings 4d are led out to the front wall 4f side of the cylinder head 4 by a bifurcated exhaust passage 16, and an exhaust pipe (not shown) is connected to the wall opening 16a of the exhaust passage 16. There is. The intake valve openings 4c are led out to the rear wall 4g side of the cylinder head 4 by the intake passages 17, respectively. The two intake passages 17 extend linearly in a direction perpendicular to the cam shaft when viewed in the cylinder axis direction, and when viewed in the cam shaft direction, form an arc shape from the intake valve opening 4c to the cylinder rear wall 4g side. After bending, it extends in a substantially straight line. A throttle body 24 is connected to the rear wall opening 17a of the intake passage 17 via an intake manifold 18, and a throttle valve 24a is rotatably arranged in the body 24.

Downstream linear portions 17b of the intake passages 17
A valve hole 17c is formed therethrough in the cam shaft direction.
The valve hole 17c is arranged closer to the cylinder shaft side than a cylinder head fastening bolt (not shown), and its axis is located near the bottom wall surface of the intake passage 17, and the inner portion of the intake passage 17 is substantially half. It is formed in a circular shape and communicates two adjacent cylinder intake passages. An intake control valve 25 for changing the passage sectional area and the sectional shape of each intake passage 17 is inserted and arranged in the valve hole 17c. The intake control valve 25 is formed by forming a valve portion 25a for opening and closing each intake passage 17 by cutting a part of a round bar so as to form a continuous surface with a lower inner surface of the intake passage 17. The fully open position where the valve portion 25a is recessed in the valve hole 17c and is flush with the inner surface of the intake passage, and the valve portion 25a stands up from the bottom wall surface of the intake passage to narrow the intake passage 17 to about 1/2 and It is rotatable with respect to a fully closed position (see FIG. 1) in which the passage sectional shape is elongated in the cam axis direction. In this case, the valve portion 25a is rotated such that the outer peripheral surface thereof is located on the upstream side.

Fuel injection valves 26 are mounted on the top wall portions of the intake passages 17, respectively. Each fuel injection valve 2
The injection nozzle 6 has an injection hole 26a formed in the rear wall 4g of the cylinder from the upper end portion of the intake control valve 25, that is, the portion where the intake passage area is most narrowed, to the back surface of the valve head 11a of the intake valve 11. Suitable for crossing parts. Therefore, a part of the injected fuel hits the intake control valve 25 and the rectifying member 30 described later.

A rectifying member 30 is provided downstream of the intake control valve 25 in the intake passage 17. The rectifying member 30 extends along a substantially center line of the intake passage 17, and the upstream end portion of the rectifying member 30 is located at the fully closed position.
Is located above the valve portion 25a. The downstream end of the intake valve 11 is located closer to the spark plug 9 than the intake valve 11 and immediately upstream of the intake valve opening 4c.

A control device 40 is provided in this engine. The control device 40 includes an opening signal a of the throttle valve 24a from the throttle opening sensor 41, a cam angle signal b of the cam shaft 15 from the cam angle sensor 42,
And the engine rotation speed signal c from the rotation sensor 43, respectively, and based on each input signal, the fuel injection valve 26
Are controlled as described below.

Next, the operation of this embodiment will be described. In an operating region where the intake air amount is small, such as when the engine is operating at a low speed and a low load, the intake control valve 25 is rotated to the fully closed position shown in FIG. 1 by a control signal (not shown) from the control device 40. To do. Then, the bottom wall side of the intake passage 17 is narrowed by the valve portion 25a of the intake control valve 25, and the intake air flows while being rectified by the rectifying member 30 so as to be biased toward the top wall of the intake passage 17. As a result, the intake air is blown into the combustion chamber at high speed with directionality, and tumble occurs as shown by the arrow in FIG.

In this case, the injection timing of the fuel injection valve 26 is controlled by the control signal A from the control device 40, and the fuel is injected in the intake stroke, that is, when the intake valve 11 is open as shown in FIG. To be done. The injected fuel is introduced into the vicinity of the ignition plug 9 through the intake valve opening 4c, thereby creating a state in which the fuel is concentrated near the ignition plug 9 although the fuel injection amount is small corresponding to lean combustion. It is possible to easily ignite the fuel. As a result, stratified combustion can be performed, and combustion stability during lean combustion can be ensured.

Further, when the load is high at the time of the low speed rotation, the fuel injection valve 26 is controlled by the control signal A from the control device 40, and as shown in FIG. When 11 is closed, that is, in the immediately preceding exhaust stroke, the remaining fuel is injected when the intake valve 11 is open. In this way, a part of the fuel is injected when the intake valve 11 is closed, and is introduced into the fuel chamber as a uniform air-fuel mixture in the next intake stroke. It is possible to prevent excessive fuel concentration that occurs when the fuel is injected into the cylinder. In this way, the air utilization rate can be improved, overrich can be eliminated, the generation of black smoke due to the excessive concentration that tends to occur during stratification can be suppressed, and high horsepower can be obtained.

When the intake control valve 25 is open, all the fuel is injected in the exhaust stroke immediately before, as in the conventional case. Further, in the above embodiment, the fuel injection valve is provided in each of the two intake passages, but in the present invention, one fuel injection valve may be provided in each of the two intake passages.

[0021]

As described above, according to the fuel injection control apparatus for a four-cycle engine of the present invention, when the intake control valve is closed and the load is low, at least the fuel injection by the fuel injection valve is Since it is performed while the fuel cell is open, ignition of the fuel is facilitated, whereby stratified combustion can be performed and combustion stability during lean combustion can be ensured.

When the intake control valve is closed and the load is high, the fuel injection by the fuel injection valve is performed both when the intake valve is closed and when it is open.
Since the injected fuel becomes a uniform air-fuel mixture when the intake valve is closed, overrich can be eliminated, black smoke generation due to excessive concentration can be suppressed, and high horsepower can be obtained.

[Brief description of drawings]

FIG. 1 is a cross-sectional side view of a 4-cycle engine including a control device according to an embodiment of the present invention.

FIG. 2 is a plan view showing an arrangement state of fuel injection valves in the above embodiment.

FIG. 3 is a diagram for explaining a control operation of the apparatus of the above embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 engine 3 cylinder block 4 cylinder head 4b combustion recess 10 exhaust valve 11 intake valve 26 fuel injection valve 40 control device

Claims (1)

[Claims] 1. A four-cycle engine including a fuel injection valve for injecting fuel from an intake valve opening toward a combustion chamber and an intake control valve for variably controlling an intake passage cross-sectional area, wherein the intake control valve is closed and When the load is low, the fuel injection by the fuel injection valve is performed at least when the intake valve is open, and when the intake control valve is closed and the load is high, the fuel injection by the fuel injection valve is performed. Is provided both when the intake valve is open and when the intake valve is closed during the preceding stroke, the fuel injection control means for drivingly controlling the fuel injection valve is provided. Injection control device.