JP3727357B2 - 4-cycle engine fuel injection control system - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a fuel injection control device for a four-cycle engine, and more particularly to a device capable of ensuring combustion stability in a low load region and further eliminating overrich in a high load region.
[0002]
[Prior art]
A four-cycle engine having a fuel injection valve that injects fuel into a combustion chamber and an intake control valve that variably controls an intake passage cross-sectional area has been proposed. In this type of engine, the fuel injection by the normal fuel injection valve is performed once each toward the back surface of the valve head of the intake valve in each exhaust stroke when 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 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 rate of the intake air is increased, the direction of the intake air is generated, and lean combustion (lean air-fuel ratio combustion) can be stabilized.
[0003]
[Problems to be solved by the invention]
However, in the above-described engine, when the engine rotates at a low speed and has a low load, the fuel injection amount decreases, and the combustion state may become unstable. In view of this, the present inventor considers that the lean combustion is stabilized by stratifying the fuel in the vicinity of the spark plug when the load is low.
[0004]
On the other hand, if the fuel is concentrated even at a low speed and a high load, the stratification proceeds more and more as the air flow rate increases and the amount of fuel increases. In extreme cases, black smoke may be generated.
[0005]
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 region and eliminating overrich in a high load region. It is an object.
[0006]
[Means for Solving the Problems]
The present invention includes a combustion chamber in which a spark plug is disposed substantially in the center, an intake passage communicating with an intake valve opening that opens to the combustion chamber, an intake valve that opens and closes the intake valve opening, and the intake valve opening a fuel injection valve for injecting fuel into the combustion chamber, closing the intake passage in a small operation range of the intake air amount, the 4-cycle engine having an intake control valve opening at high operating range of the intake air amount, the The intake control valve forms a valve portion by cutting out a part of a round bar, and is disposed in a valve hole formed in the bottom portion of the intake passage. When the intake control valve is closed and the load is low, the fuel injection by the fuel injection valve is at least open. As sometimes done, also above intake control When the engine is closed and the load is high, the fuel injection valve is driven and controlled so that fuel injection by the fuel injection valve is performed both when the intake valve is open and when it is closed in the previous stroke. Provided with fuel injection control means, and a rectifying member is disposed downstream of the intake control valve in the intake passage, the rectifying member extends along a substantially center line of the intake passage, and an upstream end thereof is in a fully closed position. Is located above the valve portion of the intake control valve located at the downstream end portion of the intake control valve is located closer to the ignition plug side than the intake valve and immediately upstream of the intake valve opening, and further includes the upstream end portion and the downstream end portion. And both ends in the cam shaft direction are in contact with the inner surface of the intake passage, and the fuel injection valve is disposed upstream of the rectifying member.
[0007]
[Action]
In the present invention, during low load and low speed rotation, the intake control valve reduces the intake passage cross-sectional area, and the fuel injection by the fuel injection control means is performed at least when the intake valve is open by the drive control of the fuel injection control means. Is called. 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 amount of fuel supply corresponding to lean combustion, and fuel ignition is facilitated. Thereby, stratified combustion can be performed and the combustion stability at the time of lean combustion can be ensured.
[0008]
In addition, at the time of high load and low speed rotation, the intake control valve reduces the intake passage cross-sectional area, and the fuel injection control means drives the fuel injection by the fuel injection valve when the intake valve is open and its previous stroke ( It is performed both when closed in the exhaust stroke). In other words, a part of the fuel is injected when the intake valve is closed during the exhaust stroke, resulting in a uniform mixture, and the remaining fuel is injected when the intake valve is open, so that Concentrated supply. As a result, excessive concentration of fuel that occurs when all the fuel is injected in the intake stroke can be avoided, air utilization can be improved, over-rich can be eliminated, and black smoke is generated due to over-concentration that tends to occur during stratification. Can be suppressed and high horsepower can be obtained.
[0009]
【Example】
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 four-cycle engine according to an embodiment of the present invention.
[0010]
In the figure, reference numeral 1 denotes a water-cooled four-cycle parallel four-cylinder four-valve engine, in which a cylinder block 3 and a cylinder head 4 are stacked on a crankcase 2 and fastened with a head bolt. The head cover 5 is mounted on the surface. A piston 7 is slidably inserted in a cylinder bore 3 a formed in the cylinder block 3, and the piston 7 is connected to a crankshaft (not shown) by a connecting rod 8.
[0011]
A combustion recess 4b that constitutes a combustion chamber is formed in the lower joint surface 4a of the cylinder head 4 on the cylinder block 3 side. 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, respectively. The openings 4c and 4d are formed by the openings of generally ring-shaped valve seats 28 and 29 attached to these portions. Further, the valve head 10a of the exhaust valve 10 can be opened and closed by each exhaust valve opening 4d, and the valve head 11a of the intake valve 11 can be opened and closed by each intake valve opening 4c, that is, each of the valve seats 28 and 29 can be opened and closed. It arrange | positions so that contact | abutting to a sheet | seat surface is possible. The valve stems 10b and 11b of the exhaust and intake valves 10 and 11 extend obliquely upward in the cylinder axial direction so as to form a predetermined sandwich angle when viewed in the cam shaft direction, and the exhaust and intake lifter 12 and 13 are respectively mounted. On each of the lifters 12 and 13, exhaust and intake camshafts 14 and 15 for pressing and driving the lifters 12 and 13 are arranged in a direction perpendicular to the cylinder shaft and parallel to each other.
[0012]
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 surface opening 16a of the exhaust passage 16. The intake valve openings 4c are led out to the rear wall 4g side of the cylinder head 4 by 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 axis direction, the two intake passages 17 have an arc shape from the intake valve opening 4c toward the cylinder rear wall 4g. After bending, it extends substantially linearly. 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 disposed in the body 24.
[0013]
A valve hole 17c is formed through the downstream straight portion 17b of each intake passage 17 in the camshaft direction. This valve hole 17c is arranged on the cylinder shaft side from 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 with two adjacent cylinder intake passages. An intake control valve 25 for changing the passage cross-sectional area and the cross-sectional shape of each intake passage 17 is inserted into the valve hole 17c. The intake control valve 25 is formed by forming a valve portion 25 a that opens and closes each intake passage 17 by cutting out a part of a round bar so as to form a continuous surface with the lower inner surface of the intake passage 17. The valve portion 25a is inserted into the valve hole 17c so as to be flush with the inner surface of the intake passage, and the valve portion 25a rises from the bottom surface of the intake passage to narrow the intake passage 17 to approximately ½. It can be rotated between a fully closed position (see FIG. 1) in which the passage cross-sectional shape is a horizontally long shape elongated in the cam shaft direction. In this case, it rotates so that the outer peripheral surface of the said valve part 25a may be located in an upstream.
[0014]
A fuel injection valve 26 is mounted on the top wall portion of each intake passage 17. The injection nozzle of each fuel injection valve 26 is a valve of the intake valve 11 from the upper end portion of the intake control valve 25, that is, the most narrowed portion of the intake passage area through an injection hole 26a formed in the cylinder rear wall 4g. It is suitable for the part across the back surface of the head 11a. Therefore, a part of the injected fuel hits the intake control valve 25 and a rectifying member 30 described later.
[0015]
A rectifying member 30 is provided downstream of the intake control valve 25 in the intake passage 17. The flow regulating member 30 extends along a substantially center line of the intake passage 17, and an upstream end portion thereof is located above the valve portion 25a of the intake control valve 25 located at the fully closed position. Further, the downstream end thereof is located closer to the spark plug 9 than the intake valve 11 and is located immediately upstream of the intake valve opening 4c.
[0016]
The engine 40 is provided with a control device 40. The control device 40 includes an opening degree signal a of the throttle valve 24a from the throttle opening degree sensor 41, a cam angle signal b of the camshaft 15 from the cam angle sensor 42, and an engine speed signal c from the rotation sensor 43. Based on each input signal, the fuel injection valve 26 is controlled as described later.
[0017]
Next, the operation of this embodiment will be described.
In an operation region where the intake air amount is small, such as during low speed rotation and 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 throttled 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 side of the intake passage 17. As a result, the intake air is blown into the combustion chamber at high speed and with directivity, and tumble occurs as shown by arrows in FIG.
[0018]
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 fuel is injected during the intake stroke, that is, when the intake valve 11 is open as shown in FIG. The injected fuel is introduced into the vicinity of the spark plug 9 through the intake valve opening 4c, thereby creating a state where the fuel is concentrated in the vicinity of the spark plug 9 while being a small fuel injection amount corresponding to lean combustion. This makes it easy to ignite the fuel. As a result, stratified combustion can be performed, and combustion stability during lean combustion can be ensured.
[0019]
Further, in the case of a high load 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 a part of the fuel closes the intake valve 11 as shown in FIG. That is, in the previous exhaust stroke, the remainder of the 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, so that all the fuel is removed while the intake valve is closed. It is possible to prevent excessive fuel concentration that occurs when the fuel is injected into the tank. In this way, the air utilization rate can be improved, over-rich can be eliminated, the generation of black smoke due to over-concentration that tends to occur during stratification can be suppressed, and high horsepower can be obtained.
[0020]
When the intake control valve 25 is open, all the fuel is injected in the immediately preceding exhaust stroke as in the conventional case. In the above embodiment, the fuel injection valve is provided in each of the two intake passages. However, in the present invention, of course, one fuel injection valve may be provided for the two intake passages.
[0021]
【The invention's effect】
As described above, according to the fuel injection control device for a four-cycle engine according to the present invention, when the intake control valve is closed and the load is low, the fuel injection by the fuel injection valve is at least when the intake valve is open. Therefore, the ignition of the fuel is facilitated, whereby stratified combustion can be performed, and combustion stability during lean combustion can be ensured.
[0022]
In addition, when the intake control valve is closed and the load is high, fuel injection by the fuel injection valve is performed both when the intake valve is closed and when it is open, so that the injection is performed when the intake valve is closed. Since the fuel becomes a uniform air-fuel mixture, it is possible to eliminate over-rich conditions, suppress the generation of black smoke due to over-concentration, and obtain high horsepower.
[Brief description of the drawings]
FIG. 1 is a cross-sectional side view of a four-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 embodiment.
FIG. 3 is a diagram for explaining a control operation of the apparatus according to the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Engine 3 Cylinder block 4 Cylinder head 4b Combustion recessed part 10 Exhaust valve 11 Intake valve 26 Fuel injection valve 40 Control apparatus

Claims (1)

A combustion chamber in which a spark plug is disposed substantially in the center, an intake passage communicating with the intake valve opening that opens to the combustion chamber, an intake valve that opens and closes the intake valve opening, and the intake valve opening toward the combustion chamber In a four-cycle engine having a fuel injection valve that injects fuel and an intake control valve that closes the intake passage in an operation region where the intake air amount is small and opens in an operation region where the intake air amount is large, the intake control valve is The valve portion is formed by cutting out a part of the round bar, and is disposed in the valve hole formed in the bottom portion of the intake passage. The fully open position is flush with the intake passage inner surface, and the intake passage bottom wall side 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. Whether the intake control valve is closed In the case of a high load, fuel injection control that drives and controls the fuel injection valve so that fuel injection by the fuel injection valve is performed both when the intake valve is open and when it is closed in the previous stroke. And a rectifying member is disposed downstream of the intake control valve in the intake passage, the rectifying member extends along a substantially center line of the intake passage, and an upstream end portion thereof is located at a fully closed position. Located above the valve portion of the intake control valve, the downstream end portion thereof is located on the ignition plug side of the intake valve and immediately upstream of the intake valve opening, and further between the upstream end portion and the downstream end portion. A fuel injection control device for a four-cycle engine, wherein both ends of the camshaft direction are in contact with the inner surface of the intake passage, and the fuel injection valve is disposed upstream of the rectifying member.

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