JPH0781544B2 - Intake device for 4-cycle internal combustion engine - Google Patents

Description

TECHNICAL FIELD The present invention has three intake valves adjacent to each other for one cylinder and injects fuel from one fuel injection valve into an intake passage. The present invention relates to an intake system for a 4-cycle internal combustion engine.

(Background of the Invention) There is a four-cycle internal combustion engine in which three adjacent intake valves are provided for one cylinder. In this type of engine, when one fuel injection valve is used for one cylinder and fuel is injected into the intake passage by this injection valve, the mounting position of the injection valve greatly affects combustion. That is, if the fuel is injected to a position far from the intake valve, the fuel adheres to the inner wall of the intake passage to form a wall surface flow, and the atomization of the fuel deteriorates. In addition, if the fuel is injected too close to the intake valve, the fuel will be concentrated and supplied only to a specific intake valve, and favorable combustion cannot be obtained against changes in operating conditions such as rotation speed. There is a problem that can occur.

If each intake passage is guided to the side of the combustion chamber and the radius of curvature of the central intake passage is smaller than the radius of curvature of the intake passages on both sides when viewed from the axial direction of the camshaft, the center of the upper wall of the communication chamber When fuel is injected toward the center of the end surface of the intake valve of the intake valve, the fuel adheres to the lower wall of the central intake passage, forming a wall flow, and the amount of fuel entering the central intake valve increases further. As a result, the atomization of fuel deteriorates.

(Object of the Invention) The present invention has been made in view of the above circumstances, and a four-cycle internal combustion engine having three adjoining intake valves is provided.
An object of the present invention is to provide an intake system for a four-cycle internal combustion engine, in which atomization of fuel is good and combustion can be favored when the fuel is supplied to the intake passage by two fuel injection valves. Is.

(Constitution of the Invention) According to the present invention, an object of the present invention is to arrange three intake valves adjacent to each other so as to be symmetrical with respect to a plane that surrounds the cylinder center line and is orthogonal to the cam axis. The intake passages connected to the valves are guided to the side of the combustion chamber, and the radius of curvature of the central intake passage when viewed from the axial direction of the camshaft is made smaller than the radius of curvature of the intake passages on both sides. , The lower wall of the central intake passage bulges toward the space between the injection port of the fuel injection valve provided on the upper wall of the communication chamber and the center of the end surface of the central intake valve on the umbrella side. In a four-cycle internal combustion engine, the center line of the fuel injection valve is the end face of the central intake valve on the side of the central part of the intake valve when viewed from the axial direction of the cam shaft within the range surrounded by the outer periphery of the central part of the central intake valve. Being directed within the range closer to the cylinder center line than the center of This is achieved by the characteristic four-stroke internal combustion engine intake device.

(Operation) The fuel injected from the fuel injection valve is injected with a certain spread from the fuel injection valve. When the lower wall of the central intake passage bulges toward the center between the fuel injection valve and the center of the end surface of the central intake valve on the umbrella side, the fuel adheres to this lower wall. However, the center line of the fuel injection valve is closer to the cylinder center line side than the center of the end face of the central intake valve on the umbrella portion side as viewed from the axial direction of the cam shaft in the range surrounded by the outer periphery of the central intake valve umbrella portion. Since it is directed within the range, it is difficult to adhere to the lower wall of the central intake passage. Therefore, the fog of the fuel is improved.

(Embodiment) FIG. 1 is a plan view in which a first embodiment of the present invention is partially sectioned, FIG. 2 is a sectional view taken along line II-II, and FIG. 3 is a torque characteristic diagram.
In FIGS. 1 and 2, reference numeral 10 is a cylinder body, 12 is a cylinder head, and 14 is a piston.
16 are formed. 2 per cylinder for cylinder head 12
An exhaust valve 18 (18a, 18b) and three intake valves 20 (20a, 20b, 20c) adjacent to each other are provided. These exhaust / intake valves 18 and 20 are opened and closed by a well-known swing arm type two-head camshaft type valve operating mechanism including overhead camshafts 22 and 24 and swing arms 26 and 28, respectively. Reference numeral 30 is a cylinder head cover, 32 is an exhaust passage communicating with the exhaust valve 18, and 34 in FIG. 1 is an ignition plug.

36 is a surge tank, and 38 is an intake pipe connecting the surge tank 36 and the cylinder head 12 for each cylinder. Inside the intake pipe 38, a first intake passage 40a and a second intake passage 40b are formed. The first intake passage 40a and the second intake passage 40b have substantially the same diameter, and the valve shaft 42 passing through these passages 40a, 40b has
A butterfly type control valve 44 for opening and closing the second intake passage 40b is attached. The control valve 44 is controlled to open and close in response to operating conditions such as an operating load and an increase / decrease in engine speed.

A communication chamber provided in the cylinder head 12 on the downstream side of the intake passage 40.
It is connected to 46, and this communication chamber 46 approaches and communicates with the three intake valves 20. Here, each intake valve 20a, 20b, 20
The three intake passages communicating with c are guided to the side of the combustion chamber, and the radius of curvature of the central intake passage as viewed in the axial direction of the camshafts 22 and 24 is smaller than the radius of curvature of the outer intake passages.

Reference numeral 48 is an electromagnetic fuel injection valve. As shown in FIG. 2, the injection valve 48 is located between the distribution pipe 50 arranged in the upper part of the intake pipe 38 and the upper part of the communication chamber 46 of the cylinder head 12, and its center line z is the camshaft. Center intake valve 20 when viewed from the axial direction of 24
Intake valves 20a, 20c outside the center y of the side surface on the umbrella side of b
Side, that is, the cylinder center line side. Further, the center line z is located at the center of the intake valve 20 in plan view as shown in FIG.
It is oriented in the direction of b.

Although the lower wall of the central intake passage bulges toward the center between the fuel injection valve 48 and the center of the end face of the central intake valve 20b on the umbrella side, the center line z of the fuel injection valve 48 is a plane. Since it is directed toward the cylinder center line side with respect to the center y of the end face of the intake valve 20b at the center in the visual direction, the interference with the bulging portion of the lower wall of the central intake passage can be avoided.

This injection valve 48 opens at a predetermined timing by an electric signal output by a controller (not shown), and intermittently injects the fuel in the distribution pipe 50 pressurized to a predetermined pressure into the communication chamber 46. .

The operation of the first embodiment is as follows. During low load / low speed operation, the control valve 44 is closed and the intake air is guided from the first intake passage 40a to the communication chamber 46. At low speed operation, the pulsation of intake air is large, and since the first intake passage 40a has a small diameter, the intake inertia is large. Therefore, when the intake valve 20 is closed, the intake air enters the communication chamber 46 from the first intake passage 40a and generates a strong turbulent flow. The fuel intermittently injected into the communication chamber 46 is quickly and favorably atomized by the turbulent flow of the intake air, and becomes a uniform air-fuel mixture, and flows into the combustion chamber 16 when the intake valve 20 opens. At this time, the turbulent flow in the communication chamber 46 also strengthens the swirl, and the combustion can be stabilized.

At high load and high speed operation, the control valve 44 opens and intake is the first,
The communication chamber 46 enters from the second intake passages 40a and 40b. The fuel injected from the injection valve 48 not only has a certain spread but also diffuses in a relatively wide communication chamber 46 for a long distance without hitting the inner wall. Therefore, the amount of fuel adhering to the inner wall is reduced, and atomization of the distance is promoted.

In FIG. 3, the solid line A shows the torque characteristic when the control valve 44 is kept open, and shows that the torque decrease is remarkable due to the reduction of the intake inertia effect at medium and low speeds. A chain line B indicates a control valve 44.
Is a torque characteristic when is closed. By opening and closing the control valve 44 in the medium speed range, these two characteristics A and B can be combined to improve the torque characteristics.

FIG. 4 is a plan view in which the second embodiment is partially sectioned. In this embodiment, the first intake passage 40a in the first embodiment has a smaller diameter than the second intake passage 40b. According to this embodiment, the injection port of the injection valve 48 has the first and second intake passages.
It is deviated to the second intake passage 40b side from the wall between 40a and 40b. As a result, when the control valve 44 opens at high load and high speed, the intake air flowing into the communication chamber 46 from the second intake passage 40b hits the fuel injected from the injection valve 48 better than in the first embodiment, and the Atomization is further promoted. The second intake passage
Since the diameter of 40b is small, it is possible to increase the torque due to the intake inertia from a lower speed than in the first embodiment. Further, since the eccentric position of the first intake passage 40a with respect to the communication chamber 46 becomes larger than that in the first embodiment, the vortex flow generated in the communication chamber 46 becomes stronger at the low speed when the control valve 44 is closed, and the intake valve When the valve 20 is opened, a stronger swirl (intake vortex) is generated in the combustion chamber 16 by this vortex. Therefore, the combustion at low speed is stabilized, and the effect of smoothing the low speed operation becomes more remarkable.

FIG. 5 is a partially sectional plan view of the third embodiment. In this embodiment, the first intake passage 40a is arranged in the center while the second intake passage 40b is divided into two, and the control valve 44 is provided for each. , 44 are provided.

According to this embodiment, the intake air passing through the first intake passage at the time of low load and low speed when the control valve 44 is closed satisfactorily hits the fuel injected from the injection valve 48, and the atomization particularly at low load and low speed is the first. It is further improved as compared with the first and second embodiments.

FIG. 6 is a partial cross-sectional plan view of the fourth embodiment. This embodiment includes first, second, and third intake passages 40a, 40b, 40c, and a second intake passage 40a sandwiching the second intake passage 40a. Third intake passage 40b, 40
Control valves 44a and 44b having different opening and closing timings are arranged in c.

According to this embodiment, not only the atomization at low speed is promoted as in the third embodiment (FIG. 5), but also the torque characteristic can be improved at the same time. That is, FIG. 7 is a torque characteristic diagram of the fourth embodiment. The solid line A in the figure is the characteristic when the control valves 44a and 44b are kept open, and the broken line B is the control valves 44a and 44b in the low speed range.
2 is the characteristic when both of them are closed, and the chain line C is the characteristic when only the control valve 44b is opened in the medium speed range. Control valves 44a, 44b
By opening and closing at different operating speeds and combining these characteristics A, B, and C, it is possible to improve the torque in the medium speed range as compared with the first to third embodiments.

FIG. 8 is a partially sectional plan view of the fifth embodiment, which is the first intake passage 40 in the fourth embodiment (FIG. 6).
The positions of a and the second intake passage 40b are interchanged.

According to this embodiment, as in the fourth embodiment (FIG. 6), not only is the torque increased in the medium speed range, but also in the low speed range as in the second embodiment (FIG. 4). Is enhanced, the rotation during low speed operation becomes smoother.

In the second to fifth embodiments, the center line of the fuel injection valve 48 is the same as in the first embodiment. That is, in the area surrounded by the outer periphery of the umbrella portion of the intake valve 20b at the center in plan view, the cylinder center line side is oriented with respect to the center y of the end surface of the central intake valve 20b on the umbrella portion side when viewed from the axial direction of the cam shaft. is doing.

In FIGS. 4, 5, 6, and 8, the same parts as those in FIG. 1 are designated by the same reference numerals, and the description thereof will not be repeated.

According to the above-described embodiment, the fuel injection valve is within the range surrounded by the peripheral edge of the central intake valve head portion, and the end surface of the central intake valve on the head portion side of the central intake valve when viewed from the axial direction of the camshaft. Since the fuel is injected toward the range closer to the cylinder center line than the center y, the fuel is not only supplied to the central intake valve during high-speed operation with a large intake amount, but also in the communication chamber. Due to the strong intake flow, the fuel is more easily supplied to the intake valves on both sides of the cylinder that are located closer to the center of the cylinder than the central intake valve, and the fuel is well distributed to the intake valves and combustion is stabilized.

Further, the fuel injection valve is provided on a plane that is orthogonal to the cam shaft and includes the cylinder center line so that the fuel is injected into the communication chamber in the direction of the intake valve at the center of the plan view. Since the central intake valve was located between the spark plug and the nearby spark plug, the fuel flow injected from the fuel injection valve slowed down when the intake air amount was low and the fuel injected from the fuel injection valve was affected by the gravity of the central intake valve. Inhale well. For this reason, a rich air-fuel mixture is introduced to the ignition portion of the spark plug, and the ignitability is good and combustion is good.

Further, since at least a part of the edge of the partition wall of each intake passage on the side of the communication chamber is located closer to the cylinder center line side than the inner surface of the cylinder when viewed from the cam axis direction, the intake passage is shortened. The length in the intake flow direction can be increased. Therefore, the fuel injected from the fuel injection valve into the communication chamber is favorably atomized while moving in the communication chamber. In addition, since the amount of wall flow that adheres to the inner wall of the intake passage decreases, during high-speed operation when the intake amount increases, the strong intake flow in the communication chamber makes it easier for fuel to be supplied to the intake valves on both sides. The distribution to each intake valve is improved and combustion is stabilized.

Further, on the upstream side of the partition wall between the intake passages, the lower surface of the central intake passage is located below the lower surfaces of the intake passages on both sides, so the intake flow velocity becomes slow during low-speed operation with a small amount of intake air, and the communication chamber The fuel adhering to the lower surface of the is favorably guided to the central intake passage due to the effect of its gravity, and it becomes possible to conduct a stable combustion by guiding a rich air-fuel mixture near the center of the combustion chamber. On the upstream side of the partition wall between the intake passages, the upper surfaces of the intake passages on both sides are located above the upper surface of the central intake passage, so the centrifugal force of intake air is used during high-speed operation when the intake volume increases. Intake can be satisfactorily guided to the intake passages on both sides. For this reason, the fuel is easily supplied to the intake valves on both sides, and the fuel is well distributed to the intake valves, so that the combustion is stabilized.

(Effects of the Invention) As described above, according to the present invention, the center line (z) of the fuel injection valve (48) is viewed from the axial direction of the cam shaft within the range surrounded by the peripheral edge of the central intake valve head portion. Since the cylinder center line side is oriented from the center (y) of the end face of the central intake valve (20b) on the umbrella part side, the fuel injection valve (48) and the central intake valve (20b) on the umbrella part side. Even if the lower wall of the central intake passage bulges toward the center (y) of the end face of the fuel, it becomes difficult for fuel to attach to the lower wall of the intake passage, and the relatively long distance in the communication chamber (46). While being scattered, it is diffused and atomization becomes good, and combustion can be made good.

[Brief description of drawings]

FIG. 1 is a plan view in which a first embodiment of the present invention is partially sectioned, FIG. 2 is a sectional view taken along the line II-II, and FIG. 3 is a torque characteristic diagram. Further, FIGS. 4, 5, 6 and 8 are partially sectional plan views of other embodiments, and FIG. 7 is a torque characteristic diagram of the embodiment of FIG. 20a, 20c ... Intake valves on both sides, 20b ... Central intake valve, 40 ... Intake passage, 46 ... Communication chamber, 48 ... Fuel injection valve, y ... Center intake valve end face on umbrella side , The center of the z ... injection direction.

Claims (1)

[Claims] 1. Three adjacent intake valves are arranged so as to be symmetrical with respect to a plane that surrounds a cylinder center line and is orthogonal to a cam axis, and each intake passage connected to each intake valve is a combustion chamber. Guided to the side and making the radius of curvature of the central intake passage smaller than the radius of curvature of the intake passages on both sides when viewed from the axial direction of the camshaft, these intake passages are communicated with each other in the communication chamber, and In a four-cycle internal combustion engine in which a lower wall of a central intake passage bulges between an injection port of a fuel injection valve provided on an upper wall and a center of an end surface of a central intake valve on the umbrella side. The center line of the injection valve is closer to the cylinder center line than the center of the end face of the central intake valve on the umbrella part side as viewed from the axial direction of the cam shaft within the range surrounded by the outer periphery of the central intake valve umbrella part. Four-cycle internal combustion engine characterized by being oriented in the range of Intake device.