JPH0666233A - Intake device of four-cycle internal combustion engine - Google Patents

Abstract

(57) [Summary] [Purpose] A 4-cycle internal combustion engine in which three intake valves and two exhaust valves are arranged so as to surround a spark plug facing the vicinity of the center of combustion, and exhaust gas is blown back particularly at low speed operation. This prevents combustion from becoming unstable, enables smooth operation at low speed, and widens the degree of freedom in setting valve overlap. A control valve in which a plurality of intake passages that guide intake air to three intake valves are arranged in parallel in the cam axis direction, and the intake passages including the center of the overall width of the plurality of intake passages in the cam axis direction are closed at least during low-speed operation. Was set up.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to one cylinder,
3 on one side of the center plane including the cylinder center line and parallel to the cam axis
4 intake valves and 2 exhaust valves on the other side
The present invention relates to an intake device for a cycle internal combustion engine.

[0002]

2. Description of the Related Art A four-cycle cycle in which three intake valves are arranged on one side and two exhaust valves are arranged on the other side of a cylinder with a center plane including the cylinder center line and parallel to the camshaft sandwiched therebetween. There is an internal combustion engine.

In this type of engine, it is also known that two intake valves on both sides of the three intake valves are closer to the center plane than the central intake valve. For example, a spark plug is arranged so as to face the center of the combustion chamber, and three intake valves and two exhaust valves are arranged so as to surround the spark plug.

[0004]

[Problems of the prior art] In an engine having such an intake / exhaust valve arrangement, if exhaust gas is blown back from the exhaust valve into the combustion chamber and the blown back exhaust gas covers the vicinity of the spark plug, the ignition performance of the spark plug deteriorates, There may be a problem that combustion tends to be unstable. This problem usually occurs during low-speed operation, but becomes more important especially when a high-speed engine with a large valve overlap is operated at low speed because exhaust gas is blown back.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and it is necessary to surround the spark plug facing the center of combustion.
When one intake valve and two exhaust valves are provided, it is possible to prevent instability of combustion due to exhaust gas blowback especially at low speed operation, smooth operation at low speed, and valve overlap. It is an object of the present invention to provide an intake system for a 4-cycle internal combustion engine capable of expanding the degree of freedom in setting.

[0006]

According to the present invention, the object of the present invention is to combust three intake valves on one side and two exhaust valves on the other side across a center plane including the cylinder center line and parallel to the camshaft. In a four-cycle internal combustion engine, which is arranged so as to surround a spark plug facing the vicinity of the center of the chamber, the intake valves on both sides of the three intake valves are closer to the center plane than the central intake valve is. A plurality of intake passages that guide intake air to the intake valve are arranged in parallel in the cam axis direction, and a control valve that closes at least during low speed operation is provided in the intake passage including the center of the entire width of the plurality of intake passages in the cam axis direction. This is achieved by the intake system of a four-cycle internal combustion engine characterized by the above.

[0007]

A plurality of intake passages for introducing fresh air to the three intake valves are arranged in parallel in the cam axis direction, and the intake passages including the center of the entire width of all the intake passages in the cam axis direction are closed by the control valve at low speed operation. To be At this time, since at least one of the intake passages on both sides is open, the fresh air introduced into the open intake passage flows into the combustion chamber through the corresponding intake valves on both sides or one side.

On the other hand, when such an intake / exhaust valve arrangement is adopted, since a spark plug is interposed between the intake valve and the exhaust valve in the center, both valves are separated from each other, but both sides are separated. The intake valves of the above will face the exhaust valves, respectively, and will approach each other.

Therefore, the fresh air entering from the intake valves on both sides can push back the exhaust gas blown back from the exhaust valve, and reduce the amount of exhaust gas blown back. Also, when one of the intake passages on both sides is closed by the control valve, a swirl is formed in the combustion chamber in which fresh air that enters from the open intake passage of these intake passages flows toward the spark plug. Become. Therefore, the exhaust gas blown back around the ignition plug is not covered.
As a result, ignitability by the spark plug is improved and combustion is stabilized.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a plan view of a part of the first embodiment of the present invention partially sectioned, FIG. 2 is a sectional view taken along the line II-II, and FIG. 3 is a torque characteristic diagram. 1 and 2, reference numeral 10 is a cylinder body, 12 is a cylinder head, and 14 is a piston, and these form a combustion chamber 16.

The cylinder head 12 is provided with two exhaust valves 18 (18a, 18b) per cylinder and three intake valves 20 (20a, 20b, 20c) adjacent to each other. 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. 30 is a cylinder head cover,
32 is an exhaust passage communicating with the exhaust valve 18, and 34 in FIG.
Is a spark plug.

Here, three intake valves 20a, 20b, 20
c is disposed on one side of a plane (center plane) β that passes through the cylinder center line α and is parallel to the cam shafts 22 and 24. The two exhaust valves 18, 18 are on the other side of this center plane β. The intake valve 20 and the exhaust valve 18 are arranged around the spark plug 34 facing the vicinity of the center of the combustion chamber 16 at substantially equal intervals around the spark plug 34 in a plan view (FIG. 1).

As a result, the intake valves 20a, 20c on both sides of the three intake valves 20 are closer to the center plane β than the central intake valve 20b. Further, the two exhaust valves 18, 18 approach the intake valves 20a, 20c on both sides.

Reference numeral 36 is a surge tank, and 38 is an intake pipe connecting the surge tank 36 and the cylinder head 12 for each cylinder. The intake pipe 38 extends along a plane (orthogonal plane γ) that includes the cylinder center line α and is orthogonal to the center plane β. In the intake pipe 38, the first intake passage 40
a, a second intake passage 40b, and a third intake passage 40c are formed. These first, second and third intake passages 40
a, 40b and 40c have substantially the same diameter, and the second intake passage 40b at the center includes the orthogonal surface γ.

The second and third intake passages 40b and 40c are provided with vertically extending valve shafts 42a and 42b, and the valve shafts 42a and 42b are provided with the second and third intake passages 40b and 4b.
A butterfly type control valve 44 (44a, 44b) for opening and closing 0c is attached. These control valves 44 are controlled to open and close in response to operating conditions, for example, operating load and increase / decrease in engine speed.

The cylinder head 1 is located downstream of the intake passage 40.
2 through the communication chamber 46 provided on the side of the intake valve 20 side
It communicates with one intake valve 20. Therefore, the three intake passages 40a, 40b, 40c communicating with the respective intake valves 20 pass through the communication chambers 46 and the corresponding intake valves 20a, 20b,
Intake air smoothly to 20c.

Reference numeral 48 is an electromagnetic fuel injection valve. As shown in FIG. 2, the fuel injection valve 48 includes a distribution pipe 50 arranged above the intake pipe 38 and a communication chamber 46 of the cylinder head 12.
Located between the upper part. That is, this fuel injection valve 48
Is located below the fulcrum 28a of the intake-side swing arm 28, and utilizes the space surrounded by the swing arm 28 and the intake valve 20 to communicate with the communication chamber which is a space through which fuel injected by the fuel injection valve 48 passes. 46 is formed.

The injection valve 48 is opened at a predetermined timing by an electric signal output from a controller (not shown), and the fuel in the distribution pipe 50 pressurized to a predetermined pressure is intermittently introduced into the communication chamber 46. To spray.

The operation of the first embodiment is as follows.
During low load / low speed operation, the control valves 44a and 44b are closed, and the intake air is guided from the first intake passage 40a to the corresponding intake valve 20a through the communication chamber 46. During medium load / medium speed operation, the control valve 44b opens, and the intake air is guided from the first and third intake passages 40a, 40c to the intake valves 20a, 20c on both sides. During high load / high speed operation, the control valves 44a and 44b are both opened, and intake air is supplied to the first, second and third intake passages 40a and 4b.
0b, 40c to the intake valves 20a, 20b, 20c.

Therefore, during low load / low speed operation, fresh air is introduced only from the first intake passage 40a, and this fresh air is mainly introduced to the intake valve 20a. Therefore, the fresh air that enters the combustion chamber 16 from the intake valve 20a is exhausted by the exhaust valve 18a facing the fresh air.
Flow in the direction, and when exhaust gas is blown back from this exhaust valve 18a, it pushes it back. Therefore, exhaust blowback from the exhaust valve 18a can be suppressed.

At this time, since the other intake passage 40c is closed, the intake valve 20c facing the intake passage 40c is connected to the combustion chamber 16
There is little freshness to enter. Therefore, the fresh air entering from the intake valve 20c cannot sufficiently suppress the blowback from the exhaust valve 18b facing the intake valve 20c. However, since the fresh air entering from the other intake valve 20a is strong, a strong swirl is formed in the combustion chamber 16.

In this way, the effect of suppressing the blowback of exhaust gas by the fresh air from one intake valve 20a and the strengthening of the swirl can stabilize the combustion during low speed operation.

During medium load / medium speed operation, the third side
Since the control valve 44b of the intake passage 40c is opened, fresh air is supplied from the intake passages 40a, 40c on both sides to the intake valves 20a on both sides,
Led to 20c. Therefore, these intake valves 20c, 20
The fresh air entering the combustion chamber 16 from c sufficiently suppresses the blowback of the exhaust gas from the exhaust valves 18a and 18b facing them. Therefore, combustion becomes stable.

At the time of higher load and higher speed operation, the control valve 4
4a, 44b open together and the three intake valves 20a, 20
Fresh air is introduced into the combustion chamber 16 from b and 20c. Therefore, blowback of exhaust gas from the exhaust valves 18a and 18b is sufficiently suppressed, and smooth operation is possible.

Further, according to this embodiment, it is possible to finely improve the torque at the same time. FIG. 3 is a torque characteristic diagram of the first embodiment, and the solid line A in this figure is the control valve 44a,
44b is a characteristic when the control valve 44a is kept open, a broken line B is a characteristic when both the control valves 44a and 44b are closed in the low speed region, and a chain line C is a characteristic when only the control valve 44b is opened in the medium speed region. By opening and closing the control valves 44a and 44b at different operating speeds and combining these characteristics A, B, and C, it is possible to finely improve the torque according to the speeds.

FIG. 4 is a plan view of the second embodiment with a partial cross section. In this embodiment, two first and second different diameters are used.
The intake passages 40a and 40b are provided, and both intake passages 40a and 4b are provided.
The center of the entire width of 0b, that is, the vertical surface γ is included in the second intake passage 40b having a large diameter. And the control valve 44
Is provided in the large-diameter second intake passage 40b.

According to this embodiment, the control valve 44 is closed at the time of low load / low speed operation, and the fresh air which enters the combustion chamber 16 from the first intake passage 40a through the one side intake valve 20c is discharged from the exhaust valve 18b. Generates a strong swirl while suppressing the blowback exhaust. Therefore, combustion becomes stable. Further, at the time of high load / high speed operation, the control valve 44 is opened, and both intake passages 40a, 4a,
Fresh air is introduced into the combustion chamber 16 from 0b through the three intake valves 20a, 20b, 20c.

According to this embodiment, especially at low speed, the intake flow velocity passing through the small-diameter first intake passage 40a increases, and the intake inertia can be utilized to improve the torque characteristic. FIG. 5 shows this torque characteristic, and 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 decrease in the intake inertia effect at medium and low speeds. In the figure, the chain line B is the torque characteristic when the control valve 44 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. In FIG. 4, the same parts as those in FIG. 1 are designated by the same reference numerals, and the description thereof will not be repeated.

[0029]

As described above, according to the present invention, among the plurality of intake passages (40a, 40b, 40c) arranged in parallel in the cam shaft (22, 24) direction, the intake passage Since the control valve (44) is provided in the intake passage (40b) including the center of the entire width in the cam axis direction and the control valve (44) is closed at least during low speed operation, at least one of both sides is closed. The fresh air entering from the intake valves (20a, 20c) pushes back the exhaust gas blown back from the exhaust valves (18a, 18b) opposed thereto. Therefore, it is possible to improve the ignitability of the spark plug and stabilize the combustion. Further, since the blowback of exhaust gas can be suppressed, the valve overlap can be set wide, and the degree of freedom in setting the valve overlap can be increased particularly in a high-speed engine.

When each intake passage (40) is formed along an orthogonal plane (γ) that includes the cylinder center line (α) and is orthogonal to the center plane (β), the corresponding intake passage 40 is exhausted. Fresh air flows smoothly through the valve (20), and the effect of the present invention is further enhanced (claim 2).

[Brief description of drawings]

FIG. 1 is a plan view in which an embodiment of the present invention is partially sectioned.

FIG. 2 is a sectional view taken along line II-II.

[Fig. 3] Torque characteristic diagram

FIG. 4 is a plan view of another embodiment.

[Figure 5] Torque characteristic diagram

[Explanation of symbols]

 16 Combustion chamber 18 Exhaust valves 20a, 20c Both side intake valves 20b Central intake valve 40 Intake passage 44 Control valve α Cylinder center line β Center plane γ Orthogonal plane

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display area F02M 69/04 P 7825-3G

Claims (2)

[Claims] 1. A spark plug that surrounds a center plane that includes a cylinder center line and is parallel to a camshaft, and that has three intake valves on one side and two exhaust valves on the other side that face the vicinity of the center of the combustion chamber. In the four-cycle internal combustion engine in which the intake valves on both sides of the three intake valves are closer to the center plane than the central intake valve, a plurality of intake valves that guide intake air to the three intake valves are arranged. The intake passages are arranged in parallel in the cam axis direction, and a control valve that is closed at least during low speed operation is provided in the intake passages including the centers of the entire widths of the plurality of intake passages in the cam axis direction.
Intake device for a cycle internal combustion engine. 2. The intake system for a four-cycle internal combustion engine according to claim 1, wherein the plurality of intake passages extend along a plane orthogonal to the center plane including the cylinder center line.