JPH0688532A - Air intake device of four-stroke internal combustion engine - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] Combustibility of a four-stroke internal combustion engine with one central intake valve on the cylinder bore diameter line and two side intake valves laterally on both sides of the central intake valve. To improve. A cylinder head is provided with a downstream portion of a first intake passage 9, a downstream portion of a second intake passage 10, three intake valves, and two or more exhaust valves 5, 6, and one central portion. The intake valves 2 are arranged near the diameter line of the cylinder bore, and the two side intake valves 3 and 4 are arranged on both lateral sides of the central intake valve so as to be symmetrical with respect to the cylinder bore diameter line.
The intake passage of is communicated with only one side intake valve 3, and the second intake passage is communicated with each of the side intake valve 4 and the central intake valve via bifurcated branch passages 10b, 10a.
An on-off valve 16 is arranged in the second intake passage. In the medium to low speed rotation range, the on-off valve is closed and the intake air flows into the combustion chamber 1 from the first intake passage through only one side intake valve by a strong flow, so a strong swirl is generated in the combustion chamber. Can be made.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a first cylinder head.
Downstream part of the intake passage, downstream part of the second intake passage, 3
One intake valve and two or more exhaust valves are provided, and one of the three intake valves is arranged in the vicinity of the cylinder bore diameter line on the plane perpendicular to the cam axis, and the central intake valve is arranged. The two side intake valves are arranged on both sides of the central intake valve in the lateral direction so as to be symmetrical with respect to the cylinder bore diameter line.

[0002]

2. Description of the Related Art In a four-stroke internal combustion engine having a first intake passage and a second intake passage, and having three intake valves and two exhaust valves in a cylinder head, the flow of intake air is made smooth. In order to equalize the amount of intake air supplied to each intake valve, 3
One central intake valve A of the four intake valves is located on the diameter line in the front-rear direction of the cylinder bore, and the remaining two side intake valves B and C are laterally arranged so as to be symmetrical with respect to the diameter line. It is arranged on both sides. The first intake passage and the second intake passage are formed symmetrically with respect to the cylinder center line, and the first intake passage communicates with the side intake valve B and branches so as to smoothly follow the flow of intake air. The branch passage X communicates with the central intake valve A. Similarly, the second intake passage communicates with the side intake valve C and branches so as to smoothly follow the flow of intake air, and the branch passage Y communicates with the central intake valve A. An intake device for such a four-stroke internal combustion engine is disclosed in Japanese Patent Laid-Open No. 57-
It is known from Japanese Patent No. 183553. In this intake system, the three intake valves A, B, and C are simultaneously opened, and the same amount of intake air flows through each of the three intake valves into the cylinder. There are drawbacks that the inflow speed is slow, swirl cannot be generated, and the combustibility is poor.

[0003]

First, a cylinder head is provided.
Downstream part of the intake passage, downstream part of the second intake passage, 3
One intake valve and two or more exhaust valves are provided, and one of the three intake valves is arranged in the vicinity of the cylinder bore diameter line on the plane perpendicular to the cam axis, and the central intake valve is arranged. In the intake system for a four-stroke internal combustion engine in which the two side intake valves are arranged laterally on both sides of the central intake valve so that the two side intake valves are symmetrical with respect to the cylinder bore diameter line, three intake valves are installed in the high speed rotation range. It is an object of the present invention to improve the combustibility by allowing intake air to flow into the cylinder through the intake air, and in a medium to low speed rotation range to allow the intake air to flow into the cylinder by a strong flow through only one side intake valve.

[0004]

In order to solve the above problems, in the intake system for a four-stroke internal combustion engine of the present invention, the cylinder head has a downstream portion of the first intake passage and a downstream portion of the second intake passage. Three intake valves and two or more exhaust valves are provided, and one central intake valve among the three intake valves is disposed near the cylinder bore diameter line on a plane perpendicular to the cam axis. , The remaining two side intake valves are arranged laterally on both sides of the central intake valve so as to be symmetrical with respect to the cylinder bore diameter line, and the first intake passage is communicated with only one side intake valve, The second intake passage communicates with each of the remaining side intake valve and the central intake valve via the bifurcated branch passage, and the downstream portion of the first intake passage and the downstream portion of the second intake passage / forked branch passage (Downstream portion of the second intake passage including the bifurcated branch passage) Are arranged so as to be gradually separated from each other as they approach the end of the cylinder head away from each intake valve, an opening / closing valve is arranged in the second intake passage, and the intake air is the first in the high speed rotation range. Of the side intake valve from the first intake passage through the three intake valves from the second intake passage and the second intake passage into the cylinder, and the opening / closing valve is closed in the medium to low speed rotation range. It is configured to flow into the cylinder through only. Further, the three intake valves and the two exhaust valves may be arranged so as to be parallel valves.

In the above construction, the "parallel valve" means 3
This means a valve in which all the valve axes of the intake valve and the exhaust valves of two or more are arranged on respective planes perpendicular to the cam axis. Further, as a means for supplying fuel to the intake system of the four-stroke internal combustion engine of the present invention, known means such as a carburetor and a fuel injection device can be used.

[0006]

When the on-off valve is closed (medium / low speed rotation range), intake air is supplied only from the first intake passage, and intake air passes from the first intake passage to only one side intake valve. Flow into the combustion chamber due to the strong flow, and a strong swirl is generated in the combustion chamber. When the on-off valve is open (high speed rotation range), intake air is supplied from the first intake passage and the second intake passage, and the intake air flows into the combustion chamber through the two side valves and the central valve. However, a sufficient intake amount can be secured.

[0007]

Embodiments of the present invention will be described with reference to the drawings. 1 to 3, the combustion chamber 1 is provided above the cylinder body 25, and a spark plug mounting hole 7 is formed in the center of the cylinder head 27 on the upper surface of the combustion chamber 1. In the cylinder head 27 on the upper surface of the combustion chamber 1, three intake valves 2 to 4 having the same valve diameter as each other are arranged on the circumference around the mounting hole 7 of the spark plug.
And two exhaust valves 5 and 6 having the same diameter as each other are provided.
The intake valves 2 to 4 and the exhaust valves 5 and 6 are arranged so as to be parallel valves. As described above, the parallel valve means that all the valve axes of the three intake valves 2 to 4 and the two exhaust valves 5 and 6 are located on the respective surfaces perpendicular to the cam shaft 28. By disposed valve, it is shown in FIGS. One central intake valve 2 is arranged near the cylinder bore diameter line 8 (in the front-rear direction) of the cylinder bore 26, and the other two side intake valves 3 and 4 are symmetrical with respect to the cylinder bore diameter line 8. Are arranged on both lateral sides of the central intake valve 2. Then, the cylinder bore diameter line 8
Is located on a plane perpendicular to the camshaft 28.

The first intake passage 9 and the second intake passage 10 are provided independently of each other, and the ventilation cross-sectional area of the first intake passage 9 is smaller than that of the second intake passage 10. There is. The downstream side of the first intake passage 9 is communicated with only one side intake valve 3 of the three intake valves, and is communicated with the combustion chamber 1 via the side intake valve 3. The downstream side of the second intake passage 10 is branched into bifurcated branch passages 10a and 10b, and the branch passages 10a and 10b pass through the remaining two intake valves, the central intake valve 2 and the side intake valve 4, respectively. Is communicated with the combustion chamber 1. The downstream portion of the first intake passage 9 (the cylinder head 27 is
3), a downstream portion of the second intake passage 10 (a portion of the second intake passage 10 formed in the cylinder head 27), and a bifurcated branch passage are clearly shown in FIG. Cylinder head end away from intake valves 2-4
They are arranged so as to gradually separate from each other as they approach 13. The upstream sides of the first intake passage 9 and the second intake passage 10 are connected to a common air cleaner.

The first exhaust passage 11 and the second exhaust passage 12 are provided independently of each other, and their upstream sides are connected to the combustion chamber 1 via exhaust valves 5 and 6, respectively.
The first exhaust passage 11 and the second exhaust passage 12 have the same ventilation cross-sectional area, and may be integrally merged on the downstream side.

The first intake passage 9 and the second intake passage 10 are provided with carburetors 14 and 15 which are interlocked with each other. Vaporizer 14 disposed in the first intake passage 9
Has a piston valve 14a that traverses the first intake passage 9 and a float chamber 14b provided below it. The piston valve 14a is pivotally supported by the tip of an arm 18 fixed to the rotary shaft 17, and moves up and down in accordance with the rotation of the rotary shaft 17. In the low speed rotation range, the opening of the piston valve 14a is small and in the high speed rotation range. It is designed to increase the opening as it shifts to
The flow rate is controlled in this way. The rotating shaft 17 and the grip portion 19 of the handle are connected by a wire 20, and the turning operation of the grip portion 19 of the handle is transmitted to the rotating shaft 17.

A carburetor 15 arranged in the second intake passage 10.
Like the carburetor 14, is a piston valve 15a that traverses the second intake passage 10 and a float chamber 15 provided below the piston valve 15a.
b, and a butterfly valve 16 as an opening / closing valve is disposed downstream of the piston valve 15a. The piston valve 15a is a butterfly valve 16
The flow rate is controlled by moving up and down according to the negative pressure generated corresponding to the opening degree.

A lever 22 is fixed to the end of the rotary shaft 21 of the butterfly valve 16, and the lever 22 is arranged so as to be close to a disc 23 fixed to the end of the rotary shaft 17 of the carburetor 14. Has been done. The adjusting screw 24 is attached to the surface of the disk 23,
The tip of the is disposed so as to face the lever 22 with a constant space S therebetween. Therefore, when the disc 23 is rotated by the rotation of the rotary shaft 17 by a set angle or more, the lever 22 contacts the tip of the adjusting screw 24, and thereby the rotary shaft 21 of the butterfly valve 16 is rotated. As described above, the first intake passage 9 and the second intake passage 10 are arranged so as to gradually separate from each other as the first intake passage 9 and the second intake passage 10 approach the cylinder head end portion 13 away from the intake valves 2 to 4. Since the portions of the first intake passage 9 and the second intake passage 10 apart from the cylinder have a predetermined interval, the rotary shaft 17, the disc 23, the adjusting screw 24, and the lever 22.
It is possible to dispose the interlocking mechanism consisting of between the vaporizers 14 and 15.

A carburetor 14 disposed in the first intake passage 9
Supplies the air-fuel mixture in both the medium speed range and the high speed range, but the carburetor installed in the second intake passage 10
15 does not supply the air-fuel mixture in the medium-low speed rotation range, and supplies the air-fuel mixture for the first time when the adjusting screw 24 reaches a high-speed rotation range above a set value for pressing and rotating the lever 22. Has been done. The start time of the air-fuel mixture supply to the carburetor 15 can be arbitrarily changed by adjusting the gap S with the adjusting screw 24.

2 to 11 show an example of a four-stroke internal combustion engine to which the intake device can be attached. The cylinder head 27 has a combustion chamber 1 corresponding to an upper portion of a cylinder bore 26 in a cylinder body 25. Are formed. 3 in combustion chamber 1
Intake ports 2a, 3a, 4a (4a is not shown) corresponding to the intake valves 2 to 4 and exhaust ports 5a, 6a corresponding to the two exhaust valves 5 and 6
Are respectively arranged. Rocker shaft 29 parallel to cam shaft 28
Is provided, a rocker arm 30 is swingably supported on a rocker shaft 29, and one end of the rocker arm 30 has intake valves 2 to 2
4. Contact the upper part of the valve shaft of the exhaust valves 5 and 6. Camshaft 28
Is rotated, the movement of the cam 31 of the cam shaft 28 is transmitted to the upper portion of the valve shaft via the rocker arm 30, and the intake valves 2-4
-The exhaust valves 5 and 6 are opened and closed.

In the embodiment, since the three intake valves and the two exhaust valves are arranged so as to be parallel valves, the equipment above the cylinder head can be packed and arranged to be compact as a whole. The intake system of the embodiment can be applied to a multi-cylinder internal combustion engine. Since the distance between the first intake passage and the second intake passage can be set to a desired value, the fuel injection device can be arranged in each of the first intake passage and the second intake passage. Is.

[0016]

In the medium to low speed rotation range, the on-off valve is closed, and the intake air flows from the first intake passage through only one side intake valve into the combustion chamber by a strong flow. Compared with the prior art in which a flow of almost the same weakness is simultaneously introduced from the holes, a strong swirl can be generated in the combustion chamber to increase the combustion speed, and the air-fuel mixture can be burned lean. For example, when the spark plug is attached to the center of the cylinder head 27, the tip of the side intake valve communicating with the first intake passage is directed slightly toward the center so that it is strong near the center where the spark plug is located. Swirl can be generated and ignition can be performed reliably and easily. Further, in the high speed rotation range, intake air flows into the cylinder from the first intake passage and the second intake passage through the three intake valves, and a high filling rate can be secured.

The downstream portion of the first intake passage and the downstream portion of the second intake passage (including the bifurcated branch passage) are gradually separated from each other as they approach the end of the cylinder head away from each intake valve. The distance between the first intake passage and the second intake passage can be set to a desired value.
Therefore, in view of the space, it is possible to arrange the on-off valve in the second intake passage, arrange the various air-fuel mixture supply devices in the first intake passage and the second intake passage, and An interlocking mechanism or the like can be provided in series between the on-off valve and the air-fuel mixture supply device.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an intake device according to an embodiment of the present invention.

FIG. 2 is one of a four-stroke internal combustion engine to which the intake device can be applied.
It is a longitudinal cross-sectional view showing an example.

FIG. 3 shows the cylinder head of the four-stroke internal combustion engine of FIG.
It is the figure seen from the III-III arrow.

4 is a view taken along the line IV-IV in FIG.

5 is a view taken along the line VV of FIG.

FIG. 6 is a plan view showing only a combustion chamber and an intake / exhaust passage of a four-stroke internal combustion engine to which the intake device is applied.

FIG. 7 is a side view showing one branch passage of the second intake passage shown in FIG.

FIG. 8 is a side view showing the other branch passage of the second intake passage shown in FIG.

FIG. 9 is a side view of a first intake passage.

FIG. 10 is a side view of an exhaust passage.

[Explanation of symbols]

 1 combustion chamber 2 center intake valve 3 side intake valve 4 side intake valve 5,6 exhaust valve 8 cylinder bore diameter line 9 first intake passage 10 second intake passage 10a, 10b bifurcated branch passage 16 butterfly valve

Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location F02M 35/10 301 B 9247-3G

Claims (1)

[Claims] 1. A cylinder head has a downstream portion of a first intake passage, a downstream portion of a second intake passage, three intake valves, and 2
More than three exhaust valves are provided, and one of the three intake valves is arranged in the vicinity of the cylinder bore diameter line on the plane perpendicular to the cam axis, and the other two side intake valves are arranged. The valves are arranged laterally on both sides of the central intake valve so as to be symmetrical with respect to the cylinder bore diameter line, the first intake passage communicates with only one side intake valve, and the second intake passage has a bifurcated shape. The downstream side portion of the first intake passage and the downstream portion of the second intake passage / the bifurcated branch passage are separated from each intake valve by communicating with each of the remaining side intake valve and the central intake valve via the branch passage. The cylinder head is arranged so as to be gradually separated from each other as it approaches the end portion of the cylinder head, and an opening / closing valve is arranged in the second intake passage. It flows from the intake passage through the three intake valves into the cylinder, Intake system for a four-stroke internal combustion engine in the speed range speed which opening and closing valve is closed intake air is flowing into the cylinder through only one of the side air intake valve from the first intake passage.