JPH0433980B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a four-stroke engine for a motorcycle.

A four-valve engine, in which each cylinder has two intake valves and two exhaust valves, for a total of four valves, has the advantage of producing a large amount of output because there is little resistance to intake and exhaust flow. When installing such an engine with multiple cylinders, such as a 4-cylinder engine, on a motorcycle, the exhaust side is generally placed at the front due to the relationship with other equipment such as a carburetor and the cooling efficiency of the running wind. It is mounted with the intake side at the rear. especially,
On the exhaust side, air holes are provided between each exhaust port on the outside of the engine to improve cooling by the wind from the front.

However, in a 4-valve engine like the one above,
Since two exhaust valves are arranged in each cylinder and tappets for operating the exhaust valves are provided correspondingly, the space occupied by the air hole is reduced accordingly. For this reason, conventional 4-stroke, 4-valve engines had the problem of not being able to provide sufficient cooling through the air holes.

Additionally, since as many as four valves are placed above the cylinder, the lack of space forces the spark plug to be placed close to the high-temperature exhaust valve, resulting in the spark plug becoming overheated and prone to knocking. There was also this problem.

The purpose of the present invention is to provide a four-stroke motorcycle engine that solves the above-mentioned conventional problems, further enhances the cooling effect of the air holes, and suppresses the knocking phenomenon caused by overheating of the spark plug. The goal is to provide the following.

To achieve the above object, the present invention provides a multi-cylinder four-stroke engine for motorcycles in which a plurality of cylinders are arranged side by side in the direction of travel, and each cylinder is provided with an exhaust valve on the front side and an intake valve on the rear side. , the exhaust valve of each cylinder is unevenly distributed on one side in the cylinder width direction, and only one spark plug is provided, and the spark plug is unevenly distributed on the opposite side in the cylinder width direction from the exhaust valve, and its upper end side is separated from the exhaust valve. It is characterized by providing an air hole that extends from the front of the engine to above the cylinder head at a position that is tilted away from the exhaust port and is sandwiched between adjacent exhaust ports.

In this way, by having only one exhaust valve installed at the front side of each cylinder and unevenly distributing it to one side in the cylinder width direction, the number of air holes is reduced compared to the case where two exhaust valves are installed. It becomes possible to enlarge the space and increase the cooling effect. In addition, by locating the spark plug unevenly on the opposite side of the exhaust valve, and slanting the upper end away from the exhaust valve, the spark plug is not only kept away from the high-temperature exhaust valve, but also cooled by fresh air from the front. can be applied directly, providing even better cooling effects.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained below with reference to embodiments shown in the drawings.

Figure 1 is a side view showing a motorcycle equipped with the DOHC engine of the present invention with a rider M riding on it, and Figure 2 is a side view of the motorcycle with the upper head cover removed. FIG. 3 is a plan view showing only the left half with respect to the center line in the direction. Since the right half has a symmetrical structure, it has approximately the same configuration as the left half. FIG. 3 is an arrow diagram of the same engine, partially shown in cross section.

In FIG. 1, 50 is a 4-cylinder DOHC engine, and the DOHC engine 50 is mounted so that the 4 cylinders are arranged horizontally in the aircraft body. 60
is the front wheel, and 70 is the rear wheel.

In FIGS. 2 and 3, numeral 1 denotes a cylinder head, and this cylinder head 1 is fixed to a lower cylinder block by bolts 2.

Cam chambers 3, 3 are formed on both front and rear sides of the upper surface of the cylinder head 1, respectively. These cam chambers 3
and a head cover 5 on the top of the cam chain chamber 4.
It is removably attached so that it covers it. Reference numeral 6 denotes cylinders installed in a cylinder block below the cylinder head 1, and there are a total of four cylinders, two cylinders on each side, with a central cam chain chamber 4 in between. Above each cylinder 6, there are two cylinders on the rear side of the aircraft.
Intake valves 7, 7 are provided, one exhaust valve 8 is provided on the front side of the fuselage, and one spark plug 9 is provided on the opposite side from the exhaust valve 8. It is being Here, exhaust valve 8
The uneven distribution relationship between the spark plug 9 and the spark plug 9 is that the cam chain chamber 4
The cylinder 6 located on the side is different from the cylinder 6' located on the outer wall side, and in the former cylinder 6, the spark plug 9 is located on the cam chain chamber 4 side, and the exhaust valve 8 is located on the opposite side. In the latter cylinder 6', the exhaust valve 8 is located on the side of the adjacent cylinder 6, and the spark plug 9 is located unevenly on the outer wall side. In this way, the spark plugs 9, 9 are unevenly distributed on the outer wall side and the cam chain chamber 4 side, which have lower temperatures, respectively, and are separated from the exhaust valve 8, which has a higher temperature, so that overheating can be prevented.

Since there is only one exhaust valve 8 for each cylinder, the exhaust opening area opened and closed by this exhaust valve 8 is made large enough to correspond to the intake opening area of the two intake valves 7, 7.

Each of the front and rear cam chambers 3, 3 is faced with a tappet 11a that is connected to the intake valves 7, 7 and the exhaust valve 8, respectively, corresponding to each cylinder.
A cam 11 fixed to a camshaft 10 faces each tappet in a corresponding manner. two camshafts 1
Of the two cams 10, a camshaft 10 corresponding to the intake valves 7, 7 side is supported by a bearing 12 interposed between two cams 11, 11. Further, the camshaft 10 corresponding to the exhaust valve 8 side is supported by a bearing 12 with the cams 11, 11 sandwiched therebetween. Each of these camshafts 10 is driven by the power of the crankshaft via a sprocket 13 fixed to the cam chain chamber 4, respectively. Reference numeral 14 denotes a positioning projection fixed on the camshaft 10 to stop the thrust of the camshaft.

In addition, on the front side of the engine, there is an adjacent exhaust port 8.
An air hole 15 is provided corresponding to the position between a and 8a. As shown by the dashed line in Fig. 2, this air hole 15 is provided as a through hole up to near the exhaust valve 8, which has the highest temperature in the engine, and guides the running wind from the front to the upper part of the cylinder head. This makes cooling even more effective.

The air that cools the upper part of the cylinder as described above flows over the air hole (not shown) provided below the intake camshaft and the intake camshaft cover.

FIG. 4 shows another embodiment of the invention.

In this embodiment, the uneven distribution relationship between the exhaust valve 8 of the cylinder 6 located on the cam chain chamber 4 side and the spark plug 9 is opposite to that of the above embodiment.

That is, the exhaust valve 8 and the spark plug 9 are arranged in the same manner as in the cylinder 6' on the outer wall side.

In this embodiment, the two spark plugs 9, 9 on one side from the center of the engine are arranged so that they both face the outside of the vehicle body, so the plug 9 on the outside of the engine is of course the spark plug on the center side of the engine. 9
It also has the advantage of being easier to attach and detach, improving maintainability. Also, the air hole 15 between cylinders 6 and 6'
Since the space is further increased, the cooling effect can be further improved.

The DOHC engine of each embodiment described above does not have a four-valve configuration, but has an exhaust valve 8 that becomes hot.
Because it has a 3-valve configuration with only one,
The air hole 1 located between the DOHC 4-valve engine is approximately equivalent to the space of the reduced exhaust valve without substantially reducing the high performance of the 4-valve engine.
5 can be made larger, and the cooling effect of the cooling air from the front can be further enhanced. Furthermore, by improving the cooling performance due to the air holes 15, blow-through of the cylinder head gasket due to thermal deformation can be prevented. Furthermore, since there is only one exhaust valve 8, the distance between the spark plug 9 and the high-temperature exhaust valve 8 can be increased, and as a result, the occurrence of knocking phenomena due to overheating of the spark plug 9 can be suppressed. becomes possible.

As described above, the multi-cylinder four-stroke engine for motorcycles of the present invention has an engine structure in which the exhaust valve is provided on the front side of the cylinder and the intake valve is provided on the rear side, and the exhaust valve of each cylinder is arranged in the cylinder width direction. Only one air hole is provided unevenly located on one side, and the air hole that penetrates from the front of the engine to the upper part of the cylinder head is provided at a position sandwiched between adjacent exhaust ports. The space of the air hole increases, making it possible to enhance the cooling effect of the cooling air. In addition, there is only one high-temperature exhaust valve, and the ignition plug is unevenly distributed on the side opposite to the exhaust valve, and its upper end is inclined in a direction away from the exhaust valve, so the ignition plug is connected to the high-temperature exhaust gas. Not only can the spark plug be moved further away from the valve, but it can also be directly exposed to fresh cooling air from the front, which can prevent the knocking phenomenon caused by overheating the spark plug.

[Brief explanation of drawings]

Fig. 1 is a side view of a motorcycle equipped with a multi-cylinder four-stroke engine according to the present invention, Fig. 2 is a plan view showing only the left half of the same engine with the head cover removed, and Fig. 3 is a partial view of the same engine. FIG. 2 is a cross-sectional view in the direction of arrows, and FIG. 4 is a plan view showing only the left half of a device according to another embodiment with the head cover removed. 1...Cylinder head, 6...Cylinder, 7...Intake valve, 8...Exhaust valve, 8a...Exhaust port, 9...Spark plug, 15...Air hole.

Claims (1)

[Claims] 1 Multi-cylinder motorcycle for motorcycles 4 in which multiple cylinders are arranged side by side in the direction of travel, and each cylinder has an exhaust valve on the front side and an intake valve on the rear side.
In a cycle engine, the exhaust valve of each cylinder is unevenly distributed on one side in the cylinder width direction, and only one spark plug is provided, and the spark plug is unevenly distributed on the opposite side in the cylinder width direction from the exhaust valve. A multi-cylinder for a motorcycle, characterized in that an air hole is provided so as to be inclined in a direction away from the exhaust valve, and penetrates from the front of the engine to above the cylinder head at a position sandwiched between adjacent exhaust ports. 4 cycle engine.