JPS6327046Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a so-called overhead valve type internal combustion engine in which the intake and exhaust valve seats are located on the ceiling of the combustion chamber of the cylinder head. This relates to an internal combustion engine in which the height of the engine is lowered and the overall structure is made more compact by arranging the fuel tank above the crankcase and cylinders and the air cleaner above the cylinder head and head cover. .

Intake and exhaust valve 1 of an overhead valve type internal combustion engine in which the above cylinder is inclined with respect to the crankcase
As shown in FIG.
→ Push rod 8 → Rocker arm 9 → Intake/exhaust valve 1 (with return spring 10) The fuel tank 21 (first
(see figure) and the air cleaner 20, the tappet 7 and push rod 8 are provided along the lower surface of the cylinder 11.

and the valve guide pipe 1 for the cylinder head 12.
Generally, the intake/exhaust valve 1 and the push rod 8 are provided parallel to the direction of movement of the piston 14, taking into consideration the machinability of the press-fit hole 3 and the ease of inserting and assembling the push rod 8.

Therefore, the tubular guide portion 15 passing through the push rod 8 and the cylinder 11 are brought closer together, and the cooling air passage 16 between the rod guide portion 15 and the cylinder 11 is narrowed. Therefore, there is a possibility that cooling of the lower surface side of the cylinder 11 may become insufficient.

Therefore, the diameter of timing gears 3 and 4 was increased,
If the rocker arm 9 with a long arm is used, the distance between the cylinder 11 and the rod guide part 15 will be increased, but the mass of the entire valve opening/closing mechanism will increase, resulting in a lack of smooth operation, and the height of the engine will increase. Put it away.

In the present invention, a cylinder 11 with an overhead valve type intake and exhaust valve arrangement is installed slightly above horizontal with respect to a crankcase 22, a fuel tank 21 is placed above the crankcase 22 and the cylinder 11, and an air cleaner 20 is placed on the cylinder head. 12 and head cover 18, respectively, and an intake/exhaust valve drive push rod 8, which is passed through a rod guide 15, is provided along the lower surface of the cylinder 11 in the direction of movement of the piston 14. The purpose of this system is to increase the cooling effect of the cylinder without impairing the engine, and to keep the height of the engine low.As shown in Figure 1, the push rod 8 is tilted downward with respect to the cylinder center axis. The push rod 8 is attached to the cylinder 11 together with the rod guide section 15.
It is characterized by being separated from

When the push rod 8 is arranged with respect to the cylinder 11 as described above, the distance between the cylinder 11 and the rod guide portion 15 is widened, and a cooling air passage 16' having a large opening area is formed.

Therefore, a fan (not shown) integrated with the crankshaft 2
A large amount of air sent by the cooling air guide cover 17 passes through the passage 16', and the entire circumference of the cylinder 11 is well cooled.

Also, the push rod 8 for the cylinder 11
When configuring the arrangement as described above, the position of the camshaft 5 and the arm length of the rocker arm 9 are not changed in order not to increase the mass of the valve opening/closing mechanism. Push rod 8 relative to the direction of movement of piston 14
can be tilted at an angle α to the side of .

Furthermore, the spark plug 19 can also be tilted toward the intake/exhaust valve 1 and supported by the cylinder head 12.

As the push rod 8 is tilted away from the cylinder 11 together with the rod guide 15, the intake/exhaust valve 1 and the ignition plug 19 are tilted downward and supported, so that the push rod 8 is disposed above the cylinder head 12 and the head cover 18. Air cleaner 2
The zero position is lowered, which has the effect of lowering the height of the engine.

Furthermore, since the push rod 8 is tilted away from the cylinder 11, the rod length becomes shorter, the rocker arm only needs to be as long as possible, and the diameters of the timing gears 3 and 4 do not need to be increased. This reduces the mass of the valve opening/closing mechanism, which reduces the mass of inertia, which has the effect of reducing cam surface pressure and preventing valve jumps. The cylinder 11, which has an overhead valve type valve arrangement, is installed slightly above the horizontal with respect to the crankcase 22, the fuel tank 21 is placed above the crankcase 22 and the cylinder 11, and the air cleaner 20 is placed between the cylinder head 12 and the head cover 18.
The push rods 8 for driving intake and exhaust valves, which are placed on top of the cylinders 1 and passed through the rod guide part 15, are connected to the cylinder 1.
1 in the direction of movement of the piston 14 along the lower surface of the piston 1 .

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view of the overhead valve type internal combustion engine of the present invention, and FIG. 2 is a longitudinal sectional front view of the cylinder and cylinder head portion of a conventional example. 1 is an intake and exhaust valve, 2 is a crankshaft, 3 and 4 are timing gears, 5 is a camshaft, 6 is a cam, 7 is a tappet, 8 is a push rod, 9 is a rocker arm, 1
1 is a cylinder, 12 is a cylinder head, 14 is a piston, 15 is a rod guide, 16, 16' are cooling air passages, 18 is a head cover, 19 is a spark plug, 20 is an air cleaner, 21 is a fuel tank, 2
2 is the crankcase.

Claims (1)

[Scope of utility model registration request] A cylinder with an overhead valve type intake and exhaust valve arrangement is installed slightly above the horizontal with respect to the crankcase, and the fuel tank is placed above the crankcase and cylinder, and the air cleaner is placed above the cylinder head and head cover. In an internal combustion engine in which a push rod for driving intake and exhaust valves that passes through a guide part is installed along the bottom surface of the cylinder in the direction of movement of the piston, the push rod is tilted downward with respect to the cylinder center axis, and the push rod is connected to the cylinder together with the rod guide part. An overhead valve internal combustion engine separated from the engine.