JP2647528B2 - Vertical overhead valve type internal combustion engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vertical overhead valve type internal combustion engine having a vertically arranged crankshaft.

[Conventional technology]

As one example of this type of vertical overhead valve type engine, Japanese Utility Model Publication No. 63-32343 is provided. 5 to 7 show the above-mentioned conventional vertical overhead valve type engine. In the figure, reference numeral 1 denotes a cylinder block composed of a cylinder barrel 1A, a cylinder head 1B, and a head cover 1C, in which the axial direction of the cylinder barrel 1A is horizontal, and 2 denotes a crankcase integrally formed with the cylinder barrel 1A of the cylinder block 1. A crankshaft 4 is vertically supported at the center of the crankcase 2 via a bearing 3. 5 is a piston and 6 is a connecting rod.

An intake valve 7 and an exhaust valve 8 are arranged in the cylinder head 1B in an overhead valve manner. The intake valve 7 and the exhaust valve 8 are rotated by a cam shaft 9 synchronized with the crank shaft 4, and the rotation of the cam shaft 9 A pair of upper and lower prosthetic rods 107, 108 which are linearly reciprocated by
A pair of rocker arms 1 swung by the operation of 108
17, 118, and a valve operating mechanism including a return spring 127 provided for each of the valves 7, 8 is provided.

And the cylinder head 1B viewed from the side of the head cover 1C
Has an intake hole 137 on the right side and an exhaust hole 138 on the left side. That is, the intake hole 137 and the exhaust hole 138 are provided so that the intake and the exhaust cross flow.

The intake valve 7 and the exhaust valve 8 are arranged vertically in parallel in a common vertical plane, particularly with the intake valve 7 facing upward. The intake hole 137 passes between the push rod 107 for the intake valve and the push rod 108 for the exhaust valve, and has a substantially linear upward gradient toward the intake valve 7.

As shown in FIG. 7, the intake hole of the cylinder head 1B
The bottom of the opening of 137 is lower than the top of the opening of the exhaust hole 138 on the opposite side.

Therefore, the connection portion of the carburetor and the connection portion of the muffler in each of the openings have substantially the same height. Above intake hole 13
The carburetor 14 is directly connected to the opening 7, the air cleaner 15 is connected to the carburetor 14, and the muffler 16 is connected to the opening of the exhaust hole 138. Reference numeral 17 denotes an elbow connecting the carburetor 14 and the air cleaner 15, and reference numeral 18 denotes an air cleaner element.

A wind guide cover 19 is attached so as to cover the upper part of the cylinder block 1 and the crankcase 2, and a flywheel 20 and a fan 21 integrated with the crankshaft 4 are located therein. 22 is a recoil starter and 23 is a fuel tank. The spark plug 24 and the scooter motor 25 are arranged on the same side as the muffler 16.

[Problems to be solved by the invention]

However, the conventional one has the following problems.

There are restrictions on where the plug 24 is installed. When the intake / exhaust ports are opened on both sides of the cylinder head, the direction of attachment / detachment of the spark plug inserted into the head is maintained as large as possible with respect to the exhaust port in the lateral direction where the temperature of the exhaust heat rises due to the engine operation. Because of the simplicity, the location of the spark plug is restricted.

The cylinder head combustion chamber cannot be cooled sufficiently.

Exhaust gas is difficult to cool downwind, cooling down to the exhaust valve is impossible, and the valve guide may fall off due to a difference in thermal expansion between the valve guide fixed in the cylinder head and the cylinder head.

Since the intake hole has a linear upward slope, the droplet fuel easily flows back to the carburetor side.

Since the axis of the carburetor and the axis of the intake hole obliquely intersect with each other, the flow of the air-fuel mixture is likely to be disturbed, and the output cannot be improved.

The present invention has been made to solve the above problems, and provides a vertical overhead valve type engine that improves the flow state of an intake air mixture, improves the cooling effect of cooling air, and further improves maintainability. Aim.

[Means for solving the problem]

The present invention is directed to an overhead valve type vertical internal combustion engine having a vertical crankshaft and a horizontal cylinder, wherein a carburetor is provided on one side of the cylinder and opposed to the carburetor. In an internal combustion engine equipped with a muffler, the intake hole opened on one side of the cylinder head is composed of a horizontal straight part and a curved part, and the axis of the horizontal straight part and the axis of the carburetor are almost in the same horizontal plane. The exhaust holes are arranged on the same straight line, and the exhaust hole is arranged such that a line connecting the exhaust hole and the exhaust valve is oblique to the horizontal straight portion from below.

[Action]

(1) Since the exhaust hole is opened to the lower surface side of the cylinder head, the muffler can be bent and attached to the left side surface of the cylinder head, thereby increasing the degree of freedom of arrangement of the ignition plug.

(2) Since there is no exhaust hole in the flow path of the cooling air as in the related art, a smooth flow of the cooling air is not hindered. This ensures that the combustion chamber around the spark plug is cooled.

(3) The cooling air flows to the vicinity of the exhaust valve, so that overheating of the valve guide can be prevented.

(4) The length of the exhaust hole portion of the cylinder head is shorter than that of the conventional one, and the muffler is insulated by the gasket, so that the amount of heat stored on the exhaust side of the cylinder head can be reduced.

(5) Since the axis of the carburetor and the axis of the horizontal straight line portion of the intake hole are arranged on substantially the same straight line in the same horizontal plane, disturbance of the intake air-fuel mixture does not occur. In addition, since the pilot hole of the screw hole for vaporizer tightening can be cast, it is possible to prevent the occurrence of a hole in the screw hole portion.

〔Example〕

Referring to FIGS. 1 to 4, one embodiment of the present invention will be described. Reference numeral 51 denotes a cylinder block, which comprises a cylinder barrel 51a, a cylinder head 51b, and a head cover 51c, and an axis 51a1 of the cylinder barrel 51a is horizontally disposed. It is arranged to become. 52 and 53 are an intake valve and an exhaust valve, respectively. An overhead valve (overhead valve) is arranged on the cylinder head 51b. Reference numerals 54 and 55 denote a pair of upper and lower push rods, which are reciprocated linearly by rotation of a cam rotating in synchronization with a crankshaft (not shown), and together with a pair of rocker arms 56 and 57 which are rocked by the operation thereof. It constitutes a valve train. 58 is an intake hole, and the cylinder head 51
When viewed from the side b (as viewed in the direction of the arrow II in FIG. 1), the cylinder head 51b opens on the right side surface. The intake hole 58 is provided in the horizontal straight section 5.
The curved portion 60 is connected to the intake valve 52 and the horizontal straight portion 59 is connected to the carburetor 62. Reference numeral 70 denotes a cooling air hole through which cooling air flows in the output shaft direction, which is surrounded by the crankcase side wall of the horizontal straight portion 59, the upper surface of the cylinder mounting wall, and the peripheral wall of the push rod hole. Reference numeral 61 denotes an exhaust hole, and a line connecting the center line 61a of the exhaust hole 53 and the exhaust valve 53 is disposed obliquely to the horizontal straight portion 59 of the intake hole 58 from below. The exhaust hole 61
Is 5 between the center line 61a and the crankshaft center line 100.
It is inclined in the range of ゜ ~ 45 ゜.

Note that the intake valve 52 and the exhaust valve 53 are arranged vertically in parallel in a common vertical plane, and the intake valve 52 is located above. The horizontal straight portion 59 is a push rod for an intake valve.
A carburetor 62 is arranged so as to pass between the exhaust valve push rod 55 and the exhaust valve push rod 55, and its axis 62 a is aligned with the horizontal straight line 5 of the intake hole 58.
As shown in FIG. 1, a bolt 63 is screwed into a screw hole 64 provided in a cast hole of the cylinder head 51b, and the cylinder head 51b is disposed in the same horizontal plane as the shaft center 59a of FIG. Attached to A muffler 65 is composed of a right main body 65a and a left main body 65b. The right main body 65a is wound around the left main body 65b to form an integral structure. The muffler has an exhaust hole
A nut 67 is screwed into a bolt 66 implanted in 61 and attached. Reference numeral 65c denotes a drawing portion provided on the left main body 65b. 68
Is screwed into a screw hole 69 of the cylinder head 51b with a spark plug.

In the vertical overhead valve type engine having the above configuration, the mixer from the carburetor 62 is introduced into the cylinder by opening the intake valve 52 through the horizontal straight portion 59 and the curved portion 60 of the intake hole 58. At this time, since the curved portion 60 is close to the exhaust hole 61, the exhaust gas is cooled by the air-fuel mixture. Further, the mixer is swirled by the curved portion 60 and flows into the cylinder.

Further, since the axis 62a of the carburetor 62 and the axis 59a of the horizontal straight line portion of the intake hole 58 are arranged on substantially the same straight line in the same horizontal plane, the occurrence of disturbance of the intake air-fuel mixture is prevented.
Next, the exhaust gas from inside the cylinder flows into the muffler 65 through the exhaust hole 61 by opening the exhaust valve 53, where it is silenced and discharged to the outside. In this case, since the exhaust hole 61 is oblique to the intake hole 58 and opens downward, and the muffler 65 is directly attached to the cylinder head 51b without passing through the exhaust pipe, the muffler is connected to the cylinder as shown in FIG. Block 51
Can be arranged from the bottom to the side. As a result, the capacity of the muffler can be increased, and the noise reduction effect is improved.

Further, cooling air from a cooling fan (not shown) flows through the air guide plate 71 as shown by the arrow A in FIG. 2 to cool the ignition plug 6a, the cylinder head 51b, and the like. In this case, since the low-temperature cooling air directly hits the spark plug 69 from inside the air guide plate 71 and cools the periphery thereof, the combustion chamber around the spark plug 69 is sufficiently cooled.

Further, since the cooling air also sufficiently cools the valve guide portion of the exhaust valve 53, burning of the exhaust valve 53 to the valve guide is prevented.

〔The invention's effect〕

The present invention is configured as described above, and has the following effects according to the present invention.

(1) Since the exhaust hole is opened to the lower side of the cylinder head,
The muffler can be bent and attached to the left side surface of the cylinder head, thereby increasing the degree of freedom in the arrangement of the spark plug and facilitating maintenance.

(2) Since there is no exhaust hole in the flow path of the cooling air as in the related art, a smooth flow of the cooling air is not hindered. This ensures that the combustion chamber around the spark plug is cooled.

(3) Since the cooling air can flow into the vicinity of the exhaust valve, and the overheating of the valve guide can be prevented, the occurrence of the trouble of the valve guide falling off can be prevented.

(4) The length of the exhaust hole of the cylinder head is shorter than that of the conventional one, and the muffler is insulated by a gasket, so the amount of heat stored on the exhaust side of the cylinder head can be reduced.
The cooling effect is improved.

(5) Since the axis of the carburetor and the axis of the horizontal straight line portion of the intake hole are arranged almost in the same horizontal plane in the same horizontal plane, the turbulence of the intake air-fuel mixture does not occur and high output can be achieved. In addition to being able to cope with the problem, since the pilot hole of the screw hole for the carburetor tightening hole can be cast, it is possible to prevent the occurrence of nests in the screw hole portion.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view of a vertical overhead valve type internal combustion engine according to a first embodiment of the present invention, FIG. 2 is a view taken in the direction of the arrow II in FIG. 1, and FIG. FIG. 4 is a vertical sectional view of an intake hole and an exhaust hole of a cylinder head portion, FIG. 5 is a partial vertical sectional view of a conventional vertical overhead valve type internal combustion engine, and FIG. FIG. 7 is a partial cross-sectional view taken along line VI in FIG. 5, and FIG. 7 is a partial cross-sectional view taken along line VII in FIG. 51 …… Cylinder block, 51b …… Cylinder head, 62…
… Vaporizer, 65 …… muffler, 58 …… intake hole, 61 …… exhaust hole, 59
… Horizontal straight section, 60… Curved section, 52… Intake valve, 53… Exhaust valve, 68… Spark plug.

Claims (2)

(57) [Claims] 1. A vertical overhead valve type internal combustion engine having a crankshaft arranged vertically and a cylinder center arranged horizontally, wherein a carburetor is arranged on one side of a cylinder and a muffler is arranged opposite the carburetor. In an internal combustion engine, the intake hole opened on one side of the cylinder head consists of a horizontal straight part connected to the carburetor and a curved part connected to the intake valve, and the axis of the horizontal straight part and the axis of the carburetor are The exhaust holes connected to the muffler are arranged so that the line connecting the center and the exhaust valve crosses the horizontal straight portion obliquely from below in the same horizontal plane. A vertical overhead valve type internal combustion engine. 2. The vertical overhead valve type internal combustion engine according to claim 1, wherein said muffler is directly attached to said cylinder head.