JPH0339185B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to the structure of an overhead valve type internal combustion engine, and particularly to the arrangement structure of an intake system and an exhaust system of an overhead valve type internal combustion engine.

[Conventional technology]

Overhead valve internal combustion engines have a structure in which the intake valve and exhaust valve are placed directly above the combustion chamber, and are widely used as vehicle engines and engines for work equipment such as agricultural work and civil engineering work. .

Generally, general-purpose internal combustion engines are used as engines for work equipment, and there are two types of general-purpose internal combustion engines: one type in which the crankshaft is placed vertically (therefore the cylinder is horizontal), and the other type in which the crankshaft is placed horizontally (the cylinder is vertically placed). It can be broadly divided into

In particular, as a drive source for lawn mowers and grass cutters, models with a crankshaft arranged vertically and an output shaft taken out from the bottom are preferred, since the height of the engine can be reduced and the stability of the machine can be easily ensured. Preferred and used.

By the way, in conventional overhead valve type internal combustion engines, the opposing sides of the cylinder head are generally
An intake hole and an exhaust hole are opened on opposite sides at 180 degrees, and a carburetor and an air cleaner are connected to the intake hole, and a muffler is connected to the exhaust hole.

In addition, as a cooling method for cylinders and cylinder heads, a fan is generally provided at the end of the crankshaft opposite to the normal output shaft, and the cooling air generated by the fan is guided to the desired location using a wind guide cover, etc. A cooling method is used.

The configuration of such a conventional overhead valve internal combustion engine is
For example, it is disclosed in Japanese Patent Application Laid-Open No. 59-70838 (Japanese Patent Application No. 57-180867).

[Problem that the invention seeks to solve]

However, in this conventional structure, since the intake and exhaust holes are open on both sides of the cylinder head, the flow of cooling air from the fan is blocked by the intake and exhaust hole forming part and the built-in part of the push rod. The drawback was that the head section could not be cooled sufficiently.

Furthermore, since the cylinder head is poorly cooled, abnormal combustion such as knocking is likely to occur, making it impossible to improve output and making it difficult to achieve low fuel consumption, which is an advantage of overhead valve internal combustion engines.

In addition, the valve guide (usually made of iron-based material) that is press-fitted into the cylinder head is prone to thermal problems, especially when the valve guide for the exhaust valve is placed on the output shaft side. (This is a commonly used arrangement), it becomes difficult to cool this part with cooling air, and the valve guide section is heated by the combustion gas, causing a serious problem such as the valve guide falling off from the cylinder head (usually cast aluminum). there is a possibility.

[Purpose of the invention]

The purpose of the present invention is to overcome the drawbacks of the prior art,
It is an object of the present invention to provide an overhead valve type internal combustion engine which can improve the performance and reliability of the engine by eliminating the above problems and increasing the cooling effect of the cylinder head.

[Means for solving problems]

In the overhead valve type internal combustion engine of the present invention, the intake and exhaust valves are arranged parallel to the crankshaft and the exhaust valve is placed on the side opposite to the output shaft, the intake hole is opened in a direction substantially perpendicular to the crankshaft, and the exhaust hole is opened in a direction substantially perpendicular to the crankshaft. The opening is on the opposite side of the intake hole and is inclined at approximately 45 degrees toward the side opposite to the output shaft. A cooling fan is provided on the side opposite to the output shaft, a carburetor is connected to the intake hole, a muffler is placed on the opposite side of the carburetor, and the exhaust hole is connected to the muffler with an exhaust pipe. The holes are arranged so that they are directly exposed to the air from the cooling fan on the side opposite to the output shaft, thereby increasing the cooling effect of the cylinder head and greatly reducing the temperature difference around the cylinder. The present invention provides an overhead valve internal combustion engine with improved performance and reliability.

In addition, in another overhead valve type internal combustion engine of the present invention, the intake and exhaust valves are arranged parallel to the crankshaft and the exhaust valve is placed on the side opposite to the output shaft, and the intake hole is opened in a direction substantially perpendicular to the crankshaft. , the exhaust hole is opened in a direction opposite to the intake hole and inclined toward the side opposite to the output shaft, and the swing bearing of the rocker arm for operating the intake and exhaust valves is placed on the intake hole side with respect to the intake and exhaust valves, and the crankshaft A cooling fan is provided on the opposite side of the output shaft, a carburetor is connected to the intake hole, a muffler is arranged on the opposite side of the carburetor, and the exhaust hole and the muffler are connected with an exhaust pipe, and the exhaust hole and the exhaust pipe are connected. By placing a gasket at the joint of the cylinder head and using this gasket as a guide for cooling air, the exhaust hole is placed so that the air from the cooling fan on the side opposite to the output shaft directly hits the cylinder head. The present invention provides an overhead valve type internal combustion engine that can enhance the cooling effect and significantly reduce the temperature difference around the cylinders, thereby improving the performance and reliability of the engine.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional side view of a main part of an overhead valve type internal combustion engine according to an embodiment, and FIGS. 2 and 3 are a cross-sectional view and a cross-sectional end view of a main part, respectively, as seen from line - and line - in FIG. 1. It is a diagram. The illustrated engine is an overhead valve type internal combustion engine with a vertical crankshaft.

1 and 2, a crankshaft 2 is supported vertically through a crankcase 1, and a connecting rod 4 is connected to the crank pin 3.
A piston 6 fitted into a cylinder 5 is connected to the other end of the connecting rod 4. In the illustrated engine, the crankcase 1 and the cylinder 5 are integrally molded, and the cylinder 5 is arranged horizontally.

A cylinder head 7 is hermetically joined to the top surface (tip surface) of the cylinder 5, and a combustion chamber 8 is formed at the joint. An intake valve 9 and an exhaust valve 10 are arranged directly above the combustion chamber 8 (with respect to the piston stroke direction), and these valves 9 and 10 are fitted into a valve guide 11 that is press-fitted into the cylinder head 7 or the like. ing.

As shown in FIGS. 1 to 3, an intake hole 12 and an exhaust hole 13, whose communication with the combustion chamber 8 is controlled by the intake and exhaust valves 9 and 10, are formed in the cylinder head 7. There is. In the illustrated example, the intake and exhaust valves 9 and 10 are arranged one above the other, with the intake valve 9 located at the bottom.

As shown in FIG. 3, the intake hole 12 and the exhaust hole 13 are formed in directions oblique to each other (angle α is about 45°), and the intake hole 12 extends horizontally and opens on one side of the cylinder head 7. However, the exhaust hole 13 extends obliquely upward and opens on the upper slope of the cylinder head 7.

As shown in FIGS. 1 and 2, the cylinder head 7 has a pair of rocker arms 1 that open the intake and exhaust valves 9 and 10 against a return spring.
4 and 14 are pivotably supported. Further, a head cover 15 that covers the pair of rocker arms 14, 14 for the intake and exhaust valves is hermetically joined to the cylinder head 7, and a rocker arm chamber 16 is formed inside the head cover 15.

On the other hand, a shaft 17 is provided in the crankcase 1 and is driven to rotate at twice the frequency by the crankshaft, and a pair of cams 1 for intake and exhaust valves are provided on the camshaft.
7a and the pair of rocker arms 14, 14, a reciprocating mechanism consisting of a tappet 18 and a push rod 19 is provided as shown in FIGS. 2 and 3, and as the crankshaft rotates, the pair of rocker arms The intake valve 9 and the exhaust valve 10 are driven to open at a predetermined timing during the piston stroke through the pistons 14 and 14.

Note that each push rod 19, 19 passes through the intake hole 12 side of the cylinder head 7, as shown in FIG. However, in the illustrated example, the push rod passage 20 is formed across approximately the center of the intake hole 12. The passage 20 is formed, for example, by press-fitting and fixing a pipe material into the cylinder head 7. Since the push rods 19, 19 for the intake and exhaust valves are arranged on the side of the intake hole 12, as shown in FIG.
The swing bearings 21 of rocker arms 14, 14 for exhaust valves are also arranged closer to the intake hole 12 than the intake and exhaust valves 9, 10. In addition, the intake hole is push rod 19,1
It may be placed between 9 and 9.

A carburetor 22 is connected to the intake hole 12 (in the illustrated example, it is directly connected without intervening an intake pipe or the like). Further, an air cleaner (not shown) is normally connected to the inlet side of the carburetor 22.

As shown in FIGS. 2 and 3, a muffler 23 is arranged on the opposite side of the carburetor 22 across the cylinder head 7, and the exhaust hole 13 and the muffler 23 are connected by an exhaust pipe 24. .

An output shaft 25 is taken out from the lower side of the crankcase 1 by protruding the crankshaft 2 downward. Note that a mounting case 26 is attached to the lower side of the crankcase 1 for mounting the engine on a working machine or the like.

On the other hand, the crankshaft 2 also protrudes from the upper side of the crankcase 1, and a flywheel 27 and a cooling fan 28 (in the illustrated example, a cooling fan that also serves as a flywheel) are attached to this upwardly protruding part. A recoil starter 29 for starting is attached.

Further, a fan housing 30 is provided at a position covering the cooling fan 28 and the upper half of the engine,
The cooling air is configured to flow along the surfaces of the cylinder 5 and cylinder head 7.

Furthermore, the cylinder head 7 and the muffler 23
A baffle plate 31 is installed between the cylinder head 7 and the cylinder 5 to guide the cooling air from above along the surfaces of the cylinder head 7 and the cylinder 5 to the lower side thereof, and to guide the cooling air from the output side.

As shown in the figure, cooling fins 32, 32 are provided on the surfaces of the cylinder 5 and the cylinder head 7 to enhance the cooling effect.

According to the above configuration, the valve guides 11, 11 and the exhaust hole 1 are provided on the reaction side surface of the intake passage 12 of the cylinder head 7, as shown in FIGS. 2 and 3.
Sufficient cooling fins 32 can be provided around the periphery of the cooling fan 28, and the cooling air from the cooling fan 28 can be smoothly flowed into the area of these cooling fins 32, as shown by the dashed line arrow A in FIG. Since the exhaust gas is sufficiently supplied to the cylinder head 7, the high-temperature parts of the surface of the cylinder head 7, particularly the exhaust valve guide 11 and the surrounding area of the exhaust hole, can be sufficiently cooled. In the illustrated example, the gasket 33 is provided extending in the direction of the cooling fan, so that the flow of cooling air in this region can be rectified and strengthened, thereby further improving the cooling effect.

Note that on the intake hole 12 side, the cooling air does not flow as fully as on the opposite side because it is blocked by the intake hole 12 and the push rod 19, and the cooling fins cannot be formed sufficiently, but the vicinity of the intake hole 12 is thermally There are few problems, and the air-fuel mixture can be cooled to some extent, so there is no problem. If necessary, the cooling effect on the intake hole 12 side can be enhanced by providing a cooling air passage 34 that vertically passes through the cylinder head 7, as shown in FIG.

The cooling air flowing on the opposite side of the intake hole 12 (the left side of the cylinder head 7 in FIG. 3) can easily flow downward as shown by the chain arrow B in FIG. It is possible to cool the cooling fins 32 provided on the lower side. In the illustrated example, a baffle plate 31 is provided, and by guiding the flow with this, the cooling effect can be further improved. In the illustrated example, the baffle plate 31 and the fan housing 30 are formed as separate parts, but depending on the case, they may be formed as an integrated part.

In this way, it is possible to obtain an arrangement of the engine that not only has an excellent cooling effect but also can actively cool high-temperature parts so that each part can be cooled in a well-balanced manner.

Furthermore, according to the above configuration, as is clear from FIG. 3, the cooling air first cools the high temperature parts such as the exhaust valve guide 11, the surroundings of the exhaust hole 13, and the cylinder head 7, and then cools the output side (as shown in the figure). Since the air is discharged to the lower side in the example, the heated air does not hit the carburetor 22, thus preventing problems such as percolation (a phenomenon in which air bubbles occur and the fuel flow deteriorates) in the fuel passage. can do.

Furthermore, as is clear from FIG. 3, the intake hole 12 is opened on one side of the cylinder head 7, and the carburetor 22 is connected to this, and the side obliquely intersecting this (in the illustrated example, the upper counter-intake hole Since the configuration is such that the exhaust pipe 23 connects the exhaust hole 13 opened on the side) and the muffler 23 placed on the opposite side of the carburetor 22, W (width of the engine) and H (width of the engine) in Fig. It is possible to obtain an overhead valve type internal combustion engine that can be made small in size (height), can be made compact as a whole, is convenient to be mounted on a working machine, and is easy to handle.

In the above embodiment, the engine type in which the camshaft 17 is disposed within the crankcase 1 has been described as an example, but the present invention is applicable to an overhead camshaft (OHC) in which the camshaft is disposed within the rocker arm chamber 16.
The same applies to type engines.

Further, in the above embodiment, an example of an engine in which the crankshaft 2 is arranged vertically (the cylinder 5 is arranged horizontally) is explained, but the present invention is applicable to an engine in which the cylinder is arranged vertically or inclined. It can be applied to

〔Effect of the invention〕

As is clear from the above description, according to the overhead valve type internal combustion engine of the present invention, the intake and exhaust valves are arranged parallel to the crankshaft, the exhaust valve is placed on the side opposite to the output shaft, and the intake hole is arranged substantially perpendicular to the crankshaft. At the same time, the exhaust hole is opened in the direction opposite to the intake hole and inclined at an angle of about 45 degrees toward the side opposite to the output shaft, and the rocking bearing of the rocker arm for operating the intake and exhaust valves is opened in the direction opposite to the intake and exhaust valves. A cooling fan is placed on the intake hole side, a cooling fan is provided on the side opposite to the output shaft of the crankshaft, a carburetor is connected to the intake hole, a muffler is placed on the opposite side of the carburetor, and the exhaust hole and the muffler are connected to an exhaust pipe. Since the configuration is such that the air outlet is connected with
In addition to increasing the cooling effect of the cylinder head,
An overhead valve internal combustion engine is provided in which temperature differences around the cylinders can be significantly reduced, improving engine performance and reliability.

According to another overhead valve type internal combustion engine of the present invention, the intake and exhaust valves are arranged parallel to the crankshaft and the exhaust valve is placed on the side opposite to the output shaft, and the intake hole is opened in a direction substantially perpendicular to the crankshaft. At the same time, the exhaust hole is opened in a direction opposite to the intake hole and inclined toward the side opposite to the output shaft, and the swing bearing of the rocker arm for operating the intake and exhaust valve is arranged on the intake hole side with respect to the intake and exhaust valve.
A cooling fan is provided on the side opposite to the output shaft of the crankshaft, a carburetor is connected to the intake hole, a muffler is arranged on the opposite side of the carburetor, and the exhaust hole and the muffler are connected with an exhaust pipe. A gasket is placed at the joint of the exhaust pipe, and this gasket is used as a guide for cooling air, so the exhaust hole is installed so that it is directly hit by the air from the cooling fan on the side opposite to the output shaft. An overhead valve type internal combustion engine is provided that can enhance the cooling effect of the cylinder head and significantly reduce the temperature difference around the cylinder, thereby improving the performance and reliability of the engine.

[Brief explanation of the drawing]

FIG. 1 is a sectional side view of essential parts of an overhead valve type internal combustion engine according to an embodiment of the present invention, FIG. 2 is a sectional view taken along the line - in FIG. 1, and FIG. line -
FIG. 7...Cylinder head, 9...Intake valve, 10...
...Exhaust valve, 12...Intake hole, 13...Exhaust hole, 1
4...Rotzker arm, 21...Rotsker arm swing bearing part, 22...carburizer, 23...muffler, 24...exhaust pipe, 25...output shaft, 28...
Cooling fan, 33... gasket.

Claims (1)

[Claims] 1. The intake and exhaust valves are arranged parallel to the crankshaft, with the exhaust valve facing away from the output shaft, the intake hole is opened in a direction substantially perpendicular to the crankshaft, and the exhaust hole is opened in a direction substantially perpendicular to the crankshaft. The opening is on the opposite side and is inclined approximately 45 degrees toward the opposite output shaft side, and the swing bearing of the rocker arm for operating the intake and exhaust valves is placed on the intake hole side with respect to the intake and exhaust valve, and the opposite output shaft of the crankshaft is opened. An overhead valve type internal combustion engine, characterized in that a cooling fan is provided on the side, a carburetor is connected to an intake hole, a muffler is arranged on the opposite side of the carburetor, and the exhaust hole and the muffler are connected by an exhaust pipe. . 2 Arrange the intake and exhaust valves parallel to the crankshaft, with the exhaust valve facing away from the output shaft, and open the intake hole in a direction substantially perpendicular to the crankshaft, and open the exhaust hole on the opposite side of the intake hole. It is opened in a direction inclined toward the output shaft side, and the swing bearing of the rocker arm for operating the intake and exhaust valves is placed on the intake hole side with respect to the intake and exhaust valves.
A cooling fan is provided on the side opposite to the output shaft of the crankshaft, a carburetor is connected to the intake hole, a muffler is arranged on the opposite side of the carburetor, and the exhaust hole and the muffler are connected with an exhaust pipe. An overhead valve type internal combustion engine characterized in that a gasket is arranged at the joint of an exhaust pipe, and this gasket is used as a guide for cooling air.