JPS6153422A - Overhead-valve type internal-combustion engine - Google Patents

Abstract

PURPOSE:To improve a cooling effect in a cylinder head as well as make improvements in engine performance and reliability, by letting both suction and exhaust ports open to the side being almost orthogonal with the cylinder head, while connecting a muffler to be set up at the opposite side of the suction port to the exhaust port with an exhaust pipe. CONSTITUTION:A suction port 12 and an exhaust port 13 being controlled for interconnection with a combustion chamber 8 by both suction and exhaust valves 9 and 10 are formed inside a cylinder head 7 in a direction being almost orthogonal with each other. And a carburetor 22 is connected to the suction port 12, and a muffler 23 is set up at the opposite side of the carburetor 22 with the cylinder head 7 held in between, while the exhaust port 13 and the muffler 23 are connected with each other through an exhaust pipe 24. According to this method, sufficient cooling fans are able to be installed centering the circumference of a valve guide 11 on a surface at the opposite side of a suction passage 12 in the cylinder head 7 and, what is more, cooling air out of these cooling fans set up inside a housing 30 is sufficiently feedable so that the circumference of the valve guide 11 can be cooled so ample enough.

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.

[Prior art]

Overhead valve internal combustion engines have a structure in which the intake and exhaust valves 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. .

General-purpose internal combustion engines are generally used as engines for work equipment, and there are two types of general-purpose internal combustion engines: those with a vertical crankshaft (thus, the cylinders are horizontal) and those with horizontal crankshafts (the cylinders are vertical). We can separate.

In particular, as a drive source for lawn mowers, grass cutters, etc., the crankshaft is arranged vertically and the output shaft is taken out from the bottom, because the height of the engine can be reduced and the stability of the machine body can be easily ensured. things are used favorably.

By the way, conventional overhead valve type internal combustion engines generally have an intake hole and an exhaust hole opened on opposite sides of the cylinder head, that is, 180 degrees opposite sides, and a carburetor and an air cleaner are installed in the intake hole. It has a structure in which a muffler is connected to the exhaust hole.

In addition, as a cooling method for cylinders and cylinder heads, a fan is generally installed 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 11 J, t.
Japanese Patent Application Publication No. 59-70838 (% patent application No. 57-18086)
7).

However, in this conventional structure, the intake and exhaust holes are open on both sides of the cylinder head, so
The flow of cooling air from the fan is obstructed by the intake/exhaust hole forming portion and the push rod built-in portion, resulting in a drawback that the cylinder head cannot be sufficiently cooled.

Furthermore, since the cylinder head is not cooled, abnormal combustion such as non-king tends 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 pulp guide (usually made of iron-based material) that is press-fitted into the cylinder head is prone to thermal problems, especially when the pulp guide for the exhaust valve is placed on the output shaft side. (This is a commonly practiced arrangement), it is difficult to cool this part with cooling air, and the pulp guide section is heated by the combustion gas, causing the pulp guide to fall off from the cylinder head (usually made of aluminum casting). It may cause trouble.

[Purpose of the invention]

The purpose of the present invention is to eliminate such drawbacks of the prior art,
It is possible to provide an overhead valve type internal combustion engine that can enhance the cooling effect of the cylinder head and improve the performance and reliability of the engine.

[Structure of the invention]

The present invention achieves the above object by opening an intake hole and an exhaust hole at substantially perpendicular sides, and by connecting a muffler installed on the opposite side of the intake hole and the exhaust hole with an exhaust pipe. It is.

That is, according to the present invention, an intake hole is opened on one side of the cylinder head, an exhaust hole is opened on a side substantially perpendicular to this, a carburetor is connected to the intake hole, and a carburetor is connected to the opposite side of the carburetor. There is provided an overhead valve type internal combustion engine in which a muffler is disposed in the exhaust hole and the muffler is connected to the exhaust hole through two exhaust ports.

〔Example〕

The present invention will be described in detail below with reference to the drawings.

FIG. 1 is a cross-sectional side view of essential parts of an overhead valve type internal combustion engine according to one embodiment, and FIG. Figure and main part cross-sectional end view.

The illustrated engine is an overhead valve type internal combustion engine with a vertically disposed crankshaft.

In FIGS. 1 and 2, a crank [1:*2] is supported by a crank case 1 passing through it vertically, a connecting rod 4 is connected to the crank pin 3, and a cylinder 5 is connected to the other end of the connecting rod. The fitted piston 6 is connected. 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 mounted on an iron base to a valve guide 11 that is fixed to the cylinder head γ by press fitting 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 9.10 are formed in the cylinder head γ. In the illustrated example, the intake and exhaust valves 9.10 are arranged one above the other,
The intake valve 9 is located at the top.

As shown in FIG. 3, the intake hole 12 and the exhaust hole 13 are formed in directions substantially perpendicular to each other, the intake hole 12 extending horizontally and opening on one side of the cylinder head 7, and the exhaust hole 13 extending downward. It extends and opens at the lower side surface of the cylinder head 7.

As shown in FIGS. 1 and 2, a pair of rocker arms 14.14 are pivotally supported on the cylinder head 7 to open the intake and exhaust valves 9.10 against a return spring. There is. Further, a pair of rocker arms 14, 14t-G head force bars 15 for the intake and exhaust valves are joined to the cylinder head 7 in a sealed state, and a rocker arm chamber 16 is formed inside thereof.

On the other hand, a camshaft 1T is provided in the crankcase 1 and is driven to rotate at twice the cycle (by the crankshaft), and a pair of cams for intake and exhaust valves provided on the camshaft 17 and a pair of rocker arms are provided on the camshaft 17. As shown in FIGS. 2 and 3, a reciprocating mechanism consisting of a tab 18 and a bushing rod 19 is provided between each of the rocker arms 14.14, and as the crankshaft rotates, the rocker arms 14. The intake valve 9 and the exhaust valve 10' are configured to be driven to open at a predetermined timing during the piston stroke.

Note that each bushing rod 19, 19 passes through the intake hole 12 side of the cylinder head 7 as shown in FIG.
For this reason, the bushing rod for the intake valve (Ill)
19 will interfere with the intake hole 12, but in the illustrated example, a bushing rod passage 20 is formed across approximately the center of the intake hole 12. This passage 20 is formed, for example, by press-fitting and fixing a pipe material into the cylinder head T.

Since the bushing rod 19.19 for the intake and exhaust valves is disposed on the side of the intake hole 12 in this way, the swing bearing 21 of the rocker arm 14.14 for the intake and exhaust valves is also attached to the intake and exhaust valves 9.19 as shown in FIG. It is arranged on the side of the intake hole 12.

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 vaporizer 22.

As shown in FIGS. 2 and 3, a 77 roller 23 is disposed on the opposite side of the carburetor 22 across the cylinder head 7, and the exhaust hole 13 and the muffler 23 are connected to the exhaust pipe 24.
connected with.

An output shaft 25 is taken out from the lower side of the crank 1 by projecting the crank @If 2 downward. In addition,
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.

Therefore, in the illustrated SEIZO, the exhaust hole 13 is located on the output side (
It opens at the bottom of the engine.

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 super oil starter 29 for starting is attached.

A fan housing 30 is provided at a position covering the cooling fan 28 and the upper middle part of the engine, and has a grooved bottom so that cooling air flows along the surfaces of the cylinder 5 and cylinder head 7.

Further, between the cylinder head 7 and the muffler 23, a guide air is provided which guides cooling air from above to the lower side along the surfaces of the cylinder head T and cylinder 5, and guides the cooling air to the exhaust hole 130. A board 31 is installed.

As shown in the figure, cooling fans are provided on the cylinder 5 and the cylinder head 70 to enhance the cooling effect.

According to the above configuration, the intake passage 12 of the cylinder head 7
On the surface opposite to the pulp guide 1 as shown in Figure 2,
1. Sufficient cooling fins can be provided centered around 11, and the area of these cooling fins is
As shown by the chain line arrow in FIG. 3, the cooling air from the cooling fan 28 flows smoothly and is sufficiently supplied to I8, so that the surface of the cylinder head I, especially around the pulp guides 11 and 11, is sufficiently cooled. Can be done. In the illustrated example, since the baffle plate 31 is provided, the flow of cooling air in this region can be strengthened and the cooling effect can be further improved.

Note that on the side of the intake hole 12, the cooling air is blocked by the intake hole and the bushing rod 19, so the cooling air does not flow sufficiently on the opposite side, and the cooling fins cannot be formed sufficiently. Since there is little and the air-fuel mixture can be cooled to some extent, there is no problem. If necessary, as shown in FIG. 2, a cooling air passage 3 that vertically passes through the cylinder head T
2, the cooling effect on the intake hole 12 side can be enhanced.

The opposite side of the intake hole 12 (cylinder head 7 in FIG.
The cooling air flowing through the exhaust pipe 24 can be easily directed downward as shown by the chain arrow in FIG. ) can be cooled. In the illustrated example, the air guide plate 31 is provided, so that the cooling effect can be further improved by guiding the flow. The cooling air that has cooled the region of the exhaust hole 13 through which the high-temperature gas flows is discharged downward. 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, an arrangement of the engine that not only has an excellent cooling effect but also can cool each part in a well-balanced manner is created.

Moreover, according to the above configuration, as is clear from FIG.
The cooling air cools each part such as the cylinder head T and is then blown toward the exhaust hole 13 side (lower side in the illustrated example), so the heated air does not hit the carburetor 22, and therefore, It is possible to prevent problems such as percolation in the fuel passage (Z and IA phenomena where air bubbles are generated and the fuel flow is poor).

Furthermore, as is clear from Fig. 3, the cylinder head 7
An intake hole 12 is opened on one side, and a carburetor 22 is connected to this, and an exhaust hole 13 is opened on the side perpendicular to this (lower output side in the illustrated example) and the opposite side of the carburetor 22. Since the exhaust pipe 23 connects the muffler 23 located at Therefore, it is possible to obtain an overhead valve type internal combustion engine that is convenient to be mounted on a working machine and has excellent handling properties.

In the above embodiment, the engine type in which the camshaft 17 is disposed within the crankshaft cage 21 has been described as an example, but the present invention provides an overhead camshaft (O) IC) 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 was given of an engine in which the crankshaft 2 is arranged vertically (the cylinder 5 is arranged horizontally), but the present invention can be similarly applied to an engine in which the cylinder is arranged vertically or inclined. Can be applied.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, an overhead valve type internal combustion engine can be obtained that can enhance the cooling effect of the cylinder head and improve the performance and reliability of the engine.

[Brief explanation of the drawing]

FIG. 1 is a side view of the essential part 1 of an overhead valve type internal combustion engine according to an embodiment of the present invention, FIG. 2 is a cross-sectional view taken along line -H in FIG. 1, and FIG. A sectional end view of the main part of 1c is seen from line 1--2 in FIG. 7... Cylinder head, 9... Intake valve, 10.
...Exhaust valve, 12...Intake hole, 13...
Exhaust hole, 14... Rocker arm, 21... Swing bearing of rocker arm 1, 22... Air device,
23...Muffler, 24...Exhaust, pipe,
25...Output shaft, 28...Cooling degree 7 Ang. 1N Kaisho Gl-53422 (5) Figure 2 M1 Go

Claims (3)

[Claims] (1) An intake hole is opened on one side of the cylinder head, an exhaust hole is opened on a side substantially perpendicular to this, a carburetor is connected to the intake hole, and a muffler is arranged on the opposite side of the carburetor. An overhead valve internal combustion engine characterized in that the exhaust hole and the muffler are connected by an exhaust pipe. (2) The overhead valve type internal combustion engine according to claim 1, wherein the exhaust hole is opened on the output shaft side, and a cooling fan is provided on the opposite side of the output shaft. (3) An overhead valve type internal combustion engine according to claim 1 or 2, characterized in that the rocking bearing of the rocker arm for operating the intake and exhaust valves is arranged on the intake hole side with respect to the intake and exhaust valves. .