JP2000220519A - Ohc type air-cooled engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently cool high temperature portions such as an exhaust port or an ignition plug in OHC air cooled engine. SOLUTION: In this engine, a cylinder head 10 is spaced from a housing 13a housing a valve system through a valve support part 10b. The valve support part 10b is divided into an intake side and an exhaust side through a blowing introduction part 10e. An ignition plug 12 is faced to a portion in the vicinity of the blowing introduction part 10e. When cooling air is introduced to the blowing introduction part 10e, high temperature portions such as an exhaust port 10d, an ignition plug 12 positioned on the base of the exhaust side valve support part 10b are directly cooled by the cooling air. Cooling performance is thus improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an O head for directly introducing cooling air to a high heat generating portion on a combustion chamber side of a cylinder head.
It relates to an HC type air-cooled engine.

[0002]

2. Description of the Related Art Conventionally, when an OHC type air-cooled engine is mounted on a motorcycle, as disclosed in, for example, Japanese Patent Application Laid-Open No. 3-50084, many radiation fins are provided on a cylinder body and a cylinder head. By forming, the engine body can be directly cooled by the traveling wind.

On the other hand, in a stationary air-cooled engine, running wind cannot be expected, so that cooling air generated by a cooling fan is guided to required cooling portions using a baffle plate or the like, and each of these required cooling portions is cooled. ing.

[0004]

However, in the OHC engine, as disclosed in the above prior art,
Because the valve chamber is formed integrally on the cylinder head,
It is difficult to directly guide cooling air to a high heat generating portion such as an exhaust port.

For this reason, measures have been taken to increase the heat radiation efficiency by forming a large number of cooling fins on the cylinder head, or to form cooling ribs near the high heat generating area by forming guide ribs.

However, since the valve chamber is integrally formed on the cylinder head, the shape of the cooling fins or the guide ribs becomes complicated, resulting in an inconvenience of increasing the product cost.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide an OHC type air-cooled engine capable of efficiently cooling a high heat generating portion of a cylinder head on a combustion chamber side with a simple structure.

[0008]

In order to achieve the above object, a first OHC type air-cooled engine according to the present invention comprises a housing for accommodating a valve mechanism on a cylinder head. The housing and the housing are separated from each other, and the combustion chamber of the cylinder head and the housing are connected to each other via a valve support for supporting the intake and exhaust valves so as to be able to move forward and backward.

A second OHC type air-cooled engine is provided with a first OHC type air-cooled engine.
In the HC type air-cooled engine, the valve support portion is divided into an intake-side valve support portion and an exhaust-side valve support portion, and an ignition plug faces a vicinity of a baffle formed between the two valve support portions. And

The third OHC type air-cooled engine is the same as the first or second OHC type air-cooled engine, except that a guide rib for guiding cooling air from the housing to the combustion chamber portion of the cylinder head toward the valve support portion is provided. It is characterized by having been formed.

A fourth OHC type air-cooled engine is provided in any one of the first to third OHC type air-cooled engines, wherein a case for accommodating an endless transmission member is disposed on one side of the engine body. An air guide hole for guiding cooling air to the engine body side is opened.

That is, in the first OHC type air-cooled engine, the valve supporting portion for supporting the intake / exhaust valve to move forward and backward is exposed between the combustion chamber portion of the cylinder head and the housing accommodating the valve operating mechanism. In addition, cooling air can be directly guided to the base of the valve support portion for cooling.

In this case, as shown in the second OHC type air-cooled engine, the valve support portion is divided into an intake side valve support portion and an exhaust side valve support portion, and a guide formed on both of these valve support portions is provided. By allowing the spark plug to approach the wind portion, the cooling air is guided to the vicinity of the valve support and to the spark plug, and these high heat generating portions are directly cooled.

Further, as shown in the third OHC type air-cooled engine, a guide rib for guiding cooling air to the valve support portion is formed from the housing to the combustion chamber portion of the cylinder head, thereby cooling the valve support portion. Can be cooled directly by wind.

Further, as shown in a fourth OHC type air-cooled engine, an air guide hole is formed in a case for accommodating an endless transmission member provided on one side of the engine main body, so that the outside of the case is provided. Can be guided to the cylinder body and the valve support.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. 1 and 2 show a schematic front view and a schematic rear view of an OHC type air-cooled engine employed in the present embodiment.

In these figures, reference numeral 1 denotes an inclined SO.
In the engine body of the HC engine, a crankcase 2 and a cylinder body 3 are integrally formed, a fuel tank 4 is mounted on an upper portion of the engine body 1, and an air cleaner 5 and a muffler (not shown) are provided around the fuel tank 4. And so on.

A crankshaft 6 is provided horizontally in the crankcase 2, and a cylinder body 3 is formed diagonally above the crankshaft 6 in a radial direction. Further, a piston 7 inserted into the cylinder body 3 is connected to the crankshaft 6 via a connecting rod 8. Reference numeral 9 denotes a scraper that scrapes up the oil stored in the oil pan.

The cylinder body 3 has a length of 60 with respect to the vertical axis.
It is inclined within the range of ~ 70 °. A cylinder head 10 is fixed to an upper surface of the cylinder body 3, and a combustion chamber 10 a is formed on an inner surface of the cylinder head 10.

As shown in FIG. 3, an intake port 10c, an exhaust port 10d, and an ignition portion of a spark plug 12 are assembled at a substantially central portion of the combustion chamber 10a. The port 10d is opened slightly below the extension of the cylinder center axis Lc (see FIGS. 1 and 2), and the ignition portion of the ignition plug 12 faces slightly above the extension of the cylinder center axis Lc.

An intake / exhaust valve 11 having valve bodies disposed at both ports 10c and 10d is supported by a valve support portion 10b formed integrally with the cylinder head 10 so as to be able to advance and retreat, and extends in a substantially horizontal direction. The spark plug 12 is disposed substantially parallel to the cylinder center axis Lc.

As shown in FIG. 3, a valve supporting portion 10b for supporting each intake / exhaust valve 11 is provided with an air guiding portion 10e formed at the center.
, And is divided into an intake side and an exhaust side, and a spark plug 12
On the other hand, the lower part of the air guide 10e communicates with a step 10f formed on the end face side of the cylinder head 10.

As shown in FIG. 2, a camshaft 14 is disposed at a position slightly lower than the crankshaft 6 below the stem end 11a of the intake / exhaust valve 11 in parallel with the crankshaft 6. Further, between the stem end 11a and the camshaft 14, a rocker arm 15 that presses the stem end 11a in synchronization with the rotation of the camshaft 14 is disposed substantially vertically.

A valve operating chamber 13 for accommodating a valve operating mechanism such as the cam shaft 14, the rocker arm 15 and the like on the stem end 11a side of the intake / exhaust valve 11 is located on the side of the cylinder head 10 and relative to the cylinder center axis Lc. It is disposed at a position deviated downward.

The valve operating chamber 13 is formed by a housing 13a on the cylinder head 10 side and a valve operating chamber cover 13b mounted on an opening of the housing 13a. The housing 13a connects the valve supporting portion 10b to the cylinder head 10. It is formed integrally through the intermediary.

Reference numeral 17 denotes a belt case, which is divided into a rear case 17b fixed to the engine body 1 and a front case 17c mounted on the rear case 17b. 14 accommodates timing gears 18a and 18b which are respectively mounted on the shaft 14, and a valve train driving force transmission mechanism such as a timing belt 19 which is an example of an endless transmission member connected to the timing gears 18a and 18b.

The endless transmission member is a timing belt 19.
The present invention is not limited to this, and any belt-shaped one such as a timing chain that can synchronously rotate the camshaft 14 at half the speed of the crankshaft 6 may be used.

A horizontally long air guide hole 17a is opened between the timing gears 18a and 18b of the belt case 17 and at a position where it does not interfere with the timing belt 19, that is, at the center of the belt case 17.

On the other hand, guide ribs 24 are formed on the bottom surface of the housing 13a to guide cooling air from the air guide holes 17a opened in the belt case 17 to the step 10f.
The opening end face of the guide rib 24 is formed on the same plane as the mating face of the cylinder head 10, and one end is formed by a ridge portion on the side opposite to the belt case 17 below the cylinder head 10 and a housing 13 a opposed to the ridge portion. The other end is in contact with the back surface of the belt case 17. As a result, a wind guide plate 22 that is continuous with the guide ribs 24 is formed on the lower edge of the wind guide hole 17a on the back surface of the belt case 17.

One end of the crankshaft 6 protrudes through the belt case 17, and a cooling fan 20 serving also as a flywheel is mounted on the shaft end (see FIG. 1). The cooling air generated by the cooling fan 20 is guided toward the engine body 1 from a fan cover (not shown).

Next, the operation of the present embodiment having the above configuration will be described. When the engine operates, the cooling air generated by the cooling fan 20 which is mounted on the crankshaft 6 and disposed outside the belt case 17 is guided to the engine body 1 from a fan cover (not shown), Cool the cooling section.

A part of the cooling air passes through the air guide hole 17a opened in the center of the belt case 17, passes through the lower surfaces of the cylinder body 3 and the cylinder head 10, and cools them. The air guide plate 22 and the guide ribs 24 contacting the rear surface of the belt case 17 allow the cylinder head 1
It is guided to the step 10f formed at 0.

The cooling air guided to the step portion 10f is supplied to the air guide portion 10b formed between the valve support portions 10b on the intake side and the exhaust side.
e, and between the exhaust-side valve support portion 10b and the end of the guide rib 24, and at this time, each of the intake-side and exhaust-side valve support portions 10b is cooled and exposed near the air guide portion 10e. The spark plug 12 is cooled.

As a result, the high heat generating portion such as the exhaust port 10d and the ignition plug 12 located at the base of the valve support portion 10b can be directly cooled without forming a radiation fin having a complicated shape.

In this embodiment, the cylinder center axis L
c, with the valve body of the intake / exhaust valve 11 facing downward.
The camshaft 14 is disposed below the cylinder head 10 so that the valve chamber 13 can be retracted below the cylinder head 10. 1 can be lowered.

Further, since the valve operating chamber 13 is retracted below the cylinder head 10, the ignition plug 12 is
Without interfering with the valve operating chamber 13, it is possible to arrange the combustion chamber 10a substantially at the center, that is, at the optimum ignition position, and to improve the combustion efficiency.

Further, since the camshaft 14 is provided at a position slightly lower than the crankshaft 6, the timing gears 18a, 1
8b and a belt case 17 accommodating a valve train driving force transmission mechanism such as a timing belt 19 can be disposed on the lower side of the cylinder body 3. , Cylinder head 1
Since 0 and the like are exposed, it is possible to directly guide the cooling air to these portions, and the cooling performance can be improved.

Further, by opening the air guide holes 17a in the belt case 17, the thickness of the belt case 17 is reduced in a relatively wide range. Therefore, when the belt case 17 is made of sheet metal or casting, In addition, it is possible to reduce the weight of the entire engine by removing the thickness.

The present invention is not limited to the above-described embodiment. For example, the engine employed is not limited to an inclined engine, but may be any of a vertical engine, a horizontal engine, a vertical shaft engine, and the like.

[0040]

According to the first aspect of the present invention, the valve supporting portion for supporting the intake and exhaust valves so as to be able to move forward and backward is exposed between the combustion chamber of the cylinder head and the housing accommodating the valve operating mechanism. Therefore, the cooling air can be guided directly to the valve support, particularly around the exhaust port located at the base of the valve support, and the cooling performance is improved. Since the valve support portion is simply exposed from the combustion chamber portion of the cylinder head, manufacturing is easy.

In this case, as in the invention according to claim 2,
By dividing the valve support into an intake-side valve support and an exhaust-side valve support, and allowing the spark plug to face the vicinity of the air guide formed between the two valve supports, cooling air flows around the valve support, In particular, the high heat generating portions such as the exhaust port and the ignition plug located at the base of the valve support portion are guided, so that these high heat generating portions can be efficiently cooled.

According to the third aspect of the present invention, a guide rib for guiding cooling air to the valve support portion from the housing to the combustion chamber portion of the cylinder head is formed, so that the cooling air flows to the valve support portion, particularly to the exhaust port. And the cooling efficiency can be improved.

Further, as in the fourth aspect of the present invention, a ventilation hole is formed in a case for accommodating an endless transmission member provided on one side of the engine body, so that cooling air is blown on the rear side of the case. It can be easily guided, and the engine body, valve support, and the like located on the rear side of the case can be efficiently cooled.

[Brief description of the drawings]

FIG. 1 is a schematic front view of an OHC type air-cooled engine.

FIG. 2 is a schematic rear view of an OHC type air-cooled engine.

FIG. 3 is a sectional view taken along line III-III of FIG. 2;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Engine main body 3 ... Cylinder main body 10a ... Combustion chamber 10b ... Valve support part 10e ... Air guide part 11 ... Intake / exhaust valve 13a ... Housing 17 ... Belt case 17a ... Air guide hole 19 ... Endless transmission member (timing belt) 24 ... Guide rib

Claims (4)

[Claims] In an OHC type air-cooled engine having a housing for accommodating a valve mechanism on a cylinder head, a combustion chamber of the cylinder head is separated from the housing, and a combustion chamber of the cylinder head is separated from the combustion chamber. Housing and
An OHC-type air-cooled engine, wherein an intake / exhaust valve is continuously provided via a valve support portion for supporting the intake / exhaust valve to move forward and backward. 2. The fuel cell system according to claim 1, wherein said valve support portion is divided into an intake side valve support portion and an exhaust side valve support portion, and a spark plug faces a vicinity of an air guide portion formed between said two valve support portions. The OHC type air-cooled engine according to claim 1. 3. The OHC type air-cooled engine according to claim 1, wherein a guide rib for guiding cooling air toward the valve support is formed from the housing to the combustion chamber of the cylinder head. 4. A case for accommodating an endless transmission member is provided on one side of the engine body, and a ventilation hole for guiding cooling air to the engine body side is opened in the case. The OHC type air-cooled engine according to any one of claims 1 to 3.