JPH0141858Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention mainly relates to a cooling device for a forced air-cooled engine that is capable of cooling a muffler in addition to cylinder cooling of a general-purpose engine.

In general, mufflers installed on general-purpose engines rarely have a structure that actively cools them.
In the case of an OHV (overhead valve type) engine, lean combustion is performed to improve fuel efficiency, and there is a risk that the muffler may become red hot as the exhaust temperature rises. This is particularly noticeable in engines that are used for long periods of time, and the atmospheric temperature around the muffler increases, potentially causing adverse thermal effects on surrounding devices.

Incidentally, Japanese Utility Model Application Publication No. 141029/1987 proposes a conventional technique regarding a muffler cooling structure for a forced air-cooled engine. This conventional technology is configured such that a portion of the cooling air from the cooling fan is directly taken out from an outlet in a fan cover mounting wall, and is passed through a guide plate that covers the muffler to cool the muffler.

However, in the case of this prior art, the muffler is covered with a guide plate or the like and cooled separately from the cylinder. Therefore, special parts are required for cooling the muffler, and the engine cannot be made more compact.

The present invention was developed in view of the above circumstances, and mainly relates to general-purpose engines, and it is possible to cool the muffler at the same time as the cylinder cooling without requiring any special parts, thereby preventing adverse thermal effects on the muffler and its surrounding equipment. It is an object of the present invention to provide a cooling device for a forced air-cooled engine that can make the engine compact without adding additional cost.

Another purpose is to enable sufficient cooling of the muffler, thereby making it possible to use a surface-treated steel plate as the muffler member or to use plating for the muffler cover.

In order to achieve the above object, the present invention provides a forced air-cooled engine in which cooling air introduced into a fan cover by a cooling fan is guided to cool a cylinder head and a cylinder barrel.
One side wall of the muffler connected to the exhaust port of the cylinder head is curved according to the shape of the outer wall of the cylinder barrel, and is provided close to the outer wall of the cylinder barrel so as to extend along the axial direction of the cylinder. The side wall and the outer wall of the cylinder barrel communicate with the inside of the fan cover to form a flow passage for cooling air that cools the cylinder barrel and the muffler.

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

1 and 2 relate to a first embodiment of the present invention, in which FIG. 1 is a sectional view perpendicular to the axis of an OHV engine, and FIG. 2 is an enlarged sectional view taken along the line A--A in FIG. 1. In these figures, numeral 1 is an OHV engine, 2 is a crankcase, and 3 is a cylinder head. The crankcase 2 integrally forms an upper cylinder barrel 4, and fins 5 are formed on the outer circumference of the cylinder barrel 4. Also, a cylinder barrel 4 and a cylinder head 3 having fins.
A push rod chamber 6 that communicates with the cylinder head 3 in the vertical direction and opens at the top of the cylinder head 3 is formed on one side of the cylinder. By swinging and pressing the energized valve 10, an exhaust port 12 communicating with an exhaust passage 11 formed in the cylinder head 3 is opened and closed. A muffler 13 is attached to the exhaust passage 11 at a downstream end on one side of the cylinder head 3. The muffler 13 is a substantially vertically elongated box-shaped body made of sheet metal, and is fixed in contact with the cylinder head 3 with bolts 14 passing through the upper part of the box-shaped body in the horizontal direction, and is fixed to the downstream end of the exhaust passage 11. The lower end of the muffler 13 reaches the lower side of the cylinder barrel 4, and the width is approximately equal to the outer diameter of the upper cylinder barrel 4 on which the fins 5 are formed. Further, the side wall of the muffler 13 facing the cylinder barrel 4 on which the fins 5 are formed is formed so as to create a narrow space along the outer wall of the cylinder barrel 4. That is, Finn 5
A narrow flow passage 15 is formed between the cylinder barrel 4, which is formed with the cylinder barrel 4, and the side wall of the muffler 13, as shown by the satin pattern. Further, the outer peripheral portion of the muffler 13 except for the cylinder barrel 4 side and the lower side is covered with a muffler cover 16. On the other hand, a cooling fan 17 for introducing cooling air is provided on one side of the crankcase 2, and a fan cover 18 is provided to cover part of the cooling fan 17, cylinder head 3, and cylinder barrel 4. ing. or,
Inside the fan cover 18, the cooling fan 1
A baffle plate 19 is provided on the 7 side so as to guide the cooling air toward the flow path 15 side.

In the figure, reference numeral 20 indicates a crankshaft, 21 a piston, 22 an air cleaner, 23 a carburetor, 24 a fuel tank, and 25 an oil pan that forms the lower part of the crankcase 2 and stores lubricating oil.

In the forced air cooling engine cooling system configured in this way, the cooling air introduced into the fan cover 18 by the cooling fan 17 is guided to the baffle plate 19, and is directed to the side walls of the cylinder head 3 and the muffler 13 and the cylinder. Air passage 15 formed with barrel 4
2, as shown by the arrow a in FIG. This cooling air cools the cylinder head 3 and cylinder barrel 4 where the fins 5 are formed, and at the same time cools the muffler 13 whose temperature has risen due to the exhaust gas.
is cooled from the side wall side of the muffler 13 facing the cylinder barrel 4. Therefore, the ambient temperature around the muffler 13 does not rise, and there is no adverse thermal effect on surrounding devices. Further, the entire engine can be made compact without requiring any special parts. Furthermore, since the muffler can be sufficiently cooled, it is also possible to use a surface-treated steel plate as the muffler member or to plate the muffler cover 16.

FIG. 3 is a sectional view of a cylinder barrel portion equipped with a muffler according to a second embodiment of the present invention.
Note that the same parts and members as in the first embodiment are denoted by the same reference numerals. In this embodiment, a muffler 31 is attached to the downstream end of one side of the cylinder head 3, substantially the same as in the first embodiment. and the muffler 3
The side wall facing the cylinder barrel 4 on which the first fin 5 is formed forms a narrow space along the outer wall of the cylinder barrel 4, and has a wavy surface 32 in cross section.

In the forced air cooling engine cooling system constructed in this way, the cylinder head 3 and the cylinder barrel 4 are cooled, and the muffler 31 is cooled at the same time, as in the first embodiment. In this embodiment, since the corrugated surface 32 is formed, the heat exchange area can be made larger than in the first embodiment, and cooling can be performed sufficiently.

4 and 5 relate to a third embodiment of the present invention, in which FIG. 4 is a cross-sectional view of a cylinder barrel portion equipped with a muffler, and FIG. 5 is a cross-sectional view taken along the line B--B in FIG. 4. Note that the same parts and members as in the first embodiment are denoted by the same reference numerals. In this example, the muffler 4
1 is attached to the downstream end of one side of the cylinder head 3 in substantially the same manner as in the first embodiment. The side wall of the muffler 41 facing the cylinder barrel 4 on which the fins 5 are formed creates a narrow space along the outer wall of the cylinder barrel 4, and
A muffler cooling fin 42 having a U-shaped cross section is bonded to the side wall along and interlocking with the fin 5 of the cylinder barrel 4.

In the forced air cooling engine cooling system constructed in this way, the cylinder head 3 and the cylinder barrel 4 are cooled, and the muffler 41 is cooled at the same time, as in the first embodiment. In this embodiment, by adhering the muffler cooling fins 42 to the side walls of the muffler 41, the heat exchange area can be easily increased, and cooling can be performed sufficiently.

Note that the shape of the muffler is not limited to the shape of the embodiment, as long as it forms a cooling air flow path by at least the outer wall of the cylinder barrel in which the fins are formed and one side wall of the muffler.

Also, in the example, an OHV engine is used, but
It can also be applied to side valve type engines and other types of engines.

As explained above, according to the present invention, one side wall of the muffler and the outer wall of the cylinder barrel are configured to form a cooling air flow path, so the muffler can be cooled at the same time as the cylinder is cooled. There will be no adverse thermal effect on the equipment surrounding the muffler. Furthermore, since no special parts are required for muffler cooling, the entire engine can be made more compact.

[Brief explanation of the drawing]

1 and 2 relate to the first embodiment of the present invention, in which FIG. 1 is a sectional view at right angles to the axis of the OHV engine, FIG. 2 is an enlarged sectional view taken along the line A-A in FIG. 1, and FIG. 4 and 5 are cross-sectional views of the cylinder barrel portion equipped with a muffler according to the second embodiment of the present invention, and FIG. 4 is a sectional view of the cylinder barrel portion equipped with a muffler according to the third embodiment of the present invention. FIG. 5 is a sectional view taken along the line B--B in FIG. 4. 1...OHV engine, 3...cylinder head,
4...Cylinder barrel, 11...Exhaust port, 13,
31, 41...muffler, 15...distribution path, 16
...Muffler cover, 17...Cooling fan, 18...
... Fan cover, 19 ... Wind guide plate, 32 ... Waveform diagram, 42 ... Muffler cooling fin.

Claims (1)

[Scope of utility model registration request] In a forced air-cooled engine in which a cylinder head and a cylinder barrel are cooled by guiding cooling air introduced into a fan cover by a cooling fan, one side wall of a muffler connected to an exhaust port of the cylinder head is provided with The muffler is curved according to the shape of the outer wall of the cylinder barrel and is provided close to the outer wall of the cylinder barrel along the axial direction of the cylinder, and the side wall of the muffler and the outer wall of the cylinder barrel communicate with the inside of the fan cover. A cooling device for a forced air-cooled engine, characterized by forming a cooling air flow path for cooling a cylinder barrel and a muffler.