JPH0110407Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is a forced air-cooled engine in which the air in the cylindrical air duct covering the cylinder and cylinder head is sucked in by a cooling fan, while improving the cooling performance around the cylinder head. The present invention relates to a seal structure designed to improve sealing performance between spaces.

A cooling fan is installed at the end of the crankcase of an engine for a stationary engine or a working machine such as a lawn mower.The cylinder and cylinder head are covered with guide plates from three sides, and cooling air from the fan is sent into the guide plates to cool the engine. It is common practice to forcibly cool the high temperature part of the guide plate, and it is also possible to suck the air inside the guide plate by rotating the fan in the opposite direction.

However, in either case, since the guide plate is open on one side of the cylinder and its head, it is not possible to efficiently cool the entire circumference of the cylinder and head, and the speed of the cooling air cannot be increased. If an attempt is made to improve the cooling performance, the capacity of the fan must be increased, which makes it impossible to downsize the engine and reduce its load.

Therefore, the cylinder and cylinder head are covered with a cylindrical air duct, and both ends of the air duct in the direction of the crankshaft axis facing the crankcase are opened, and the air in the air duct is sucked into one end of the crankcase that faces one opening. It is conceivable to provide a cooling fan to efficiently cool the cylinder and cylinder head all around by utilizing the speed of outside air taken in from the other opening and increased in the air duct.

However, in order to improve the cooling performance for the cylinder head, which is at the highest temperature, gaps were created between the cylinder head's most advanced heat dissipation fin, the muffler and carburetor connected to the cylinder head, and the air duct, and the cooling fan was inserted through each gap. When outside air is taken in directly around the cylinder head by suction, foreign matter such as dust can also enter through these gaps.For example, in the case of a lawnmower engine, grass can enter the air duct through the gaps. Since it is stored away, measures to seal it are desired.

The present invention was developed in response to such a request, and its purpose is to create a gap between the air duct, the most advanced heat dissipation fin, muffler, and carburetor in the cylinder head for direct intake of outside air into the cylinder head. To provide a sealing structure around a cylinder head of a forced air-cooled engine, which effectively prevents foreign matter from entering through each gap while improving the cooling performance around the cylinder head by maintaining the gaps between the cylinder heads.

In order to achieve the above objectives, the present invention was developed in a forced air-cooled engine in which air in a cylindrical air duct that covers the cylinder and cylinder head is sucked in by a cooling fan. The gist is that a labyrinth is formed between the muffler and carburetor that are connected.

A preferred embodiment of the present invention will be described below in detail with reference to the accompanying drawings.

FIG. 1 is a longitudinal sectional side view of the engine and the air duct, and FIG. 2 is a longitudinal sectional front view of the crankcase showing the suction side opening of the air duct.

In the embodiment, the engine 1 includes a crankshaft 1
1 is supported vertically and cantilevered at the bottom, the cylinder 5 is oriented horizontally, and the crankcase 3 is oriented vertically, and the crankcase 3, cylinder 5, and cylinder head 6 are cast as one piece. Thus, a cylinder barrel 2 is formed. Crankcase 3 of such cylinder barrel 2
An opening 3a is formed in the upper part of the cylinder 5 and is cut diagonally from the base of the cylinder 5, and a crankcase cover 8 made of a steel plate is attached to the opening 3a.

On the other hand, a piston 14 slidably fitted into the cylinder 5 is connected to a crank pin 12 of a crankshaft 11 via a connecting rod 15, and the crankshaft 11 is perpendicular to the crankcase 3 at a shaft portion 13 constituting its lower part. A cooling fan 16 is fixed to the lower end of a shaft portion 13 which projects from the lower surface of the crankcase 3. This fan 16 is of a type that sucks air from above and flows it downward.

Further, the cylinder head 6 is provided with two left and right intake/exhaust valves 21, 21, the stem 21a of the valve 21 engages with the upper end of a rocker arm 22, and the lower end of the arm 22 engages with the tip of a push rod 23. , the push rod 23 is inserted into a passage 7 formed at the bottom of the cylinder 5 and the cylinder head 6, and a lifter 24 connected to the base end of the push rod 23 is connected to a horizontally supported camshaft 25 which is orthogonal to the shaft portion 13 and engages with gears. is engaged with the cam 26 of. Therefore, engine 1 is an OHV (overhead valve) engine.

A cylinder head cover 9 made of a steel plate is attached to the cylinder head 6 to cover the valve drive system.

The cylinder 5 and cylinder head 6 of the engine 1 described above are covered with a cylindrical air duct 30, the air duct 30 is almost closed on the cylinder head 6 side, and both sides of the cylinder 5 are closed on the crankcase 3 side.
The upper part is opened 31 toward the crankcase cover 8 as shown in FIG. 2, and the lower part is opened 32 toward the cooling fan 16. The air duct 30 has stays 33, 3 extending on both sides of the lower opening 32, as shown in FIG.
3 are fixed by screws to brackets 3a, 3a provided on both sides of the cylinder 5 side of the crankcase 3, and by screws to a mounting boss 6a protruding from the cylinder head 6.

Further, as shown in FIG. 3, a flange circumferential piece 34 having a less arcuate planar shape is formed to hang down from the periphery of the lower opening 32 of the air duct 30, and a flange circumferential piece 4 which is continuous with this and has a more arcuate planar shape is formed to hang down from the cylinder case 3. The flange circumferential pieces 4, 34 having a continuous planar annular shape are arranged close to the inside of the ribs 18 of each blade 17 of the cooling fan 16,
This seals.

In the present invention, as shown in FIG. 4, which shows the engine 1 and air duct 30 in a cross-sectional plane, an effective seal is achieved between the cylinder head 6 and the air duct 30.

That is, first, the air duct 30 covers all the heat dissipation fins 60 of the cylinder head 6, and an inward flange peripheral piece 35 is attached to the end of the air duct 30 so as to surround the most advanced heat dissipation fin 61 of the cylinder head 6 from the front. While being bent, an annular rib 62 close to the inner peripheral edge of the flange peripheral piece 35 is formed on the front surface of the radiating fin 61 near the peripheral edge. Thus, a labyrinth 7 is formed between the flange peripheral piece of the air duct 30 and the annular rib 62 of the heat radiation fin 61, and the inner circumference of the end of the air duct 30 and the peripheral edge of the radiation fin 61.
1 is formed all around.

Furthermore, a circular recess 37 is formed in the side plate 36 of the air duct 30 on the side of the exhaust port 65 formed in the cylinder head 6.
A circular hole 37a is formed in the recess 37, and the tip of an exhaust port cylindrical portion 66 protruding from the side surface of the cylinder head 6 faces into the circular hole 37a.
A gasket 42 having a larger diameter than the circular hole 37a is interposed on the end face of the cylindrical portion 66 to connect the muffler 41. In this way, a labyrinth 72 is formed between the circumferential wall of the circular concave portion 37 of the air duct side plate 36 and the gasket 42, the circumferential edge of the circular hole 37a of the circular concave portion 37, and the outer periphery of the tip of the exhaust port cylinder portion 66.

Also, the intake port 6 formed in the cylinder head 6
A circular recess 39 is also formed in the air duct side plate 38 on the 7 side, and a circular hole 39a is formed in the recess 39, and the tip of the intake port cylindrical portion 68 protruding from the side surface of the cylinder head 6 is inserted into the circular hole 39a. Furthermore, a flange peripheral piece 46 having a larger diameter than the circular hole 39a is formed on the outer periphery of the connecting end of the carburetor 45, and the carburetor 45 is connected to the end surface of the intake port cylindrical portion 68. In this way, the peripheral wall of the circular recess 39 of the air duct side plate 38, the flange peripheral piece 46 of the carburetor 45, the peripheral edge of the circular hole 39a of the circular recess 39, and the intake port cylindrical portion 6
8. A labyrinth 73 is formed between the tip and the outer periphery of the tip.

Note that the gaps between the labyrinths 71, 72, and 73 are narrow.

Next, the functions of the labyrinths 71, 72, and 73 will be explained together with the functions of the cooling fan 16 and the air duct 30.

First, when the engine 1 is operated, the rotation of the crankshaft 11 causes the cooling fan 16 coaxial with the crankshaft 11 to rotate, and the air in the air duct 30 is sucked by the rotation of the cooling fan 16 .

Due to the suction action of the cooling fan 16, outside air is sucked into the air duct 30 from the upper opening 31, and in the process of flowing from above through the heat radiation fins 50..., 60... of the cylinder 5 and the cylinder head 6 from above to both sides and downward. The entire circumference is cooled, and the cooled air is discharged to the atmosphere by the cooling fan 16 through the lower opening 32.

In this way, the cylinder 5 and the cylinder head 6 are covered all around with the air duct 30, and outside air is sucked in through the upper opening 31 facing the crankcase 3 side, and the outside air is sucked in by a suction type cooling fan placed on the lower opening 32 side. 16, the outside air flowing in from the upper opening 31 is rectified in the air duct 30 by the suction action of the cooling fan 16, and flows to the cylinder head 6 side where the temperature is highest, and the flow rate is gradually increased from the upstream side to the downstream side. It will rise and flow. Therefore, of course, the entire circumference cold part around cylinder 5,
In particular, the entire circumference around the high-temperature cylinder head 6 can be cooled efficiently.

In the above, since there are gaps, although narrow, between the air duct 30 and the heat dissipation fin 61 at the most distal end of the cylinder head 6, the muffler 41 and the carburetor 45 connected to the cylinder head 6, and the cooling fan 16 from each gap. Due to the suction effect, foreign matter such as dust tries to enter along with the outside air.

However, in the present invention, in the gap between the air duct 30 and the radiation fin 61, a labyrinth 71 consisting of the flange peripheral piece 35 of the duct 30, the annular rib 62 of the fin 61, the inner periphery of the duct 30, and the peripheral edge of the fin 61 is added. 30 and muffler 41
The gap between the peripheral wall of the circular recess 37 of the duct 30 and the muffler gasket 42 and the circular hole 37 of the circular recess 37 are provided.
The labyrinth 72 consisting of the peripheral edge a and the outer periphery of the exhaust port cylindrical portion 66, and also the gap between the air duct 30 and the carburetor 45, the peripheral wall of the circular recess 39 of the duct 30, the flange peripheral piece 46 of the carburetor 45, and the circle of the circular recess 39. Periphery of hole 39a and intake port cylindrical portion 68
Since the labyrinths 73 each consist of the outer periphery, foreign substances such as dust can be prevented from entering the labyrinths 71 and 73.
72 and 73, the amount of air is reduced, and therefore only the outside air from which foreign objects have been removed is sucked in, albeit in a small amount.

That is, for example, when the engine 1 is mounted on a lawnmower and a cutter blade (not shown) is attached to the lower end of the shaft portion 31 of the crankshaft 11 to perform lawn mowing work, it is necessary to prevent grass from entering through the gaps around the cylinder head 6. can be effectively prevented.

By the way, as described above, the labyrinths 71, 72, and 73 prevent the intrusion of foreign matter while allowing outside air to be drawn directly around the cylinder head 6, so that the cooling performance for the cylinder head 6, which is at the highest temperature, is further improved. becomes. In other words, since the cooling performance can be improved with the minimum necessary cooling air, in addition to downsizing the cooling fan 16, the radiation fins 50..., 6 of the cylinder 5 and its head 6 can be
Since it is possible to reduce the number of 0..., it is also possible to downsize the engine 1.

In the example, a vertical engine was used, but
It may be a horizontal engine.

As is clear from the above description, according to the present invention, in a forced air-cooled engine in which air in a cylindrical air duct covering the cylinder and cylinder head is sucked in by a cooling fan, the most advanced heat dissipation fin of the cylinder head is connected to the cylinder head. A labyrinth is formed between the air duct and the muffler and carburetor, respectively, to form a seal structure around the cylinder head, which effectively prevents foreign matter such as dust from entering around the cylinder head while allowing outside air to flow directly into the cylinder. The cooling performance around the cylinder head can be further improved, and the cooling fan can be made smaller and the number of heat dissipation fins can be reduced, making it possible to make the engine more compact. has advantages.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal side view of the engine and air duct, Fig. 2 is a longitudinal sectional front view of the crankcase showing the intake side opening of the air duct, Fig. 3 is a bottom view of the air duct and crankcase, and Fig. 4 is a view of the present invention. FIG. 2 is a cross-sectional plan view of an engine and an air duct showing such a seal structure. In the drawing, 1 is the engine, 3 is the crankcase,
5 is a cylinder, 6 is a cylinder head, 11 is a crankshaft, 16 is a cooling fan, 18 is its rib, 30 is an air duct, 31 is its suction side opening,
32 is the discharge side opening, 35 is the flange peripheral piece, 3
7 and 39 are circular recesses, 37a and 39a are circular holes thereof,
41 is a muffler, 42 is a gasket, 45 is a carburetor, 46 is a flange circumferential piece thereof, 61 is a radiation fin, 62 is an annular rib thereof, 66, 68 are intake/exhaust port cylinder parts, 71, 72, and 73 are labyrinths. .

Claims (1)

[Scope of utility model registration request] In a forced air-cooled engine that covers the cylinder and cylinder head of the engine with a cylindrical air duct and is equipped with a cooling fan that sucks the air in the air duct, the cylinder head includes a heat dissipation fin at the leading edge of the cylinder head, a muffler and a carburetor connected to the cylinder head;
A seal structure around a cylinder head of a forced air-cooled engine, characterized in that a labyrinth is formed between each cylinder head and the air duct.