JP2580133B2 - Forced air-cooled vertical engine - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) In the present invention, a crankshaft is arranged vertically, and a cylinder is forcibly forced by cooling air generated by a cooling fan attached to an upper end of the crankshaft. The present invention relates to an improvement of a forced air-cooled vertical engine that is cooled.

(Prior art) This type of forced air-cooled vertical engine is used as a drive source for a working machine such as a lawnmower or a mower. However, it is necessary to keep the height of the working machine high and to keep the working machine stable.・
It has been proposed that the exhaust valve be replaced with an overhead valve type (including an overhead camshaft type) instead of the side valve type (JP-A-59-70838 and JP-A-61-534).
No. 22).

In this type of forced air-cooled vertical engine, a cooling fan is attached to the upper end of a vertically disposed crankshaft, and the cooling air generated by the cooling fan is guided downward to forcibly force the cylinder and cylinder head. Cooling is performed.

(Problems to be Solved by the Invention) However, in the conventional forced air-cooled vertical engine, since the exhaust passage formed in the cylinder head is disposed below the intake passage, high-temperature exhaust gas flows. Therefore, the periphery of the exhaust passage, which is higher in temperature than the periphery of the intake passage, is not first cooled by the cooling air, and the periphery of the exhaust passage is cooled to the periphery of the intake passage and cooled by the already-cooled cooling air. However, the cooling effect is low, the cooling efficiency of the cylinder head as a whole deteriorates, abnormal combustion such as knocking occurs, and there is a possibility that the output is reduced.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide a forced air-cooled vertical engine capable of stably maintaining high performance characteristics by improving cooling efficiency. It is in.

(Means for Solving the Problems) In order to achieve the above object, the present invention disposes a crankshaft vertically so that cooling air generated by a cooling fan attached to an upper end of the crankshaft is directed downward. In a forced air-cooled vertical engine that guides and cools a cylinder and a cylinder head, a spark plug is provided so as to be deviated to one side of a combustion chamber, and an exhaust valve and an intake valve are vertically arranged on the opposite side of the ignition plug. The intake passage extends outwardly below the spark plug, and the exhaust passage extends above the intake passage so as to be inclined toward the anti-deflection side of the ignition plug. A carburetor is connected, and a muffler is connected to the exhaust passage.

(Operation) According to the present invention, since the exhaust passage is provided above the intake passage, the periphery of the exhaust passage, which becomes hotter than the periphery of the intake passage due to the flow of high-temperature exhaust gas, is first effectively cooled by the cooling air. As a result, the cooling efficiency of the entire cylinder head is increased. As a result, abnormal combustion such as knocking is prevented, and the performance characteristics of the forced air-cooled vertical engine are maintained high.

Further, since the exhaust passage is formed on the opposite side of the ignition plug, the wrap length between the exhaust passage and the combustion chamber is reduced, and the heating of the combustion chamber by exhaust gas flowing through the exhaust passage is suppressed.
The above effect is further enhanced.

Embodiment An embodiment of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a longitudinal side view of a forced air-cooled vertical engine according to the present invention, and FIG. 2 is a cross-sectional plan view of the engine (first embodiment).
FIG. 3 is a view in the direction of arrow A in FIG. 1 with the cylinder head cover removed, and FIG.
The figure is a sectional view taken along the line IV-IV in FIG.

The illustrated forced air-cooled vertical engine 1 has a cylinder 2 arranged horizontally and a crankshaft 3 arranged vertically, and a cooling fan 4 connected to an upper end of the crankshaft 3 by a nut 5. The fan 4 is covered with a wind guide cover 6. In FIG. 1, 7 is a recoil starter, 8 is a fuel tank, 9 is a cap, and a plurality of suction holes 9a are formed in the cap 9.

A piston 10 is slidably fitted in the cylinder 2, and the piston 10 is connected to the crankshaft 3 via a connecting rod 11. And cylinder 2
A cylinder head 12 is attached to an end of the cylinder head 12, and the cylinder head 12 is covered with a cylinder head cover 13. In the cylinder 2, a combustion chamber S defined by a piston 10 and a cylinder head 12 is formed.

At a position deviated to one side (upward in FIG. 2, leftward in FIG. 3) with respect to the center in the width direction of the cylinder head 12, an ignition plug 30 whose front end faces the combustion chamber is mounted. Have been. In addition, as shown in FIG.
Is formed with a plug hole 36 for mounting the ignition plug 30.

As shown in FIG. 1 and FIG. 4, the end face facing the inside of the cylinder 2 on the anti-deflection side (right side in FIG. 4) of the spark plug 30 with respect to the center in the width direction of the cylinder head 12 The exhaust port 14 opens upward, and the intake port 15 opens downward.The exhaust port 14 and the intake port 15 are opened and closed by an exhaust valve 16 and an intake valve 17, which are slidably inserted into the cylinder head 12. , These exhaust valve 16 and intake valve 17
Is biased toward the closing side by springs 18 and 19.
The intake / exhaust ports 15, 14 and the intake / exhaust valves 17, 16
As shown in the figure, the combustion chamber S is provided so as to be deviated to one side (the right side in FIG. 4).

The top of each of the exhaust valve 16 and the intake valve 17 is in contact with one end of each of the rocker arms 20 and 21 that can swing. The other end of each of the rocker arms 20 and 21 is connected to the cylinder 2 and the cylinder head. Push rods 22 and 23 slidably inserted through 12
(See FIGS. 2 to 4).
The other end of the push rod 22 is connected to a cam 25 rotatably disposed in a crankcase 24 as shown in FIG.
Although not shown, the other end of the other push rod 23 is also in contact with a cam (not shown). Note that a cam shaft (not shown) provided with the cam 25 has
As shown in FIG. 2, a gear 26 is coaxially connected, and the gear 26 is a gear connected to an intermediate portion of the crankshaft 3.
27 mesh.

Further, in the cylinder head 12, as shown in FIG. 4, an exhaust passage 28 connected to the exhaust port 14 is provided with an ignition plug.
30 is formed with an upward slope (downward in the direction of the exhaust valve 16) toward the anti-deflection side (the right side in FIG. 4). A series of intake passages 29 extend outward with a rising gradient (downward in the direction of the intake valve 17) toward the deflection side (left side in FIG. 4) of the ignition plug 30.

A carburetor 31 is connected to one side (upper side in FIG. 2) of the cylinder head 12 so as to communicate with an intake passage 29, and an air cleaner 32 is connected to the carburetor 31.

On the other hand, a muffler 33 is disposed on the other side of the cylinder head 12 (downward in FIG. 2), and the muffler 33 and the exhaust passage 28 are connected by an exhaust pipe 34. In FIG. 2, reference numeral 35 denotes a protector that covers the muffler 33.

Next, the operation of the forced air-cooled vertical engine 1 will be described.

When the crankshaft 3 is driven to rotate during the operation of the vertical engine 1, the cooling fan 4 attached to the upper end of the crankshaft 3 rotates integrally. Atmosphere is sucked from the suction holes 9a, where cooling air is generated, and the cooling air is guided downward to cool the cylinder 2 and the cylinder head 12.

However, as described above, the exhaust passage is provided in the cylinder head 12.
Since 28 is formed above the intake passage 29,
The periphery of the exhaust passage 28, which becomes hotter than the periphery of the intake passage 29 due to the flow of high-temperature exhaust gas, is first effectively cooled by the cooling air, and then the periphery of the intake passage 29 is cooled. As a result, the cooling efficiency of the entire cylinder head 12 is increased, abnormal combustion such as knocking is prevented from occurring, and the performance characteristics of the forced air-cooled vertical engine 1 are always kept high.

Further, in the present embodiment, as described above, the exhaust passage 28
Is formed on the anti-deflection side of the spark plug 30 and upwardly outward (downwardly toward the exhaust valve 16), so that the length l can be shortened and the exhaust passage 28 and the combustion The wrap length with the chamber S is shortened, and as a result, the time during which the cylinder head 12 and the combustion chamber S are heated by the exhaust gas passing through the exhaust passage 28 is shortened, and the heating of the combustion chamber S is suppressed. Also, the performance characteristics of the forced air-cooled vertical engine 1 are maintained high.

Further, in the present embodiment, since the exhaust passage 28 is provided in a ring with the push rods 22 and 23, the heat of the exhaust gas flowing through the exhaust passage 28 has a high heat capacity around the push rods 22 and 23 and a relatively low temperature. A considerable amount of heat is also transmitted to the flesh portion a (see FIG. 4), and as a result, the temperature around the exhaust passage 28 decreases, and a high cooling effect can be obtained with a small amount of cooling air. The temperature distribution is averaged, the occurrence of thermal strain in the cylinder head 12 is suppressed, and the durability is improved.

In the above embodiments, the forced air-cooled vertical engine of the type in which the camshaft is arranged in the crankcase has been described. However, the present invention relates to a so-called overhead camshaft in which the camshaft is arranged in the rocker arm chamber in the cylinder head cover. The same applies to a forced air-cooled vertical engine of the (OHC) type.

(Effects of the Invention) As is apparent from the above description, according to the present invention, the crankshaft is arranged vertically, and the cooling air generated by the cooling fan attached to the upper end of the crankshaft is guided downward. In a forced air-cooled vertical engine that cools a cylinder and a cylinder head, a spark plug is displaced to one side of a combustion chamber, and an exhaust valve and an intake valve are vertically arranged on the opposite side of the spark plug. The intake passage extends outwardly below the spark plug, and the exhaust passage extends above the intake passage so as to be inclined toward the anti-deflection side of the ignition plug. Since a carburetor is connected and a muffler is connected to the exhaust passage, the area around the exhaust passage, which is heated by the high-temperature exhaust gas, is first effectively cooled by the cooling air, thereby increasing the cooling efficiency of the entire cylinder head. In addition, the effect of suppressing the heating of the combustion chamber to prevent occurrence of abnormal combustion such as knocking, and maintaining the performance characteristics of the forced air-cooled vertical engine always high.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view of a forced air-cooled vertical engine according to the present invention, FIG. 2 is a cross-sectional plan view of the engine (sectional view taken along the line II-II in FIG. 1), and FIG. FIG. 4 is a sectional view taken along the line IV-IV of FIG. 1 ... forced air-cooled vertical engine, 2 ... cylinder, 3 ... crankshaft, 4 ... cooling fan, 12 ... cylinder head, 16 ... exhaust valve, 17 ... intake valve, 22, 23 ...
Push rod, 28 ... Exhaust passage, 29 ... Intake passage, 30
... spark plug, 31 ... vaporizer, 33 ... muffler, S ...
... combustion chamber.

Claims (1)

(57) [Claims] 1. A forced air-cooled vertical engine in which a crankshaft is arranged vertically and a cooling air generated by a cooling fan attached to an upper end of the crankshaft is guided downward to cool a cylinder and a cylinder head. An ignition plug is provided offset to one side of the combustion chamber, an exhaust valve and an intake valve are vertically arranged on the opposite side of the ignition plug, and the intake passage extends outward below the ignition plug. Extend,
The exhaust passage is extended above the intake passage so as to be inclined toward the anti-deflection side of the ignition plug, a carburetor is connected to the intake passage, and a muffler is connected to the exhaust passage. Air-cooled vertical engine.