JP2002054432A - Secondary air supplying device of small-sized air-cooled four-cycle engine with vertical crank shaft - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a secondary air supplying device for small-sized air-cooled, four-cycle engine with a vertical crank shaft capable of purifying the exhaust gas and cooling the cylinder head effectively by introducing such a structure that a cooling fan is installed at the top of the crank shaft arranged vertically, an exhaust hole is provided in the sideways facing cylinder head in its part below the center, and a reed valve is installed on the undersurface of the cylinder head. SOLUTION: A suction valve 7 and an exhaust valve 8 are installed in line over and under the combustion chamber 6 of the cylinder head 5, and a valve seat 14 is installed on the undersurface of the cylinder head 5 so that the inside is put in communication to the exhaust hole 10 via a through hole 15, and the reed valve 16 is inserted to the valve seat 14 and held down by a valve cover 17, which is coupled by a hose 18 with an air cleaner 12 located on the side opposite the exhaust hole 10. Because the cylinder head undersurface where the reed valve 16 is installed, is positioned as downstream of the cooling wind, there is no risk that the reed valve 16 hinders passage of the cooling wind.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary air supply device for a small air-cooled four-stroke engine vertically mounted on a crankshaft used for a lawn mower or the like.

[0002]

2. Description of the Related Art Recently, even in a small general-purpose engine, secondary air is injected into an exhaust hole of the engine, oxygen is supplemented to the exhaust gas by the secondary air, and HC in the exhaust gas is reduced.
The CO is oxidized by a thermal reaction to clean the exhaust gas.

For example, Japanese Unexamined Utility Model Publication No. 5-19520 discloses a crankshaft horizontal engine in which a reed valve for injecting secondary air is mounted on a lower slope of a tilted cylinder head. ing. In a small air-cooled four-stroke engine with a vertical crankshaft used for lawn mowers, a cooling fan is attached to the upper end of the crankshaft, and downward cooling air is blown to the upper side of the horizontal cylinder and cylinder head. And no cylinder head is equipped with a secondary air injection device.

[0004]

In an engine with a crankshaft placed sideways, cooling air is blown laterally, and a reed valve for secondary air injection provided on a lower slope of an inclined cylinder head is provided with a cooling valve. Since the wind is blocked, there is a portion where the cooling air does not sufficiently hit the cylinder head portion which is leeward of the reed valve for the secondary air injection. For this reason, it is necessary to take measures such as increasing the cooling fan and increasing the air volume, thereby increasing power consumption.

In view of the foregoing, the present invention has a cooling fan attached to the upper end of a vertically installed crankshaft, the cylinder and the cylinder head are set sideways, and an exhaust hole is provided below the center of the cylinder head to provide a cooling hole on the lower surface of the cylinder head. It is an object of the present invention to provide a secondary air supply device for a small air-cooled four-cycle engine with a vertically mounted crankshaft, which is equipped with a reed valve for secondary air injection and can purify exhaust gas and efficiently cool a cylinder head.

[0006]

Means for Solving the Problems To achieve the above object, the present invention has the following configuration. That is, according to the present invention, an intake valve and an exhaust valve are mounted side by side on the upper and lower sides of a combustion chamber of a cylinder head, a reed valve seat is provided on the lower surface of the cylinder head, and an inner through hole communicates with the exhaust hole. A secondary air supply device for a small air-cooled four-stroke engine with a vertically mounted crankshaft, wherein a valve cover is inserted and covered with a valve cover, and the valve cover is communicated with an air cleaner on a side opposite to the exhaust hole through a passage. In the present invention, it is preferable that a cooling fan be attached to the upper end of the crankshaft to blow the cooling air downward from above the cylinder head.

According to the present invention, when a negative pressure is caused by the pulsation of the exhaust gas intermittently discharged into the exhaust hole, the reed valve opens, air flows from the air cleaner, and secondary air flows into the exhaust hole. The exhaust gas is supplied with oxygen. Then, the oxidation reaction of the exhaust gas is promoted by the catalyst in the muffler, and the exhaust gas is cleaned.

The cooling air from the cooling fan is blown downward from above the cylinder head to the cylinder head, and the reed valve is located on the lower surface of the cylinder head.
It is possible to cool the cylinder head efficiently without being leeward and not hindering the cooling of the cylinder head by the cooling wind. Therefore, it is not necessary to increase the cooling fan to increase the air volume.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In the embodiment, the crankshaft 1 is positioned vertically (disposed vertically) in a normal state, the cooling fan 2 is attached to the upper end of the crankshaft 1, and the power of a lawnmower or the like is attached to the lower end. It is a general-purpose engine linked to the target of use.

In the general-purpose engine, the crankcase 2
The crankshaft 1 is rotatably supported at 0, and a cylinder 4 is provided in the crankcase 20 so as to protrude in a lateral direction perpendicular to the crankshaft 1. The cylinder 4 is covered with the fan cover 3 from the cooling fan 2.

The cylinder head 5 connected to the tip of the cylinder 1 is provided with a recess corresponding to the inner diameter of the cylinder 4 as a combustion chamber 6. An intake hole 9 and an exhaust hole 10 are formed in the cylinder head 5 so as to communicate with the combustion chamber 3, and the intake hole 9 and the exhaust hole 10 are opened and closed by an intake valve 7 and an exhaust valve 8, respectively. . The intake valve 7 and the exhaust valve 8 are driven to advance and retreat along the cylinder axis direction. As shown in FIG. 3, the valves 7, 8 are arranged vertically along the direction of the crankshaft 1. An intake hole 9 and an exhaust hole 10 connected to the intake valve 7 and the exhaust valve 8, respectively, extend from the combustion chamber 6 along the central axis of the cylinder 1 with a short length, and are perpendicular to the cylinder 4 axis and the crankshaft 1 in the middle. Directions, each extending in opposite directions. A carburetor 11 (an air cleaner 12 is connected to the intake side) is connected to the intake hole 9, while a muffler 13 is connected to the exhaust hole 8.

A bowl-shaped fan cover 3 including the cooling fan 2 attached to the upper end of the crankshaft 1 to the cylinder head 5 is covered from above.
With this fan cover 3, the cooling air generated by the cooling fan 2 is transferred to the lower cylinder 4 and the cylinder head 5.
And the air is efficiently blown by the cooling air.

A timing pulley 22 is disposed between the cylinder 4 of the crankshaft 1 and the cooling fan 2, and a cooling fan 2 of a camshaft 23 mounted on the cylinder head 5.
A timing pulley 24 is provided at the side end,
A timing belt 25 is stretched over these pulleys 22 and 24. Thereby, the timing belt 25 is
The cylinder 4 and the upper part of the cylinder head 5 are arranged so as to pass through the side close to the cooling fan 2. 26 is a rocker arm and 27 is a spark plug.

The reed valve seat 14 is formed by recessing the lower surface of the cylinder head 5 so that the reed valve seat 14 is formed.
In the vicinity of the opening / closing opening by the exhaust valve 8 of FIG. Reed valve seat 1
The reed valve 16 is inserted into 4, and the valve cover 17 is attached so that the outside can be pressed by the valve cover 17. Valve cover 17
Is connected to the air cleaner 12 by a hose 18. A dome-shaped head cover 19 is attached to the cylinder head 5.

Each time the exhaust valve 8 is opened, the exhaust gas intermittently and rapidly flows through the exhaust hole 10, and the exhaust gas flows in a pulsating manner. When a negative pressure is generated due to the pulsation of the exhaust gas, the reed valve 16 is opened, air is sucked from the air cleaner 12, and the exhaust hole 10 is formed as secondary air through the through hole 15.
And enters the exhaust gas. Oxygen is replenished to the exhaust gas by the secondary air, and the catalyst in the muffler 13 promotes the oxidation reaction of the exhaust gas to purify the exhaust gas.

The cooling air sent from the upper cooling fan 2 is blown downward onto the upper surface of the cylinder head 5 to cool the cylinder head 5. The reed valve seat 14 on which the reed valve 16 is mounted is located on the lower surface of the cylinder head 5 and is located downstream of the cooling air.
The cooling of the cylinder head 5 can be efficiently performed without obstructing the cooling of the cylinder head 5.

[0017]

As described above, the present invention is constructed as described above. Therefore, in a small air-cooled four-stroke engine vertically mounted on a crankshaft, a secondary valve is connected to an exhaust hole through a reed valve mounted on the lower surface of a cylinder head. By supplying air, the oxidation reaction of the exhaust gas is promoted and the exhaust gas can be cleaned. And, since the reed valve is attached to the lower surface of the cylinder head that is downwind of the cooling air, the reed valve can cool the cylinder head efficiently without obstructing the flow of the cooling air, and the cooling fan can be downsized. With a small power loss, it can be improved.

[Brief description of the drawings]

FIG. 1 is a side view showing a main part of an engine according to an embodiment of the present invention, in which a head cover is removed, a part of a cylinder head and an air cleaner are cut away, and viewed from a head cover side.

FIG. 2 is a cross-sectional plan view showing the engine.

FIG. 3 is a vertical sectional side view showing the engine.

FIG. 4 is a plan view of the engine with a fan cover removed.

FIG. 5 is a side view of the engine as viewed from a muffler side.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Crankshaft 2 Cooling fan 5 Cylinder head 6 Combustion chamber 7 Intake valve 8 Exhaust valve 10 Exhaust hole 12 Air cleaner 14 Reed valve seat 15 Through hole 16 Reed valve 17 Valve cover 18 Hose

Claims (2)

[Claims] An intake valve and an exhaust valve are mounted side by side on the upper and lower sides of a combustion chamber of a cylinder head, a reed valve seat is provided on the lower surface of the cylinder head, and an inner hole communicates with the exhaust hole, and a reed valve is connected to the reed valve seat. A secondary air supply device for a small air-cooled four-stroke engine with a vertically mounted crankshaft, wherein the secondary air supply device is inserted and covered with a valve cover, and the valve cover is communicated with an air cleaner on a side opposite to the exhaust hole through a passage. 2. The small air-cooling system according to claim 1, wherein a cooling fan is attached to an upper end of the crankshaft to blow cooling air downward from above the cylinder head. Secondary air supply for four-cycle engine.