JP3951571B2 - Valve structure of general-purpose air-cooled four-cycle engine - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a valve operating structure of a general-purpose air-cooled four-cycle engine such as a crankshaft vertically mounted small air-cooled four-cycle engine used in a lawn mower or the like.
[0002]
[Prior art]
There is a general-purpose four-cycle engine with a small one that has a cooling fan attached to one end of the crankshaft, covered with a fan cover, and sent cooling air to the cylinder head and cylinder to cool the heat generated by the engine. . There is also a cylinder head camshaft and crankshaft connected by a timing belt to open and close an intake valve and an exhaust valve.
[0003]
For example, the one disclosed in Japanese Patent Application Laid-Open No. 8-177441 has a cooling fan attached to one end of a horizontally placed crankshaft and sends cooling air toward the cylinder and the cylinder head for cooling. The camshaft and crankshaft of the cylinder head are connected by a timing belt to open and close the intake valve and exhaust valve of the cylinder head.
[0004]
[Problems to be solved by the invention]
With the above structure, the timing belt becomes leeward of cooling air for cooling the cylinder and the cylinder head, and the cylinder and the cylinder head can be efficiently cooled. However, the timing belt receives hot air after cooling the cylinder and cylinder head. The timing belt is made mainly of rubber and has a problem with heat resistance, so the timing belt deteriorates quickly and is durable. There is a problem with sex.
Further, when a normal timing belt is disposed on the cooling fan side, the large-diameter pulley may hinder the flow of cooling air and may reduce cooling efficiency.
[0005]
In view of this point, the present invention cools adjacent cylinder heads and cylinders with a cooling fan at one end of a vertically placed crankshaft, and the timing belt that drives the camshaft of the cylinder head is less affected by heat, and Another object of the present invention is to provide a valve operating structure for a general-purpose air-cooled four-cycle engine that can efficiently cool a cylinder head and a cylinder.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention has the following configuration.
The present invention relates to a valve operating structure of a general-purpose four-cycle engine for driving the cam shaft is transmitted to the cam shaft power of the engine crankshaft cooling fan is provided at one end with a timing belt, a cylinder head An intake valve and an exhaust valve that open and close an intake hole and an exhaust hole formed in communication with the combustion chamber are disposed along the crankshaft direction, and the intake hole and the exhaust hole are connected to the cylinder shaft and the crankshaft. While extending perpendicularly to the shaft and in directions opposite to each other, the timing belt is spanned between the end of the camshaft on the cooling fan side and the position of the crankshaft between the cylinder and the cooling fan. cylinder its central axis, Rutotomoni provided so as to bias the intake hole formed side direction of the cylinder head than the cylinder central axis, than the spark plug cylinder center axis And screwed Tilt exhaust hole side of the head, said a cooling air of the cooling fan and valve operating structure of a general-purpose air-cooled four-cycle engine, characterized by being configured to direct the exhaust hole side.
[0007]
In the present invention, a rocker arm is provided between the intake cam and exhaust cam on the camshaft and the intake valve and exhaust valve, and the rocker arm is rocked by driving the cam to open and close the intake valve and exhaust valve. Is preferred.
[0008]
According to the present invention, the camshaft rotates in conjunction with the crankshaft and the timing belt, and opens and closes the intake valve and the exhaust valve via the rocker arm. A cooling fan at one end of the crankshaft rotates with the crankshaft and blows cooling air to the cylinder side to cool the heat generated by the cylinder and the cylinder head. The timing belt spans between the cooling fan side end of the camshaft and the position between the cylinder and cooling fan of the crankshaft, so it is closer to the cooling fan than the cylinder and cylinder head. On the upper side of the cooling air, the heat effect can be reduced and it can be made durable.
[0009]
In addition, the cam shaft of the cylinder head to which the timing belt is attached is biased so that it is on the intake hole side of the cylinder head and the shaft center of the cam shaft is outside the combustion chamber of the cylinder head. Wind can be blown well.
In addition, cooling air blows less on the intake hole side of the cylinder head due to the pulley on which the timing belt is stretched, but the intake hole side of the cylinder head is also cooled by the intake air passing through the intake hole. There is no problem even if there is little wind blowing. On the contrary, since the exhaust passage side is not much blocked by the pulley, the cooling air is efficiently applied and the cooling efficiency is good.
If a rocker arm is provided between the intake cam and exhaust cam on the camshaft and the intake valve and exhaust valve, and the rocker arm is rocked by driving the cam to open and close the intake valve and exhaust valve, Even if the cylinder shaft and cam shaft are deviated, the intake valve and exhaust valve can be reliably driven by the cam.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
In the embodiment, the crankshaft 10 is positioned along the vertical direction in a normal use state, the cooling fan 11 is fixed in the rotational direction at the upper end, and the lower end is connected to a power usage target such as a lawn mower. It is an engine.
[0011]
In the general-purpose engine, the crankshaft 10 is rotatably supported by the crankcase 20, and the cylinder 1 is provided in the crankcase 20 so as to protrude in a lateral direction perpendicular to the crankshaft 10. The cylinder head 2 connected to the tip of the cylinder 1 is provided with a recess as the combustion chamber 3 in accordance with the inner diameter of the cylinder 1. An intake hole 6 and an exhaust hole 7 are formed in the cylinder head 1 so as to communicate with the combustion chamber 3, and the intake hole 6 and the exhaust hole 7 are opened and closed by an intake valve 4 and an exhaust valve 5, respectively. . The intake valve 4 and the exhaust valve 5 are driven to advance and retract along the cylinder axis direction, and the valves 4 and 5 are arranged along the crankshaft 10 direction as shown in FIG.
[0012]
An intake hole 6 and an exhaust hole 7 connected to the intake valve 4 and the exhaust valve 5 respectively extend from the combustion chamber 3 with a short length along the central axis of the cylinder 1 and are perpendicular to the cylinder 1 axis and the crankshaft 10 from the middle. Each extending in the opposite direction. A vaporizer 8 is connected to the intake hole 6, while a muffler 9 is connected to the exhaust hole 7.
[0013]
A cooling fan 11 is attached to the upper end of the crankshaft 10 to cover the bowl-shaped fan cover 12 from above, including the cooling fan 11 to the cylinder head 2. The fan cover 12 allows the cooling air generated by the cooling fan 11 to flow and blow toward the lower cylinder 1 and the cylinder head 2 so that air can be efficiently cooled with the cooling air.
A timing pulley 21 is disposed at a position between the cylinder 1 and the cooling fan 11 of the crankshaft 10, and a timing pulley 22 is disposed at the cooling fan 11 side end of the camshaft 13 pivoted on the cylinder head 2. The timing belt 14 is stretched around these pulleys 21 and 22. As a result, the timing belt 14 is arranged so as to pass the side near the cooling fan 11 at the top of the cylinder 1 and the cylinder head 2.
[0014]
The cam shaft 13 has its axial center biased in the direction of forming the intake hole 6 of the cylinder head 2 with respect to the center axis of the cylinder 1. Thereby, the cam shaft 13 is largely biased to the outside from the combustion chamber 3 as viewed in the cylinder axial direction.
Further, the cam shaft 13 through the rocker arm 15, the intake valve 4, so has become Let 's you open and close the exhaust valve 5, to ensure even deviate greatly to the cam shaft 13 is the intake hole 6 side direction The drive of the cam can be transmitted to the valves 4 and 5 by the rocker arm 15 .
Further, a head cover 16 is attached to the cylinder head 2 so as to cover a valve operating mechanism such as the cam shaft 3 and the rocker arm 15.
[0015]
A box-type air cleaner 23 communicates with the upstream side of the carburetor 8 communicating with the intake hole 6, and a passage for supplying secondary air to the exhaust hole 7 in addition to the carburetor 8. 24 communicates with the reed valve 25 interposed therebetween.
A spark plug 26 is screwed onto the muffler 9 side portion of the cylinder head 2 with a slight inclination from the central axis of the cylinder 1.
[0016]
Since the timing belt 14 is disposed at a position close to the cooling fan 11 above the cylinder 1 and the cylinder head 2, the timing belt 14 does not receive hot air after cooling the cylinder 1 and the cylinder head 2, There is little heat effect and it can be made durable.
[0017]
By greatly biasing the camshaft 13 toward the intake hole 5 side, cooling is performed by applying sufficient cooling air to the exhaust hole 7 side where the cylinder 1 and the cylinder head 2 become hot without being obstructed by the timing belt 14. can do.
On the camshaft 13 side through which the timing belt 14 passes, the flow of the cooling air is reduced, but the vicinity of the intake hole 6 is cooled by the intake air flowing through the intake hole 6, so there is no problem.
[0018]
【The invention's effect】
As described above , according to the present invention, the timing belt can be prevented from receiving the hot air after cooling the cylinder and the cylinder head, the thermal influence can be reduced, and the timing mainly composed of rubber or elastomer. The durability of the belt can be increased.
The camshaft connecting the timing belt is biased toward the intake hole, so that sufficient cooling air can be blown to the cylinder and the exhaust hole on the high temperature side of the cylinder head. The side can be cooled by intake air, so there is no problem even if there is little cooling air.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a general-purpose engine according to an embodiment of the present invention.
2 is a cross-sectional view of the general-purpose engine of FIG.
FIG. 3 is a side view of the general-purpose engine shown in FIG. 1 as viewed from the head cover side with the head cover removed and partly broken.
4 is a plan view of the general-purpose engine shown in FIG. 1 with a fan cover removed. FIG.
FIG. 5 is a side view of the general-purpose engine of FIG. 1 as viewed from the muffler side.
[Explanation of symbols]
1 Cylinder 2 Cylinder Head 3 Combustion Chamber 4 Intake Valve 5 Exhaust Valve 6 Intake Hole 7 Exhaust Hole 10 Crankshaft 11 Cooling Fan 13 Camshaft 14 Timing Belt 15 Rocker Arm

Claims (2)

A valve structure of a general-purpose four-cycle engine that transmits the power of an engine crankshaft provided with a cooling fan at one end to a camshaft by a timing belt and drives the camshaft,
The cylinder head is provided with an intake valve and an exhaust valve that open and close an intake hole and an exhaust hole formed in communication with the combustion chamber, respectively, along the crankshaft direction. While extending perpendicularly to the cylinder shaft and the crankshaft and in opposite directions,
The timing belt is spanned between the cooling fan side end of the camshaft and the position between the crankshaft cylinder and the cooling fan,
Its central axis the cam shaft, Rutotomoni provided so as to bias the intake hole formed side direction of the cylinder head than the cylinder center axis, screwing the spark plug is inclined to the exhaust hole side of the cylinder head than the cylinder center axis And a valve structure for a general-purpose air-cooled four-cycle engine , wherein the cooling air of the cooling fan is guided to the exhaust hole side . A rocker arm is provided between the intake cam and exhaust cam on the camshaft and the intake valve and exhaust valve, and the rocker arm is rocked by driving the cam to open and close the intake valve and exhaust valve. The valve operating structure for a general-purpose air-cooled four-cycle engine according to claim 1.

Images