JPH08158949A - Spark ignition engine - Google Patents

Abstract

PURPOSE: To prevent freezing in a carburetor by providing a cooling air discharge guide case along the peripheral wall of at least one of a cylinder head and a cylinder, placing a cooling air discharge passage in the cooling air discharge guide case, and guiding the cooling discharged air discharged from the cooling air passage to the above cooling air discharge passage. CONSTITUTION: A cooling air passage 3 for cooling one of a cylinder head 1 and a cylinder 2 is provided, and a cooling air discharge guide case is disposed along the peripheral wall of the cylinder head 1 or the like, thereby forming a cooling air discharge passage 5. A cooling discharged air 6 discharged from the cooling air passage 3 is introduced into the cooling air discharge passage 5. An exhaust pipe 9 interposed between an exhaust port 7 and an exhaust muffler 8 is stored in the cooling air discharge passage 5, a discharge air lead- out pie 11 is derived from a passage outlet 10 of the cooling air discharge passage 5, and the discharge air lead-out pipe 11 is directed to a carburetor 14. Thus, cooling discharge air 17 heated is sprayed to a carburetor 14 so as to prevent freezing in the carburetor 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spark ignition type engine, and more particularly to an engine capable of preventing freezing which may occur at a main nozzle or a throttle valve of a carburetor.

[0002]

2. Description of the Related Art Conventionally, in a spark ignition type engine, a carburetor is exposed to the outside air without any special heating means. Therefore, in cold weather, cold outside air may be sucked into the carburetor, and the water contained in the intake air may freeze at the main nozzles and the throttle valve.

[0003]

In the above prior art, during cold weather, freezing may occur at the main nozzle and throttle valve of the carburetor, the main nozzle may be clogged, or the opening and closing of the throttle valve may be hindered. Therefore, engine stall may occur or engine rotation may become unstable.

SUMMARY OF THE INVENTION An object of the present invention is to provide a spark ignition type engine which can prevent the freezing that occurs in the main nozzle and throttle valve of the carburetor.

[0005]

DISCLOSURE OF THE INVENTION The present invention is characterized in that a spark ignition type engine is constructed as follows. That is,
As illustrated in FIG. 1, a cylinder head 1 and a cylinder 2
Cooling air passage 3 for air cooling at least one of the
And a cooling exhaust guide case 4 is provided along the peripheral wall of at least one of the cylinder head 1 and the cylinder 2.
A cooling exhaust passage 5 is provided in the cooling exhaust guide case 4,
The cooling exhaust air 6 discharged from the cooling air passage 3 is introduced into the cooling exhaust air passage 5.

The exhaust pipe 9 interposed between the exhaust port 7 and the exhaust muffler 8 is housed in the cooling exhaust passage 5, and the exhaust outlet pipe 11 is led out from the passage outlet 10 of the cooling exhaust passage 5. The exhaust air outlet pipe 11 is oriented from the periphery of the air cleaner 12 toward the carburetor 14, and the outlet end opening 13 of the exhaust air outlet pipe 11 is exposed to the intake passage wall 15 of the carburetor 14 from the outside thereof. It is characterized in that the cooling exhaust air 17 emitted from the exhaust end opening 13 of the exhaust air exhaust pipe 11 is blown against the intake passage wall 15 of the carburetor 14 while moving away from the air cleaner 12.

[0007]

As shown in FIG. 1 (A), the cooling air 16 passing through the cooling air passage 3 cools at least one of the cylinder head 1 and the cylinder 2 and receives the heat radiation to raise the temperature of the cooling air. The exhaust air 6 is introduced into the cooling exhaust air passage 5.
This cooling exhaust air 6 passes through the cooling exhaust air passage 5,
The exhaust pipe 9 is cooled, further receives the heat radiation thereof, and further rises in temperature to become high-temperature cooling exhaust air 17, which is guided by the exhaust air exhaust pipe 11 and is discharged from the exhaust end opening portion 13. The cooling exhaust air 17 blows from the outside of the intake passage wall 15 of the carburetor 14 while moving away from the air cleaner 12, and prevents the main nozzle 37 and the throttle valve 38 in the carburetor 14 from being frozen.

[0008]

The present invention has the following effects. High-temperature cooling exhaust air 17 that has been heated by receiving heat from the exhaust pipe 9
Blows against the intake passage wall 15 of the carburetor 14 to prevent the main nozzle 37 and the throttle valve 38 in the carburetor 14 from freezing, so that the main nozzle 37 is blocked and the opening / closing of the throttle valve 38 is disturbed. Deficiencies do not occur. Therefore, engine stall is suppressed or engine rotation is stabilized.

The high-temperature cooling exhaust air 17 is supplied to the air cleaner 12
Since it hits the intake passage wall 15 while moving away from the
It is possible to suppress the intake of the high-temperature cooling exhaust air 17 into the air cleaner 12, avoid an excessive rise in the intake air temperature, and suppress a decrease in intake air charging efficiency and knocking.

Since the exhaust pipe 9 is cooled by the cooling exhaust wind 6 and the pressure of the exhaust gas introduced into the exhaust muffler 8 is lowered, the expansion ratio of the exhaust gas discharged from the exhaust muffler 8 to the atmosphere is reduced, and the exhaust noise is reduced. Is reduced.

[0011]

An embodiment of the present invention will be described with reference to the drawings.
In this embodiment, a forced air cooling type single cylinder gasoline engine is used. The structure of this engine is as follows.
That is, as shown in FIG. 1A, the cylinder head 1 is attached to the upper portion of the cylinder 2 and the head cover 18 is attached to the upper portion thereof. An intake port 19 is opened in a front peripheral wall of the cylinder head 1, an intake pipe 20 is laterally led out from the intake port 19 along the front peripheral wall of the cylinder head 1, and a carburetor 14 is attached to a leading end of the intake pipe 20. The air cleaner 12 is attached to this.

In this embodiment, in order to prevent the freezing of the main nozzle 37 and the throttle valve 38 of the carburetor 14, the following structure is adopted. That is, FIG.
As shown in (A), a cooling air passage 3 for air-cooling the cylinder head 1 and the cylinder 2 is provided, a cooling exhaust air guide case 4 is provided along the peripheral wall of the cylinder head 1, and the cooling exhaust air guide case is provided. A cooling exhaust air passage 5 is provided in the cooling air passage 4, and the cooling exhaust air 6 exhausted from the cooling air passage 3 is introduced into the cooling exhaust air passage 5.

The exhaust pipe 9 interposed between the exhaust port 7 and the exhaust muffler 8 is housed in the cooling exhaust passage 5, and the exhaust outlet pipe 11 is led out from the passage outlet 10 of the cooling exhaust passage 5. The exhaust air outlet pipe 11 is oriented from the periphery of the air cleaner 12 toward the carburetor 14, and the outlet end opening 13 of the exhaust air outlet pipe 11 is made to face the intake passage wall 15 of the carburetor 14 from the outside thereof. The cooling exhaust air 17 emitted from the exhaust end opening 13 of the exhaust air exhaust pipe 11 is made to blow against the intake passage wall 15 of the carburetor 14 while moving away from the air cleaner 12.

With such a structure, as shown in FIG. 1A, the cooling air 16 passing through the cooling air passage 3 cools the cylinder head 1 and the cylinder 2, and receives heat radiation to rise. It is heated and becomes cooling exhaust air 6 and is introduced into the cooling exhaust air passage 5. The cooling exhausted air 6 cools the exhaust pipe 9 in the process of passing through the cooling exhausted air passage 5, receives heat from the exhausted exhaust air 9, and further rises in temperature to become high-temperature cooling exhausted air 17 which is discharged by the exhausted air exhaust pipe 11. It is guided and discharged through its outlet opening 13. Then, the cooling exhaust air 17 blows against the intake passage wall 15 of the carburetor 14 from the outside while moving away from the air cleaner 12, and prevents the main nozzle 37 and the throttle valve 38 from being frozen.

The specific configuration is as follows. Both peripheral walls of the cylinder head 1 and the cylinder 2 are covered with a cooling air guide cover 21, a cooling air passage 3 is formed in the cooling air guide cover 21, and the cooling air 16 generated by the engine cooling fan 22 is guided to the cooling air passage 3. Is done. The engine cooling fan 22 is provided at the front of the crankcase, and the fan case 23
Covered with.

When viewed in a direction parallel to the cylinder axis 24, the cooling air guide cover 21 includes the cylinder head 1 and the cylinder 2.
It is formed in an L shape along the lateral peripheral wall and the rear peripheral wall. The passage start end portion 25 of the cooling air passage 3 is communicated with the fan case 23, and the passage end portion 26 is opened at the rear portions of the cylinder head 1 and the cylinder 2.

The exhaust port 7 is opened at the rear peripheral wall of the cylinder head 1, and the exhaust pipe 9 is led out sideways from the exhaust port 7 along the rear peripheral wall of the cylinder head 1 and the cylinder 2, and a cover mounting stay 31 is attached to the exhaust pipe 9. A cooling and exhaust air guide case 4 is attached via the.

The cooling exhaust guide case 4 is a cylinder head 1.
And the exhaust pipe 9 formed in a horizontally long shape along the rear peripheral wall of the cylinder 2.
Has a shape to cover. As shown in FIG. 2, the exhaust pipe 9 is inclined downward toward its outlet end, and the ceiling wall 35 of the cooling exhaust guide case 4 is also inclined downward in accordance with the inclination of the exhaust pipe 9. The cooling exhaust air 6 introduced into the cooling exhaust air passage 5 is guided to the passage outlet 10 along the ceiling wall 35.

A pipe insertion ring 27 is attached to the passage outlet 10 of the cooling exhaust passage 5 in a direction orthogonal to the cooling exhaust guide case 4, and a start end portion 33 of the exhaust air outlet pipe 11 is loosely fitted thereto. It is plugged in. Then, as shown in FIG. 1 (A), a pipe support stay 29 is fixed to a mounting seat 28 of the fuel tank stay of the cylinder head 1, and a lead end opening of the exhaust lead-out pipe 11 is provided in a tubular portion 30 of the pipe support stay 29. The portion 13 is fitted on the outside and fixed by the band 32. A flexible tube having heat resistance is used for the exhaust gas exhaust pipe 11. The exhaust lead-out pipe 11 is oriented from the rear periphery of the air cleaner 12 toward the carburetor 14.

As shown in FIG. 1B, the outlet end opening 13 of the exhaust outlet pipe 11 faces the intake passage wall 15 while avoiding the float chamber 34 of the carburetor 14. Therefore, it is possible to prevent the high-temperature cooling exhaust air 17 from directly hitting the float chamber 34, and suppress the occurrence of percolation. Further, as shown in FIG. 1 (A), the outlet end opening 13 of the exhaust outlet pipe 11 has a portion of the intake passage wall 15
The main nozzle 37 and the throttle valve 38 are made to face the inside of the body, avoiding the portion where the choke valve 36 is inside. For this reason, the high-temperature cooling exhaust air 17 is intensively blown to the portion where the main nozzle 37 and the throttle valve 38 are liable to be frozen, so that the freezing can be surely prevented.

Although the contents of the embodiment of the present invention are as described above, the present invention is not limited to the contents of the above embodiment. For example, the cooling air passage 3 may be one that cools at least one of the cylinder head 1 and the cylinder 2. Further, a cooling air passage 3 for cooling the cylinder head 1
May be provided in the cylinder head 1. Further, the engine to which the present invention is applied may be another spark ignition type engine such as a gas engine.

[Brief description of drawings]

FIG. 1 is a diagram illustrating an engine according to an embodiment of the present invention, FIG. 1 (A) is a partial cross-sectional plan view, and FIG. 1 (B) is a B direction in FIG. FIG.

FIG. 2 is a sectional view taken along line II-II of FIG.

[Explanation of reference numerals] 1 ... Cylinder head, 2 ... Cylinder, 3 ... Cooling air passage,
4 ... Cooling exhaust air guide case, 5 ... Cooling exhaust air passage, 6 ... Cooling exhaust air, 7 ... Exhaust port, 8 ... Exhaust muffler, 9 ... Exhaust pipe,
10 ... Passage outlet, 11 ... Exhaust air outlet pipe, 12 ... Air cleaner, 13 ... Outlet end opening, 14 ... Carburetor, 1
5 ... intake passage wall, 17 ... cooling exhaust air.

Claims (1)

[Claims] 1. A cooling air passage (3) for air-cooling at least one of the cylinder head (1) and the cylinder (2) is provided, and at least one of the cylinder head (1) and the cylinder (2) is provided. A cooling exhaust air guide case (4) is provided along the peripheral wall, and a cooling exhaust air passage (5) is provided in the cooling exhaust air guide case (4).
Is provided so that the cooling exhaust air (6) discharged from the cooling air passage (3) is introduced into the cooling exhaust air passage (5), and is interposed between the exhaust port (7) and the exhaust muffler (8). The exhaust pipe (9) is housed in the cooling exhaust passage (5),
The exhaust air outlet pipe (11) is led out from the passage outlet (10) of (5), and the exhaust air outlet pipe (11) is directed from the periphery of the air cleaner (12) toward the carburetor (14).
The outlet end opening portion (13) of the exhaust air outlet pipe (11) is exposed from the outside of the intake passage wall (15) of the carburetor (14) and is discharged from the outlet end opening portion 13 of the exhaust air outlet pipe (11). A spark ignition engine characterized in that cooling exhaust air 17 is blown against the intake passage wall 15 of the carburetor 14 while moving away from the air cleaner 12.