JPH045712Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial field of application> The present invention relates to a cylinder head cooling device for a forced air-cooled overhead valve engine.
To provide a cylinder head which can be powerfully cooled by smoothly passing cooling air between exhaust ports.

<Prior art> The basic structure of the cooling system for an overhead valve type air-cooled valve engine, which is the object of the present invention, is as shown in FIGS. 1 and 4. A longitudinal air passage 5 is run vertically between the intake/exhaust ports 2, 3 and the push rod chamber 4, and a cross air passage 6 is run transversely between the intake/exhaust ports 2, 3 to prevent cross wind. The outlet 7 of the passage 6 is communicated with the middle part of the longitudinal air passage 5, and the part of the longitudinal air passage 5 that is upwind of the outlet 7 of the transverse air passage 6 is defined as the upstream air passage part 8, and The cooling air passing through the upstream air passage 8 and the cooling air passing through the cross-sectional air passage 6 are configured to merge with each other and pass to the downstream air passage 10. belongs to.

As a conventional technology of this type,
As shown in Japanese Patent No. 183225 (see Fig. 4), one longitudinal air passage 5 is provided before and after the cylinder head 1, and a transverse air passage 6 is connected to the center of the longitudinal air passage 5. be.

In this case, in order to combine the inlet of the intake port 2 and the outlet of the exhaust port 3 in the cylinder, the gap between the two ports 2 and 3 becomes close, and the cross-sectional area of the cross-sectional air passage 6 to be provided in the gap becomes considerably narrow.

<Problems to be solved by the invention> In the above-mentioned conventional technology, the cross-sectional air passage 6 is narrow and its entrance 50 is open on the side of the cylinder head 1, so the cooling air guided rearward by the baffle plate is , it is difficult to enter the cross air passage 6 from the side entrance 50, and the air passage resistance is also large.

Moreover, the outlet 7 of the cross-wind passage 6 is also connected to the inlet 50.
Since the cooling air flowing from the transverse air passage 6 to the longitudinal air passage 5 is thin, the area that comes into contact with the cooling air flowing through the longitudinal air passage 5 is small, and the cooling air from the transverse air passage 6 flows into the longitudinal air passage 5. The rate of extraction due to the viscosity of the cooling air in step 5 also decreases.

As a result, the amount of cooling air flowing through the cross air passage 6 is reduced, and the cooling air is disposed in the gap between the two ports 2 and 3 in the cylinder head 1, especially in the rear part on the opposite side from the cooling fan 51 despite the high temperature. The cooling performance of the peripheral wall portion of the exhaust port 3 is degraded.

The technical problem of this invention is to improve the cooling performance of the gap between the intake and exhaust ports.

<Means for solving the problems> Means for achieving the above problems will be described below using drawings corresponding to embodiments.

That is, the present invention provides a cooling system for a cylinder head of a forced air-cooled overhead valve engine having the above-mentioned basic structure, in which the starting end 12 of the downstream side air passage section 10 of the longitudinal air passage 5 is Passage cross-sectional area A
is larger than the passage cross-sectional area B of the terminal end 24 of the upstream air passage section 8, and the pressure at the outlet 7 of the cross air passage 6 is increased by the cooling air flowing from the upstream air passage section 8 to the downstream air passage section 10. It is characterized in that it is configured so that the cooling air flowing through the cross-sectional air passage 6 is sucked into the downstream air passage portion 10 by lowering the cooling air.

<Operation> Downstream passage cross-sectional area A>Upstream passage cross-sectional area B, and since the starting end 12 of the downstream air passage section 10 is enlarged compared to the terminal end 24 of the upstream air passage section 8, At the exit 7 of the cross-sectional air passage 6, the area where the cooling air flowing through the cross-sectional air passage 6 comes into contact with the cooling air from the longitudinal air passage 5 increases, and the viscosity of the cooling air from the longitudinal air passage 5 causes the cooling air to flow from the cross-sectional air passage 6. In addition to being efficiently drawn out (that is, negative pressure is generated at the outlet 7), this cooling air smoothly enters the downstream air passage portion 10 having a large area.

For this reason, the downstream side air path portion 10 from the cross air path 6
The amount of cooling air flowing through increases, and the gap between both ports 2 and 3 is strongly cooled.

<Effects of the invention> The amount of cooling air flowing through the cross-sectional air passage is increased and the gap between the intake and exhaust ports is strongly cooled, improving the overall cooling performance of the cylinder head.

<Example> Hereinafter, an example of the present invention will be described based on the drawings.

Fig. 1 is a cross-sectional plan view of the cylinder head, Fig. 2 is a rear view of the cylinder head, and Fig. 3 is a plan view of a forced air-cooled overhead valve gasoline engine. A cooling fan 11 interlocked with the crankshaft is housed in an air guide case 14, and a cylinder head 1 and a head cover 12 are sequentially fixed above the cylinder block of an engine E.

Intake port 2 near the front of the cylinder head 1 above
Also, open the exhaust port 3 toward the rear,
An air cleaner 16 is connected to the intake port 2 via a carburetor 15, and a muffler 17 is connected to the exhaust port 3.

Then, a push rod chamber 4 is provided on the left side of the intake/exhaust ports 2, 3, and a vertical air passage 5 is passed through the wall 18 between the ports 2, 3 and the push rod chamber 4 in the front and back direction. port 2,3
A transverse air passage 6 is left in the left-right direction in the wall 20 between the ports 2 and 3, and its outlet 7 is communicated with the vicinity of the middle position of the longitudinal air passage 5, and its inlet 22 is formed at the center right side of both ports 2 and 3. The recess 23 is opened.

Of the longitudinal air passages 5, the upwind side, i.e., the front side, of the outlet 7 of the cross-sectional air passage 6 is defined as an upstream air passage section 8, and the leeward side, that is, the rear side of the exit 7, is defined as a downstream air passage section 10. As shown in FIG. to form.

Further, the longitudinal air passage 5 extends from the starting end 12 of the downstream air passage portion 10 to the terminal end 24 of the upstream air passage portion 8.
The path is intermittently enlarged so that the passage cross-sectional area A at the starting end 12 is greater than the passage cross-sectional area B at the terminal end 24.

As a result, the cooling air generated by the cooling fan 11 is guided to the air guide case 14 and blows backward through the longitudinal air passage 5, but at that time, the cooling air is introduced into the starting end 12 of the expanded downstream air passage portion 10. Since the cooling air flowing through the longitudinal air passage 5 attempts to draw out the cooling air from the cross air passage 6 with its viscosity, the pressure at the outlet 7 of the cross air passage 6 is lower than that at its inlet 22, and The cooling air flowing through the cross-sectional air passage 6 is sucked into the downstream air passage portion 10, increasing the amount of cooling air in the cross-sectional air passage 6, and improving the cooling efficiency in the gap between the intake and exhaust ports 2 and 3.

In this embodiment, the exhaust port 3 is located on the rear side of the longitudinal air passage 5, and the intake port 2 is located on the rear side of the longitudinal air passage 5.
However, both ports 2 and 3 may be placed upside down.

However, in this embodiment, FIGS.
As shown in the figure, the passage cross-sectional area of the downstream air passage portion 10 is formed larger than that of the upstream air passage portion 8,
By arranging the intake port 2 in an inclined manner with respect to the upstream air passage portion 8 and the exhaust port 3 in parallel with the downstream air passage portion 10, the exhaust port 3
By increasing the amount of cooling air on the side, the exhaust port 3 can be powerfully cooled.

[Brief explanation of the drawing]

Figures 1 to 3 show embodiments of the present invention;
2 is a cross-sectional plan view of the cylinder head, FIG. 2 is a rear view of the cylinder head, FIG. 3 is a plan view of a forced air-cooled overhead valve gasoline engine, and FIG. 4 is a view equivalent to FIG. 1 showing the prior art. 1...Cylinder head, 2...Intake port, 3
...Exhaust port, 4...Push rod chamber, 5...
...Longitudinal wind path, 6...Cross wind path, 7...Exit of 6,
8...Upstream air passage portion, 10...Downstream air passage portion, 24...Terminal portion of 8, E...Forced air cooling overhead valve engine.

Claims (1)

[Claims for Utility Model Registration] 1. A longitudinal air passage 5 runs longitudinally between the intake/exhaust ports 2, 3 and the push rod chamber 4 within the wall of the cylinder head 1 of the forced air-cooled overhead valve engine E. At the same time, a transverse air passage 6 is run transversely between the intake and exhaust ports 2 and 3, and the outlet 7 of the transverse air passage 6 is communicated with the middle part of the longitudinal air passage 5. The windward side of the outlet 7 of 6 is defined as an upstream air passage section 8, and the leeward side thereof is defined as a downstream air passage section 10. The cooling air that has passed is merged with the downstream air passage section 10.
In a cooling system for a cylinder head of a forced air-cooled overhead valve engine configured to allow air to pass through the longitudinal air passage 5 at a portion facing the outlet 7 of the cross air passage 6.
The passage cross-sectional area A of the starting end 12 of the downstream air passage portion 10 is expanded to be larger than the passage cross-sectional area B of the terminal end 24 of the upstream air passage portion 8, so that the passage cross-sectional area A of the starting end 12 of the downstream air passage portion 10 is expanded from the upstream air passage portion 8 to the downstream air passage. Forced air cooling characterized in that the pressure at the outlet 7 of the cross-sectional air passage 6 is reduced by the cooling air flowing into the section 10, and the cooling air flowing through the cross-sectional air passage 6 is sucked into the downstream air passage section 10. Overhead valve engine cylinder head cooling system. 2. The cooling device for a cylinder head of a forced air-cooled overhead valve engine as claimed in claim 1, wherein the exhaust port 3 is formed by running in parallel with the downstream air passage section 10.