JPH0232847Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates to a cylinder head for an overhead valve type air-cooled engine in which a cylindrical valve guide for guiding intake and exhaust valves is inserted into a guide mounting tube.

(Prior art) In the cylinder head of an overhead valve type air-cooled engine, as disclosed in, for example, Japanese Utility Model Publication No. 1081/1981, it is necessary to cool not only the outer periphery of the cylinder head but also specific parts that become hot. is configured to do so.

In other words, the lower wall of the intake passage provided adjacent to the connection between the lower chamber of the rock arm chamber and the side wall;
The cooling air holes are formed on the top surface of the cylinder mounting wall and surrounded by the peripheral wall of the pushrod passage hole, and are arranged so that cooling air flows in the axial direction of the crankshaft, thereby concentrating the high temperature part of the cylinder head. It is designed to cool down.

In this case, the area to be cooled is mainly limited to the bottom wall of the cylinder head.

However, in an actual cylinder head, for example, the valve guide extends into the exhaust passage, so exhaust heat is applied to the valve guide and its guide mounting tube.
As a result, the cylinder head, which is the guide mounting tube, is usually made of aluminum alloy, while the valve guide is made of iron-based alloy. Due to the difference in linear expansion coefficient between the two, the valve guide can easily come out of the cylinder head. Trouble arose.

In order to solve this problem, methods have been taken to increase the tightness with which the valve guide is press-fitted into the cylinder head. Not only is it necessary to increase the overall wall thickness, but increasing the press-fit tightness causes distortion in the inner circumference of the valve guide, causing oil in the rocker arm chamber to flow into the combustion chamber through the gap between the valve and the valve. As a result, the amount of oil consumed increases, and the oil that has flowed into the combustion chamber forms deposits, which become ignition points and cause knocking.

(Purpose of the invention) This invention was created in view of the above problems, and its main purpose is to effectively prevent the valve guide from coming off, reduce oil consumption, and prevent knocking. .

(Structure of the invention) In order to achieve the above object, this invention provides an intake passage almost perpendicular to the axial direction of the crankshaft, and connects the intake valve and the exhaust valve between the centers of both valves. The upper wall of the intake passage, the lower wall of the rocker arm chamber, the guide mounting cylinder, and the side wall forming the push rod through hole are arranged so that the lines correspond to the axial direction of the crankshaft. By forming a cooling air passage whose center is oriented in the axial direction of the crankshaft in the area surrounded by the valve guide, both the valve guide and its guide mounting cylinder are cooled.

(Example) Hereinafter, an example of this invention will be described with reference to the drawings.

FIG. 1 shows a first embodiment of an overhead valve type air-cooled engine, in which 1 is a cylinder and has a piston 2. In FIG. 3 is a cylinder head, and 4 is a head cover.

Here, the cylinder head 3 has a first
It is formed as shown in FIGS.

That is, in Figs. 1 to 5, IN indicates the intake side and OUT indicates the exhaust side. In this case, the cylinder head 3 is made of aluminum alloy, and the combustion chamber 5 is located at the bottom, as shown in Fig. 1. A bottom wall portion 6 forming a
has.

The combustion chamber 5 has an intake port 7 and an exhaust port 8, as shown in FIG. 4, and a spark plug 10 installed in a plug mounting hole 9, as shown in FIG. The above intake port 7 has an IN
From the side, the side L-shaped intake passage 11 is also
From the OUT side, the side L-shaped exhaust passage 12
(Fig. 5) are connected to each other.

In this case, O in Fig. 2 is the axial direction of the crankshaft (not shown), and is the same as the above IN side.
The direction is perpendicular to the line connecting the OUT side.

Here, 11A in FIG. 1 is the intake passage 11.
The lower wall 11B is the upper wall of the intake passage 11. Reference numeral 13 designates a lower rocker arm chamber, which is formed into a concave shape by a lower wall 14 and a side wall 15, and forms one rocker arm chamber together with the head cover 4 provided above.

One of the arm support bosses 17 is provided on the lower wall 14.
A pair of arm support bosses 17 are provided in a protruding manner.
Arm support shaft 1 having a mounting seat 18 made of a nut
9 are screwed together.

This arm support shaft 19 has a locking arm 21.
is supported by the spherical receiving portion 20 so as not to slip upward.

22 is a push rod, and the above-mentioned lock arm 2
1, and in this case, as shown in FIG. 2, it passes up and down through a pair of push rod holes 23, 23 formed through both sides of the intake passage 11.

Reference numeral 24 denotes a guide mounting cylinder, which is formed integrally with the cylinder head 3, and the guide mounting cylinders 24 are arranged in parallel in the axial direction O of the crankshaft.

As shown in FIG. 1, the guide mounting cylinder 24 includes a lower cylinder part that integrally connects the upper and lower sides of the upper wall 11B of the intake passage 11 and the lower wall 14 of the rocker arm chamber, and It consists of an upper cylindrical part that protrudes toward.

A valve guide 25 is press-fitted into each guide mounting cylinder 24, and the intake valve 26 and exhaust valve 27 (second
(Fig.) are slidably inserted into each.

Note that 28 is a valve retainer and 29 is a valve spring.

The characteristic feature of such a cylinder head 3 is that, as shown in FIG.
and exhaust valve 27 are arranged in such a manner that a line connecting the centers of both valves 26 and 27 corresponds parallel to the axial direction O of the crankshaft, and as shown in FIG. , the lower wall 14 of the lower rocker arm chamber 13, and the guide mounting tube 2.
As shown in FIG. 2, an upper cooling air passage 30 whose center is oriented in the axial direction O of the crankshaft is formed in the area surrounded by the side wall 23A forming the pushrod passage 23 and the push rod passage 23. It has been done.

In this case, the upper cooling air passage 30 is one of the cooling air passages formed between the bottom wall 6 and the lower wall 14 of the cylinder head 3, as shown in FIG. The lower cooling air passage 31 is formed by a branched passage at the upper part.
is formed by its lower passage which branches off.

In FIG. 2, 32 is a stud bolt through hole, 33 is an oil inflow hole, and 34 is an oil outflow hole.

On the other hand, the ones shown in Figures 6 to 8 are
In this second embodiment, as shown in FIG. 6, the exhaust passage 12 is provided parallel to the axial direction O of the crankshaft. Further, as shown in FIG. 8, a pair of upper and lower cooling promotion fins 35 are integrally provided on the downstream side of the outer peripheral wall of the intake passage 11 to protrude.

Therefore, in the above configuration, as shown in FIG.
The first
As shown in the figure, the area surrounded by the upper wall 11B of the intake passage 11, the lower wall 14 of the lower rocker arm chamber 13, the guide mounting tube 24, and the side wall forming the push rod through hole 23 As shown in FIG. 2, since the upper cooling air passage 30 is formed with its center facing in the axial direction O of the crankshaft, the cooling air flows from the cooling fan (not shown) provided at the shaft end of the crankshaft to the second cooling fan. Flowing straight in the direction of arrow X in the figure, the guide mounting tube 24 and the valve guide 25
and cooling.

Due to this cooling, even if the guide mounting cylinder 24 and the valve guide 25 are made of different materials and have a difference in linear expansion coefficient as described above, they are hardly affected by thermal effects, so that the valve guide from the guide mounting cylinder 24 to the valve guide 25
There is no risk of it coming off.

In this case, as shown in FIG. 3, the cooling air cools the intake passage 11, so the intake air is cooled, and as a result, the output of the engine can be increased. especially,
In the embodiment described above, since the intake passage 11 is cooled from both the upper and lower sides, the intake air can be cooled more effectively.

Furthermore, as shown in FIG. 1, since the lower wall 14 is also cooled, the lubricating oil flowing at the bottom of the lower rocker arm chamber 13 is cooled through the lower wall 14, thereby effectively preventing seizure at each lubricating part. It can be prevented.

Furthermore, since the guide mounting tube 24 is provided in a manner reinforced by the two-step wall formed by the upper wall 11B of the intake passage 11 and the lower wall 14 located apart from above, the guide mounting tube 24 To obtain high strength without increasing the wall thickness of a press-fit receiving part (24).

As a result, the distortion of the valve guide 25 is suppressed to a low level, and the variation in its inner diameter dimension is also reduced, so that the distance between the valve guide 25 and the intake valves 26 and 27 is also suppressed to a small value, and as a result, the lower rocker arm chamber The oil accumulated in 13 is in the combustion chamber 5.
Since the oil does not flow into the combustion chamber 5, the amount of oil consumed can be kept to a sufficiently low level, and the generation of the deposits in the combustion chamber 5 can be suppressed, thereby preventing knocking.

Further, in the case of the above embodiment, the bottom wall portion 6 of the cylinder head 3 is also cooled through the lower cooling air passage 31.

Furthermore, in the case of the second embodiment, as shown in FIG. 6, the exhaust passage 12 is provided along the upper and lower cooling passages 30 and 31, so that the exhaust passage 12, which tends to heat up particularly, is effectively can be cooled down. Further, as shown in FIG. 8, if a cooling promotion fin 35 is provided on the downstream side of the intake passage 11, the intake passage 1 can be cooled more effectively.

(Effects of the invention) As explained above, according to this invention, both the valve guide and its guide mounting tube are cooled, which prevents the valve guide from coming off and reduces oil consumption. This can be suppressed and prevent knocking. Furthermore, since the cooling air cools the intake passage, the intake air is cooled, and as a result, the output of the engine can be increased, and since the cooling air also cools the lower wall of the rocker arm chamber, the seizure described above can be prevented.

[Brief explanation of drawings]

Fig. 1 is a vertical sectional side view of an overhead valve type air-cooled engine showing the first embodiment of this invention, Fig. 2 is a plan view along the line shown in Fig. 1 with the cylinder head taken out, and Fig. 3 is Fig. 2. -A cross-sectional view of the line, Fig. 4 is a bottom view of the cylinder head, Fig. 5 is Fig. 4-
6 is a plan view of the cylinder head showing the second embodiment, FIG. 7 is a sectional view taken along the line of FIG. 6, and FIG. 8 is a sectional view taken along the line of FIG. 6. 11... Intake passage, 11B... Upper wall of intake passage, 14... Lower wall of rocker arm chamber, 23...
Push rod passage hole, 23A...Side wall of push rod passage hole, 24...Guide mounting tube, 25...
...Valve guide, 26...Intake valve, 27...
Exhaust valve, 30... Upper cooling air passage, O... Axial direction of the crankshaft.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) The intake passage is provided almost perpendicular to the axial direction of the crankshaft, and the intake valve and the exhaust valve are arranged so that the line connecting the centers of both valves is in the direction of the crankshaft. They are arranged parallel to each other in the axial direction, and are surrounded by the upper wall of the intake passage, the lower wall of the rocker arm chamber, the guide mounting tube, and the side wall forming the push rod passage. A cylinder head for an overhead valve type air-cooled engine, characterized in that a cooling air passage whose center is oriented in the direction of the axis of the crankshaft is formed in a portion thereof. (2) Utility model registration claim 1, in which the center of the exhaust passage is parallel to the axial direction of the crankshaft and is provided adjacent to the cooling air passage.
The cylinder head of the overhead valve type air-cooled engine described in .