JPS6337456Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) This invention relates specifically to a breather device for an overhead valve type air-cooled engine.

(Prior Art) For example, general-purpose small air-cooled engines are required to be compact, and this also applies to overhead valve type engines, which are considered advantageous in terms of combustion efficiency.

In the overhead valve type air-cooled engine mentioned above, it is common to place an air cleaner near the carburetor, as in the side valve type, but in this case, the air cleaner itself increases the size of the engine, making it difficult to make it more compact. cannot be achieved effectively.

As an idea to meet this demand, for example, the Utility Model Publication No. 58-51398, which was applied to side valve type engines,
There is a technique shown in the publication. Its structure is such that the air cleaner is housed in a space within the fan case, thereby making it possible to make the engine more compact. However, since the air cleaner in this case opposes the air flow path in the fan case, it impedes the smooth flow of cooling air, and as a result, the cooling performance of the engine is impaired.

On the other hand, overhead valve type air-cooled engines, like other types of engines, are equipped with a breather device for the purpose of suppressing the release of oil mist from the crank chamber.
There is one shown in Publication No. 58-156113.

The breather device in this case communicates the crank chamber and the rocker arm chamber (first expansion chamber) through a passage,
By providing a breather chamber (second expansion chamber) between the rocker arm chamber and the air cleaner, a so-called exhalation effect is created between the crank chamber and the air cleaner to suppress the release of oil mist.

However, in the above-described conventional technology, large pressure fluctuations occur downstream of the cleaner element due to pulsations caused by intake air from the engine. This pressure fluctuation also causes the pressure in the breather chamber to fluctuate, which causes a reduction in the oil mist separation function in the breather chamber. As a means for suppressing pressure fluctuations in the breather chamber, this prior art provides a check valve. As a result, the structure of the engine becomes complicated, and the check valve comes into close contact with oil, which may cause a decrease in breather function.

In addition, in the above-mentioned conventional technology, since the communication means between the breather chamber and the rocker arm chamber is provided by a tube, there is a possibility that the tube may come off due to vibration or heat influence, and the tube may not function effectively as a breather. arise.

(Purpose of the invention) This invention was made in view of the above.It aims to reduce the size of the engine without impairing its cooling performance, allows for a simpler structure of the engine, and also allows the breather function to be maintained at all times. The purpose is to make it effective.

(Structure of the invention) In order to achieve the above object, in this invention, first, a breather chamber inlet passage that communicates the rocker arm chamber with the breather chamber is integrally formed in the cleaner case. Further, by arranging a fan case that accommodates a cooling fan in correspondence with the cylinder and cylinder head, a side space is provided at a position corresponding to the rocker arm chamber, and an air cleaner is arranged in this side space. A fan case is communicated upstream of the cleaner element in the air cleaner.

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

In FIG. 1, a crankcase 1 has a crank chamber 2 formed therein. In this case, a crankshaft 3 extends vertically and is installed in a predetermined vehicle or equipment. A cylinder 4 is integrally provided on one side of the crankcase 1, and a piston 6 having a connecting rod 5 is provided within the cylinder 4, and the piston 6 in this case reciprocates in the horizontal direction. .

A cylinder head 7 is provided at one horizontal end of the cylinder 4, and the cylinder head 7 is provided with an intake valve 10 and an exhaust valve 11 for opening and closing an intake port 8 and an exhaust port 9, respectively. . Both valves 10 and 11 are opened and closed by a rocker arm 12 which projects from one side of the cylinder head 7 and is driven by a camshaft, tappet and bushing rod (not shown) inside the crankcase 1.

These two valves 10, 11 and the rocker arm 12
A head cover 13 is attached to cover the head cover 13, and a rocker arm chamber (first pressure fluctuation absorption chamber) 14 is formed inside the head cover 13.

In this case, the rock arm chamber 14 and the crank chamber 2
are communicated with each other by two passages, and the upper passage is a first passage 15 that guides the air and oil mist in the crank chamber 2 to the rocker arm chamber 14. On the other hand, the lower passage is a second passage 16 for returning oil from the rocker arm chamber 14 to the crank chamber 2.

On the other hand, on one side of the upper part of such an overhead valve type air-cooled engine, there is a fan case 18 having a cooling air intake part 17 to which a recoil starter (not shown) is attached.
is installed, and the cooling air from the cooling air intake (not shown) formed in the cooling air intake part 17 is sent into the cylinder 4 and cylinder head 7 side as shown by arrow A by a cooling fan (not shown). .

One end of the fan case 18 on the head cover 13 side is an inclined wall 18a, and this inclined wall 18
A side space is formed at a location corresponding to the horizontal direction a and the vertical direction above the head cover 13.
That is, by arranging the fan case 18 in correspondence with the cylinder 4 and the cylinder head 7, a side space is provided at a position corresponding to the rocker arm chamber 14. An air cleaner 19 and a breather chamber 20 are arranged using a location corresponding to this side space.

The air cleaner 19 has a cleaner case 21
The cleaner case 21 is integrally formed with the head cover 13 of resin, and the cleaner element 22 is disposed at the middle level of the head cover 13. In this way, a cleaner inlet 23 is formed at the portion where the cleaner case 21 of the air cleaner 19 and the inclined wall 18a of the fan case 18 are in contact with each other.
A portion of the cooling air indicated by arrow A is taken into the air cleaner 19 as intake air indicated by arrow B. The air taken in is purified by the cleaner element 22 and is sent to the carburetor 26 in FIG. 2 through the cleaner outlet 25 formed in the downstream space (second pressure fluctuation absorption chamber) 24 of the cleaner element 22. . As shown in FIG. 1, the cleaner case 21 has a removable cleaner cover 2 on its upper end surface.
7 is installed.

In the air cleaner 19, as shown in FIG. 2, a breather chamber 20, which is cylindrical when viewed from the front of the engine, is integrally formed within a cleaner case 21. This breather chamber 20 is
is arranged at the center of the cleaner case 21 in the width direction,
As shown in FIG. 1, it communicates with the rocker arm chamber 14 of the head cover 13 via a breather chamber inlet passage 28. This inlet passage 28 is connected to the cleaner case 2.
1 is integrally formed. Here, 29 is a rocker arm chamber outlet, 30 is a breather chamber inlet, and a breather chamber outlet 32 is opened at an upper position higher than this breather chamber inlet 30.
is covered from above with a cleaner element 22. In addition, 33 is a common partition wall, and head cover 1
3 and the air cleaner 19 are separated by one integral wall. Furthermore, 35 in FIG. 2 indicates a muffler.

Next, the operation of the above configuration will be explained.

The cooling air is sent to the cylinder 4 side as shown by arrow A, and a portion of it is sent to the air cleaner 19 through the cleaner inlet 23 as shown by arrow B.
It is sent inside for intake. On the other hand, the compressed gas in the crank chamber 2, including blow-by gas, is
As shown by arrow C, the oil is fed into the rocker arm chamber 14 through the first passage 15, and here, since the rocker arm chamber 14 acts as one expansion space, it is separated into a gas component and an oil mist, and the gas component is fed into the rocker arm chamber 14. The oil is returned to the breather chamber 20 through the outlet 29 and, after being converted into lubricating oil, to the crank chamber 2 through the second passage 16 as shown by arrow D. Since the breather chamber 20 has the breather chamber outlet 32 located higher than the inlet 30 and is covered with the element 22, only gas is captured by the element 22 at the breather chamber outlet 32. On the other hand, oil flows from the breather chamber inlet 30 to the second rocker arm chamber outlet 29 in FIG.
It is returned to the passage 16.

In the above configuration, this invention arranges the fan case 18 in correspondence with the cylinder 4, creating a side space at a position corresponding to the rocker arm chamber 14, and since the air cleaner 19 is arranged in this side space, the space is saved. be used effectively and therefore
Engine miniaturization is achieved. On the other hand, with this arrangement, the air cleaner 19 does not obstruct the flow of the cooling air A within the fan case 18, so there is no risk that the cooling performance of the engine will be impaired.

In addition, not only the breather chamber 20 but also the breather chamber entrance passage 28 are integrally formed in the cleaner case 21, so unlike the conventional case, the breather chamber inlet passage 28 is formed by a tube.
Since there is no need to communicate the breather chamber 20 and the rocker arm chamber 14, the tube will not come out unexpectedly. Therefore, the breather function is always performed.

Note that the head cover 13 and the breather chamber 20
(or the cleaner case 21) may be formed separately and connected via a gasket between the two to establish communication.

Incidentally, pressure fluctuations in the breather chamber 20 cause a decrease in the oil mist separation function in the breather chamber 20. On the other hand, in this invention, the first passage 15
The pressure fluctuations acting through the rocker arm chamber 14 are effectively absorbed by the rocker arm chamber 14 as the first pressure fluctuation absorption chamber. On the other hand, pressure fluctuations accompanying the pulsation of intake air are effectively absorbed by the downstream (downstream of the cleaner element 22) side space 24 as a second pressure fluctuation absorption chamber and the internal space of the fan case 18, and the cleaner element Since the internal space of the fan case 18 is communicated with the upstream side of the cooling fan 22, the cooling air B from the cooling fan is actively sent into the downstream space 24, so that this pressure fluctuation is reduced. In this way, pressure fluctuations upstream and downstream of the breather chamber 20 are reduced, so pressure fluctuations in the breather chamber 20 are suppressed to a sufficiently low level. Therefore, the breather chamber entrance 30 inside the breather chamber 20
There is no need to provide a breather valve (check valve) on the side, which simplifies the structure and prevents the breather function from being deteriorated due to the breather valve coming into close contact with oil.

By the way, although the above-mentioned engine is a vertical type, it may also be a horizontal type.
Further, the cleaner inlet 23 may be of a type that does not communicate with the inside of the fan case 18.

Further, as shown in FIG. 3, the cleaner case 21 containing the breather chamber 20 is attached to the head cover 1.
3 and may be formed integrally with the fan case 18. In that case, the cleaner case 21 and head cover 13 are connected in a sealed state. That is, by inserting the cylindrical protrusion 41 forming the breather chamber inlet passage 28 into the connecting hole provided in the head cover 13 via, for example, the grommet 42, the breather chamber 2 is sealed.
0 and the rocker arm chamber 14 are communicated with each other.

Note that the embodiment shown in FIG. 3 can also be applied to a horizontal type.

(Effects of the invention) As explained above, according to this invention, the fan case is arranged in correspondence with the cylinder and the cylinder head, and the air cleaner is arranged in the side space corresponding to the rocker arm chamber, which reduces the size of the engine. can be achieved without compromising engine cooling performance. Furthermore, since not only the breather chamber but also the breather chamber entrance passage are integrally formed with the cleaner case, the connection state between the breather chamber and the breather chamber entrance passage can be maintained at all times, so that the breather function is always exhibited. In addition, since the internal space of the fan case is communicated upstream of the cleaner element, cooling air is actively sent into the space downstream of the cleaner element, reducing pressure fluctuations in the breather chamber. There is no need to provide a valve, and as a result, the structure of the engine is simplified, and the breather function of the valve does not deteriorate.

[Brief explanation of the drawing]

Fig. 1 is a side view of an overhead valve type air-cooled engine partially showing an embodiment of this invention in cross section, and Fig.
A sectional view taken along the line - in the figure, and FIG. 3 is a partially sectional side view showing another embodiment. 2...Crank chamber, 4...Cylinder, 7...Cylinder head, 14...Rocker arm chamber, 15,
16...Aisle, 18...Fan case, 19...
Air cleaner, 20...breather chamber, 21...cleaner case, 22...cleaner element, 2
8...breather chamber entrance passage, 30...breather chamber entrance, 32...breather chamber exit.

Claims (1)

[Claim for Utility Model Registration] It has a cooling fan that cools the engine, the crank chamber and the rocker arm chamber are connected through a passage, and the rocker arm chamber is used as a pressure fluctuation absorption chamber, and the rocker arm chamber is connected to the rocker arm chamber via a breather chamber entrance passage. An overhead valve type air-cooled engine that communicates with a breather chamber, the breather chamber is integrally formed with a cleaner case of an air cleaner, the breather chamber outlet is set higher than the breather chamber inlet, and the breather chamber outlet is covered with a cleaner element. , the breather chamber inlet passage is integrally formed in the cleaner case, and the fan case housing the cooling fan is arranged in correspondence with the cylinder and the cylinder head, thereby providing a side space at a position corresponding to the rocker arm chamber; An overhead valve type air-cooled engine in which the above-mentioned air cleaner is arranged in a side space, and an internal space of a fan case is communicated upstream of a cleaner element in the air cleaner.