JP2002349227A - Four cycle engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize overall height size, and reduce weight and size. SOLUTION: The four cycle engine is provided with a breather device separating blow-by gas into oil and gas, and opening and closing an inlet valve 28 and an exhaust valve 29 by a pair of rocker arms 31a and 31b operated in a valve chamber 27 by receiving driving force from a cam rotating in a cam chamber in synchronization with rotation of a crankshaft. The rocker arms 31a and 31b are arranged in states slanted in the mutually separating direction toward another end in a side opposite of one end which is a side of the inlet valve 28 and the exhaust valve 28, and a gas-liquid separating chamber 27 of the breather device is arranged using a space secured between the rocker arms 31a and 31b. By this, the need for securing an extra space in an upper part of the valve chamber 27 is eliminated, the overall height is minimized, and the weight and size are reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lubricating device for a four-cycle engine mainly used for a portable working machine or the like.

[0002]

2. Description of the Related Art For example, drive engines used in portable working machines such as chain saws, lawnmowers, and mowers include:
In general, a two-stroke engine is employed because of its simple structure and light weight. However, 2
In the case of a cycle engine, there is a problem that the amount of hydrocarbons in the exhaust gas discharged to the atmosphere is large, and this is a bottleneck in purifying the exhaust gas and preserving the environment. On the other hand, in the case of the four-cycle engine, the amount of hydrocarbons in the exhaust gas is smaller than in the case of the two-cycle engine. The low noise is also advantageous in terms of the working environment. For this reason, recently, adoption of a four-stroke engine has been studied for portable work machines such as a chain saw and a mower.

[0003]

As a four-cycle engine mounted on a portable working machine, a pair of rocker arms for opening and closing an intake / exhaust valve, as disclosed in JP-A-11-125107, is used as a cylinder head. There is an engine that is arranged in parallel with the valve operating chamber on the side, and has a gas-liquid separation chamber as a breather device above the valve operating chamber. However, a gas-liquid separation chamber is installed above the valve operating chamber. The configuration goes against the downsizing because the overall height of the engine is increased.

Japanese Patent Application Laid-Open No. 2000-199419 discloses that oil mist is separated into oil and air in a valve operating chamber accommodating a rocker arm for opening and closing an intake / exhaust valve. The cause of the increase in the overall height of the engine as in the example has been eliminated. However, because the distance between the pair of rocker arms and the distance between the pair of push rods that transmit the power of the cam to these rocker arms are narrow, the spark plug must be mounted on the surface of the cylinder block opposite to the push rod. Absent. As a result,
When a working device such as a power sprayer or a water pump driven by the engine is mounted on the opposite side of the push rod, the spark plug is hidden behind the working device and the operability of attaching / detaching work (maintenance) deteriorates. .

It is an object of the present invention to reduce the overall height and reduce the weight and size.

Another object of the present invention is to make it possible to mount the spark plug compactly on the surface of the cylinder block on the push rod side.

[0007]

According to the first aspect of the present invention,
A breather device that separates blow-by gas into oil and gas is provided, and a pair of rocker arms that operate in the valve operating chamber by receiving a driving force from a cam that rotates in the cam chamber in synchronization with the rotation of the crankshaft. In a four-stroke engine of a type that opens and closes an exhaust valve, the rocker arm is disposed so as to be inclined in a direction away from each other as going from one end on the intake valve side and the exhaust valve side to the other end on the opposite side, The gas-liquid separation chamber of the breather device is disposed between the pair of rocker arms.

Therefore, by arranging the pair of rocker arms at an angle, it is possible to secure a space for arranging the gas-liquid separation chamber between them, and it is possible to reduce the overall height.

According to a second aspect of the present invention, in the first aspect of the invention, a pair of push rods for transmitting the driving force of the cam to the rocker arm communicates the cam chamber and the valve operating chamber. Are housed in a pair of push rod passages formed in the cylinder block, and the valve operating chamber shields the flow of oil mist from the opening on the outlet side of the push rod passage to the gas-liquid separation chamber. An oil mist guide wall leading to the intake valve and the exhaust valve is provided.

Therefore, as in the case of the first aspect, the overall height can be reduced. The oil mist supplied to the cam chamber flows through the push rod passage to the valve operating chamber.However, the amount of oil mist flowing to the valve operating chamber is suppressed by the oil mist guide wall toward the gas-liquid separation chamber, and the oil mist is supplied to the intake / exhaust valve. Flows enough. Accordingly, the intake and exhaust valves can be sufficiently lubricated without imposing a load on the gas-liquid separation operation in the gas-liquid separation chamber.

According to a third aspect of the present invention, in the first aspect of the invention, a pair of push rods for transmitting the driving force of the cam to the rocker arm communicates the cam chamber and the valve operating chamber. A plug mounting part for detachably mounting a spark plug is provided at a position between the pair of push rod passages in the cylinder block, which is accommodated in a pair of push rod passages formed in the cylinder block. I have.

Therefore, as in the case of the first aspect, the overall height can be reduced. Further, the spark plug can be compactly mounted on the surface of the cylinder block on the push rod side.

According to a fourth aspect of the present invention, in the second aspect of the invention, a plug mounting portion for detachably mounting a spark plug is disposed at a position between the pair of push rod passages in the cylinder block. Has been established.

Therefore, the same effects as those of the second and third aspects can be obtained.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described with reference to the drawings. 1 is a vertical side view of a four-cycle engine, FIG. 2 is a vertical front view of a four-cycle engine, FIG. 3 is a vertical front view taken along a line AA in FIG. 1, and FIG.
5, FIG. 5 is a longitudinal sectional front view taken along the line CC in FIG. 1, FIG. 6 is a horizontal sectional view showing the inside of the valve operating chamber, FIG. 7 and FIG. FIG. 9 is a horizontal sectional view showing the inside of the valve operating chamber, and FIG.
FIG. 10 is a partial front view showing a mounted state of the spark plug.

The engine body 1 of the four-cycle engine is
It has a crankcase 2, a cylinder block 3 fixed to the upper part thereof, a cylinder head 4 formed integrally with the cylinder block 3, and a rocker cover 5 attached to the upper part of the cylinder head 4. The crankcase 2 is divided into two parts in the axial direction of the crankshaft 9 with a center of a cylinder 10 described later as a boundary. The two divided crankcases 2a and 2b are integrally connected via a liquid gasket. Is formed.
A portion surrounded by the divided crankcases 2a and 2b is a crankcase 6.

In the crank chamber 6, there is provided a crankshaft 9 which is supported by a bearing 7 and a bearing 8 which is sealed on one side.
A piston 11 that reciprocates in a cylinder 10 formed therein is connected via a connecting rod 12. Further, a cam chamber 14 is formed in the split crankcase 2b by a bearing 8 and a partition wall 13 sealed on one side. A crank gear 15 is fixed to the crank shaft 9. Further, both ends of the crankshaft 9 have the crank chamber 6.
The crankshaft 9 is projected outside and the split crankcase 2
Oil seals 16 and 17 are attached to portions penetrating through a and 2b. A flywheel 19 having a cooling fin 18 for air cooling is fixed to one end of the crankshaft 9.
At the other end, a recoil starter pulley 20 for starting the engine
Is attached.

The cam chamber 14 is provided with a cam gear 21 meshed with the crank gear 15, and the cam gear 21 is integrally provided with a cam 22 which functions as an intake cam and an exhaust cam. The cam chamber 14 is formed by the cylinder block 3, the divided crankcase 2b, and the cam chamber cover 23. The cam gear 21 is rotatably supported by a cam shaft 24 supported by the cylinder block 3. Further, a pair of cam followers 25 that rotate in synchronization with the rotation of the cam 22 are provided.
a and 25b (see FIGS. 2 and 3) are swingably supported by a cam follower shaft 26 supported by the cylinder block 3.

The space covered by the rocker cover 5 in the upper part of the cylinder head 4 is a valve operating chamber 27, in which the intake valve 2 supported by the cylinder head 4 is located.
8 and an exhaust valve 29, a spring 30 for urging them in the valve closing direction, and rocker arms 31a and 31b for pressing the intake valve 28 and the exhaust valve 29 in the valve opening direction are housed therein (FIGS. 2 to 6). 4).

The cam chamber 14 and the valve operating chamber 27 communicate with each other through push rod passages 33a and 33b. The push rod passages 33a and 33b accommodate push rods 32a and 32b having one ends in contact with the rocker arms 31a and 31b and the other ends in contact with the cam followers 25a and 25b.

The cylinder head 4 has an intake port 34 for supplying air-fuel mixture to a combustion chamber in the cylinder 10 and an exhaust port 35 for exhausting exhaust gas from the combustion chamber.
Are formed (see FIG. 5). A carburetor 36 and an air cleaner 37 are sequentially connected to a tip of the intake port 34, and a muffler 38 is connected to a tip of the exhaust port 35 (see FIG. 2). Further, a spark plug 39 is attached to the cylinder 10. The cowling 40 is provided so as to cover the components, guide cooling air generated from the cooling fins 18 for air cooling, and cool the components.

An oil tank 41 is fixed below the crankcase 2. As shown in FIGS. 1 and 3, an oil storage chamber 42 for storing lubricating oil is formed in the oil tank 41. ing. The connection between the oil storage chamber 42 and the cam chamber 14 is connected by a supply passage 43 that supplies the oil mist generated in the oil storage chamber 42 to the cam chamber 14. One end of the supply channel 43 is connected to a supply channel 44 inserted into the oil storage chamber 42.
The other end is opened as an opening 45 near the outer peripheral surface 22 a of the cam 22 of the cam chamber 14. The position of the opening 45 is below the cam 22 in the upright engine state in which the cylinder head 4 is located at the top.

The distal end of the supply flow path 44 inserted into the oil storage chamber 42 is disposed substantially at the center of the oil storage chamber 42. A support shaft 46 is rotatably mounted between the supply passage 44 and the cap 47 of the oil tank 41. The support shaft 46 has an air supply port 48 for supplying the air in the oil storage chamber 42 to the cam chamber 14, and a throttle 4 having a reduced inner diameter near the air supply port 48.
9 are formed. A flexible pipe 50 having flexibility is attached to the support shaft 46, and a passage 51 connected to the flexible pipe 50 is communicated with a throttle 49, and air and oil are condensed by the throttle 49. Are mixed to convert the oil into mist.

An oil inlet 52 is formed at the distal end of the flexible pipe 50, and a weight 53 is fixed to the outer periphery of the oil inlet 52. That is, by displacing the weight 53 as the inclination of the engine body 1 changes, the support shaft 46 is rotated to deflect the flexible pipe 50,
As a result, the oil suction port 52 always moves to the bottom of the oil storage chamber 42, which is the lowermost part in the vertical direction, so that the oil mist generated by the throttle part 49 is supplied to the cam chamber 14 through the supply flow path 43 under pressure. It is configured to be.

As shown in FIG. 3, the opening 45 of the supply passage 43 on the cam chamber 14 side is opened toward the outer peripheral surface 22a of the cam 22 on which the cam followers 25a and 25b slide. Oil guide wall 54 provided on the cylinder part and oil guide wall 5 provided on the cylinder block 3
5 and the cam guides 25a, 25
5b, the oil guide wall 5
A narrow space 56 is formed by the cam followers 25a and 25b. The oil guide walls 54 and 55 are disposed symmetrically so as to surround the cam 22 from both sides near the outer peripheral surface 22a.

After the oil mist supplied to the cam chamber 14 lubricates the respective parts in the cam chamber 14, the oil mist is sent to the valve chamber 27 through the push rod passages 33a and 33b. It is configured to diverge into a bypass passage 57 that communicates with the crank chamber 6. The flow of the oil mist at this time is shown by arrows in FIG.

Specifically, as shown in FIGS. 4 and 5, between the valve operating chamber 27 and the crank chamber 6, the oil mist supplied into the valve operating chamber 27 is supplied via a breather device 58. An oil recirculation path 59 is provided for recirculation in the crank chamber 6. The oil return path 59 is formed by the cylinder block 3 and the crankcase 2 and is connected to a cylinder opening 60 communicating with the cylinder 10. Also, the intake valve 28
In the vicinity of the exhaust valve 29, oil suction pipes 61 and 62 extending from the breather device 58 to substantially the bottom of the valve operating chamber 27 are provided. Specifically, as shown in FIG. 5, the intake valve 28 and the exhaust valve 29 are slidably fitted by cylindrical valve guides 28a and 29a projecting from the bottom of the valve operating chamber 27, and the oil intake pipe 61 , 62 are formed with openings 61a, 62a which are lower than the upper ends of the valve guides 28a, 29a and open near the bottom surface of the valve chamber 27. These oil suction pipes 61 and 62 are connected to an oil return path 59.

The cylinder opening 60 is formed at a position which is closed when the piston 11 descends and which is opened when the pressure inside the crank chamber 6 becomes negative due to the elevation of the piston 11. The cylinder opening 60 and the piston 11
As a result, the oil mist is moved from the valve operating chamber 27 to the crank chamber 6.
Acts as a check valve that only allows oil to be pumped inside.

As shown in FIG. 3, the bypass passage 57 that connects the cam chamber 14 and the crank chamber 6 has an opening 63 at one end connected to the push rod passages 33a and 33b at the upper part of the cam chamber 14. The other end is communicated with the cylinder opening 60 similarly to the oil recirculation path 59 (see FIG. 4).

An oil guide wall 64 is provided in the cam chamber 14 along the outer periphery of the cam gear 21, and an oil guide passage 66 connecting the opening 63 of the bypass passage 57 of the cam chamber 14 and the guide wall 65 is provided. . The guide wall 65 is the cam gear 2
1 are provided along a substantially tangential direction.

Between the crank chamber 6 and the oil storage chamber 42 of the oil tank 41, recovery flow paths 67a and 67b for recovering the oil in the crank chamber 6 into the oil storage chamber 42.
And are connected by These recovery channels 67a, 6
As shown in FIG. 5, 7b is formed at two places, an upper part and a lower part of the crankcase 2. These recovery channels 67
The leads a and 67b open and close due to pressure fluctuations in the crank chamber 6, and allow only oil mist and blow-by gas generated in the crank chamber 6 to be fed from the crank chamber 6 to the oil storage chamber 42. It is connected via a valve 68. The reed valve 68 has a structure that opens as the pressure in the crank chamber 6 increases. The tip of the recovery flow path 67b connected to the oil storage chamber 42 is
And a return hole 69 (FIG. 1, FIG. 1) for returning the collected oil mist into the oil storage chamber 42.
(See FIG. 3).

In the oil storage chamber 42, the oil mist and the blow-by gas are constantly discharged to a space above the oil level 70. Here, by making the amount of oil in the oil storage chamber 42 equal to or less than the specified amount, the return hole 69 and the air supply port 48 located at a substantially central portion in the oil storage chamber 42 It is structured so that it will not be immersed in the oil surface 70 even if it is inclined in this manner. Accordingly, the reverse flow of the oil lubricating the inside of the engine or only the oil does not enter the supply flow path 44, and the concentration of the oil mist can be kept constant at all times. In addition, the oil that has lubricated the inside of the engine is returned to the oil storage chamber 42, and new oil is supplied, so that the oil can be changed satisfactorily.

The breather device 58 is provided inside the rocker cover 5 and has a partition plate 71, a breather 72, and a breather pipe 73. The breather pipe 73 is provided on the rocker cover 5, one end of which is connected to the breather device 58, and the other end of which is connected to the air cleaner 37 as shown in FIG. The discharged blow-by gas passes through the air cleaner 37 and the carburetor 36 and is burned again.

As shown in FIG. 1 and FIG.
Has a gas-liquid separation chamber 74 for separating blow-by gas and oil at the center. At the corner of the gas-liquid separation chamber 74, FIG.
A plurality of holes 75 are opened as shown in FIG. A plurality of passages 76 are formed by the groove 72 a provided in the breather 72 and the partition plate 71, and these passages 76 extend to the corners and communicate with a plurality of holes 77 formed in the partition plate 71. . All the passages 76 are oil recirculation passages 5 communicating with the crank chamber 6.
9 is communicated.

A ceiling chamber 78 is formed between the partition plate 71 of the breather 72 and the rocker cover 5 to store oil when the engine body 1 is inverted. A plurality of grooves 79 for flowing oil are also formed in the ceiling chamber 78 (see FIG. 8), and these grooves 79 are also connected to the breather 72 by a plurality of holes 77 formed in the partition plate 71.

As shown in FIGS. 6 and 7, the rocker arms 31a and 31b are inclined in a direction away from one end on the intake valve 28 and exhaust valve 29 side toward the other end on the opposite side. , Are arranged in a state of being inclined in the shape of "C". Thereby, the rocker arm 31
A space is secured between a and 31b with a margin. Therefore, as shown in FIG.
Of the rocker arms 31a and 31b can be disposed between the pair of rocker arms 31a and 31b.

Further, as shown in FIGS. 6, 7 and 9,
The valve operating chamber 27 has an oil mist guide wall 78a that shields the flow of oil mist from the openings on the outlet side of the push rod passages 33a and 33b to the gas-liquid separation chamber 74 and guides the oil mist toward the intake valve 28 and the exhaust valve 29. , 78b.

Further, as described above, the rocker arm 31
By inclining a and 31b in a "C" shape, a sufficient space is secured between the push rod passages 33a and 33b. At a position between the pair of push rod passages 33a and 33b in the cylinder block 3, as shown in FIGS. 1 to 4 and 10, a boss-shaped plug for detachably screwing a spark plug 39 is mounted. Part 80
Are formed.

In such a configuration, during operation of the four-cycle engine, a strong negative pressure is generated in the crank chamber 6 as the piston 11 rises, and the cylinder opening 60 is opened. Thus, the breather device 5 in the valve chamber 27
From 8, the oil mist passes through the oil recirculation path 59, and is sucked into the crank chamber 6 through the cylinder opening 60 and the cylinder 10. Oil mist is also drawn into the crank chamber 6 from the opening 63 (see FIG. 3) of the cam chamber 14 through the bypass passage 57 and the cylinder opening 60 and the cylinder 10.

In the descending stroke of the piston 11, when the pressure in the crank chamber 6 rises as the piston 11 descends,
The reed valve 68 opens, and oil mist is discharged from the crank chamber 6 to the oil storage chamber 42 through the recovery flow paths 67a and 67b to recover oil. These recovery channels 67a, 6
7b are provided at two locations, an upper portion and a lower portion, of the crank chamber 6, and the recovery flow path 67 is provided even when the engine body 1 is in an inverted state.
a, 67b so that oil does not accumulate in the crank chamber 6. At the same time, the pressure in the oil storage chamber 42 increases, so that the air in the oil storage chamber 42
6, a negative pressure is generated in the throttle portion 49, the oil is sucked up from the flexible pipe 50, and the air and the oil are mixed in the throttle portion 49 to convert the oil into mist. The generated oil mist and blow-by gas are supplied to the cam chamber 14 under pressure.

The oil mist and the blow-by gas supplied to the cam chamber 14 under pressure flow as shown by arrows in FIG. Room 2
7. The oil mist supplied into the valve operating chamber 27 lubricates the components in the valve operating chamber 27,
When a strong negative pressure is generated in the crank chamber 6 by the rise of the cylinder opening 60 and the cylinder opening 60 functioning as a check valve is opened, as shown by an arrow in FIG. Cylinder opening 60,
It is sucked into the crank chamber 6 via the cylinder 10. At this time, a part of the oil mist is supplied into the crank chamber 6 via the cam chamber 14, the bypass passage 57, the cylinder opening 60, and the cylinder 10. The above is the flow of the oil mist of the entire engine.

In the present embodiment, the pair of rocker arms 31a and 31b are disposed so as to be inclined in a direction away from one end on the intake valve 28 and exhaust valve 29 side toward the other end on the opposite side. The gas-liquid separation chamber 74 is provided with the valve operating chamber 27 that accommodates the pair of rocker arms 31a and 31b.
This eliminates the need for extra space at the top of the device, thereby keeping the overall height low.

The valve operating chamber 27 is provided with a gas-liquid separating chamber 74 through an opening on the outlet side of the push rod passages 33a and 33b.
Oil mist guide walls 78a and 78b are provided to shield the flow of oil mist to the intake valve 28 and the exhaust valve 29 side, so that the oil mist flowing to the valve operating chamber 27 is reduced to the oil mist guide walls 78a and 78b. Gas-liquid separation chamber 7
4 is suppressed, and a sufficient amount flows through the intake valve 28 and the exhaust valve 29. Thus, the intake valve 28 and the exhaust valve 29 can be sufficiently lubricated without imposing a load on the gas-liquid separation operation in the gas-liquid separation chamber 74.

Further, at a position between the pair of push rod passages 33a and 33b in the cylinder block 3, a plug mounting portion 80 for detachably mounting the spark plug 39 is provided. The spark plug 39 can be compactly attached to the surfaces of the push rods 32a and 32b. Accordingly, the push rods 32a, 32
Even when a working device such as a power sprayer or a water pump is mounted on the surface opposite to b, the spark plug can be easily attached and detached without being obstructed by the working device.

[0045]

According to the first aspect of the present invention, the rocker arm is disposed so as to be inclined in a direction away from one end on the intake valve and exhaust valve side toward the other end on the opposite side. By utilizing the space between these rocker arms, the gas-liquid separation chamber of the breather device can be provided, so that the overall height can be reduced.

According to a second aspect of the present invention, in the first aspect of the present invention, the valve operating chamber is configured to block the flow of oil mist from the opening on the outlet side of the push rod passage to the gas-liquid separation chamber and to take in the air. Since the oil mist guide wall which guides the valve and the exhaust valve is provided, the overall height can be reduced as in the case of the first aspect, and the oil mist supplied to the cam chamber is provided in the push rod passage. The oil mist flowing to the valve operating chamber passes through the valve operating chamber, but the amount of oil mist flowing toward the gas-liquid separating chamber is suppressed by the oil mist guide wall, and a sufficient amount flows to the intake / exhaust valve. It is possible to sufficiently lubricate the intake and exhaust valves without imposing a load on the gas-liquid separation action.

According to a third aspect of the present invention, in the first aspect of the present invention, a plug mounting portion for detachably mounting a spark plug is disposed at a position between the pair of push rod passages in the cylinder block. Therefore, as in the case of claim 1, the overall height can be reduced,
Further, the spark plug can be compactly mounted on the surface of the cylinder block on the push rod side.

According to a fourth aspect of the present invention, in the second aspect of the present invention, a plug mounting portion for detachably mounting a spark plug is disposed at a position between the pair of push rod passages in the cylinder block. Therefore, the same effects as those of the second and third aspects can be obtained.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view of a four-cycle engine according to an embodiment of the present invention.

FIG. 2 is a vertical sectional front view of the four-cycle engine.

FIG. 3 is a vertical sectional front view taken along line AA in FIG. 1;

FIG. 4 is a vertical sectional side view taken along a line BB in FIG. 2;

FIG. 5 is a vertical sectional front view taken along the line CC in FIG. 1;

FIG. 6 is a horizontal sectional view showing the inside of the valve chamber.

FIG. 7 is a horizontal sectional view showing the inside of a breather device and a valve operating chamber.

FIG. 8 is a horizontal sectional view showing the inside of a breather device and a valve operating chamber.

FIG. 9 is a vertical sectional side view taken along a line DD in FIG. 1;

FIG. 10 is a partial front view showing a mounted state of a spark plug.

[Explanation of symbols]

 9 Crankshaft 14 Cam chamber 22 Cam 27 Valve chamber 28 Intake valve 29 Exhaust valve 31a, 31b Rocker arm 32a, 32b Push rod 33a, 33b Push rod passage 39 Spark plug 58 Breather device 74 Gas-liquid separation chamber 78a, 78b Oil mist Guide wall 80 Plug mounting part

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) F02F 1/24 F02F 1/24 H (72) Inventor Toshio Hirabayashi 1-1-1, Ishiba, Matsumoto-shi, Nagano Ishikawajima Shibaura Machinery Co., Ltd. Matsumoto Factory (72) Inventor Kenji Yokoyama 1-1-1, Ishiba, Matsumoto City, Nagano Prefecture Ishikawajima Shibaura Machinery Co., Ltd. Matsumoto Factory F-term (reference) 3G013 AA04 AB03 BA04 BB12 BC11 BC19 BD01 BD22 3G015 AA04 AB03 BD11 BD25 BE04 BE05 CA05 DA02 DA10 DA11 EA26 3G016 AA06 AA19 BB08 BB09 BB19 BB23 BB25 CA11 CA34 CA45 CA46 CA56 FA01 FA38 GA01 3G024 AA13 AA16 AA36 AA38 BA24 DA01 DA08 DA18 EA01 FA14 GA01 GA35 HA02

Claims (4)

[Claims] 1. A pair of rockers, comprising a breather device for separating blow-by gas into oil and gas, receiving a driving force from a cam rotating in a cam chamber in synchronization with rotation of a crankshaft, and operating in a valve operating chamber. In a four-stroke engine of a type in which an arm opens and closes an intake valve and an exhaust valve, the rocker arm is inclined in a direction away from one end on the intake valve and the exhaust valve side toward the other end on the opposite side. The four-stroke engine, wherein the gas-liquid separation chamber of the breather device is disposed between the pair of rocker arms. 2. A pair of push rods for transmitting the driving force of the cam to the rocker arm are housed in a pair of push rod passages formed in a cylinder block so as to communicate the cam chamber and the valve operating chamber. In the valve chamber,
An oil mist guide wall is provided, which blocks the flow of oil mist from the opening on the outlet side of the push rod passage to the gas-liquid separation chamber and guides the flow to the intake valve and the exhaust valve. The four-stroke engine according to claim 1. 3. A pair of push rods for transmitting the driving force of the cam to the rocker arm are housed in a pair of push rod passages formed in a cylinder block so as to communicate the cam chamber and the valve operating chamber. The four-stroke engine according to claim 1, wherein a plug mounting portion for detachably mounting a spark plug is disposed at a position between the pair of push rod passages in the cylinder block. . 4. A plug mounting portion for removably mounting a spark plug at a position between the pair of push rod passages in the cylinder block. 4 cycle engine.