JPH11200830A - Breather mechanism - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent leakage of lubricating oil to an intake air passage at unused time by providing an opening/closing means to block up a breather passage when pressure in a crankcase falls within a range of a positive pressure value smaller than a reference positive pressure value or a negative pressure value smaller than a reference negative pressure value as well as to open the breather passage at time except for that. SOLUTION: In a four-cycle engine having a breather mechanism used as a prime mover for a hand-holding mowing machine, a two-way valve 70 is arranged in the connecting part of first passage piping (a breather passage) 10 and an air cleaner 50, that is, in the middle of an intake air passage leading to an oil tank 28 from a filter 50a. This two way valve 70 is opened when positive pressure not less than a reference positive pressure value is generated in a crankcase 23 by a descent of a piston 32 or when negative pressure not less than a reference negative pressure value is generated in the crankcase 23 by an ascent of the piston 32. Therefore, the valve is closed at time except for that by supplying blow-by gas in the crankcase 23 to the intake air passage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a breather mechanism, and more particularly to a breather mechanism for adjusting pressure in a crank chamber of a four-cycle engine and supplying blow-by gas existing in the crank chamber to an intake system.

[0002]

2. Description of the Related Art Conventionally, a small general-purpose engine used as a prime mover such as a mower is operated while being tilted at various angles, so that the inside of the engine can be easily lubricated regardless of the tilt state of the engine body. Can do 2
Although cycle engines were generally used, in recent years,
Due to the problem of environmental pollution caused by exhaust gas, there is an increasing need to use a four-stroke engine that can emit cleaner exhaust gas.

However, the conventional four-stroke engine employs a structure in which lubricating oil stored in an oil pan provided at the lower part of the engine is pumped up to the upper part of the engine, lubricated, flows down by its own weight, and is stored again in the oil pan. In addition, when the engine is operated in an inclined state, there is a problem that lubricating oil is not stored in the oil pan and lubrication inside the engine cannot be easily achieved.

[0004] The applicant of the present application has disclosed in Japanese Patent Application No. 9-192323, which was filed earlier than the present application, a four-cycle engine which can easily lubricate the engine without being restricted by the inclination angle of the engine body. A lubrication device is proposed.

FIG. 5 is a schematic explanatory view illustrating a small four-stroke engine to which the lubrication device proposed by the above-mentioned application is applied. The engine body 20 is, as shown,
It comprises a crankcase section 22, a cylinder section 24, a cylinder head section 26, and an oil tank section 28.

[0006] The crankcase portion 22 includes a cylinder portion 24.
A crankshaft 23 connected to a piston 32 via a connecting rod 30 is rotatably supported in the crankcase 23 by coupling with the crankshaft 23. The cylinder bore 36 of the cylinder section 24
A piston 32 is reciprocally fitted therein.
The cylinder head section 26 includes a combustion chamber 38 and a valve operating chamber 40. In the valve operating chamber 40, a valve 42 that rotates in conjunction with the crankshaft 34 and performs intake and exhaust in the combustion chamber 38 is provided. A cam shaft 44 that opens and closes is rotatably supported.

A carburetor 48 is provided on one side of the cylinder head 26 to communicate with a combustion chamber 38 via an intake port 46 to generate a mixture to be supplied into the combustion chamber 38.
At the other end of the vaporizer 48, an air cleaner 50 for removing dust contained in the intake air is provided. Also,
An exhaust port 5 is provided on the other side of the cylinder head 26.
A muffler 54 communicating with the second muffler 2 is connected.

[0008] The oil tank section 28 includes an air cleaner 50.
Is formed by a case separate from the crankcase portion 22 and has a closed interior space therein, and an appropriate amount of lubricating oil for lubricating the inside of the engine is stored in the interior space. .

In the oil tank section 28, a first opening 12 which is an opening of the first flow path pipe 10 having a predetermined flow area and the other end opening into the air cleaner 50, Are open to the second opening 16 of the second flow path pipe 14 communicating with the inside of the crank chamber 23.
It is provided at a substantially central position in a three-dimensional space in the oil tank unit 28.

Therefore, if the amount of the lubricating oil stored in the oil tank 28 is set to an appropriate amount, for example, approximately one third of the volume of the oil tank 28,
In any inclined state of the first opening 12 or the second opening 12
The opening 16 is not immersed in the lubricating oil, and the oil tank 2
8, that is, on the oil level of the lubricating oil.

An oil suction unit 1 is provided in the oil tank unit 28 to suction lubricating oil using a negative pressure in the crank chamber 23 and to supply the lubricating oil to an oil mist generator 60 described later.
Eight tip portions 19 are provided. The distal end portion 19 is constituted by a tube body 19a formed of an elastic material such as a rubber tube having a predetermined length and being easily bent, and a suction filter 19b having a distal end functioning as a weight. I have. Therefore, the tip portion 19 of the oil suction portion 18
Is always deflected vertically downward by the weight of the suction filter 19b, and always exists below the oil level of the lubricating oil accumulated in an appropriate amount regardless of the inclination state of the engine 20.

The oil mist generator 60 is provided below the crankcase 22 and mixes lubricating oil and air sucked by negative pressure in the crank chamber 23 and sprays the mist into the crank chamber 23. This lubricates the inside of the crank chamber 23, between the cylinder bore 36 and the piston 32, and the like. Therefore, when the lubricating device having the above configuration is used, the inside of the engine 20 can be lubricated regardless of the inclination state of the engine 20.

Here, the mowing machine driven by the engine 20 having the above structure is held and used by being hung from the shoulder of the worker during mowing work, that is, during operation of the engine. Therefore, the engine 20 is maintained in a state in which the cylinder head 26 is positioned above the crankcase 22 while being slightly inclined.

When the mower is not in use, the mower is stored with the engine 20 down against a wall or the like. Therefore, the engine 20 is kept in an inverted state and stored in an inverted state until it is used again for work. Even when stored in such an inverted state, the oil tank portion 28 is closed and the first opening 12
Since the second opening 16 is always located on the oil level in the oil tank 28, the lubricating oil leaks from the oil tank 28 through the first flow path pipe 10 into the air cleaner 50. It was thought that there was no danger.

[0015]

However, the first flow path pipe 10 not only supplies air to the oil tank portion 28 and supplies air to the oil mist generating device 60, but also provides the air in the crank chamber 23 when the piston 32 descends. The positive pressure generated in the crankcase 2 is adjusted to an appropriate pressure, and the
3 also serves as a blow-by gas passage for supplying the blow-by gas present in the intake passage (in the air cleaner 50 in this conventional example). That is, in the first flow path pipe 10, not only the air flow from the air cleaner 50 side,
There is also a flow of air from the crank chamber 23 side to the air cleaner 50 side.

Therefore, there is a possibility that mist-like lubricating oil may adhere to the first passage pipe 10 due to the flow of the blow-by gas from the crank chamber 23 side to the air cleaner 50 side, and when the engine 20 is turned upside down in this state. In such a case, the attached lubricating oil may leak along the inner wall surface of the first flow path pipe 10 into the air cleaner 50.

Further, when the engine 20 is inverted, there is no guarantee that the lubricating oil in the oil tank 28 will not be applied to the first opening 12 at all. May leak along the first flow path pipe 10 into the air cleaner 50.

If the lubricating oil leaks into the air cleaner 50, the filter 50a in the air cleaner 50 may absorb the lubrication oil and cause clogging. This may cause a decrease in engine output. In addition, when lubricating oil enters the combustion chamber, there is a problem that abnormal combustion causes rotation irregularities and emission of white smoke when the lubricating oil is burned in the combustion chamber. Furthermore, the lubricating oil leaked from the air cleaner 50 during storage may stain the floor of the storage place.

As a measure for preventing the leakage of the lubricating oil from the inside of the oil tank section 28 to the intake system, a first measure is taken.
Although a method of forming the flow path pipe 10 in a maze shape is also conceivable,
In a usage situation where the lubricating oil is used by swinging it, such as a mower, there is a risk that the lubricating oil may leak through the maze part due to long-term use, and the lubricating oil should be completely prevented from leaking from the intake system Can not.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problem, and an object of the present invention is to provide a breather mechanism for a small four-stroke engine which prevents leakage of lubricating oil into an intake system when not in use. It is in.

[0021]

According to a first aspect of the present invention, there is provided a breather mechanism in which a pressure in a crank chamber is set to a positive pressure smaller than a predetermined reference positive pressure. And, when it is in a range of a negative pressure value smaller than the reference negative pressure value, there is provided an opening / closing means for closing the breather passage, and opening the breather passage when the pressure value is any other value. And

Accordingly, during operation of the engine, when the piston lowers, a positive pressure equal to or higher than the reference positive pressure value is generated in the crank chamber, or when the piston rises, a negative pressure equal to or higher than the reference negative pressure value is generated in the crank chamber. When in operation, the breather passage is opened by the opening / closing means. Therefore, the pressure in the crank chamber is adjusted to an appropriate pressure value, and the blow-by gas in the crank chamber is supplied to the intake system.

When the engine is stopped, no pressure exceeding the reference positive pressure value or the reference negative pressure value is generated in the crank chamber, so that the opening / closing means shuts off the breather passage. Therefore, even when the engine is stored in an inverted state, it is possible to prevent the lubricating oil from traveling along the breather passage and leaking into the intake passage.

According to a second aspect of the present invention, in the breather mechanism, the opening / closing means is provided with a valve portion which performs an opening operation by being elastically deformed by the positive pressure when a positive pressure equal to or more than a reference positive pressure value is applied. According to this, when a positive pressure equal to or higher than the reference positive pressure value is generated in the crank chamber due to the lowering of the piston and applied to the opening / closing means, the valve portion of the opening / closing means is elastically deformed to perform an opening operation. Therefore, the opening / closing means can be formed with a simple configuration, and cost reduction and reliable operation of the valve can be ensured.

According to a third aspect of the present invention, in the breather mechanism, when the opening / closing means is constantly urged in the valve closing direction by the urging means and a negative pressure equal to or higher than the reference negative pressure value is applied, the urging force is applied. A valve portion that moves in the valve opening direction to perform a valve opening operation is provided. According to this, when a negative pressure equal to or higher than the reference negative pressure value is generated in the crank chamber due to the rise of the piston and added to the opening / closing means, the valve portion of the opening / closing means performs the opening operation. Therefore, the opening / closing means can be formed with a simple configuration, and cost reduction and reliable operation of the valve can be ensured.

According to a fourth aspect of the present invention, the breather mechanism has an oil tank in which the engine stores lubricating oil and is isolated from the crank chamber. The breather passage has a first flow passage pipe having one end opened in the intake passage and the other end opened in the indoor space area of the oil tank storing the lubricating oil, and one end opened in the crank chamber and the other end opened in the crank chamber. The opening and closing means is provided at an opening of the first passage pipe on the side of the intake system passage.

According to this, when the negative pressure in the oil tank becomes equal to or higher than the reference negative pressure value due to the negative pressure in the crank chamber, the opening / closing means opens the first flow path pipe. Therefore,
Air is sucked into the oil tank from the intake passage via the first flow path pipe. Thereby, the pressures in the oil tank and the crank chamber are adjusted to appropriate pressure values. Further, at this time, by introducing outside air into the oil tank, the lubricating oil stored in the oil tank is cooled by the outside air.

When the pressure inside the oil tank becomes equal to or higher than the reference positive pressure value due to the positive pressure in the crank chamber, the opening / closing means opens the first flow path pipe. Therefore, the blow-by gas existing in the crank chamber is guided to the intake system via the second flow path pipe and the first flow path pipe. Thereby, the pressure in the oil tank and the pressure in the crank chamber are adjusted to appropriate pressure values, and the blow-by gas in the crank chamber flows into the combustion chamber again from the intake passage and is burned.

[0029]

Embodiments of the present invention will be described below with reference to the drawings. The four-stroke engine according to the present embodiment is used as a prime mover for a hand-held mower.

FIG. 1 is a front explanatory view schematically showing a four-stroke engine provided with a breather mechanism according to the present invention in a schematic sectional view. It should be noted that the same components as those of the engine described in the above-described related art are denoted by the same reference numerals, and detailed description thereof will be omitted.

In this embodiment, the most characteristic point is that a two-way valve 70 is provided at a connection portion between the first flow path pipe 10 and the air cleaner 50 as shown in FIG. This connection portion is located in the middle of the intake system flowing from the filter 50 a provided in the air cleaner 50 to the oil tank 28.

As shown in FIG. 2 which is a longitudinal sectional view, the two-way valve 70 includes a housing 72 having a substantially cylindrical shape,
First valve portion 7 reciprocally fitted into housing 72
4, a second valve portion 76 made of an elastic member and fixed to the first valve portion 74, and a coil spring 78 for urging the first valve portion 74 in the housing 72 in one direction with a predetermined urging force. , And is constituted.

The housing 72 is an exploded explanatory view of FIG.
As shown in FIG. 3A, a substantially cylindrical body 72a is provided.
And a reduced diameter portion 72b in which both ends of the body 72a are reduced in diameter by a predetermined distance in the radial direction, and the inner diameter is formed to be constant. Also, in the figure (A), the first opening 72c located above
The second opening 72d opens in the air cleaner 50 when assembled in the air cleaner 50, and is located below the second opening 72d.
Is connected in communication with the first flow path pipe 10.

As shown in FIG. 3B, the first valve portion 74 has a substantially cylindrical shape having an upper surface portion 74a facing the first opening 72c and a lower surface portion 74b facing the second opening 72d. It has a base 74c.

A second valve fixing hole 74d through which a predetermined diameter is formed through the base of the base 74c and has a base 76a (see FIG. 2) of the second valve portion 76 inserted and fixed, and a second valve fixing hole 74d. An exhaust hole 7 penetrating from the upper surface 74a to the lower surface 74b at a position radially separated by a predetermined distance
4e, and a groove 74f which is formed at a predetermined depth in the axial direction on the peripheral surface of the base 74c.

The second valve portion 76 is made of, for example, a rubber material having a predetermined elastic force. As shown in FIG. 3C, a substantially mushroom having a base portion 76a and an umbrella portion 76b is provided. Make a shape. The base portion 76a has a fixed head portion having a diameter larger than the second valve fixing hole 74d at the distal end side, and plays a role of retaining the base portion 76a after the base portion 76a is inserted into the second valve fixing hole 74d.

The umbrella portion 76b has a substantially conical shape forming an obtuse angle at the top, and the base end of the base 76a is fixed to the center of the bottom surface. Then, the base 76a is connected to the second valve fixing hole 74.
d, and fixed to the first valve portion 74, the peripheral edge of the umbrella portion 76b forms an exhaust hole 74e opening in the upper surface portion 74a.
It is formed so as to have a size that closes.

As shown in FIG. 2, the coil spring 78 has an outer diameter slightly smaller than the inner diameter of the housing 72, and the upper surface 74a of the first valve portion 74 in the housing 72.
Is pressed against the reduced diameter portion 72b with a predetermined urging force. The depth of the groove 74f is set to a depth that is closed by the reduced diameter portion 72b when the upper surface portion 74a of the first valve portion 74 is in contact with the reduced diameter portion 72b.

Next, the two-way valve 70 having the above configuration
Will be described. First, when the piston 32 rises in the cylinder 24 toward the cylinder head 26 during the operation of the engine, a negative pressure is generated in the crank chamber 23 by an amount corresponding to the rise of the piston. Due to the negative pressure generated in the crank chamber 23, lubricating oil is sucked into the oil mist generating device 60 from the oil tank portion 28 through the oil suction portion 18 and air is sucked through the second flow passage pipe 14. You.

Therefore, in the oil tank 28,
A two-way valve 70 that generates a negative pressure corresponding to the amount of lubricating oil and air sucked into the oil mist generator 60 and communicates with the inside of the oil tank unit 28 through the first flow path pipe 10.
The negative pressure also acts on the second opening 72d to generate a force for moving the first valve portion 74 toward the second opening 72d.

The urging force of the coil spring 78 is set so as to be compressed by this force, and the first valve portion 74 moves toward the second opening 72d while compressing the coil spring 78. As a result, a gap is formed between the reduced diameter portion 72b and the groove portion 74f, and the air that has passed through the filter 50a of the air cleaner 50 flows through the first opening 72c, the groove portion 74f, and the first flow path pipe 10 to the oil tank portion. 28
Flows into. Thereby, the pressure in the oil tank portion 28 is adjusted to an appropriate value.

When the pressure in the oil tank section 28 is adjusted to an appropriate value, the negative pressure that has moved the first valve section 74 disappears, and the first valve section 74
8 again presses against the reduced diameter portion 72b inside the housing 72. Thereby, the groove 74f is closed,
The first flow path pipe 10 is closed. Here, by supplying the outside air into the oil tank section 28, the lubricating oil stored in the oil tank section is also cooled.

Next, when a positive pressure is generated in the crank chamber 23 due to the lowering of the piston 32, the positive pressure is applied to the second flow path pipe 14, the oil tank 28, and the first flow path pipe 10.
The two-way valve 70 also works via the
The positive pressure is applied to the exhaust hole 74e. Therefore, a force is generated to lift the umbrella portion 76b of the second valve portion 76 that closes the air cleaner 50 side of the exhaust hole 74e from the upper surface portion 74a.

The elastic force of the umbrella portion 76b of the second valve portion 76 is set to be elastically deformed by this force, and the peripheral portion of the umbrella portion 76b is positioned above the upper surface portion 74a by the positive pressure applied to the exhaust hole 74e. Deform to be curved. Accordingly, a gap is formed between the upper surface portion 74a and the blow-by gas compressed in the crank chamber 23.
The air cleaner 50 passes through the second flow path pipe 14, the oil tank portion 28, the first flow path pipe 10, and the exhaust hole 74e.
Is discharged into At the same time, the pressures in the crank chamber 23 and the oil tank 28 are also adjusted to appropriate values.

When the pressures in the crank chamber 23 and the oil tank 28 are adjusted to appropriate values, the positive pressure that elastically deforms the umbrella portion 76b of the second valve portion 76 disappears, and the shape of the umbrella portion 76b is reduced. Is returned to the original position, the exhaust hole 74e is closed again.

Next, a state when the engine 20 is stored will be described with reference to FIG. As described above, in the mower using the engine 20 according to the present embodiment, the cylinder head 26 is located below and the oil tank 28 is located above when the engine 20 is stored, and the engine 10 is stored in a so-called inverted state. You. FIG. 4 is an explanatory diagram illustrating a state of the engine 10 during storage.

Here, an appropriate amount of lubricating oil is stored in the oil tank 28, and the first opening 12 and the second
The opening 16 is located on the surface of the lubricating oil. Therefore, in this state, the lubricating oil in the oil tank 28 rarely flows into the first flow path pipe 10 from the first opening 12.

However, the lubricating oil contained in the blow-by gas during the operation of the engine may adhere to the inner wall surface of the first passage pipe 10. In this case, if the lubricating oil is stored in a state as shown in the figure, the lubricating oil attached to the inner wall surface of the first flow path pipe 10 gradually moves down the pipe and flows down to the two-way valve 70. It is blocked by the two-way valve 70 and does not leak to the air cleaner 50 side.

Also, when the engine 20 is turned over, the lubricating oil in the oil tank 28 is applied to the first opening 12 and enters the first flow path pipe. Leakage to the 50 side can be prevented.

The two-way valve 70 causes the lubricating oil existing in the first flow path pipe to erect and start the engine 20 when the mower is used. 1), flows through the first flow path pipe 10 toward the first opening 12, and returns to the oil tank 28. Therefore, when the engine is started, lubricating oil does not blow out from the two-way valve 70 into the air cleaner 50.

Accordingly, by providing the two-way valve 70 having such a simple structure on the air cleaner 50 side of the first flow path pipe 10, it is possible to prevent the lubricating oil from entering the intake system and to prevent the engine 20 from malfunctioning. Leakage of the lubricating oil from the air cleaner 50 during use can be prevented.

The present invention is not limited to the above embodiment, and various changes can be made without changing the gist of the present invention. For example, in the above-described embodiment, an elastic force is applied to one valve portion of the two-way valve.
Although the example in which the urging force is used for the other valve portion has been described, the invention is not limited to this. Both may use an elastic force, or both may use an urging force. Similarly, the operation and effect of the present invention can be obtained.

[0053]

As described above, according to the breather mechanism of the present invention, the opening / closing means releases the communication of the breather passage during operation of the engine to adjust the pressure in the crank chamber to an appropriate pressure value. The blow-by gas in the room can be discharged to the intake passage. And, while the engine is stopped, leakage of lubricating oil to the intake passage can be prevented.

[Brief description of the drawings]

FIG. 1 is a front explanatory view schematically showing a four-stroke engine provided with a breather mechanism according to the present invention in a cross-sectional view.

FIG. 2 is an explanatory longitudinal sectional view of a two-way valve.

FIG. 3 is an exploded explanatory view of FIG. 2;

FIG. 4 is an explanatory diagram showing a state of an engine during storage.

FIG. 5 is a schematic explanatory view illustrating a small four-stroke engine to which a conventional lubricating device is applied.

[Explanation of symbols]

 Reference Signs List 10 first flow path piping (breather passage) 12 first opening 14 second flow path piping (breather passage) 23 crank chamber 70 two-way valve (opening / closing means) 50 air cleaner (intake system passage)

Claims (4)

[Claims] 1. A breather passage communicating between a crank chamber of a four-stroke engine and an intake system, adjusting a pressure in the crank chamber and supplying blow-by gas existing in the crank chamber to the intake system. In the breather mechanism, when the pressure in the crank chamber is in a range of a positive pressure value smaller than a preset reference positive pressure value and a negative pressure value smaller than a reference negative pressure value, the breather passage is closed. A breather mechanism provided with opening and closing means for opening the breather passage when the pressure value is other than the above. 2. The valve according to claim 1, wherein the opening / closing means includes a valve portion that performs an opening operation by being elastically deformed by the positive pressure when a positive pressure equal to or higher than the reference positive pressure value is applied. Item 7. The breather mechanism according to Item 1. 3. The opening / closing means is constantly urged in a valve closing direction by an urging means, and opens when a negative pressure equal to or more than the reference negative pressure value is applied, against the urging force of the urging means. 3. A valve unit which performs a valve opening operation by moving in a valve direction.
Breather mechanism described in 1. 4. The engine includes an oil tank that stores the lubricating oil and is isolated from the crank chamber. The breather passage has one end opened in the intake passage and the other end storing the lubricating oil. A first flow path pipe that opens in the indoor space area of the oil tank, and a second end that opens in the crank chamber and the other end opens in the indoor space area of the oil tank storing the lubricating oil. 4. A flow path pipe, wherein the opening / closing means is provided at an opening of the first flow path pipe on the side of the intake passage.
The breather mechanism according to any one of the above.