JPH08200158A - Air vent device for carburetor - Google Patents

Abstract

PURPOSE: To reduce flow resistance in an air flow passage and to maintain a sufficient ram effect when supercharging of outside air is effected by means of a running wind pressure by a method wherein a switching valve is mounted without forming an uneven surface in the internal shape of the clean side of an air cleaner reducing capacity. CONSTITUTION: A switching valve 35 to switch inner and outer vents 34 and 39 is communicated with the atmosphere during the stop of an engine 13 and with an air flow passage during operation of an engine, and mounted on a connection part between the right and left air flow passages 19 and 19 of an air cleaner 20.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air vent device for a carburetor mounted on an engine, and more particularly, to a carburetor suitable for use in a vehicle engine such as a motorcycle, a three- or four-wheeled vehicle, or an automobile. The present invention relates to an air vent device for a vessel.

[0002]

2. Description of the Related Art In a carburetor for a vehicle engine such as a motorcycle, a motorcycle, a three-wheeled vehicle or an automobile, generally,
An air vent device is provided for communicating the upper space of the fuel reservoir (usually called a float chamber) with the atmosphere or the air flow path of the intake system to secure a pressure difference between the fuel reservoir and the carburetor venturi portion. . This air vent device
This is for facilitating fuel outflow by utilizing the pressure difference and ensuring an air-fuel ratio according to the engine operating state.
The opening is provided at a position where pressure fluctuation is small even when the traveling speed changes (for example, behind the air cleaner).

On the other hand, for the purpose of improving the charging efficiency of the engine, an air inlet (air passage inlet) is opened toward the front of the vehicle, and air is supercharged by utilizing wind pressure (ram pressure) during traveling. For example, Japanese Utility Model Application Laid-Open No. 63-12119
No. 0 is disclosed. In the air intake system that uses the traveling wind pressure, simply opening the air vent passage to the atmosphere fluctuates the intake pressure introduced into the carburetor due to the difference in traveling speed, and the air-fuel ratio fluctuates with changes in vehicle speed. The mixture may deviate from the proper mixture. For example, when the traveling wind pressure (supercharging pressure) increases during high-speed traveling, the negative pressure in the venturi portion decreases and its absolute pressure approaches the pressure in the fuel reservoir, so the fuel suction force decreases.

Therefore, in an air vent device of a carburetor in an intake system using a traveling wind pressure, an air vent passage is opened in an air cleaner affected by the traveling wind pressure, so that a pressure corresponding to the vehicle speed acts on a fuel reservoir. By balancing with the pressure in the intake passage (Venturi) (keeping the appropriate pressure difference for fuel suction)
A method to maintain a stable air-fuel ratio (inner vent method)
Is proposed.

On the other hand, for a fixed time (for example, 30
Minutes) When the engine is stopped, the fuel in the fuel reservoir or fuel passage evaporates due to the high engine temperature, and vaporized fuel (evaporated gas) flows into the air cleaner through the air vent passage and fills the air passage. May be. In such a case, the air-fuel mixture at the time of restarting becomes excessively rich, the startability is reduced, and the time required for starting may be increased.

As a configuration for solving such a technical problem, a switching valve for switching a communication destination of an air vent passage from an upper space of a fuel reservoir of a carburetor to one of an atmosphere and an air flow path is provided, and the switching valve is provided. Is operated in response to the engine intake negative pressure, so that the air vent passage communicates with the atmosphere when the engine is stopped, and the air vent passage communicates with the air passage (for example, inside the air cleaner) while the engine is operating. The adoption of the carburetor air vent facilitates smooth fuel supply during high-speed driving to optimize the air-fuel ratio, and at the same time, prevents the filling of evaporated fuel when the engine is stopped to improve the restartability of the engine. The apparatus is, for example, Japanese Utility Model Laid-Open No. 3-87956 (Japanese Utility Model Application 1-1).
No. 48541).

In a motorcycle, in the case of a two-cylinder or four-cylinder engine such as a two-cylinder engine, the flow of intake air to each cylinder is made smooth and the distribution of intake air to each cylinder is made as smooth as possible. From the viewpoint of equalization, install a common air cleaner on some or all of the multiple cylinders,
In some cases, air intake means having a configuration in which outside air is introduced into a common air cleaner through the air passages on both the left and right sides is employed.

[0008]

However, in a conventional air vent device having a switching valve for switching the communication destination of the air vent passage between when the engine is operating and when the engine is stopped, when the switching valve is mounted, Since a concave portion is formed in the clean side portion of the air cleaner and a switching valve is installed in the concave portion, the volume of the clean side is reduced, so that it is difficult to secure a sufficient clean side capacity. In addition, since unevenness is formed in the air cleaner that forms the air flow path, the flow resistance of the airflow may increase or the ram effect may decrease.

The present invention has been made in view of such technical problems, and an object of the present invention is to switch between an inner vent and an outer vent in an engine having a configuration in which outside air is introduced into an air cleaner through left and right intake ducts. Switching valve can be mounted on the clean side of the air cleaner without creating irregularities.
Accordingly, it is an object of the present invention to provide an air vent device for a carburetor which can easily and sufficiently secure a clean side capacity, reduce a flow resistance in an air flow path, and maintain a sufficient ram effect.

[0010]

According to a first aspect of the present invention, an engine is provided in which outside air is introduced into an air cleaner through left and right intake ducts, and the air-fuel mixture produced by a carburetor is filled into a combustion chamber using the air that has passed through the air cleaner. In the air vent device of the carburetor having a switching valve for switching the communication destination of the air vent passage from the upper space of the fuel reservoir of the carburetor to either the atmosphere or the air flow path, The above-mentioned object is achieved by arranging the switching valve between the connection portion with the suction duct.

In addition to the structure of claim 1, the invention of claim 2 to claim 4 is a structure in which outside air is supercharged to the left and right suction ducts by using traveling wind pressure, and the switching valve is in an engine stop state. To communicate with the atmosphere and to communicate with the inside of the air flow path during engine operation, or to operate in response to the negative pressure of the engine intake, or the air vent passage is arranged in a rising slope without valleys. By adopting the configuration,
The above object is achieved more efficiently.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. The same reference numerals denote the same or corresponding parts throughout the drawings. FIG. 9 is a partially cutaway left side view of a motorcycle equipped with an engine having an air vent device for a carburetor according to the present invention. In FIG. 9, front wheels 11 and rear wheels 12 are suspended before and after a body frame 10 via unillustrated front forks and rear forks, and an engine 13 is attached to the center of the body frame 10. . A fuel tank 14 and a seat 15 are attached to the upper portion of the vehicle body frame 10, and are covered by cowlings 16 from the front surface of the vehicle body to both front half portions.

The intake (air intake) to the engine 13 is controlled by a headlight 17 on the front of the cowling 16.
The air taken in from an air intake 18 formed on the lower side is introduced into an air cleaner 20 through a suction duct 19, introduced into a carburetor 21 from the air cleaner 20, and a venturi portion of the carburetor 21 (in the intake passage). This is performed by creating an air-fuel mixture at (partly) 51 and supplying it to the cylinder (combustion chamber) of the engine 13. As described later, the air intake 18 and the suction duct 19
Two air cleaners 20 are provided on each of the left and right sides.

In the case of a multi-cylinder engine, the number of cylinders sharing one air cleaner 20 can be arbitrarily selected. That is, two left and right air intake ports 18 and suction ducts 19 are provided for each of one or more air cleaners shared by one or more cylinders.
Therefore, in the following embodiment, one air cleaner 2
In the case where two or more air cleaners are provided by describing the configuration per zero, a general configuration is that a plurality of sets described below are provided.

FIG. 1 is a partially broken plan view of an embodiment of an engine having an air vent device for a carburetor to which the present invention is applied, and FIG. 2 is a partially broken longitudinal sectional view of the engine of FIG. 3 is a longitudinal sectional view of the vaporizer 21 in FIG.
FIG. 4 is a front view of the air cleaner 20 viewed from the line 4-4 in FIG. The present embodiment shows a four-cylinder engine, and is configured to supply air from one air cleaner 20 to four cylinders A, B, C, and D.

In FIGS. 1, 2 and 9, the engine 1
The three air passages 50 include two air intakes 18 on the left and right sides.
Right and left two intake ducts 19, 1 extending from
9, a flow path in one air cleaner 20 to which air is supplied from these suction ducts 19, 19, and cylinders A to D
Of the carburetor 21 (see FIG. 3) and the intake holes 52 of each of the cylinders A to D of the engine.

The left and right air intakes 18 formed on the front surface of the cowling 16 have a desired projected area when viewed from the front in the traveling direction, and the outside air is subjected to traveling wind pressure (ram pressure).
It is configured such that it is positively pushed into the air flow path 50 by utilizing the air and is supercharged. Thus, the intake system of the vehicle engine is configured to supercharge the outside air into the air flow path 50 using the traveling wind pressure and fill the air-fuel mixture created by the carburetor 21 into the combustion chamber 66 (FIG. 2) of the engine 13. Have been.

The air cleaner 20 includes an element made of a filter material in a cleaner case 23 having left and right inlets to which the left and right suction ducts 19 are connected and an outlet communicating with the intake passage 22 side of the carburetor 21. A filter 24 is attached, and the inside of the case 23 is divided into an element upstream side (dirty side) 25 and an element downstream side (clean side) 26. In the present embodiment, as shown in FIG. 2, each intake duct 19 has at least 2.0 times, preferably 3.0 to 2.0 times the engine displacement.
A surge tank 67 having a volume of 4.0 times is formed.

The surge tank 67 uses a traveling wind pressure to temporarily reduce the flow velocity of air introduced at a high speed (for example, 5 m / s or less) to separate rainwater and the like from intake air. This is for preventing intrusion into the inside 20. At the bottom of the surge tank 67, there is provided a drain 68 for discharging rainwater and the like collected and collected separately from the intake air. Also, in the middle of each intake duct 19, as shown in FIG. 2, a resonance type surge tank 83 for suppressing generation of air vibration or intake noise.
Are connected via a passage 84.

In FIG. 3 showing the structure of the carburetor 21, the carburetor 21 connected to the engine side of the air cleaner 20 (FIG. 2) stores the fuel introduced from the fuel tank 14 (FIG. 9) into the fuel reservoir 27. The mixture is jetted into the intake passage 22 (the venturi portion 51 of the carburetor 21) while being metered by the jet needle 29 and the main jet 30 connected to the suction piston 28, and is atomized and mixed into the intake air (inflow air) to form an air-fuel mixture. It is configured to create.

The oil level 27A in the fuel reservoir 27 is maintained at a predetermined level by a float 31 and a needle valve (not shown) which is opened and closed according to the height of the float 31. The upper space 70 above the oil level 27A in the fuel reservoir 27 is connected to an air vent passage 33 composed of a through hole, a tube, and the like, and a switching valve 35 is connected to the air vent passage 33. The switching valve 35 is for selectively connecting the air vent passage 33 to the atmosphere or the inside of the air flow passage 50. The switching valve 35 is connected to the atmosphere when the engine is stopped (outer vent system), and the engine is operated. Are configured to communicate with the inside of the air flow path 50 (inner vent system).

That is, the switching valve 35 connects the air vent passage 33 from the upper space 70 of the fuel reservoir 27 to
It is selectively connected to one of the inner vent passage 34 communicating with the air flow passage 50 and the outer vent passage 39 communicating with the atmosphere. It is configured to be performed. A throttle valve (throttle valve) 54 is provided on the engine side of the vacuum piston 28 of the venturi section 51.

FIG. 5 is a front view of the switching valve 35,
6 is a plan sectional view taken along line 6-6 in FIG. 5, FIG. 7 is a plan sectional view taken along line 7-7 in FIG.
FIG. 8 is a sectional view taken along line 8-8 in FIG. 6 and 7, the switching valve 35 is operated by a diaphragm 36 that responds to the presence or absence of intake negative pressure.
One side (right side) of the diaphragm 36 is formed with a drive chamber (strong negative pressure chamber) 38 communicating between the carburetor 21 of the intake passage 22 and the engine 13 via a connection port 37, and the other side (left side). The connection port 45 and the inner vent passage 34
A driven chamber (weak negative pressure chamber) 40 communicating with the inside of the clean side 26 of the air cleaner 20 is formed.

The inner vent passage 34 is guided into the clean side 26 of the air cleaner 20 as shown in FIG. 2, and the tip opening 49 of the inner vent passage 34 is located in the clean side 26. That is, the inner vent passage 34 is connected to the clean side 26 of the air cleaner 20.
Communicates inside.

The distal end of an operating shaft 41 connected to the center of the diaphragm 36 has the diaphragm 36
The valve body 43 is fixed with a predetermined space between
A switching chamber 4 is provided between the diaphragm 36 and the valve body 43.
2 is formed. The opening portions at both ends of the switching chamber 42 are valve seats that are in close contact with the diaphragm 36 and the valve body 43, respectively, and are configured to be alternately opened and closed by the movement of the diaphragm 36.

In FIG. 6, the switching chamber 42 communicates with the upper space 70 of the fuel reservoir 27 of the carburetor 21 through the connection port 44 and the air vent passage 33. on the other hand,
The valve chamber 48 opened and closed by the valve body 43 has a connection port 46.
And the outer vent passage 39 communicates with the atmosphere. The diaphragm 36 is normally pressed against the end face of the switching chamber 42 by a return spring or the like, and in this state, the other end of the switching chamber 42 is open. When the engine 13 rotates and an intake negative pressure acts on the drive chamber 38, the diaphragm 36 moves in the opening direction, the right side of the switching chamber 42 is opened, and the switching chamber 4 is opened.
The other end of 2 is sealed by a valve body 43.

When the engine 13 is stopped and no intake negative pressure is generated, the diaphragm 36 is held at the illustrated sealing position (the position for closing the right end of the switching chamber 42), and the valve body 43 interlocked with the diaphragm 36 is illustrated. It is held at an open position (a position where the left end of the switching chamber 42 is opened). Therefore, the vaporizer 21
The upper space 70 of the fuel reservoir 27 is provided with an air vent passage 33.
→ The switching chamber 42 → the valve chamber 48 → the outer vent passage 39 to communicate with the atmosphere.

On the other hand, when the engine 13 is rotating (including during normal operation and start-up) and an intake negative pressure is generated, the diaphragm 36 is moved to the open position (the right end of the switching chamber 42) by the suction force acting on the driving chamber 38. To the open position), and the valve body 43 interlocked with this moves to the closed position (the switching chamber 42).
To the position where the left end of the is closed). Therefore, the upper space 70 of the fuel reservoir 27 of the carburetor 21 passes through the air vent passage 33 → the switching chamber 42 → the driven chamber 40 → the inner vent passage 34, and passes through the clean side 2 of the air cleaner 20.
6 is communicated.

In FIGS. 1, 2 and 3, the switching valve 35 is arranged between the connection portions 80, 80 of the air cleaner 20 with the left and right suction ducts 19, 19. In the present embodiment, the switching valve 35 is mounted with the front side facing sideways, that is, the left side in FIG. 5 faces the front of the vehicle body and the upper side in FIG. 5 faces the vehicle body. Further, the switching valve 35 is vibration-isolated and supported by a stay 85 attached to a rubber tube 82 attached to a cylinder head cover portion 81 of the engine 13.
As the rubber tube 82, for example, a rubber tube for introducing the secondary air of the exhaust emission control device can be used.

In FIG. 2, the fuel reservoir 27 of the carburetor 21
To the switching valve 35 from the air vent passage 33 and the switching valve 35 to the clean side 26 of the air cleaner 20.
The inner vent system constituted by the inner vent passage 34 leading to the inner vent passage 34 is arranged with an ascending gradient over the entire area as shown in the figure, and is piped in a monotonically ascending state with no valley in the middle.

According to the embodiment described above, the left and right air flow paths (suction ducts) 1 are provided for one air cleaner 20.
In the engine 13 which introduces outside air through the air cleaners 9 and 19 and creates a mixture in the carburetor 21 using the air passed through the air cleaner 20, the air vent passage 33 from the upper space 70 of the fuel reservoir 27 of the carburetor 21 is formed. Switching valve 3 for switching the communication destination between the atmosphere and the air flow path
5 and the switching valve 35 is disposed between the connection portions of the air cleaner 20 with the left and right air flow paths 19, 19, so that the clean side 26 of the air cleaner 20 has a smooth and smooth surface. It is possible to easily and sufficiently secure a clean side capacity while having a flow path shape, and to obtain an air vent device for a carburetor capable of reducing the flow resistance in the air flow path.

Further, since the clean side 26 of the air cleaner 20 has a smooth flow path shape without unevenness and can easily secure a sufficient clean side capacity, the air intake port 18 on the front of the vehicle body can be secured. In an engine configured to supercharge the outside air into the air flow path using the traveling wind pressure from 18, it is possible to reduce the flow resistance in the air flow path and maintain a sufficient ram effect.

Further, the switching valve 35 operates in response to the negative pressure of the engine intake so that the switching valve 35 communicates with the atmosphere when the engine is stopped and communicates with the air passage during the operation of the engine. It is possible to further facilitate continuous fuel supply during high-speed running, and to prevent excess evaporated fuel from remaining in the fuel supply system while the engine is stopped. Furthermore, the air vent passage 33,
Since the fuel cell 34 is disposed in an uphill state without a valley, it is possible to completely eliminate the fuel remaining in the air vent.

In the above embodiment, the present invention is applied to the automatic 2
Although the case where it is applied to a wheeled vehicle has been described, the present invention applies to the automatic 3,
If the vehicle runs on an engine such as a four-wheeled vehicle or an automobile, the same can be applied and the same effects can be obtained. Further, if the engine is of a type in which the outside air is introduced from the left and right intake ducts to one air cleaner, it can be similarly applied regardless of the number of cylinders of the engine, and the same effect can be obtained. .

[0035]

As is apparent from the above description, according to the first aspect of the present invention, the outside air is introduced into the air cleaner through the left and right suction ducts, and the air-fuel mixture formed by the carburetor using the air passing through the air cleaner. Is provided in an engine that fills the combustion chamber with a switching valve for switching a communication destination of an air vent passage from an upper space of a fuel reservoir of the carburetor to one of an atmosphere and an air flow path. Since the switching valve is arranged between the connection portions of the air cleaner with the left and right suction ducts, the switching valve for switching between the inner vent and the outer vent can be formed without unevenness on the clean side of the air cleaner. Can be installed, so that clean side capacity can be easily and sufficiently secured, Flow resistance can be reduced, the air vent apparatus for a carburetor capable of maintaining sufficient ram effect when supercharging outside air by utilizing traveling wind pressure is provided.

According to the inventions of claims 2 to 4, in addition to the structure of claim 1, the structure in which outside air is supercharged to the left and right intake ducts by using traveling wind pressure, and the switching valve is an engine It operates in response to the negative pressure of the engine intake air so that it communicates with the atmosphere during stoppage and communicates with the air flow path during engine operation, or the air vent passage is arranged in a rising slope without valleys. Since it has been configured,
Provided is an air vent device for a carburetor capable of achieving the above effects more efficiently.

[Brief description of drawings]

FIG. 1 is a partially cutaway plan view of an embodiment of an engine having an air vent device for a carburetor to which the present invention is applied.

FIG. 2 is a partially broken longitudinal sectional view of the engine of FIG. 1;

FIG. 3 is a longitudinal sectional view of the vaporizer in FIG.

FIG. 4 is a front view of the air cleaner as viewed from line 4-4 in FIG. 1;

FIG. 5 is a front view of the switching valve in FIGS. 3 and 4;

FIG. 6 is a plan sectional view taken along line 6-6 in FIG. 5;

FIG. 7 is a plan sectional view taken along line 7-7 in FIG. 5;

8 is a cross-sectional view taken along the line 8-8 in FIG.

FIG. 9 is a left side view showing an example of a motorcycle provided with an air vent device for a carburetor according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Body frame 13 Engine 14 Fuel tank 18 Air intake 19 Intake duct (air flow path) 20 Air cleaner 21 Vaporizer 22 Intake passage 24 Cleaner element (filter) 25 Dirty side 26 Clean side 27 Fuel reservoir 33 Air vent passage 34 Inner vent passage 35 switching valve 39 outer vent passage 50 air flow passage 70 upper space

Claims (4)

[Claims] 1. An engine for introducing outside air into an air cleaner through left and right intake ducts and filling a combustion chamber with a mixture created by a carburetor using the air that has passed through the air cleaner. In the air vent device of the carburetor having a switching valve for switching the communication destination of the air vent passage from the upper space of the air to either the atmosphere or the air flow path, the air cleaner is provided between the connection portion between the left and right suction ducts of the air cleaner. An air vent device for a carburetor, characterized in that a switching valve is arranged. 2. The air vent device for a carburetor according to claim 1, wherein outside air is supercharged into the left and right suction ducts by using a traveling wind pressure. 3. The switching valve operates in response to a negative pressure of an intake air of an engine such that the switching valve communicates with the atmosphere when the engine is stopped and communicates with the air passage during operation of the engine. Item 1. An air vent device for a vaporizer according to Item 1 or 2. 4. The air vent passage according to claim 1, wherein the air vent passage is disposed in a state of a rising slope without a valley.
An air vent device for a vaporizer according to claim 3.