JP2007231762A - Gas vent device of fuel tank - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inhibit discharge of evaporative emission from a fuel tank in an engine having a carburetor. <P>SOLUTION: A fuel supply system comprises the fuel tank 20, the carburetor 10 including a float chamber 12a and an air vent 17 for communication of an upper space A of the float chamber 12a with the atmosphere and a fuel supply passage 30a bringing the fuel tank 20 and the float chamber 12a into communication with each other for supplying fuel, and a gas introduction passage 40a is provided for bringing an upper space A of the fuel tank 20 and the upper space A of the float chamber 12a into communication with each other to introduce the evaporative emission generated. The evaporative emission generated in the fuel tank 20 is thus introduced to the upper space A of the float chamber 12a through the gas introduction passage 40a, is temporarily stored and is then discharged from the upper space A of the float chamber 12a to the atmosphere though the air vent 17 while being subjected to passage resistance. A discharge amount of the evaporative emission is suppressed as compared with a case where the fuel tank 20 is directly opened to the atmosphere. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a fuel tank degassing device for extracting evaporated gas generated in a fuel tank of an internal combustion engine having a carburetor, and more particularly to a general-purpose engine or a generator in which the fuel tank is disposed above or near the carburetor. The present invention relates to a degassing device for a fuel tank to be applied.

  As a conventional fuel supply system for an internal combustion engine, a fuel tank disposed above the engine, a float chamber disposed in the intake system of the engine and one end of fuel is stored, and a fuel is ejected from the float chamber to a venturi in the intake passage. Nozzle, carburetor equipped with an air vent or the like that opens the upper part (gas phase) of the float chamber to the atmosphere, a fuel supply pipe that connects the upper part (gas phase) of the float chamber and the lower part (liquid phase) of the fuel tank, and the float chamber The fuel tank is provided with a fuel return pipe that communicates the lower part (liquid phase) of the fuel tank with the upper part (gas phase) of the fuel tank to return the fuel in the float chamber to the fuel tank. The fuel is guided to the float chamber of the engine and injected into the venturi (intake passage) from the nozzle. By utilizing the pressure difference between the funnel chamber and the fuel tank, which was to return the fuel is known to the fuel tank via the fuel return pipe from the float chamber (e.g., see Patent Document 1).

  Other fuel supply systems include a fuel supply pipe that connects the upper part (gas phase) of the float chamber and the lower part (liquid phase) of the fuel tank, a fuel pump arranged in the middle of the fuel supply pipe, and a fuel pump. A fuel return pipe that branches off the fuel supply pipe on the downstream side (near the float chamber) and communicates with the upper part (gas phase) of the fuel tank is provided. When the liquid level in the float chamber reaches a specified level, an excess There is known one in which fuel is returned to a fuel tank via a fuel return pipe (see, for example, Patent Document 2).

On the other hand, countermeasures for suppressing fuel vapor (evaporated gas) released or evaporated from a fuel supply system such as a fuel tank or a fuel pipe have been studied due to recent tightening of the evaporation gas regulations.
Therefore, as a countermeasure, a degassing pipe (air vent) is provided in the fuel tank to suppress the release of evaporative gas generated in the upper space (gas phase) in the fuel tank, and a check valve is provided in the middle of the degassing pipe. A method of disposing the gas and releasing it to the atmosphere only when the vaporized gas rises to a predetermined pressure can be considered. However, in this method, since the downstream side (atmosphere) side of the check valve of the degassing pipe is opened, it is necessary to further provide a filter or the like in order to prevent intrusion of foreign matter or the like from the open end. There is.

In addition, the carburetor is usually provided with an air vent (atmosphere release passage) that allows the upper space (gas phase) of the float chamber to communicate with the atmosphere, and foreign matter and the like enter the float chamber. A filter or the like is provided to prevent this. The float chamber (air vent) of the carburetor is installed at a safe position against a fire or the like in the fuel supply system including the internal combustion engine.
JP 58-202356 A JP-A-62-39382

  The present invention has been made in view of the above circumstances, and its purpose is to effectively utilize existing fuel tanks and carburetors and their accessory parts in order to comply with transpiration gas regulations. A fuel tank that simplifies the structure, reduces costs, etc., extracts evaporative gas (fuel vapor) generated in the fuel tank and suppresses it to the atmosphere as much as possible, and ensures safety An object of the present invention is to provide a degassing apparatus.

A degassing device for a fuel tank according to the present invention includes a fuel tank, a float chamber that accommodates a float that adjusts an inflow amount of fuel, a carburetor including an air vent that communicates with an upper space of the float chamber, a fuel tank, and a float chamber And a fuel supply passage for supplying fuel, and a gas introduction passage for guiding the evaporated gas generated by communicating the upper space of the fuel tank with the upper space of the float chamber is provided.
According to this configuration, fuel is supplied from the fuel tank to the float chamber via the fuel supply passage, and fuel is injected from the nozzle of the carburetor toward the venturi of the intake passage. Further, the evaporated gas (fuel vapor) generated in the fuel tank is guided to the upper space of the float chamber via the gas introduction passage and is stored at one end. And the evaporative gas led to the upper space (gas phase space) of the float chamber receives the passage resistance of the air vent, that is, at the stage where the pressure rises to a pressure higher than a predetermined level (for example, the external space of the float chamber (for example, The air is released into the atmospheric space, a passage closer to the atmospheric pressure of the intake system, or a space preferable for releasing the evaporated gas.
Therefore, compared with the case where the fuel tank is directly opened to the atmosphere, the amount of evaporative gas released can be reduced by the amount of increase in the passage resistance, and the entire engine including the fuel supply system releases the evaporative gas. The position (discharge port) to be used is only the air vent of the carburetor without increasing, and safety can be maintained.
In addition, measures are taken in advance to prevent the entry of foreign matter or the like from the outside to the air vent of the carburetor (for example, a filter is attached or the open end of the air vent is opened downward). In this case, no new parts are required, and the structure can be simplified, the number of parts can be reduced, and the cost can be reduced.

In the above configuration, the air vent may be configured to communicate directly with the atmosphere.
According to this configuration, the air vent is directly communicated with the atmosphere via a filter or a downwardly opening passage member (rubber hose or pipe) as necessary, so that the pressure drop in the upper space of the filter chamber can be reduced as much as possible. While suppressing (that is, ensuring desired fuel injection characteristics), it is possible to suppress the emission of evaporative gas.

In the above configuration, the air vent may be connected to an outside air introduction duct located upstream of the intake system to which the carburetor is connected and downstream of the air filter.
According to this configuration, since the air vent communicates with the outside air introduction duct on the downstream side of the air filter of the intake system, a new air filter that prevents intrusion of foreign matter is unnecessary, and inundation and the like can be prevented. Further, the evaporative gas introduced into the outside air introduction duct is used for engine combustion without being released to the atmosphere, and can be suppressed from being released into the atmosphere even when the engine is stopped. .

In the above-described configuration, a configuration in which a one-way valve that allows a one-way flow from the fuel tank to the float chamber is disposed in the gas introduction passage may be employed.
According to this configuration, since the one-way valve is arranged in the gas introduction passage, the evaporated gas generated in the fuel tank can be kept in the fuel tank until the pressure reaches a predetermined level. The amount can be effectively suppressed.

In the above configuration, the gas introduction passage is opened to allow a one-way flow from the fuel tank to the float chamber with a pressure difference of a predetermined level or more, and from the float chamber to the fuel tank with a pressure difference of a predetermined level or more. A configuration may be employed in which a two-way valve that allows flow in the other direction toward is disposed.
According to this configuration, since the two-way valve is arranged in the gas introduction passage, the evaporated gas generated in the fuel tank can be kept in the fuel tank until the pressure reaches a predetermined level. When the pressure in the upper space in the float chamber reaches a predetermined level, the evaporation gas can be recirculated from the float chamber toward the fuel tank. As a result, an appropriate amount of evaporative gas can be released from the air vent while preventing the foot chamber from becoming extremely high pressure.

In the above configuration, the fuel tank may have a cap that closes an opening for injecting fuel, and the gas introduction passage may be led out from the cap.
According to this configuration, since the gas introduction passage is led out from the cap, it is possible to meet the transpiration gas regulation by changing only the cap without making any changes to the existing fuel tank. Therefore, the structure can be simplified and the cost can be reduced.

  According to the degassing device for a fuel tank having the above-described configuration, the existing fuel tank and carburetor and their accessory parts are effectively used to achieve a simplified structure, lower costs, etc. As the evaporative gas (fuel vapor) that is generated can be prevented from being released into the atmosphere as much as possible, it is possible to comply with the transpiration gas regulation, and the number of outlets through which the evaporative gas is released does not increase throughout the engine. Safety is ensured.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described with reference to the accompanying drawings.
FIG. 1 is a configuration diagram of a fuel supply system including an embodiment of a degassing device for a fuel tank according to the present invention.
As shown in FIG. 1, this fuel supply system includes a carburetor 10 disposed in the intake system of the engine E, a fuel tank 20 disposed above the engine E, and a fuel supply pipe 30 connecting the fuel tank 20 and the carburetor 10. Further, a gas introduction pipe 40 for connecting the fuel tank 20 and the carburetor 10 is provided.

  As shown in FIG. 1, the carburetor 10 is a body 11 that defines a venturi (throttle passage) 11a connected to the intake passage of the engine E, and is detachably connected below the body 11 to define a float chamber 12a. The side case 12, the nozzle 13 communicating with the venturi 11a and the lower region of the float chamber 12a, the float 14 accommodated in the float chamber 12a so as to be movable up and down, the connectors 15 and 16 joined to the body 11, and the body 11 are formed. The air vent 17 is connected to the air vent 17 and has a rubber hose 17 ′ that opens downward and forms part of the air vent.

The body 11 is molded using an aluminum material or a resin material, and pipes 15 and 16 are press-fitted.
The lower case 12 is formed into a concave shape using an aluminum material or a resin material, and is fastened to the lower surface of the body 11 using screws or the like. The lower case 12 cooperates with the body 11 to define a float chamber 12a that accommodates the float 14 so as to be movable up and down. The float chamber 12a is divided into a lower space (liquid phase) F in which fuel is accumulated and an upper space (gas phase) A in which evaporative gas and the like are accumulated.

The nozzle 13 is formed of a metal pipe or the like, is fitted to the body 11, has a lower end opened to the lower space (liquid phase) F of the float chamber 12a, and an upper end protruded from the venturi 11a.
The float 14 is molded so as to confine air inside using a resin material or the like, and has a valve 14 a that opens and closes the opening of the pipe 15 on the upper surface thereof, and a through hole 14 b that passes the nozzle 13 in the approximate center thereof. Is formed. In more detail, the valve 14a opens and closes by being seated on or removed from the valve seat (not shown) via a float pin (not shown) that swings in conjunction with the vertical movement of the float 14.
The connector 15 is formed of a metal pipe or the like, and has one end opened to the upper space (gas phase) A of the float chamber 12a and the other end connected to an end (lower end) of the fuel supply pipe 30 described later. The body 11 is press-fitted.
The connector 16 is formed of a metal pipe or the like, and has one end opened to the upper space (gas phase) A of the float chamber 12a and the other end connected to an end (lower end) of a gas introduction pipe 40 described later. The body 11 is press-fitted.

The air vent 17 is formed to have a predetermined passage area with respect to the body 11, and opens the upper space (gas phase) A of the float chamber 12a to the atmosphere.
The rubber hose 17 ′ is connected to the air vent 17 and forms a part of the air vent as a whole. The rubber hose 17 ′ has a downward opening to the atmosphere so as to suppress or prevent foreign substances from entering as much as possible. It has become.

  As shown in FIG. 1, the fuel tank 20 is molded using a metal material or the like so as to contain fuel therein, and a lower space F in which fuel is stored and an upper space in which air and fuel evaporative gas (fuel vapor) are stored. A is defined, a connector 21 protruding from the lower part thereof, a cock 22 arranged in the middle of the connector 21 for opening and closing the passage, a filter 23 arranged upstream of the connector 21, and an opening at the upper part for injecting fuel An opening 24 that opens and closes, a cap 25 that opens and closes the opening 24, a connector 26 that protrudes upward from the upper portion, and the like.

The fuel supply pipe 30 is molded of a metal material, a resin material, or a rubber material to define a fuel supply passage 30a. As shown in FIG. 1, its upper end is connected to the connector 21 of the fuel tank 20, and its lower end is a carburetor. 10 connectors 15 are connected.
The fuel supply pipe 30 guides the fuel accumulated in the lower space F in the fuel tank 20 to the upper space A of the carburetor 10 and supplies it to the float chamber 12a.

The gas introduction pipe 40 is molded from a metal material, a resin material, or a rubber material to define a gas introduction passage 40a. As shown in FIG. 1, its upper end is connected to the connector 26 of the fuel tank 20, and its lower end is a carburetor. 10 connectors 16 are connected.
The gas introduction pipe 40 guides the evaporated gas accumulated in the upper space A in the fuel tank 20 to the upper space A of the float chamber 12 a of the carburetor 10.

In this gas venting device, fuel is supplied from the fuel tank 20 to the float chamber 12a through the fuel supply pipe 30, and the fuel is ejected from the nozzle 13 of the carburetor 10 toward the venturi 11a forming a part of the intake passage.
Further, the evaporative gas (fuel vapor) generated in the fuel tank 20 is guided to the upper space A of the float chamber 12a of the carburetor 10 through the gas introduction pipe 40 and is stored at one end. Then, the evaporative gas guided to the upper space A is released to the atmosphere while receiving the passage resistance of the air vent 17 and the rubber hose 17 ', that is, at a stage where the pressure rises to a predetermined level or higher.

Therefore, compared with the case where the fuel tank 20 is directly opened to the atmosphere, the amount of evaporative gas released can be suppressed, and predetermined evaporation gas regulations can be dealt with.
In addition, since the engine E including the fuel supply system as a whole emits evaporative gas only in the area of the air vent 17 (and the rubber hose 17 ') of the carburetor 10, safety against fires and the like is maintained as in the prior art. In addition, the pressure hose in the upper space A is suppressed as much as possible, that is, the desired fuel ejection characteristics are ensured, because it is communicated directly to the atmosphere via the rubber hose 17 ′ (passage member) that opens downward. However, it is possible to suppress the release of the evaporated gas.
Further, the air vent 17 and the rubber hose 17 ′ of the carburetor 10 are preliminarily provided with a structure (downward opening) for preventing the entry of foreign matters from the outside, so that no new parts are required and the structure is simplified. , Reduction in the number of parts, cost reduction, etc. can be achieved.

FIG. 2 is a configuration diagram of a fuel supply system including another embodiment of the degassing apparatus according to the present invention. This embodiment is the same as the above-described embodiment except that a filter 18 is provided on the air vent 17 of the carburetor 10 and a one-way valve 50 is added. Description is omitted.
That is, in this gas venting device, as shown in FIG. 2, a one-way valve 50 that allows a one-way flow of evaporating gas is disposed in the middle of the gas introduction pipe 40.
The one-way valve 50 opens when the pressure difference exceeds a predetermined level, opens the gas introduction passage 40a, and evaporates gas from the upper space A of the fuel tank 20 toward the upper space A of the float chamber 12a. Is allowed to flow.
Further, the air vent 17 is provided with a filter 18 in the middle thereof (in this case, the open end region) so as to prevent foreign matters and the like from entering from the outside.
According to this degassing device, the evaporative gas generated in the fuel tank 20 can be kept in the fuel tank 20 (upper space A) until the pressure reaches a predetermined level. Can be suppressed.

  FIG. 3 is a configuration diagram of a fuel supply system including still another embodiment of the degassing apparatus according to the present invention. This embodiment is the same as the embodiment shown in FIG. 2 except that the position where the gas introduction pipe 40 is led out is changed to the cap 25 ′. Therefore, the same components are denoted by the same reference numerals. The description is omitted.

That is, in this degassing apparatus, as shown in FIG. 3, a connector 25a ′ protruding upward is provided with respect to the cap 25 ′ of the fuel tank 20 ′. The upper end of the gas introduction pipe 40 is connected to the connector 25a ′ of the cap 25.
According to this degassing device, since the gas introduction passage 40a is led out from the cap 25 ', only the cap 25' is changed without any change to the existing fuel tank to which no countermeasures for the transpiration gas regulation are applied. Therefore, since it is possible to comply with the transpiration gas regulation, the cost required for the change can be suppressed as much as possible, and the structure can be simplified and the cost can be reduced.

  FIG. 4 is a configuration diagram of a fuel supply system including still another embodiment of the degassing apparatus according to the present invention. In this embodiment, except that the two-way valve 60 is adopted instead of the one-way valve 50, it is the same as the embodiment shown in FIG. 2 described above. Description is omitted.

That is, in this gas venting device, as shown in FIG. 4, a two-way valve 60 that allows the two-way flow of the evaporating gas is disposed in the middle of the gas introduction pipe 40.
The two-way valve 60 is opened to allow a one-way flow from the upper space A of the fuel tank 20 to the upper space A of the float chamber 12a with a pressure difference of a predetermined level or more, thereby opening the gas introduction passage 40a. The evaporative gas is allowed to flow from the upper space A of the fuel tank 20 toward the upper space A of the float chamber 12a, and the upper space of the fuel tank 20 from the upper space A of the float chamber 12a with a pressure difference of a predetermined level or more. The valve is opened to allow the flow in the other direction toward A to open the gas introduction passage 40a, and the evaporative gas is allowed to flow from the upper space A of the float chamber 12a toward the upper space A of the fuel tank 20.
According to this degassing device, by arranging the two-way valve 60 in the gas introduction passage 40a, the evaporated gas generated in the fuel tank 20 can be kept in the fuel tank 20 until the pressure reaches a predetermined level. Therefore, the amount of discharge to the outside can be effectively suppressed, and when the pressure in the upper space A in the float chamber 12a reaches a predetermined level, the flow from the float chamber 12a to the fuel tank 20 is reversed. By recirculating the evaporative gas, it is possible to eliminate (cancel) the state when the fuel tank 20 has a negative pressure.
As a result, an appropriate amount of evaporated gas can be released from the air vent 17 while preventing the foot chamber 12a from becoming extremely high pressure.

  FIG. 5 is a configuration diagram of a fuel supply system including still another embodiment of a gas venting apparatus according to the present invention. In this embodiment, the air vent 17 is the same as the embodiment shown in FIG. 2 except that the air vent 17 is not directly opened to the atmosphere but communicated with the outside air introduction duct D. The description is omitted.

That is, in this degassing apparatus, as shown in FIG. 5, the air vent 17 formed in the body 11 is upstream of the intake system to which the carburetor 10 is connected via the rubber hose 17 ″ and the air filter. It communicates with an outside air introduction duct D located downstream of the AF.
According to this degassing device, the air vent 17 communicates with the outside air introduction duct D on the downstream side of the air filter AF of the intake system, so that a new air filter for preventing the intrusion of foreign matters is unnecessary, such as inundation. Can also be prevented. Further, the evaporative gas led to the outside air introduction duct D is used for combustion of the engine E without being released to the atmosphere, and even when the engine E is stopped, the emission to the atmosphere is suppressed. it can.

  In the above embodiment, the case where the gas venting device according to the present invention is applied to the engine E in which the fuel tanks 20 and 20 ′ are disposed above the carburetor 10 is shown, but the present invention is not limited thereto. Even in an engine in which the fuel tank is disposed below the carburetor, the gas venting device of the present invention can be applied by adding a fuel pump or the like to the fuel supply passage.

  In the above-described embodiment, the case where the gas venting device of the present invention is applied to the engine including the carburetor 10 in which only the nozzle 13 is arranged in the venturi 11a has been described. However, the present invention is not limited thereto. The degassing device of the present invention can be similarly applied to an engine including a carburetor including a throttle valve having a jet needle.

  In the above embodiment, the configuration in which the air vent 17 is communicated with the outside air introduction duct D is shown only for the case where the one-way valve 50 is provided, but the present invention is not limited to this, and as shown in FIG. In a configuration in which the directional valve 50 is not provided, a configuration in which the gas introduction passage 40a is led out from the cap 25 'as shown in FIG. 3, or a configuration in which the two-way valve 60 is provided as shown in FIG. A configuration for communicating with the introduction duct D may be employed.

  As described above, the degassing device for a fuel tank according to the present invention achieves simplification of the structure, cost reduction, etc., while evaporating gas (fuel vapor) generated in the fuel tank is released into the atmosphere. Can be applied to general-purpose engines, generators, agricultural engines, etc., as well as engines equipped with carburetors, etc. It is also useful in an engine to be mounted or an engine mounted on other vehicles.

1 is a configuration diagram of a fuel supply system including an embodiment of a degassing device for a fuel tank according to the present invention. It is a block diagram of the fuel supply system containing other embodiment of the degassing apparatus of the fuel tank which concerns on this invention. It is a block diagram of the fuel supply system containing further another embodiment of the degassing apparatus of the fuel tank which concerns on this invention. It is a block diagram of the fuel supply system containing further another embodiment of the degassing apparatus of the fuel tank which concerns on this invention. It is a block diagram of the fuel supply system containing further another embodiment of the degassing apparatus of the fuel tank which concerns on this invention.

Explanation of symbols

10 carburetor 11 body 11a venturi 12 lower case 12a float chamber A upper space F lower space 13 nozzle 14 float 15, 16 connector 17 air vent 17 ', 17 "rubber hose 18 filter 20, 20' fuel tank 21 connector 22 cock 23 Filter 24 Opening 25, 25 'Cap 25a' Connector 26 Connector 30 Fuel supply pipe 30a Fuel supply passage 40 Gas introduction pipe 40a Gas introduction passage 50 One-way valve 60 Two-way valve D Outside air introduction duct AF Air filter

Claims (6)

A fuel tank, a float chamber that houses a float that adjusts the amount of inflow of fuel, a carburetor that includes an air vent that communicates with the upper space of the float chamber, and a fuel that supplies fuel by communicating the fuel tank and the float chamber A supply passage,
A gas introduction passage is provided to guide the evaporated gas generated by communicating the upper space of the fuel tank with the upper space of the float chamber;
A degassing device for a fuel tank. The air vent is in direct communication with the atmosphere;
The degassing apparatus for a fuel tank according to claim 1. The air vent communicates with an outside air introduction duct located on the upstream side of the intake system to which the carburetor is connected and on the downstream side of the air filter.
The degassing apparatus for a fuel tank according to claim 1. A one-way valve that allows a one-way flow from the fuel tank to the float chamber is disposed in the gas introduction passage.
The degassing device for a fuel tank according to any one of claims 1 to 3. The gas introduction passage is opened to allow a one-way flow from the fuel tank to the float chamber with a pressure difference of a predetermined level or more, and from the float chamber with a pressure difference of a predetermined level or more. A two-way valve that allows flow in the other direction towards the tank is arranged,
The degassing device for a fuel tank according to any one of claims 1 to 3. The fuel tank has a cap for closing an opening for injecting fuel;
The gas introduction passage is led out from the cap,
The degassing device for a fuel tank according to any one of claims 1 to 5, wherein

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