Fuel return device

A fuel return device includes a fuel collector and a return system. The fuel collector is located in a passage between a fuel tank and a vapor fuel processing device that processes vapor fuel discharged from the fuel tank. The fuel collector collects the fuel and stores the collected fuel as a storage fuel. The return system extends from the fuel collector, and is connected to a low-pressure generation part that generates a low pressure by a flow of fuel refueled through a filler pipe into the fuel tank, to return the storage fuel to the fuel tank.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase Application under 35 U.S.C. 371 of International Application No. PCT/JP2016/084874 filed on Nov. 25, 2016 and published in Japanese as WO 2017/104377 A1 on Jun. 22, 2017. This application is based on and claims the benefit of priority from Japanese Patent Application No. 2015-246452 filed on Dec. 17, 2015. The entire disclosures of all of the above applications are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a fuel return device.

BACKGROUND ART

Patent Literature 1 and Patent Literature 2 disclose a fuel tank system which controls discharge of vapor fuel from a fuel tank. Patent Literature 1 discloses a control valve which controls discharge of air from a fuel tank when liquid fuel is refueled. Furthermore, Patent Literature 1 discloses a jet pump for returning fuel caught by the control valve to the fuel tank.

PRIOR ART LITERATURES

Patent Literature

Patent Literature 1: JP 2010-59826 A

Patent Literature 2: JP 2008-132989 A

SUMMARY OF INVENTION

In the conventional arts, it is necessary to actuate an electric pump for supplying fuel that is a source of power for the jet pump to return the fuel caught by the control valve to the fuel tank. The caught fuel cannot be returned to the fuel tank while the electric pump is stopped. In the above-described viewpoints, or other viewpoints which are not mentioned, a fuel return equipment and a fuel tank system are further to be improved.

It is an object of the present disclosure to provide a fuel return device which can return collected fuel to a fuel tank without being dependent on an electric pump.

It is another object of the present disclosure to provide a fuel return device which can return collected fuel to a fuel tank at a refueling time.

According to an aspect of the present disclosure, a fuel return device includes: a fuel collector located in a passage between a fuel tank and a vapor fuel processing device that processes vapor fuel discharged from the fuel tank, the fuel collector collecting fuel and storing the collected fuel as a storage fuel; and a return system extending from the fuel collector, the return system being connected to a low-pressure generation part that generates a low pressure by a flow of fuel refueled through a filler pipe into the fuel tank, to return the storage fuel to the fuel tank.

According to the disclosed fuel return device, the return system returns the storage fuel stored out of the fuel tank to the fuel tank. The return system returns the storage fuel to the fuel tank by the low pressure generated by the low-pressure generation part. The low-pressure generation part generates the low pressure by the flow of fuel refueled through the filler pipe into the fuel tank. Therefore, the storage fuel can be returned to the fuel tank, without being dependent on an electric pump. Further, the storage fuel can be returned to the fuel tank during the refueling period. Therefore, the fuel collector can continuously collect and store fuel while fuel is contained in gas discharged from the fuel tank during the refueling period.

The present disclosure employs the following technical means, in order to attain the above-mentioned object. The symbols in the parenthesis indicated in claims merely show correspondence relations with concrete elements described in embodiments later mentioned as one example, and are not intended to limit the technical scope of this disclosure. The above and other objects, features and advantages of the present disclosure will become more apparent from the following detailed description made with reference to the accompanying drawings.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure will be described hereafter referring to drawings. In the embodiments, portions functionally and/or structurally corresponding to each other, and/or related to each other may be assigned with the same reference numeral or reference numerals in which hundreds or more are different. The corresponding portion and/or the related portion can be referred to the explanation in the other embodiment.

Embodiment

InFIG. 1, a fuel tank system1is mounted in a conveyance such as vehicle or vessel. For example, the fuel tank system1is disposed in a vehicle that travels on a road. The fuel tank system1has a fuel tank2in which liquid fuel is stored. The liquid fuel evaporates at a temperature for which the fuel tank system1is usually used, and generates vapor fuel. The vapor fuel is mixed with air. The liquid fuel is, for example, gasoline or light oil. The fuel tank system1stores fuel to be supplied to a fuel consumption equipment such as internal combustion engine. The fuel tank system1has a filler pipe3for supplying fuel to the fuel tank2. The filler pipe3extends upward from the fuel tank2.

In many cases, in the following explanation, the liquid fuel is called just as fuel. In many cases, a gas mixture of vapor fuel and air is called just as vapor fuel. The words of “up” and “down” correspond to the gravity direction when the fuel tank2is in a regular installation state.

When fuel is refueled, the fuel is supplied from the inlet end3aof the filler pipe3. Fuel flows downward through the passage in the filler pipe3, involving the surrounding gas such as air. Fuel arrives at the outlet end3bof the filler pipe3. Fuel is supplied into the fuel tank2from the outlet end3b. In the drawing, a flow of fuel is represented by an arrow LF. In the drawing, a flow of vapor fuel is represented by an arrow GF.

The fuel tank2may have complicated form for loading to a vehicle. Furthermore, some components of the fuel tank system1may be located to separate from the fuel tank2. Some components may be located at positions higher than the fuel tank2.

The fuel tank system1has a vapor fuel processing unit (EVPD)4. The vapor fuel processing unit4processes vapor fuel. The vapor fuel processing unit4is an equipment which controls the quantity of the vapor fuel emitted to the atmosphere from the fuel tank2. The vapor fuel processing unit4has a canister including activated carbon which adsorbs vapor fuel. The vapor fuel processing unit4catches and accumulates the vapor fuel discharged from the fuel tank2. Furthermore, the vapor fuel processing unit4includes a purge equipment which supplies the caught vapor fuel to a fuel consumption equipment for combusting the vapor fuel. An example of the purge equipment desorbs the vapor fuel from the activated carbon by supplying air to the activated carbon. Furthermore, the purge equipment mixes the desorbed vapor fuel to intake air of the internal combustion engine. The vapor fuel is processed by the internal combustion engine by combustion.

The fuel tank system1has an exhaust system5. The exhaust system5is arranged between the fuel tank2and the vapor fuel processing unit4. The exhaust system5supplies vapor fuel in the fuel tank2to the vapor fuel processing unit4. The exhaust system5provides a passage for the exhaust gas from the fuel tank2. For example, at a refueling time, the vapor fuel in the fuel tank2flows towards the vapor fuel processing unit4via the exhaust system5, as shown by an arrow VF.

The exhaust system5has an upward extension pipe5a. The upward extension pipe5ais a piping extending upward from the fuel tank2. The upward extension pipe5aextends from the upper part2aof the fuel tank2only by a predetermined height further upward. The end of the upward extension pipe5ais open in the upper part2a. The end of the upward extension pipe5ais open at a location upper than the outlet end3b. The upward extension pipe5acan be understood as a part of the fuel tank2.

The upward extension pipe5aenables a valve mechanism6and a fuel collector7, to be mentioned later, to be located to separate from the fuel tank2. The upward extension pipe5aenables the valve mechanism6and the fuel collector7to be positioned at a location higher than the end of the upward extension pipe5a. Such an arrangement raises the flexibility for selecting the installation positions of the valve mechanism6and the fuel collector7in case where the top wall of the fuel tank2has non-flat shape. The other end of the upward extension pipe5ais connected to the valve mechanism6.

The exhaust system5has the valve mechanism6. The valve mechanism6restricts leak of fuel via the exhaust system5. The valve mechanism6is a valve which switches a passage of the exhaust system5from the open state to the closed state in response to the reaching of fuel, and/or a valve which switches the passage of the exhaust system5from the open state to the closed state when the inclination angle of the fuel tank2exceeds a predetermined angle. The valve mechanism6is also called as a fuel shutoff valve. The valve mechanism6may be offered, for example, by a valve called a rollover valve. In this case, the valve mechanism6is closed to stop leak of fuel when the inclination angle exceeds the predetermined angle, in case where the fuel tank2inclines from a regular posture. The valve mechanism6may be offered by a valve called a float valve. In this case, if fuel reaches the valve mechanism6, the valve mechanism6is closed to restrict the leak of fuel. In the illustrated example, the valve mechanism6is a float valve.

The exhaust system5has the fuel collector7. The fuel collector7provides a container storing fuel. The fuel collector7is located in a passage between the fuel tank2and the vapor fuel processing unit4. The fuel collector7is located between the valve mechanism6and the vapor fuel processing unit4. The fuel collector7is located immediately downstream of the valve mechanism6. The fuel collector7catches fuel and stores the caught fuel. The fuel collector7is offered by a container located adjacent to the valve mechanism6. The fuel collector7is formed to surround the radially outer side of the valve mechanism6.

The fuel collector7is positioned to separate from the fuel tank2. In the illustrated example, the fuel collector7is separated from the fuel tank2by the upward extension pipe5a. In case where the upper wall of the fuel tank2has a large protrusion, the protrusion of the fuel tank2may reach near the fuel collector7. Also in this case, it can be said that the fuel collector7is positioned to separate from the fuel tank2, because the fuel collector7is separated from a connection part between the upward extension pipe5aand the fuel tank2. In other words, the fuel collector7is positioned upper than the connection part of the upward extension pipe5aand the fuel tank2.

The valve mechanism6and the fuel collector7are integrally formed as one-piece element. The valve mechanism6and the fuel collector7are provided by the collector unit20. Within this configuration, the fuel collector7includes the valve mechanism6. The collector unit20has a housing21. The housing21is a product made of, for example, resin. The housing21has an inlet22, an outlet23, and a return outlet24. The inlet22is connected to the upward extension pipe5a. The inlet22introduces the fuel and the vapor fuel which are supplied from the fuel tank through the upward extension pipe5ainto the housing21. The flow of fuel passing through the inlet22is shown by an arrow L1. The outlet23is connected to the vapor fuel processing unit4. The outlet23supplies the vapor fuel from the housing21to the vapor fuel processing unit4. The return outlet24is connected to the return system9to be mentioned later. The return outlet24supplies the storage fuel from the collector unit20to the return system9.

InFIG. 1andFIG. 2, the collector unit20is formed as one piping part which provides the valve mechanism6and the fuel collector7. The collector unit20has a float valve25of the valve mechanism6. The float valve25provides a movable valve object. The float valve25works with a fixed valve seat21aformed in the housing21, to switch the inlet22and the inside of the housing21to communicate with each other or be intercepted from each other. The valve closed state is illustrated in the drawing.

The collector unit20has a gas-liquid separation chamber26. The gas-liquid separation chamber26is formed between the valve mechanism6and the outlet23. The gas-liquid separation chamber26separates the fuel which passes through the valve mechanism6between the liquid fuel and the vapor fuel. The gas-liquid separation chamber26has a passage portion defined by the housing21and a barrier defined by the housing21. The fuel which flows through the passage portion is separated between the liquid fuel and the vapor fuel by colliding with the barrier. The vapor fuel bypasses the barrier, and reaches the outlet23. The flow of liquid fuel is shown by an arrow L2in the drawing. The liquid fuel flows downward on the inner surface of the housing21by colliding with the barrier. The flow of liquid fuel is shown by an arrow L3in the drawing. The gas-liquid separation chamber26may include plural barriers and/or plural barriers which define a zigzag passage.

The collector unit20has a storage chamber27. The storage chamber27is arranged under the gas-liquid separation chamber26. The storage chamber27stores the fuel separated in the gas-liquid separation chamber26as storage fuel. The storage chamber27annularly extends to surround the valve mechanism6including the float valve25. The storage chamber27is formed as an annular container. An outlet hole21bis formed in the bottom wall of the storage chamber27, and the storage chamber27and the return outlet24are able to communicate with each other through the outlet hole21b. The storage fuel can reach the return outlet24through the outlet hole21b.

The gas-liquid separation chamber26and the storage chamber27form the fuel collector7. The fuel collector7is formed to collect fuel between the valve mechanism6and the vapor fuel processing unit4.FIG. 2illustrates a liquid surface CF of the storage fuel.

The collector unit20has a check valve28. The check valve28is disposed between the storage chamber27and the return outlet24. The check valve28is a valve that responds to a pressure difference applied between the upstream and the downstream of the valve. The check valve28is a valve which responds to the weight of the storage fuel accumulated in the storage chamber27. The check valve28is a duckbill valve having an inlet28aadjacent to the fuel collector7, and an outlet28badjacent to the circulation system8corresponding to a low-pressure generation part to be mentioned below. The duckbill valve has a cylindrical body28c. The outlet28bis a slit formed in the body28c. The body28cgenerates a biasing force so that the outlet28bmaintains the valve closed state. The outlet28bis opened when a difference between a pressure which acts inside the body28cand a pressure which acts outside the body28cexceeds a predetermined valve-opening pressure difference.

The check valve28permits or forbids a flow of the storage fuel from the storage chamber27to the return system9. The check valve28allows the storage fuel to flow from the storage chamber27to the return system9, but prevents the fuel and the vapor fuel from flowing from the return system9to the storage chamber27. The check valve28permits the fuel to flow to the fuel tank2through the return system9in the forward direction, and prevents the backward flow from the fuel tank2in the opposite direction. The check valve28opens when the pressure of the fuel collector7is higher than the pressure adjacent to the low-pressure generation part by a predetermined threshold pressure difference. The check valve28can be opened also by the weight of the storage fuel accumulated in the storage chamber27. The check valve28is opened by the storage fuel stored in the storage chamber27when the amount of the storage fuel exceeds a predetermined quantity. Furthermore, the pressure difference makes the check valve28easy to open. Thus, the storage fuel stored in the storage chamber27is returned to the fuel tank2through the return system9. In the drawing, an arrow L4represents a flow of the storage fuel which passes through the check valve28.

The buoyancy of the float valve25is set up so as to offer the valve mechanism6which prevents leak of the fuel from the fuel tank2to the vapor fuel processing unit4. Furthermore, the valve mechanism6has a coiled spring29for adjusting the operational characteristic of the float valve25. The coiled spring29pushes the float valve25in the valve closing direction. The float valve25is in the valve open state, when fuel has not reached to the collector unit20, such that the exhaust system5is made in the communication state. When fuel reaches the collector unit20, the float valve25floats in the fuel, and is seated on the fixed valve seat21a, such that the exhaust system5is set in the interception state.

Returning toFIG. 1, the fuel tank system1has the circulation system8. The circulation system8is provided by a passage. The circulation system8is also called as a circulation passage. The circulation system8circulates gas between the inside of the fuel tank2and the adjacency of the inlet end3aof the filler pipe3. The circulation system8makes the upper part2aof the fuel tank2and an inlet inside3cnear the inlet end3aof the filler pipe3to communicate with each other. The circulation system8returns the gas from the fuel tank2to the inlet inside3c. The circulation system8supplies gas involved in liquid fuel from the inside of the fuel tank2. The circulation system8restricts the quantity of the vapor fuel discharged from the inlet end3ato outside, when a refueling is conducted.

The circulation system8provides a low-pressure generation part. The circulation system8generates low pressure by the flow of the fuel refueled through the filler pipe3into the fuel tank2, when the refueling is conducted into the fuel tank2. The low pressure generated by the circulation system8is lower than a pressure inside the storage chamber27. The low pressure generated by the circulation system8is lower than a pressure inside the fuel collector7. The low pressure generated by the circulation system8acts on the outlet28bside of the check valve28so that the check valve28is easily opened.

The circulation system8has a passage pipe8bcommunicated with the upper part2a, and a passage pipe8acommunicated with the inlet inside3c. The passage pipe8bextends out from the fuel tank2. The passage pipe8aextends out from the filler pipe3. The control valve unit30is disposed between the passage pipe8aand the passage pipe8b. The control valve unit30provides a part of the circulation system8.

The control valve unit30has a housing31. The housing31is a product made of, for example, resin. The housing31has an inlet32, an outlet33, and a return inlet34. The inlet32is connected to the passage pipe8b. The inlet32introduces the vapor fuel supplied from the fuel tank2through the passage pipe8binto the housing31. The flow of fuel passing through the inlet32is shown by an arrow GF. The outlet33is connected to the passage pipe8a. The outlet33supplies vapor fuel in the housing31to the inlet inside3c. The return inlet34is connected to the return system9to be mentioned later. The return inlet34makes the low pressure to act on the return system9via the unification part11. The return inlet34supplies the storage fuel from the return system9to the unification part11.

The fuel tank system1has the unification part11. The unification part11is a passage portion where the circulation system8and the return system9join with each other. The unification part11functions as a part of the circulation system8, and contributes to the generation of the low pressure. The return system9and the circulation system8are connected with each other in the unification part11. The storage fuel is returned to the fuel tank2via the return system9and the circulation system8.

The fuel tank system1has a control valve12. The control valve12is disposed in the circulation system8. The control valve12is located between the fuel tank2and the unification part11. The control valve12control the passage cross-section area of the circulation system8so that the low pressure acts on the unification part11.

The control valve12changes the passage cross-section area of the circulation system8between a small cross-section area and a large cross-section area. The control valve12controls the passage cross-section area based on a difference between a pressure applied to the upstream end and a pressure applied to the downstream end of the circulation system8. The control valve12provides the small cross-section area, when the pressure difference between the upstream end and the downstream end of the circulation system8is less than a predetermined level. When the pressure difference exceeds the predetermined level, the control valve12provides the large cross-section area. In other words, the control valve12permits a small flow rate when the pressure difference is less than the predetermined level, and permits a large flow rate when the pressure difference exceeds the predetermined level.

InFIG. 1andFIG. 3, the control valve unit30is formed as one piping part which provides the unification part11and the control valve12. The housing31forms an upper passage35communicated with the inlet32, and a downstream passage36communicated with the outlet33. The housing31further forms a return passage37which joins the downstream passage36in the unification part11. The unification part11is located downstream of the control valve12in the flow direction of the circulation system8.

The return passage37joins the downstream passage36in the unification part11. The return passage37is also called as a recovering passage for collecting the storage fuel. The unification part11is formed so that the return passage37is made to join the downstream passage36along the flow of the vapor fuel. The return passage37is formed to gradually join the downstream passage36along a direction from the fuel tank2to the filler pipe3in the downstream passage36. The downstream passage36and the return passage37are inclined to each other so that an acute angle is formed therebetween, and the unification part11corresponds to the peak of the acute angle. The return passage37extends from the upper side of the downstream passage36, and joins the downstream passage36. The unification part11forms a Venturi and can also be called as a Venturi part.

In the drawing, an arrow L5represents the flow of vapor fuel in the circulation system8. The flow L4of the storage fuel which reaches the unification part11through the return system9flows towards the outlet33, joining with the flow L5of the vapor fuel in the circulation system8.

The housing31has a first through hole31awhich makes the upper passage35and the downstream passage36to communicate with each other. The first through hole31ais set up to generate the low pressure at the downstream passage36when the flow of vapor fuel in the circulation system8is less than a predetermined threshold value. The housing31has a second through hole31bwhich makes the upper passage35and the downstream passage36to communicate with each other. The second through hole31bis set up to generate the low pressure at the downstream passage36when the flow rate of vapor fuel in the circulation system8exceeds the predetermined threshold value. The first through hole31ais smaller than the second through hole31b. The first through hole31ais always open. The second through hole31bis a variable passage opened and closed by the control valve12.

The control valve unit30has a movable valve object38which provides the control valve12. The movable valve object38is housed in the housing31.

The movable valve object38works with a fixed valve seat formed around the second through hole31b. The control valve12has a coiled spring39for adjusting the operational characteristic of the movable valve object38. The coiled spring39is arranged in the compression state between the movable valve object38and the housing31. The coiled spring39pushes the movable valve object38in the valve closing direction. The movable valve object38is seated on the fixed valve seat to make the second through hole31bin the communication state. The movable valve object38is separated from the fixed valve seat to make the second through hole31bin the interception state. The movable valve object38moves in response to a difference between a pressure acting on the upstream and a pressure acting on the downstream of the valve object, i.e., in the move direction. The movable valve object38is switched between the valve open state and the valve closed state by responding to the pressure difference between the upstream and the downstream of the valve object.

When the movable valve object38makes the second through hole31bin the interception state, the flow rate of the vapor fuel flowing through the circulation system8is restricted by the first through hole31a. As a result, the flow rate of the vapor fuel flowing through the circulation system8is restricted, and sufficiently low pressure acts on the unification part11. When the low pressure generated by the fuel flowing through the filler pipe3is large, a large pressure difference acts between the upstream and the downstream of the movable valve object38. While the movable valve object38makes the second through hole31bin the communication state, the flow rate of the vapor fuel flowing through the circulation system8becomes large. As a result, the low pressure can be made to act on the unification part11while permitting the circulation of a lot of vapor fuel, that is required as the circulation system8.

Returning toFIG. 1, the fuel tank system1has the return system9. The fuel collector7and the low-pressure generation part are communicated with each other by the return system9. The return system9returns the fuel accumulated in the fuel collector7into the fuel tank2by the low pressure generated by the low-pressure generation part. The return system9is provided by a passage which makes the fuel collector7and the circulation system8to communicate with each other. The return system9has a passage pipe9awhich makes the collector unit20and the control valve unit30to communicate with each other. The passage pipe9ais connected to the return outlet24and the return inlet34. In this embodiment, a fuel return device is formed of the fuel collector7and the return system9.

The low pressure in the unification part11acts on the check valve28via the return passage37. The low pressure makes the check valve28to easily open. When the check valve28opens, the storage fuel reaches the unification part11via the return outlet24, the passage pipe9a, and the return passage37. The storage fuel is transported to the inlet inside3cby the flow of the vapor fuel flowing through the circulation system8in the unification part. Furthermore, the storage fuel is returned to the fuel tank2through the filler pipe3. When sufficiently low pressure does not act on the unification part11, the check valve28may not be opened.

On the other hand, when the storage fuel is sufficiently accumulated in the storage chamber27, the check valve28may be opened by the weight of storage fuel. In this case, the storage fuel reaches the unification part11via the return outlet24, the passage pipe9a, and the return passage37. The storage fuel is made to flow in the circulation system8due to the gravity, and is returned to the fuel tank2. For example, the storage fuel can return to the fuel tank2by flowing backwards in the circulation system8through the control valve12from the unification part11.

According to the embodiment, the return system9returns the storage fuel stored out of the fuel tank2to the fuel tank2. The return system9returns the storage fuel to the fuel tank2by the low pressure generated by the circulation system8which is a low-pressure generation part. The low-pressure generation part generates the low pressure by the flow of fuel refueled through the filler pipe3into the fuel tank2. Therefore, the storage fuel can be returned into the fuel tank2, without being dependent on an electric pump. Further, the storage fuel can be returned to the fuel tank2during a refueling period. Therefore, even if fuel is included in gas discharged from the fuel tank2during the refueling period, the fuel collector7can continue the collection and the storage of fuel.

The disclosure in this description is not restricted to the illustrated embodiment. The disclosure includes the illustrated embodiments and modifications by a person skilled in the art based on the illustrated embodiments. For example, disclosure is not limited to the component and/or the combination of the components shown in the embodiments. The disclosure can be carried out with various combinations. The disclosure may use additional parts which can be added to the embodiments. The disclosure may contain modifications in which component and/or element of the embodiments are removed. The disclosure may contain modifications in which component and/or element of the embodiments are exchanged or combined. Technical scope of disclosure is not limited to the embodiments. It should be understood that some disclosed technical scope may be shown by description in the scope of claim, and contain all modifications which are equivalent to and within description of the scope of claim.

In the embodiment, the valve mechanism6and the fuel collector7are arranged in the one collector unit20. Alternatively, the valve mechanism6and the fuel collector7may be formed as separate components. In the embodiment, the fuel collector7is formed immediately downstream of the valve mechanism6in the exhaust system5. Alternatively, the fuel collector7may be formed in various positions in the fuel tank system1. For example, the fuel collector7may be located immediately upstream of the vapor fuel processing unit4. Moreover, the fuel collector7may be formed in the middle of piping.

In the embodiment, the control valve12is disposed in the circulation system8. Alternatively, the circulation system8may be equipped with a fixed orifice, instead of the control valve12. The low-pressure generation part is offered by the circulation system8in the embodiment. Alternatively, the low-pressure generation part may have the other various configurations. For example, the low-pressure generation part may be offered by a Venturi provided in the filler pipe3. Moreover, in the embodiment, the unification part11is formed in the control valve unit30. Alternatively, the unification part11and the control valve12may be formed as another piping parts.

Moreover, the low pressure may be generated using a flow of vapor fuel and/or fuel in a breather system, instead of the circulation system8. Moreover, a passage equipped with the function as the circulation system8and the function as the breather system may be used. In many cases, a fueling nozzle inserted in the filler pipe3is equipped with an automatic shutoff which stops the refueling by detecting fuel. The breather system is a passage for operating the automatic shutoff, when the liquid surface of fuel in the fuel tank2exceeds a predetermined level, by making fuel to flow to the inlet inside3c.

In the embodiment, the check valve28is provided by a duckbill valve. Alternatively, a check valve which has a movable valve object and a spring which biases the movable valve object in the valve closing direction may be used as the check valve28. In the embodiment, the check valve28is disposed in the collector unit. Alternatively, the check valve may be located in arbitrary positions in the return system9. For example, the check valve may be arranged in the control valve unit30. For example, the check valve may be disposed immediately upstream of the unification part11. Moreover, the check valve28may be understood as an element belonging to the fuel collector7.

In the embodiment, the upward extension pipe5aand the passage pipes8a,8b, and9aare provided plural pipings independent from each other. Alternatively, the plural pipes may be partially or entirely united with other component or piping. For example, the upward extension pipe5aand the passage pipe9amay be bundled partially. Moreover, the collector unit20and the control valve unit30may be formed as one piping part.