Fuel supply device

A swirling wall structure-extends from a lower side toward an upper side in a sub-tank, and a fuel flow, which is outputted into an inside of the sub-tank from a flow outlet of a diffuser passage opened toward a lateral side, is swirled by the swirling wall structure. The swirling wall structure-includes a curved wall surface and a U-turn wall surface. The curved wall surface is curved about a longitudinal axis, which extends from the lower side toward the upper side in the sub-tank, to bend the fuel flow outputted from the flow outlet. The U-turn wall surface extends continuously from the curved wall surface to make a U-turn of the fuel flow, which is bent by the curved wall surface.

CROSS REFERENCE TO RELATED APPLICATION

This application is the U.S. national phase of International Application No. PCT/JP2015/005068 filed on Oct. 6, 2015 which designated the U.S. and claims priority to Japanese Patent Application No. 2014-209562 filed on Oct. 13, 2014, the entire contents of each of which are hereby incorporated by reference.

TECHNICAL FIELD

The present disclosure relates to a fuel supply device that supplies fuel stored in a fuel tank to an internal combustion engine located at an outside of the fuel tank.

BACKGROUND ART

A fuel supply device, which pressurizes fuel stored in the fuel tank and discharges the pressurized fuel to the internal combustion engine through use of a fuel pump, is known from, for example, the patent literature 1. The device disclosed in the patent literature 1 has a swirling wall structure that swirls a fuel flow.

Specifically, the swirling wall structure of the device disclosed in the patent literature 1 is placed along a path, which extends from the fuel pump to the internal combustion engine, to swirl the fuel flow about an axis that extends in a vertical direction. In this way, air bubbles, which are contained in the fuel and have a small specific gravity, are concentrated in a center part of the swirl flow, so that a cluster of air bubbles is formed in the center part of the swirl flow in a manner that increases a buoyant force exerted to the air bubbles. Thus, the cluster of air bubbles is expelled from the path, which extends from the fuel pump to the internal combustion engine, through a vent hole, which extends through an upper wall of the swirling wall structure. Thereby, in the internal combustion engine, it is possible to limit deterioration of a performance, which would be caused by the intake of the fuel containing the air bubbles.

However, in the swirling wall structure of the device disclosed in the patent literature 1, the presence of the vent hole in the path, which extends between the fuel pump and the internal combustion engine, causes that a portion of the fuel to be supplied to the internal combustion engine is escaped through the vent hole, so that a sully loss of the fuel is induced. The fuel supply loss of this kind causes wasting of the drive energy of the fuel pump. Therefore, there is a need for improvement in view of the energy saving. When the leakage of the fuel is reduced by reducing a diameter of the vent hole, the air bubbles cannot be effectively expelled through the vent hole having the reduced diameter. Thereby, the air bubbles may remain in the fuel to possibly cause deterioration of the performance of the internal combustion engine.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

The present disclosure is made in view of the above disadvantages. Thus, it is an objective of the present disclosure to provide a fuel supply device that can achieve both of the energy saving and ensuring of the required performance of the internal combustion engine.

In order to achieve the above objective, according to a first aspect of the present disclosure, there is provided a fuel supply device that supplies fuel from a fuel tank toward an internal combustion engine located at an outside of the fuel tank, the fuel supply device including: a sub-tank that is placed in an inside of the fuel tank and is shaped into a tubular body that has a bottom, wherein an opening of the sub-tank is opened toward an upper side; a jet pump that is received in an inside of the sub-tank, wherein the jet pump discharges pressurized fuel from a nozzle passage into a diffuser passage in the jet pump and thereby pumps stored fuel, which is stored in the fuel tank, into the inside of the sub-tank through the diffuser passage; a fuel pump that is received in the inside of the sub-tank, wherein the fuel pump draws the fuel pumped into the sub-tank by the jet pump and discharges the drawn fuel toward the internal combustion engine; and a swirling wall structure that extends from a lower side toward an upper side in the sub-tank, wherein a fuel flow, which is outputted into the inside of the sub-tank from a flow outlet of the diffuser passage opened toward a lateral side, is swirled by the swirling wall structure, and the swirling wall structure, which is assumed to have a longitudinal axis extending from the lower side to the upper side of the sub-tank, includes: a curved wall surface that is curved about the longitudinal axis to bend the fuel flow outputted from the flow outlet; and a U-turn wall surface that extends continuously from the curved wall surface to make a U-turn of the fuel flow, which is bent by the curved wall surface.

At the diffuser passage, which draws the accumulate fuel from the fuel tank through the discharge of the fuel from the nozzle passage, the flow outlet opened toward the latera side discharges the fuel flow into the sub-tank, and this fuel flow is swirled by the swirling wall structure of the first aspect. Specifically, the fuel flow, which is outputted from the flow outlet, is bent along the curved wall surface that is curved about the longitudinal axis that extends from the lower side to the upper side of the sub-tank, and then this fuel flow makes the U-turn along the U-turn wall surface that extends continuously from the curved wall surface. Thereby, the fuel flow is swirled. In this way, the air bubbles, which are contained in the fuel and have the small specific gravity, are concentrated in the center part of the swirl flow to form a cluster of air bubbles in a manner that increases a buoyant force of the air bubbles. Thereby, movement of the cluster of air bubbles is less likely interfered by the swirling wall structure that extends from the lower side to the upper side in the sub-tank. Furthermore, in the sub-tank, which is shaped into the tubular body that has the bottom, an opening of the sub-tank, through which the jet pump and the fuel pump are insertable into the inside of the sub-tank, opens toward the upper side. Therefore, the cluster of air bubbles can be easily expelled by the upward movement of the cluster of air bubbles. Furthermore, the fuel, which is received in the sub-tank and from which the air bubbles are removed by the swirling wall structure, can be entirely drawn into and discharged from the fuel pump toward the internal combustion engine. Thereby, the supply loss of the fuel can be limited.

According to the first aspect of the present disclosure, in addition to the energy saving, which is implemented by limiting the supply loss of the fuel, the required performance of the internal combustion engine can be achieved by the removal of the air bubbles.

Furthermore, in the fuel supply device according to a second aspect of the present disclosure, the jet pump described above is a first jet pump, which pumps the stored fuel of the fuel tank from a location on a lower side of the sub-tank into the inside of the sub-tank, and the fuel supply device includes a second jet pump that is received in the inside of the sub-tank. The second jet pump discharges pressurized fuel from a nozzle passage into a diffuser passage in the second jet pump and thereby pumps the stored fuel of the fuel tank from a corresponding location of the fuel tank, which is other than the location on the lower side of the sub-tank, into the inside of the sub-tank through the diffuser passage of the second jet pump, and the swirling wall structure includes a confluence opening, through which a fuel flow outputted from a flow outlet of the diffuser passage of the second jet pump is merged with the fuel flow outputted from the flow outlet of the diffuser passage of the first jet pump.

According to the second aspect, the fuel flow, which is outputted from the second jet pump, is merged with the fuel flow, which is outputted from the flow outlet of the first jet pump and is swirled by the swirling wall structure, through the confluence opening to form the swirl flow. Therefore, it is possible to remove the air bubbles from the fuel, which is pumped by the first jet pump from the location on the lower side of the sub-tank, and also the air bubbles from the fuel, which is pumped by the second jet pump from the other location that is other than the location on the lower side of the sub-tank. Thereby, the swirling wall structure, which removes the air bubbles and limits supply loss of the fuel, is commonly used by the first jet pump and the second jet pump to simplify the structure and to achieve both of the energy saving and the required performance of the internal combustion engine.

DESCRIPTION OF EMBODIMENTS

Various embodiments of the present disclosure will be described with reference to the drawings. In the following respective embodiments, similar components are indicated by the same reference signs and may not be redundantly described. In a case where only some parts of the construction of each of the embodiments are described, the construction of the previously described embodiment may be applied to the rest of the construction of the embodiment. Furthermore, besides the explicitly indicated combination of the components described in each of the following embodiments, the components of different embodiments may be partially combined as long as such a combination does not cause a problem.

First Embodiment

As shown inFIG. 1, a fuel supply device1according to a first embodiment of the present disclosure is installed in a fuel tank2of a vehicle. The device1supplies fuel, which is stored in the fuel tank2, to fuel injection valves of an internal combustion engine3indirectly through another intervening device, such as a high pressure pump, or directly without through such an intervening device. The fuel tank2, in which the device1is installed, is made of resin or metal and is shaped into a hollow form to accumulate the fuel to be supplied to the internal combustion engine3. The internal combustion engine3, to which the fuel is supplied from the device1, may be a diesel engine or a gasoline engine. InFIGS. 1 and 3-6, a top-to-bottom direction and a transverse direction respectively coincide with a vertical direction and a horizontal direction of the vehicle placed on a horizontal plane (hereinafter, simply referred to as a vertical direction and a horizontal direction).

Hereinafter, a structure and an operation of the device1will be described.

As shown inFIGS. 1 to 4, the device1includes a flange10, a sub-tank20, an adjusting mechanism30, a pump unit40, and a swirling wall structure50.

As shown inFIG. 1, the flange10is made of resin and is shaped into a circular plate form. The flange10is installed to a top plate portion2aof the fuel tank2. A packing10ais clamped between the top plate portion2aand the flange10, so that a through-hole2b, which is formed in the top plate portion2a, is closed. As shown inFIGS. 1 and 2, the flange10has a fuel supply conduit12, a return conduit14and an electrical connector16, which are integrally assembled to the flange10.

The fuel supply conduit12is communicated with the pump unit40, which is received in the fuel tank2, though a flexible tube12athat is flexible. Furthermore, at the outside of the fuel tank2, the fuel supply conduit12is communicated to a fuel path4that connects between the fuel tank2and the internal combustion engine3. The fuel supply conduit12supplies the fuel, which is pumped by a fuel pump42of the pump unit40, from the inside of the fuel tank2to the internal combustion engine3located at the outside of the fuel tank2. The return conduit14is communicated with a branch passage4a, which is branched from the fuel path4at the outside of the fuel tank2. Furthermore, the return conduit14is communicated with the pump unit40received in the fuel tank2through a flexible tube14athat is flexible. The return conduit14returns the return fuel, which is branched at the outside of the fuel tank2from the flow of the supply fuel to be supplied to the internal combustion engine3, to a residual pressure holding valve45of the pump unit40received in the fuel tank2. As shown inFIG. 2, the electrical connector16electrically connects the fuel pump42to a control circuit (not shown) located at the outside of the fuel tank2.

With reference toFIGS. 1, 3 and 4, the sub-tank20is made of resin and is shaped into a cylindrical tubular body having a bottom, and the sub-tank20is placed in the inside of the fuel tank2. An opening20cof the sub-tank20opens toward the upper side. A bottom portion20aof the sub-tank20is placed on a bottom portion2cof the fuel tank2. As shown inFIGS. 3 and 4, a flow inlet24is formed in a recessed bottom part20b, which is upwardly recessed from a deepest bottom part20eof the bottom portion20a. The flow inlet24is communicated with an inflow space22, which is defined between the recessed bottom part20band the bottom portion2c. Furthermore, the flow inlet24is communicated with a jet pump46of the pump unit40. The fuel stored in the fuel tank2flows into the flow inlet24through the inflow space22located on the lower side of the sub-tank20, and then this fuel is pumped by the jet pump46into the inside of the sub-tank20. An umbrella valve27shown inFIG. 4is installed on the recessed bottom part20bof the present embodiment in such a manner that the umbrella valve27opens the flow inlet24when a negative pressure is applied to the umbrella valve27from the jet pump46as described in detail later.

As shown inFIG. 1, the adjusting mechanism30includes a pair of support shafts32and an adjusting spring (not shown). Each support shaft32is made of metal and is shaped into a cylindrical form. The support shaft32extends in the top-to-bottom direction in the inside of the fuel tank2. An upper end part of each support shaft32is fixed to the flange10. A portion of each support shaft32, which is located below the upper end part of the support shaft32, is guided by the sub-tank20in such a manner that the support shaft32is slidable in the top-to-bottom direction. The adjusting spring is placed coaxially around a corresponding one of the pair of support shafts32in the inside of the sub-tank20and is thereby interposed between the sub-tank20and the corresponding support shaft32. As shown inFIGS. 1, 3 and 4, the adjusting spring urges the bottom portion20aof the sub-tank20against the bottom portion2cof the fuel tank2.

The pump unit40is received in the inside of the sub-tank20. As shown inFIGS. 2 to 4, the pump unit40includes a suction filter41, the fuel pump42, a pump holder43, a relief valve44, the residual pressure holding valve45and the jet pump46.

The suction filter41is, for example, a nonwoven fabric filter and is placed above the deepest bottom part20eof the bottom portion20ain the inside of the sub-tank20. The suction filter41filters the fuel, which is drawn from the inside of the sub-tank20into the fuel pump42, to remove foreign objects contained in the drawn fuel.

The fuel pump42is connected to an upper side of the suction filter41in the inside of the sub-tank20. The fuel pump42is an electric pump in the present embodiment and is electrically connected to the electrical connector16through a flexible wiring42athat is flexible. The operation of the fuel pump42is controlled by the control circuit through the electrical connector16. When the fuel pump42is operated, the fuel pump42pressurizes the fuel drawn through the suction filter41in the inside of the sub-tank20.

With reference toFIGS. 1, 3 and 4, the pump holder43is made of resin and is shaped into an arm form. The pump holder43is installed to the opening20cof the sub-tank20. The pump holder43supports the fuel pump42from a radially outer side of the fuel pump42.

As shown inFIGS. 2 to 4, the relief valve44is connected to a lateral side of the fuel pump42in the inside of the sub-tank20. The relief valve44is communicated with an outlet (not shown) of the fuel pump42. Also, the relief valve44is communicated with the fuel supply conduit12through the flexible tube12a. Furthermore, the relief valve44is also communicated with the inside of the sub-tank20. When the pressure of the fuel, which is discharged from the fuel pump42and is supplied to the internal combustion engine3side, is less than a relief pressure, the relief valve44is closed to ensure the required pressure of the supplied fuel that is supplied to the internal combustion engine3. In contrast, when the pressure of the fuel, which is supplied to the internal combustion engine3, becomes equal to or larger than the relief pressure, the relief valve44is opened to release the fuel to the inside of the sub-tank20.

The residual pressure holding valve45is connected to the lateral side of the fuel pump42in the inside of the sub-tank20. The residual pressure holding valve45is communicated with the return conduit14through the flexible tube14a. The residual pressure holding valve45is also communicated with the jet pump46. When the pressure of the fuel, which is supplied to the internal combustion engine3, is equal to or larger than a valve opening pressure of the residual pressure holding valve45, the residual pressure holding valve45is opened, so that a portion of the fuel supplied to the internal combustion engine3side is discharged from the discharge outlet450to the jet pump46side. In contrast, when the pressure of the fuel, which is supplied to the internal combustion engine3side, becomes less than a valve closing pressure of the residual pressure holding valve45, the residual pressure holding valve45is closed to hold the pressure of the fuel supplied to the internal combustion engine3side.

The jet pump46is made of resin and is shaped into a hollow form. The jet pump46is connected to a lateral side of the residual pressure holding valve45in the inside of the sub-tank20. As shown inFIGS. 3 and 4, the jet pump46is placed on the recessed bottom part20bof the bottom portion20aof the sub-tank20. The jet pump46includes a pressurizing portion460, a nozzle portion461, a suctioning portion462and a diffuser portion463, which are molded integrally.

The pressurizing portion460forms a pressurizing passage464that is in a form of a cylindrical hole, which extends straight in the top-to-bottom direction. Specifically, the pressurizing portion460is a resin portion that forms the pressurizing passage464. An upstream end464uof the pressurizing passage464is communicated with the discharge outlet450of the residual pressure holding valve45. The pressurizing passage464guides the pressurized fuel, which is discharged from the discharge outlet450to the upstream end464u, toward a downstream end464dof the pressurizing passage464.

The nozzle portion461includes a communication forming part461aand a flow restriction forming part461bon the lower side of the pressurizing portion460. The communication forming part461aforms a communicating passage part465aas an upstream part of a nozzle passage465. The flow restriction forming part461bforms a flow restricting passage part465bas a downstream part of the nozzle passage465. Specifically, the nozzle portion461, which is a resin portion that forms the nozzle passage465, is formed by a combination of the communication forming part461a, which is a resin part that forms the communicating passage part465a, and the flow restriction forming part461b, which is a resin part that forms the flow restricting passage part465b.

The communication forming part461ais a space that is shaped in a form of a substantially ⅛ sphere. An upstream end465auof the communicating passage part465ais communicated with a downstream end464dof the pressurizing passage464. The transverse direction inFIGS. 6 to 8is defined as a common width direction Dcp, which defines a passage width Wc of the communicating passage part465aand a passage width Wp of the pressurizing passage464. The passage width Wc of the communicating passage part465ais set to be smaller than the passage width Wp of the pressurizing passage464. Furthermore, in order to implement the above settings, as shown inFIGS. 5 to 7, a tapered passage wall surface460ais formed in a part of the pressurizing portion460, which forms the downstream end464dof the pressurizing passage464, except a connection to the communicating passage part465a. The tapered passage wall surface460ais in a form of a conical surface and has a progressively reducing diameter that is progressively reduced toward the communicating passage part465a.

As shown inFIGS. 5 to 8, a first passage wall surface461afand a second passage wall surface461asare formed at two opposite sides, respectively, of the communicating passage part465a, which are opposed to each other in the common width direction Dcp, in the communication forming part461a. The first passage wall surface461afis in a form of a planar surface that extends in both of the transverse direction, which is substantially perpendicular to the common width direction Dcp, and the top-to-bottom direction. An upstream end465buof the flow restricting passage part465bopens in a part of the first passage wall surface461af, which forms a downstream end465adof the communicating passage part465a. In the present embodiment, the upstream end465buof the flow restricting passage part465bis formed at a location that is further spaced from the second passage wall surface461asin comparison to the first passage wall surface461afexcept a projected part of the upstream end465bu, which projects from the first passage wall surface461aftoward the second passage wall surface461as.

In comparison to the first passage wall surface461afdiscussed above, the second passage wall surface461asis curved toward the flow restricting passage part465band is shaped in a form of a substantially ⅛ sphere. The second passage wall surface461asof the present embodiment is continuously curved from a location, which is spaced toward the downstream side from the downstream end464dof the pressurizing passage464, to the flow restricting passage part465b. Furthermore, in the cross sectional view ofFIG. 6, which shows the upstream end465buof the flow restricting passage part465bseen from the communicating passage part465aside, the second passage wall surface461asof the present embodiment is curved in a counterclockwise direction from the pressurizing passage464side. The passage width We of the communicating passage part465a, which is located between the wall surfaces461af,461as, is progressively reduced toward the flow restricting passage part465bwithin an extent that is smaller than the passage width Wp of the pressurizing passage464. In the communicating passage part465a, as indicated by an arrow inFIG. 9(a), a fuel flow Ff is generated when the pressurized fuel flows from the pressurizing passage464into the communicating passage part465a. The fuel flow Ff flows along the second passage wall surface461asand is thereby swirled and enters the flow restricting passage part465blocated on the downstream side of the communicating passage part465a.

As shown inFIGS. 5 to 8, the flow restriction forming part461b, which is molded integrally at a lateral side of the communication forming part461a, forms the flow restricting passage part465bin a form of a cylindrical hole that extends straight in the transverse direction that is substantially perpendicular to the common width direction Dcp. The upstream end465buof the flow restricting passage part465bopens in the first passage wall surface461af, so that the upstream end465buof the flow restricting passage part465bis communicated with the downstream end465adof the communicating passage part465a. A flow rate of the fuel in the flow restricting passage part465bis further restricted in comparison to a flow rate of the fuel in the communicating passage part465a. As indicated by the arrow inFIG. 9(a), the fuel flow Ff is swirled along the second passage wall surface461asand is supplied from the communicating passage part465ato the flow restricting passage part465b. Therefore, as shown inFIG. 9(b), the fuel flow Ff, the flow rate of which is restricted, is outputted in a swirling state from a downstream end465bdof the flow restricting passage part465b.

As shown inFIGS. 5 and 6, the suctioning portion462forms a suction passage468in a form of a planar space. The suction passage468is placed on the upper side of and covers the flow inlet24, which extends through the recessed bottom part20b. Specifically, the suctioning portion462is a resin portion that forms the suction passage468. At the lower side of the pressurizing portion460and the nozzle portion461, the suction passage468is communicated with the flow inlet24. The fuel, which is stored in the fuel tank2, can flow into the suction passage468through the inflow space22and the flow inlet24held in the valve opening state.

The diffuser portion463forms a diffuser passage469in a form of a cylindrical hole that coaxially extends from the flow restricting passage part465btoward the lateral side in the transverse direction. Specifically, the diffuser portion463is a resin portion that forms the diffuser passage469. An upstream end of the diffuser passage469cooperates with the suction passage468to form a confluence passage portion469a, which is communicated with the downstream end465bdof the flow restricting passage part465bon the lower side of the pressurizing portion460. As shown inFIG. 3, a downstream end of the diffuser passage469forms a flow outlet469b, which opens in the transverse direction and is communicated with the inside of the sub-tank20. With the above-described structure, the pressurized fuel, the flow rate of which is restricted, is discharged from the downstream end465bdof the flow restricting passage part465binto the confluence passage portion469a, so that a negative pressure is generated around the discharged fuel flow, and thereby, the supplied fuel, which is supplied from the opened flow inlet24into the suction passage468, is drawn into the diffuser passage469. Thus, the drawn fuel receives a diffuser effect in the diffuser passage469and is thereby pumped, so that the fuel is pumped into the sub-tank20through the flow outlet469bof the diffuser passage469.

At this time, as shown inFIGS. 9(b) and 9(c), the fuel in the swirling state is discharged into the confluence passage portion469a, so that the fuel flow Ff generated in the diffuser passage469forms a liquid film along the entire passage cross section and is outputted from the flow outlet469binto the inside of the sub-tank20. In the present embodiment, a transverse axis Lc, which extends in the transverse direction from the flow restricting passage part465b, is assumed to be present. Under this assumption, since the second passage wall surface461asis curved from the pressurizing passage464in the counterclockwise direction, the fuel flow Ff is generated in the diffuser passage469in such a manner that the fuel flow Ff is swirled in the counterclockwise direction about the transverse axis Lc in a view taken from the flow restricting passage part465b.

As shown inFIGS. 3, 10 and 11, the swirling wall structure50extends from the lower side toward the upper side in the inside of the sub-tank20. Specifically, the swirling wall structure50includes a curved wall surface52, a guide wall surface54and a U-turn wall surface56.

The curved wall surface52is formed by a portion of a specific plate surface28aof a longitudinal wall portion28, which is shaped into a plate form and is integrally molded together with the sub-tank20. The curved wall surface52is substantially perpendicular to the deepest bottom part20e, which is formed in the bottom portion20aof the sub-tank20and extends in the horizontal direction, so that the curved wall surface52extends in the vertical direction that substantially coincides with the top-to-bottom direction. Furthermore, the curved wall surface52extends continuously on both of the upper side and the lower side of the flow outlet469b, which is located on the lateral side of the curved wall surface52and is opposed to the curved wall surface52.

As shown inFIGS. 3 and 10, in the swirling wall structure50, a longitudinal axis LI, which extends from the lower side to the upper side of the sub-tank20, particularly in the vertical direction is assumed to be present. The curved wall surface52is curved about the longitudinal axis LI in a form of a cylindrical concave surface (i.e., a form of an arcuate surface) that circumferentially extends substantially ¼ turn. In a top view, the curved wall surface52of the present embodiment is curved from an adjacent end52aof the curved wall surface52, which is adjacent to the flow outlet469b, in a clockwise direction.

Furthermore, in the swirling wall structure50, as indicated by a cross hatching inFIG. 12, a projected area Ap, which is formed by projecting the flow outlet469btoward the lateral side along the transverse axis Lc, is assumed to be present. Under this assumption, in the top view of the curved wall surface52, the adjacent end52a, which is adjacent to the flow outlet469b, is located at an outside of the projected area Ap. Furthermore, a portion of the curved wall surface52, which is placed in the projected area Ap, forms a spaced curved portion52b(see alsoFIGS. 3, 10 and 11), which is curved and is further spaced from the flow outlet469bin comparison to the adjacent end52ain the top view of the curved wall surface52.

With the above-described structure, the fuel flow Ff, which is outputted from the flow outlet469bas indicated by an arrow inFIG. 13, collides against the spaced curved portion52bof the curved wall surface52, so that the fuel flow Ff is bent along the curved wall surface52. At this time, the fuel flow Ff of the present embodiment is bent in the clockwise direction in the top view.

As indicated inFIGS. 3, 10 and 11, the guide wall surface54is formed by another portion of the specific plate surface28aof the longitudinal wall portion28, which is in common with the curved wall surface52. Similar to the curved wall surface52, the guide wall surface54is substantially perpendicular to the deepest bottom part20eof the bottom portion20a, so that the guide wall surface54extends in the vertical direction, and the guide wall surface54continuously extends on both of the upper side and the lower side of the flow outlet469b. The guide wall surface54is in a form of a planar surface and continuously extends from the adjacent end52aof the curved wall surface52, which is adjacent to the flow outlet469b, toward the flow outlet469bin the top view.

As shown inFIG. 10, the guide wall surface54of the present embodiment is formed along a tangent plane St, which is tangent to the arcuate curved wall surface52at the adjacent end52a, so that the guide wall surface54extends along the transverse axis Lc, which is substantially perpendicular to the longitudinal axis LI. With the above-described structure, the guide wall surface54guides the fuel flow Ff, which is outputted from the flow outlet469b, to the curved wall surface52, as indicated by the arrow inFIG. 13. The fuel flow Ff, which is guided by the guide wall surface54, can collide against the spaced curved portion52bof the curved wall surface52, which is curved continuously from the guide wall surface54, so that the fuel flow Ff can receive the curving effect described above.

The U-turn wall surface56is formed by another portion of the specific plate surface28aof the longitudinal wall portion28, which is in common with the curved wall surface52and the guide wall surface54, and a portion of an inner peripheral surface20diof a tank outer wall portion20dof the sub-tank20, which is shaped into a plate form. Similar to the curved wall surface52and the guide wall surface54, the U-turn wall surface56is substantially perpendicular to the deepest bottom part20eof the bottom portion20aand thereby extends in the vertical direction, and the U-turn wall surface56continuously extends on both of the upper side and the lower side of the flow outlet469b. The U-turn wall surface56continuously extends in a form of a U-shape in the top view from an opposite end52cof the curved wall surface52, which is opposite from the adjacent end52a.

A portion of the U-turn wall surface56of the present embodiment, which is formed in the longitudinal wall portion28and extends smoothly and continuously from the curved wall surface52, forms a first continuous curved portion56a. The first continuous curved portion56ais in a form of a cylindrical concave surface and is slightly curved toward the flow outlet469bwith a curvature, which is smaller than a curvature of the curved wall surface52. Furthermore, another portion of the U-turn wall surface56, which is formed in the tank outer wall portion20dand is bent from the first continuous curved portion56atoward the flow outlet469b, forms a second continuous curved portion56b. The second continuous curved portion56bis in a form of a cylindrical concave surface and is curved toward the flow outlet469bwith a curvature, which is larger than the curvature of the first continuous curved portion56a. Additionally, another portion of the U-turn wall surface56, which is formed in the tank outer wall portion20dand is bent from the second continuous curved portion56btoward the guide wall surface54, forms a return portion56c. The return portion56cis returned in a two-step form in the top view. With the above-described structure, as indicated by the arrow inFIG. 13, the fuel flow Ff, which is curved by the curved wall surface52, is turned to make a U-turn along the U-turn wall surface56, so that the fuel flow Ff is swirled in the clockwise direction in the top view in the present embodiment.

With the swirling wall structure50of the first embodiment, the fuel flow Ff, which is outputted into the inside of the sub-tank20from the flow outlet469bthat is directed toward the lateral side and is formed in the diffuser passage469provided for drawing the fuel from the fuel tank2through the fuel discharge from the nozzle passage465, is swirled. Specifically, the fuel flow Ff, which is outputted from the flow outlet469b, is curved along the curved wall surface52, which is curved about the longitudinal axis LI that extends from the lower side toward the upper side in the sub-tank20. Thereafter, this fuel flow Ff is turned to make the U-turn along the U-turn wall surface56, which extends continuously from the curved wall surface52, so that the fuel flow Ff is swirled. In this way, air bubbles, which are contained in the fuel and have a small specific gravity, are concentrated in a center part of the swirl flow, so that a cluster of air bubbles is formed in the center part of the swirl flow in a manner that increases a buoyant force exerted to the air bubbles. Therefore, upward movement of the cluster of air bubbles is not likely interfered by the swirling wall structure50, which extends from the lower side toward the upper side. Furthermore, in the sub-tank20, which is shaped into the tubular form having the bottom, the opening20c, through which the jet pump46and the fuel pump42can be inserted into the inside of the sub-tank20, is upwardly opened. Therefore, because of the upward movement of the cluster of air bubbles, the cluster of air bubbles can be easily discharged. Furthermore, the fuel pump42can draw all of the fuel of the sub-tank20, from which the air bubbles are removed through use of the swirling wall structure50, and the fuel pump42can discharge this drawn fuel toward the internal combustion engine3. Therefore, the supply loss of the fuel can be limited.

As discussed above, according to the first embodiment, the energy saving can be achieved by limiting the supply loss of the fuel, and at the same time, ensuring of the required performance of the internal combustion engine3can be achieved by removing the air bubbles.

Furthermore, because of the curved wall surface52and the U-turn wall surface56of the swirling wall structure50, which extend continuously on both of the upper side and the lower side of the flow outlet469b, the fuel flow Ff, which is outputted from the flow outlet469b, can be curved and turned to make the U-turn in the reliable manner while limiting escape of the fuel flow Ff. Thus, a generation efficiency of the swirl flow in the fuel flow Ff as well as a removal efficiency of the air bubbles can be increased, and thereby the reliability with respect to the ensuring of the required performance of the internal combustion engine3can be improved.

Furthermore, the curved wall surface52and the U-turn wall surface56of the swirling wall structure50, which extend upwardly from the bottom portion20aof the sub-tank20in the vertical direction, can adjust the axial direction of the central axis of the swirl flow, which is generated in the fuel flow Ff, to coincide with the vertical direction. Thereby, the cluster of air bubbles, which is concentrated in the center part of the swirl flow, can be smoothly moved in the vertical direction, in which the buoyant force is applied to the cluster of air bubbles. Thus, the removal efficiency of the air bubbles can be improved, and thereby the reliability with respect to the ensuring of the required performance of the internal combustion engine3can be improved.

Furthermore, the air bubbles are discharged along with fuel in the projected area Ap, which is formed by projecting the flow outlet469bon the lateral side of the flow outlet469b. Therefore, at the curved wall surface52, the fuel flow Ff, which contains the air bubbles, has a higher rate of colliding against the spaced curved portion52b, which is spaced from the flow outlet469bon the downstream side of the flow outlet469b, in comparison to the adjacent end52a, which is spaced from the projected area Ap in the top view. Thus, the fuel flow Ff is reliably curved along the curved configuration of the curved wall surface52. Thereby, it is possible to limit an occurrence of that the fuel flow Ff, which contains the air bubbles, does not flow to the curved wall surface52, to cause remaining of the air bubbles in the fuel. Thus, the reliability with respect to the ensuring of the required performance of the internal combustion engine3can be improved.

In addition, the fuel flow, which is discharged from the flow outlet469b, is curved along the curved wall surface52that is curved about the longitudinal axis LI in the form of the cylindrical concave surface that circumferentially extends substantially ¼ turn, so that the fuel flow can reliably swirled about the longitudinal axis LI. Additionally, the fuel flow Ff, which is discharged from the flow outlet469b, is guided along the continuous curved portions56a,56bof the U-turn wall surface56, which are continuously curved from the curved wall surface52toward the flow outlet469b, so that the swirl flow about the longitudinal axis LI is not likely interfered. Thus, the generation efficiency of the swirl flow in the fuel flow Ff as well as the removal efficiency of the air bubbles can be increased, and thereby the reliability with respect to the ensuring of the required performance of the internal combustion engine3can be improved.

Furthermore, the fuel flow Ff, which is discharged from the flow outlet469b, is guided by the guide wall surface54, so that the fuel flow Ff can be reliably curved along the curved configuration of the curved wall surface52, which extends continuously from the guide wall surface54and is curved about the longitudinal axis LI. Thus, a generation efficiency of the swirl flow in the fuel flow Ff as well as a removal efficiency of the air bubbles can be increased, and thereby the reliability with respect to the ensuring of the required performance of the internal combustion engine3can be improved.

Furthermore, in the diffuser passage469, the fuel flow Ff, which is discharged from the nozzle passage465, is swirled about the transverse axis Lc, which extends from the nozzle passage465toward the lateral side. At this time, the fuel flow Ff is discharged from the flow outlet469bof the diffuser passage469in such a manner that the fuel flow Ff is swirled in the counterclockwise direction in the view taken from the nozzle passage465. Then, this fuel flow Ff collides against the curved wall surface52, which is curved from the adjacent end52ain the clockwise direction in the top view, so that this fuel flow Ff is upwardly swirled in this clockwise direction. Accordingly, the action of the swirling and the action of the buoyant force are combined, so that the moving speed of the cluster of air bubbles, which is directed from the center part of the swirl flow toward the upper side, can be increased. Therefore, the removal efficiency of the air bubbles can be increased, and thereby the reliability with respect to the ensuring of the required performance of the internal combustion engine3can be improved.

Second Embodiment

As shown inFIGS. 14 to 17, a second embodiment of the present disclosure is a modification of the first embodiment. In a jet pump2046of the second embodiment, in a cross sectional view ofFIGS. 15, 16, which show the upstream end465buof the flow restricting passage part465btaken from the communicating passage part465aside, the second passage wall surface2461asis curved from the pressurizing passage464side in the clockwise direction. The rest of the construction of the second passage wall surface2461as, which is other than the above-described points, is the same as that of the second passage wall surface461asof the first embodiment. Because of the above structure, as indicated by an arrow inFIG. 18(a), the fuel flow Ff is swirled along the second passage wall surface2461asand enters the flow restricting passage part465b. Thereby, as indicated by an arrow inFIGS. 18(b) and 18(c), the fuel flow Ff is swirled in the diffuser passage469in the clockwise direction about the transverse axis Lc in the view taken from the flow restricting passage part465b.

As shown inFIGS. 14 and 17, in the swirling wall structure2050of the second embodiment, the curved wall surface2052is formed in a portion of the inner peripheral surface2028aof the longitudinal wall portion2028, which is molded integrally with the sub-tank20and is shaped into a partially cylindrical form. The curved wall surface2052is curved about the longitudinal axis LI in a form of a cylindrical concave surface that circumferentially extends substantially ¼ turn. This curved wall surface2052is curved from the adjacent end2052aof the curved wall surface2052, which is adjacent to the flow outlet469b, in the counterclockwise direction in the top view. The rest of the construction of the curved wall surface2052, which is other than the above-described points, is the same as that of the curved wall surface52of the first embodiment. Because of the construction of the curved wall surface2052, as indicated by the arrow inFIG. 19, when the fuel flow Ff collides against the spaced curved portion52b, the fuel flow Ff flows along the curved wall surface2052. Thereby, the fuel flow Ff is curved in the counterclockwise direction in the top view.

As shown inFIGS. 14 and 17, the guide wall surface54of the first embodiment is not formed in the swirling wall structure2050of the second embodiment. Furthermore, in the swirling wall structure2050, the U-turn wall surface2056is formed by a portion of the inner peripheral surface2028aof the longitudinal wall portion2028, which is in common with the curved wall surface2052. The U-turn wall surface2056, which is in a form of a cylindrical concave surface that circumferentially extends substantially ½ turn, extends continuously in generally a U-shape form in the top view from an opposite end2052cof the curved wall surface2052, which is opposite from the adjacent end2052aof the curved wall surface2052. The U-turn wall surface2056forms a continuous curved portion2056d, which extends smoothly from the curved wall surface2052and is cured toward the flow outlet469bwith substantially the same curvature as a curvature of the curved wall surface2052along the entire circumferential extent of the continuous curved portion2056d. The rest of the construction of the U-turn wall surface2056, which is other than the above-described points, is the same as that of the U-turn wall surface56of the first embodiment. With the above-described structure, as indicated by the arrow inFIG. 19, the fuel flow Ff, which is curved by the curved wall surface2052, is turned to make the U-turn along the U-turn wall surface2056, so that the fuel flow Ff forms the swirl flow, which is swirled in the counterclockwise direction in the top view.

Even in the second embodiment described above, the fuel flow Ff, which is discharged from the nozzle passage465, is swirled in the diffuser passage469about the transverse axis Lc that extends laterally from the nozzle passage465. The fuel flow Ff is discharged from the flow outlet469bof the diffuser passage469in such a manner that the fuel flow Ff is swirled in the clockwise direction in the view taken from the nozzle passage465. In the top view, this fuel flow Ff collides against the curved wall surface2052that is curved from the adjacent end2052a, which is adjacent to the flow outlet469b, in the counterclockwise direction, so that this fuel flow Ff is upwardly swirled in this counterclockwise direction. Accordingly, the action of the swirling and the action of the buoyant force are combined, so that the moving speed of the cluster of air bubbles, which is directed from the center part of the swirl flow toward the upper side, can be increased. Therefore, the removal efficiency of the air bubbles can be increased, and thereby the reliability with respect to the ensuring of the required performance of the internal combustion engine3can be improved. Other operations and advantages of the second embodiment, which are other than the above-described ones, are the same as those of the first embodiment except the operations and the advantages with respect to the guide wall surface54.

Third Embodiment

As shown inFIGS. 20 to 22, a third embodiment of the present disclosure is a modification of the first embodiment. As shown inFIG. 20, the sub-tank3020of the third embodiment includes an inflow tube3029, which is made of resin and is molded integrally with the sub-tank3020or separately from the sub-tank3020. The inflow tube3029is communicated with the inside of the fuel tank2at a location, which is laterally displaced from the lower side of the sub-tank3020. Also, the inflow tube3029is communicated with a jet pump3047, which is provided separately from the jet pump46in the inside of the sub-tank3020in the fuel tank2. In the third embodiment, the jet pump46is defined as a first jet pump46, and the jet pump3047is defined as a second jet pump3047.

As shown inFIGS. 20-22, the second jet pump3047is received in a pump chamber3020fof the sub-tank3020. The pump chamber3020fis partitioned from the first jet pump46by a longitudinal wall portion3028, which is molded integrally with the sub-tank3020and is shaped into a plate form. The pump chamber3020f, which is partitioned in the above-described manner, is formed such that the wall surfaces52,54,3056of the swirling wall structure3050are not exposed in the pump chamber3020f. The construction of the sub-tank3020is the same as the sub-tank20of the first embodiment except the above-described points.

The second jet pump3047, which is made of resin and is shaped into a hollow form, includes a pressurizing portion3470, a nozzle portion3471, a suctioning portion3472, and a diffuser portion3473. A molded article3047b, in which the nozzle portion3471, the suctioning portion3472and the diffuser portion3473are integrally molded, is assembled to a molded article3047a, in which the pressurizing portion3470is molded, so that the second jet pump3047is formed.

The pressurizing portion3470forms a pressurizing passage3474, which is in a form of a cylindrical hole that extends in a L-shape form. An upstream end3474uof the pressurizing passage3474is communicated with the discharge outlet450of the residual pressure holding valve45along with the pressurizing passage464of the first jet pump46.

As shown inFIGS. 21 and 22, the nozzle portion3471includes a communication forming part3471aand a flow restriction forming part3471b, which are placed on the lower side of the pressurizing portion3470. The communication forming part3471aforms a communicating passage part3475aas an upstream part of a nozzle passage3475. The flow restriction forming part3471bforms a flow restricting passage part3475bas a downstream part of the nozzle passage3475. The communication forming part3471aforms the communicating passage part3475ain a form of stepped cylindrical hole. An upstream end3475auof the communicating passage part3475ais communicated with a downstream end3474dof the pressurizing passage3474. The flow restricting passage part3475bforms the flow restricting passage part3475bin a form of a conical hole (tapered hole), which has a diameter that is progressively reduced toward the lower side. A flow rate of the fuel in the flow restricting passage part3475bis further restricted in comparison to a flow rate of the fuel in the communicating passage part3475a. An upstream end3475buof the flow restricting passage part3475bis communicated with a downstream end3475adof the communicating passage part3475a.

The suctioning portion3472forms a suction passage3478in a form a cylindrical hole that extends in a form an inverted L-shape. An upstream end3478uof the suction passage3478is communicated with the inflow tube3029(seeFIG. 20) at a location that is on the lower side of the pressurizing portion3470.

The diffuser portion3473forms a diffuser passage3479in a form of a cylindrical hole that is coaxial with the flow restricting passage part3475band extends in the vertical direction. An upstream end of the diffuser passage3479cooperates with the suction passage3478to form a confluence passage portion3479a, which is communicated with a downstream end3475bdof the flow restricting passage part3475bon the lower side of the pressurizing portion3470. A downstream end of the diffuser passage3479forms a flow outlet3479b, which is directed downward and is communicated with the pump chamber3020f.

With the above-described construction of the second jet pump3047, the flow of pressurized fuel, which is guided by the pressurizing passage3474from the discharge outlet450and is supplied to the communicating passage part3475a, is restricted by the flow restricting passage part3475band is thereby discharged into the confluence passage portion3479a. Therefore, a negative pressure is generated around the discharged flow of fuel, so that the fuel stored in the fuel tank2is drawn through the inflow tube3029at the lateral part of the sub-tank3020and is drawn into the suction passage3478and the diffuser passage3479in this order. Furthermore, the drawn fuel receives a diffuser effect in the diffuser passage3479and is thereby pumped, so that the fuel is pumped into the pump chamber3020fthrough the flow outlet3479bof the diffuser passage3479.

As shown inFIG. 20, the swirling wall structure3050of the third embodiment includes the curved wall surface52and the guide wall surface54, which are substantially identical to the curved wall surface52and the guide wall surface54of the first embodiment, and the U-turn wall surface3056, which is different from the U-turn wall surface56of the first embodiment. In the top view, the U-turn wall surface3056, which is shaped into a generally U-shape form, has a continuous planar surface portion3056e, which is formed in a tank outer wall portion3020d. The continuous planar surface portion3056eextends continuously from an opposite end52cof the curved wall surface52, which is opposite from the adjacent end52aof the curved wall surface52. The continuous planar surface portion3056eis in a form of a planar surface that is bent relative to the curved wall surface52toward the flow outlet469b. Furthermore, the U-turn wall surface3056has a return portion3056c, which is formed in the longitudinal wall portion3028that partitions the pump chamber3020f. The return portion3056cis returned from the continuous planar surface portion3056etoward the guide wall surface54. The return portion3056cis in a form of a cylindrical concave surface and is curved with a curvature that is smaller than a curvature of the curved wall surface52. The rest of the construction of the U-turn wall surface3056, which is other than the above-described points, is the same as that of the U-turn wall surface56of the first embodiment.

As shown inFIGS. 20 to 22, the longitudinal wall portion3028has a portion3028bthat forms the return portion3056c. A height of this portion3028b, which is measured from the deepest bottom part20eof the bottom portion20ain the vertical direction, is set to be lower than that of the other part3028cof the longitudinal wall portion3028. With this setting, a confluence opening3056co, which communicates between the inside and the outside of the pump chamber3020f, is opened at an upper end of the return portion3056c.

With the above-described construction of the swirling wall structure3050, as indicated by an arrow inFIG. 23, the fuel flow Ff, which is guided by the guide wall surface54from the flow outlet469bof the first jet pump46and is curved by the curved wall surface52, is turned to make a U-turn along the U-turn wall surface3056. Therefore, even in the third embodiment, the fuel flow Ff is swirled in the clockwise direction in the top view. Furthermore, a fuel flow Fj, which is pumped to the pump chamber3020fby the second jet pump3047and is discharged from the pump chamber3020fthrough the confluence opening3056co, is merged with the fuel flow Ff, which is discharged from the flow outlet469b. At this time, the fuel flow Fj, which is outputted from the second jet pump3047, is merged with the fuel flow Ff, which is upwardly swirled because of the principle that is the same as that of the first embodiment. Therefore, the fuel flow Fj also forms the swirl flow in a manner similar to that of fuel flow Ff.

Thus, in the third embodiment described above, in addition to the air bubbles of the fuel, which is drawn by the first jet pump46from the location on the lower side of the sub-tank3020, the air bubbles of the fuel, which is drawn by the second jet pump3047from the other location that is other than the location on the lower side of the sub-tank3020, can be also removed. Accordingly, while the swirling wall structure, which can achieve the air bubble removing function and the fuel supply loss limiting function, is commonly used in both of the first jet pump46and the second jet pump3047to simplify the construction, both of the energy saving and the ensuring of the required performance of the internal combustion engine can be achieved. Furthermore, besides the above-described advantages, the present embodiment can achieve the advantages, which are similar to those of the first embodiment.

Other Embodiments

The various embodiments of the present disclosure are described above. However, the present disclosure should not be limited to these embodiments. The present disclosure may be applied to various other embodiments as well as combinations of the above-described embodiments without departing from the scope of the present disclosure.

Specifically, in a first modification with respect to the first to third embodiments, at least one of the wall surfaces52,2052,54,56,2056,3056of the swirling wall structures50,2050,3050may be extended downward from the opposed location, which is opposed to the flow outlet469b, so that the at least one of the wall surfaces52,2052,54,56,2056,3056is not placed above the opposing location. In a second modification with respect to the first to third embodiments, at least one of the wall surfaces52,2052,54,56,2056,3056of the swirling wall structures50,2050,3050may be extended upward from the opposed location, which is opposed to the flow outlet469b, so that the at least one of the wall surfaces52,2052,54,56,2056,3056is not placed below the opposing location. The wall surface, which is subject to the second modification, may be extended upward from the bottom portion20aof the sub-tank20,3020or may be extended upward from a location that is spaced from the bottom portion20a.

In a third modification with respect to the first to third embodiments, at least one of the wall surfaces52,2052,54,56,2056,3056of the swirling wall structures50,2050,3050may be tilted relative to the vertical direction. In a fourth modification with respect to the first to third embodiments, the longitudinal axis LI, which is tilted relative to the vertical direction, may be used for the curved wall surface52,2052of the swirling wall structure50,2050,3050as long as the longitudinal axis LI extends from the lower side to the upper side of the sub-tank20,3020. In a fifth modification with respect to the first to third embodiments, the adjacent end52a,2052aof the curved wall surface52,2052of the swirling wall structure50,2050,3050may be placed in the projected area Ap.

In a sixth modification with respect to the first to third embodiments, the curved wall surface52,2052of the swirling wall structure50,2050,3050may be curved in a form of a cylindrical concave surface that circumferentially extends more than ¼ turn about the longitudinal axis LI. In a seventh modification with respect to the first to third embodiments, the curved wall surface52,2052of the swirling wall structure50,2050,3050may be formed in a form of a cylindrical concave surface that circumferentially extends less than ¼ turn about the longitudinal axis LI. In an eighth modification with respect to the first to third embodiments, the curved wall surface52,2052of the swirling wall structure50,2050,3050may be curved in a form that is other than the cylindrical concave surface.

In a ninth modification with respect to the first and second embodiments, the continuous curved portion(s)56a,56b,2056dmay be eliminated from the U-turn wall surface56,2056of the swirling wall structure50,2050, and a continuous planar surface portion, which is similar to, for example, the continuous planar surface portion3056eof the third embodiment, may be provided. In a tenth modification with respect to the first and third embodiments, the guide wall surface54may be eliminated.

In an eleventh modification with respect to the second embodiment, as shown inFIG. 24, the respective wall surfaces2052,2056of the swirling wall structure2050may be formed by a longitudinal wall portion2028, which is molded separately from the sub-tank20and is thereafter fixed to the sub-tank20. In a twelfth modification with respect to the third embodiment, in place of the swirling wall structure3050, a swirling wall structure, which is similar to the swirling wall structure50,2050of the first or second embodiment may be used.

In the jet pump46according to a thirteenth modification with respect to the first and third embodiments, in a cross sectional view, in which the upstream end465buof the flow restricting passage part465bis seen from the communicating passage part465aside, the second passage wall surface461asmay be curved from the pressurizing passage464side in the clockwise direction. In the swirling wall structure50,3050of this case, the curved wall surface52may be curved in the counterclockwise direction from the adjacent end52a, which is adjacent to the flow outlet469b, in the top view.

In the jet pump2046according to a fourteenth modification with respect to the second embodiment, in the cross sectional view, in which the upstream end465buof the flow restricting passage part465bis seen from the communicating passage part465aside, the second passage wall surface2461asmay be curved from the pressurizing passage464in the counterclockwise direction. In the swirling wall structure2050of this case, the curved wall surface2052may be curved in the clockwise direction from the adjacent end2052a, which is adjacent to the flow outlet469b, in the top view.

In a fifteenth modification with respect to the first to third embodiments, the second passage wall surface461as,2461asmay be not curved and may be formed in a form of, for example, a planar surface to generate the fuel flow Ff, which flows in the transverse axis Lc, in the diffuser passage469. In a sixteenth modification with respect to the first to third embodiments, a portion of the jet pump46,2046may be molded separately from the rest of the jet pump46,2046and may be fixed to the rest of the jet pump46,2046later.