Fuel supply system

A fuel supply system for a vehicle having an internal combustion engine and a fuel tank, has a reservoir, a fuel pump, a suction filter, a fuel transfer and a pressure accumulator. The reservoir is located in the fuel tank and is hermetically sealed. The fuel pump is configured to suck fuel from the reservoir and to supply the fuel to the internal combustion engine. The suction filter is configured to filter the fuel sucked by the fuel pump. The fuel transfer is configured to transfer the fuel from the fuel tank into the reservoir and to pressurize the fuel in the reservoir. The pressure accumulator is connected to the reservoir in order to control a pressure of the fuel in the reservoir.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Japanese patent application Ser. No. 2014-124308, filed Jun. 17, 2014, the contents of which are incorporated herein by reference.

Not applicable.

BACKGROUND

This disclosure relates to a fuel supply system for supplying fuel from a fuel tank to an internal combustion engine of a vehicle such as automobile.

Japanese Laid-Open Patent Publication No. 2010-71098 discloses a conventional fuel supply system. The fuel supply system has a reservoir cup, a reservoir lid, a fuel supply pipe, an electric wire, and a jet pump. The reservoir cup houses a fuel pump therein and is configured to reserve fuel in the fuel tank. The reservoir lid covers an upper opening of the reservoir cup. The fuel pump pumps fuel from the fuel tank through the fuel supply pipe to the outside of the fuel tank. The electric wire is connected to the fuel supply pump. The jet pump sends fuel from the fuel tank into the reservoir. The reservoir lid has an opening where the fuel supply pipe and the electric wire are inserted. Here, the reservoir is composed of the reservoir cup and the reservoir lid.

According to the fuel supply system, in a condition that the fuel supply pipe and the electric wire are inserted into the opening of the reservoir lid, an opening area between the reservoir lid, the fuel supply pipe and the electric wire is not decreased. Thus, it is not able to pressurize the inner space of the reservoir. Therefore, because the fuel and the air in the reservoir are sucked into a suction filter only by suction power of the fuel pump, there is a possibility that pressure loss of the suction filter increases, and that the load of the fuel pump increases. The increase of the load of the fuel pump may decrease efficiency and machine life of the fuel pump. Accordingly, there has been a need for improved fuel supply systems.

BRIEF SUMMARY

In one aspect of this disclosure, a fuel supply system for a vehicle having an internal combustion engine and a fuel tank, has a reservoir, a fuel pump, a suction filter, a fuel transfer and a pressure accumulator. The reservoir is located in the fuel tank and is hermetically sealed. The fuel pump is configured to suck fuel from the reservoir and to supply the fuel to the internal combustion engine. The suction filter is configured to filter the fuel sucked by the fuel pump. The fuel transfer is configured to transfer the fuel from the fuel tank into the reservoir and to pressurize the fuel in the reservoir. The pressure accumulator is connected to the reservoir in order to control a pressure of the fuel in the reservoir.

According to the aspect of this disclosure, because the fuel in the reservoir is pressurized, the fuel is pressed into the suction filter from the reservoir. Thus, an increase in the pressure loss caused by clogging of the suction filter can be prevented, and a decrease in the fuel suction amount of the suction filter can be prevented. The pressure accumulator controls the pressure of the fuel in the reservoir. Accordingly, even when the fuel pressure in the reservoir decreases due to an increase in a fuel consumption of the internal combustion engine or a decrease of a transfer fuel amount by the fuel transfer, the pressure accumulator pressurizes the fuel in the reservoir such that the fuel in the reservoir is pressed into the suction filter. Therefore, a pressure loss of the suction filter can be decreased, and a load on the fuel pump and a suction negative pressure of the fuel pump can be decreased. Further, a machine life of the suction filter can be improved due to the decrease in the pressure loss of the suction filter. And, the decrease in the load on the fuel pump can improve an efficiency of the fuel pump, decrease a power consumption, and prevent a generation of a vapor lock.

DETAILED DESCRIPTION

A first embodiment of the fuel supply system will be described.FIGS. 1-3are a sectional front view, a sectional side view and a sectional plan view of the fuel supply system, respectively. As shown inFIG. 1, a fuel supply system10is attached to a fuel tank12of, for example, an automobile and is configured to supply fuel from the fuel tank12to an internal combustion engine (engine). An upper wall12aof the fuel tank12has an opening13.

The fuel supply system10has a set plate14, a reservoir16, a fuel pump18, a suction filter20, a high pressure filter22, a pressure regulator24, a jet pump26, and a sender gauge28. The set plate14is mounted on the upper plate12afor covering the opening13of the fuel tank12. The set plate14has a fuel discharge pipe30and an external coupling electric connector31. The fuel discharge pipe30is connected to the internal combustion engine, in detail, to an injector via a fuel supply pipe (not shown). The external coupling electric connector31is connected to both an external source and an electric control unit (ECU) via an external connector (not shown). Here, the set plate14corresponds to “lid” in this disclosure.

The reservoir16is hermetically composed of a reservoir cup33and a cover35. The reservoir cup33is formed in a hollow cylinder shape having an upper opening and a lower closed bottom and is made from resin materials. The cover35is made from resin materials and is formed to close the upper opening of the reservoir cup33. The reservoir16houses the fuel pump18and the suction filter20therein. The reservoir16is inserted into the fuel tank12through the opening13and is mounted on a bottom wall12bof the fuel tank12. A bottom wall33bof the reservoir16contacts an upper surface of the bottom wall12bof the fuel tank12in a surface contact condition.

The cover35has a cover portion36, a pump case portion37, and a filter case portion38. The cover portion36is formed in a circular plate shape. The pump case portion37is formed in a hollow cylinder shape extending downward from a center region of the cover portion36and having a lower closed bottom. The filter case portion38is formed in a flattened hollow ring shape at an outer circumference of the cover portion36. The filter case38is a part of the cover portion36.

At an inner circumference of the filter case portion38, a fuel inlet port40for introducing the fuel is formed. At an upper surface of the filter case portion38, a fuel outlet port41for discharging the fuel is formed. Here, the cover35can be made by separately forming the cover portion36(including the filter case portion38) and the pump case portion37and then integrating them by snap-fit, welding or the like. Further, the cover35can be made by separately forming the cover portion36and the filter case portion38and then integrating them by snap-fit, welding or the like. The cover portion36and the filter case portion38can be separately formed and then can be integrated with each other by snap-fit, welding or the like.

The cover35is attached to the reservoir cup33for closing the upper opening of the reservoir cup33. The upper opening of the reservoir cup33is mainly closed with the cover portion36(including the filter case portion38). A seal member43is attached to an upper end of a circumferential wall33aof the reservoir cup33. The seal member43seals between the circumferential wall33aof the reservoir cup33and the cover portion36(including the filter case portion38) of the cover35. Here, the cover portion36(including the filter case portion38) of the cover35can be pressed into the circumferential wall33aof the reservoir cup33or can be hermetically contacted on the circumferential wall33aof the reservoir cup33due to the weight of the cover35and the weight of the fuel pump18, etc. In this case, the seal member43can be omitted.

The fuel pump18is a motor integrated pump where an electric motor and an impeller pump are installed vertically. When the impeller of the pump is rotated by the operation of the motor, the pump sucks, pressurizes, and discharges the fuel. At a lower end18bof the fuel pump18, a fuel inlet port45projecting downward is provided. At an upper end18aof the fuel pump18, a fuel outlet port46projecting upward and an electric connector47are provided. The pump case portion37of the cover35houses the fuel pump18therein such that the fuel pump18is mounted vertically. The fuel inlet port45is fitted into a fitting hole49formed in a bottom plate37aof the pump case portion37.

As shown inFIG. 3, the suction filter20has a filter member51, a frame52and a connecting pipe53. The filter member51is formed in a C-type cylinder shape having a C-shape in a plan view. The filter member51is formed in a bag shape having an inner circumferential filter portion51aand an outer circumferential filter portion51b. The frame52is provided between the inner circumferential filter portion51aand the outer circumferential filter portion51bof the filter member51for holding the distance between the filter portions51aand51b. The connecting pipe53is connected to both a lower end of the filter portion51aof the filter member51and a lower end of the frame52, and extends in a radial direction of the filter member51(seeFIGS. 1 and 2). The connecting pipe53is communicated with an inner space of the inner circumferential filter portion51a.

The suction filter20is positioned to surround the pump case portion37below the filter case portion38of the cover35with respect to the inside of the reservoir cup33of the reservoir16. A predetermined distance is held between the circumferential wall33aof the reservoir cup33and the outer circumferential filter portion51bof the filter member51. A predetermined distance is held between the inner circumferential filter portion51aof the filter member51and the pump case portion37. An end of the connecting pipe53is connected to the fuel inlet port45of the fuel pump18(seeFIGS. 1 and 2). The filter member51can be formed to surround the entirety or nearly the entirety of the pump case portion37or can be formed to have a bottom closing or partially closing a lower opening of the filter member51.

The circumferential wall33aof the reservoir cup33includes a flat plate-shaped wall portion33cnot corresponding to the filter member51of the suction filter20(seeFIG. 2). The circumferential wall33aincluding the flat plate-shaped wall portion33cof the reservoir cup33is formed in a D-shape in a plan view (seeFIG. 3). The flat plate-shaped wall portion33cis positioned near the pump case portion37.

As shown inFIG. 1, a ring plate shaped filter57is provided horizontally in the filter case portion38of the cover35. Thus, the high pressure filter22is composed. The filter case portion38is formed by holding the filter member57between an upper half and a lower half and then engaging the halves with each other by welding. The fuel inlet port40of the filter case portion38is communicated with the inner space of the lower half and is connected to the fuel outlet port46of the fuel pump18. The fuel outlet port41of the filter case portion38is communicated with the inner space of the upper half and is connected to the fuel discharge pipe30of the set plate14via a connecting pipe59.

The filter member57is made from the same material of the filter member51of the suction filter20. The filter member51of the suction filter20and the filter member57of the high pressure filter22are set, for example, to be capable of trapping 90% or more of foreign materials having a diameter larger than 40 micrometer, which a strainer of the injector can trap. Alternately, the filter member51of the suction filter20is set to trap foreign materials having a diameter equal to or smaller than those trapped by the filter member57of the high pressure filter22. Thus, an increase of pressure loss caused by clogging of the filter member57having a smaller filtration area than the filter member51can be prevented. Here, the filter member51can be set to trap foreign materials having the diameter larger than those trapped by the filter member57. Further, the filter member57can be made from a different material from that of the filter member51.

The filter member51of the suction filter20is formed in a substantial hollow cylinder shape. The filter case portion38of the high pressure filter22is formed in a flattened shape. The high pressure filter22is positioned above the suction filter20. Accordingly, the filtration area of the filter member51of the suction filter20can be increased while preventing an increase in the height of the reservoir16.

The pressure regulator24is mounted on the filter case portion38of the cover35. The filter case portion38has a connection port61formed in the upper wall of the filter case portion38and communicated with the inner space of the upper half of the filter case portion38(seeFIG. 2). The connection port61is connected with a fuel inlet port (not shown) of the pressure regulator24. The pressure regulator24controls the inner pressure of the filter case portion38and discharges surplus fuel.

The jet pump26is positioned in a recess16aformed in a lower surface of the bottom of the reservoir16. A drive fuel inlet26aof the jet pump26is connected to the pressure regulator24, in detail a surplus fuel outlet (not shown), via a return pipe63. A transfer fuel inlet26bof the jet pump26opens to the inside of the fuel tank12, that is, the outside of the reservoir16. A fuel outlet26cof the jet pump26is connected to the inside of the reservoir cup33of the reservoir16. The jet pump26utilizes surplus fuel discharged from the pressure regulator24as drive fuel to transfer, that is, to pump the fuel from the inside of the fuel tank12(outside the reservoir16) to the inside of the reservoir16. Thus, the reservoir16is filled with the fuel. The fuel discharged from the reservoir16corresponds to the fuel supplied to the internal combustion engine by the fuel pump18and the fuel flowing out from the inside of the reservoir16into the fuel tank12. Here, the jet pump26corresponds to “fuel transfer” in this disclosure.

As shown inFIG. 2, the sender gauge28has a gauge body65, an arm66and a float67. The gauge body65is attached to an outer facing surface of the flat plate-shaped wall portion33cof the circumferential wall33aof the reservoir cup33of the reservoir16. The arm66is arranged on the gauge body65and is configured to rotate vertically. The float67is attached to a free end of the arm66and is configured to be able to float on a liquid surface in the fuel tank12. The sender gauge28is a liquid level meter detecting a remaining fuel, that is, the level of the fuel in the fuel tank12based on an electric resistance value and is configured to output detection signals to the ECU. The sender gauge28is connected to the external coupling electric connector31of the set plate14via a wire (not shown). The external coupling electric connector31of the set plate14is connected to an electric connector47of the fuel pump18via a harness69(seeFIG. 2).

At an upper end of the reservoir16, for example, at the cover portion36of the cover35, a fuel discharge opening (not shown) is formed. When the fuel overflows from the inside of the reservoir16, the fuel is discharged via the fuel discharge opening into the inside of the fuel tank12. The fuel discharge opening can function as vent hole. The open area of the fuel discharge opening is configured to make the fuel discharge amount from the inside of the reservoir16smaller than the fuel transfer amount by the jet pump26. The fuel transfer amount includes the surplus fuel amount (the drive fuel amount) from the pressure regulator24. Here, the fuel discharge opening can be composed of one or more openings.

As shown inFIG. 2, at the upper end of the reservoir16, for example, at an upper surface of the filter case portion38of the cover35, a pressure accumulator71is horizontally located. The pressure accumulator71has a cylinder portion72, a piston73, and a spring74. The cylinder portion72is formed on an upper surface side of the filter case portion38of the cover35. The piston73is slidably arranged in the cylinder portion72. The piston73divides an inner space of the cylinder portion72into a pressure accumulation chamber76and a back pressure chamber77. When the piston73moves in the cylinder portion72, the piston73changes the volume of the pressure accumulation chamber76.

A communication path78is communicated with the pressure accumulation chamber76. The communication path78extends downward from the cylinder portion72and is opened near the upper end of the fuel pump18. Thus, the pressure accumulation chamber76is communicated with the inner space of the reservoir16via the communication path78. The spring74is composed of, for example, a coil spring, and is located between opposite faces of the back pressure chamber77and the piston73. The spring74biases the piston73in a direction for decreasing the volume of the pressure accumulation chamber76(leftward inFIG. 2).

When the fuel pressure in the reservoir16becomes high, the piston73is moved in a direction for decreasing the volume of the back pressure chamber77, that is, for increasing the volume of the pressure accumulation chamber76(rightward inFIG. 2) against a biasing force of the spring74such that the pressure accumulator71stores fuel pressure of the reservoir16. Then, when the fuel pressure in the reservoir16decreases, the piston73is moved in the direction for decreasing the volume of the pressure accumulation chamber76(leftward inFIG. 2) due to the biasing force of the spring74such that the fuel is discharged from the pressure accumulation chamber76into the reservoir16. Here, the piston73corresponds to “volume variable member” in this disclosure. The spring74corresponds to “elastic material” in this disclosure.

The operation of the fuel supply system10will be described. When the fuel pump18is driven, the fuel in the reservoir16is sent to the filter member51of the suction filter20and is filtered by the filter member51, and then is sucked into the fuel pump18through the connecting pipe53. The fuel is pressurized by the fuel pump18and is discharged to the high pressure filter22via the fuel outlet port46. The fuel is filtered by the filter member57of the high pressure filter22. Then, the pressure of the fuel is adjusted by the pressure regulator24depending on the operating condition of the internal combustion engine. The adjusted fuel is supplied to the internal combustion engine via the connecting pipe59, the fuel discharge pipe30of the set plate14and the fuel supply pipe (not shown).

The surplus fuel discharged from the pressure regulator24is returned into the reservoir16via the jet pump26. The fuel in the fuel tank12, i.e., outside the reservoir16is transferred, that is, pumped into the reservoir16by the jet pump26. The amount of the fuel discharged from the inside of the reservoir16via the fuel discharge opening is smaller than the amount of the fuel transferred by the jet pump26(including the drive fuel amount). Accordingly, the inner space of the reservoir16is filled with the fuel, and the fuel is pressurized.

According to the fuel supply system10, the fuel in the reservoir16is pressurized due to the transfer pressure of the fuel applied by the jet pump26. In the result, the fuel in the reservoir16is pressed into the suction filter20. Thus, the increase in the pressure loss caused by clogging of the suction filter20can be prevented. And, the decrease in the amount of the fuel sucked by the suction filter20can be prevented.

When the fuel pressure in the reservoir16increases, for example, becomes higher than a first predetermined value, the pressure accumulator71accumulates the fuel pressure. Then, when the fuel pressure in the reservoir16decreases, for example, becomes lower than a second predetermined value, the pressure accumulator71discharges the fuel into the reservoir16. Thus, even when the fuel pressure in the reservoir16decreases due to an increase in the fuel consumption of the internal combustion engine, a decrease in the fuel transfer amount by the jet pump26or the like, the fuel in the reservoir16is pressurized due to fuel pressure in the pressure accumulator71such that the fuel in the reservoir16is pressed into the suction filter20.

Accordingly, the pressure loss of the suction filter20can be decreased, and the load on the fuel pump18and the suction negative pressure of the fuel pump18can be decreased due to a pressurization effect of the fuel in the reservoir16by the jet pump26and a pressurization effect of the fuel in the reservoir16by the pressure accumulator71. And, because the pressure loss of the suction filter20is decreased, the machine life of the suction filter20can be extended. Further, because the load on the fuel pump18is decreased, the efficiency of the fuel pump18can be improved, the power consumption of the fuel pump18can be decreased, and a generation of the vapor lock can be prevented.

The piston73of the pressure accumulator71changes the volume of the pressure accumulation chamber76. Thus, when the fuel pressure in the reservoir16becomes high, the pressure accumulator71can accumulate the fuel pressure. Then, when the fuel pressure in the reservoir16decreases, the pressure accumulator71can discharge the fuel into the reservoir16.

The jet pump26can be used as the fuel transfer. The jet pump26does not include any mechanical movable part, so that its configuration can be simplified.

When one member is used for the cover35of the reservoir16, a pump case (the pump case portion37) holding the fuel pump18, and a filter case (the filter case portion38) of the high pressure filter22, the number of components and the number of assembly work can be decreased.

A second embodiment will be described. Following embodiments correspond to the first embodiment with some changes. Thus, the changes will be described, and the same configuration will not be described again.FIG. 4is a sectional side view of the fuel supply system10of the second embodiment. As shown inFIG. 4, the fuel supply system10of this embodiment has a pressure accumulator81. The pressure accumulator81has a hollow cylindrical wall82and a diaphragm83. The hollow cylindrical wall82has a bottom. The hollow cylindrical wall82is formed on the upper surface side of the filter case portion38of the cover35. The hollow cylindrical wall82is shaped vertically and is opened upward.

The diaphragm83is made from a rubber-like elastic material having flexible and stretching properties. A circumference of the diaphragm83is engaged with the whole circumference of an upper end of the hollow cylindrical wall82. The hollow cylindrical wall82and the diaphragm83form a sealed pressure accumulation chamber85. When the diaphragm83elastically deforms into a balloon shape, the volume of the pressure accumulation chamber is changed. The communication path78is communicated with the pressure accumulation chamber85and extends downward from the pressure accumulation chamber85. And, the communication path78is opened near the upper end of the fuel pump18. Thus, the pressure accumulation chamber85is communicated with the inside of the reservoir16via the communication path78.

When the fuel pressure in the reservoir16becomes high, the diaphragm83elastically deforms toward a direction for increasing the volume of the pressure accumulation chamber85such that the pressure accumulator81stores the fuel pressure of the reservoir16. Then, when the fuel pressure in the reservoir16decreases, the diaphragm83elastically deforms toward a direction for decreasing the volume of the pressure accumulation chamber85due to an elastic restoring force such that the pressure accumulator81discharges the fuel from the pressure accumulation chamber85into the reservoir16. Here, the diaphragm83corresponds to “volume variable member” and “elastic volume variable member” in this disclosure. The diaphragm83can be replaced with a bellows.

A third embodiment will be described.FIG. 5is a sectional side view of the fuel supply system10of the third embodiment. As shown inFIG. 5, a relief valve88is provided in the cylinder portion72of the pressure accumulator71. The relief valve88is configured to keep the inner pressure of the pressure accumulator71, in detail the pressure accumulation chamber76, at a predetermined value. The relief valve88is closed in a normal condition. When the accumulated inner pressure of the pressure accumulator71increases above a predetermined value, the relief valve88is opened in order to discharge the fuel from the inside of the pressure accumulation chamber76to the outside of the reservoir16. Accordingly, because the relief valve88can keep the inner pressure of the pressure accumulation chamber76at the predetermined value, an excessive pressurization of the inner pressure of the pressure accumulation chamber76can be prevented.

A fourth embodiment will be described.FIG. 6is a sectional side view of the fuel supply system10of the fourth embodiment. In this embodiment, the pressure accumulator71is vertically located on the outer circumferential side of the pump case portion37of the cover35. The pressure accumulation chamber76is positioned on the lower side, and the back pressure chamber77is positioned on the upper side. The communication path78is composed of an aperture opening at a wall on the lower end side of the cylinder portion72. In accordance with this embodiment, the maximum volume of the pressure accumulation chamber76of the pressure accumulator71can be easily increased.

A fifth embodiment will be described.FIG. 7is a sectional side view of the fuel supply system10of the fifth embodiment. As shown inFIG. 7, the pressure accumulator71is vertically located on the outer side of the circumferential wall33aof the reservoir cup33. The pressure accumulation chamber76is positioned on the lower side, and the back pressure chamber77is positioned on the upper side. The communication path78is composed of an aperture opening at a lower end of the circumferential wall33aof the reservoir cup33. In accordance with this embodiment, the maximum volume of the pressure accumulation chamber76of the pressure accumulator71can be easily increased.

The fuel supply system of this disclosure can be modified without departing from the scope of this disclosure. For example, the fuel transfer can be composed of any type pumps other than the jet pump26. The jet pump26can use the fuel discharged from a vapor jet of the fuel pump18as the drive fuel or can use the fuel separated from the discharge fuel from the fuel pump18as the drive fuel.