US20070122300A1

US20070122300A1 - Electric fuel pump

Info

Publication number: US20070122300A1
Application number: US11/288,360
Authority: US
Inventors: Makoto Sakai; Jun Kimura
Original assignee: Keihin Corp
Current assignee: Keihin Corp
Priority date: 2005-11-29
Filing date: 2005-11-29
Publication date: 2007-05-31

Abstract

To provide an electric fuel pump suitable for marineuse, wherein calcium is not generated at a winding of a motor part and rust is not generated, even when fuel containing sea water is sucked to a pump part, a pump part P is provided at one end of a housing 1, a discharge part T is provided at another end, a motor part M is provided at a middle part, fuel is passed through the motor part M and discharged from a discharge passage 13, the motor part M has a winding 7 around a stator 6 and a rotor 10 with a yoke 11 and a magnet 12 and is mounted on a rotary shaft 8 for rotationally driving the pump part P, and the yoke 11 and the magnet 12 are subjected to a rustproof treatment such as plating, resin-molding and the winding 7 is resin-molded.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to an electric fuel pump, where fuel in a fuel tank is pressurized, and the pressurized fuel is supplied toward a fuel injection valve. The electric fuel pump is used for a fuel supply device of an internal combustion engine of a vehicle, a two-wheeled vehicle, a general-purpose machine, an engine for marine use or the like.
2. Description of the Conventional Art
A conventional electric fuel pump is indicated in Japanese Patent Publication No. 8-9995.
This electric fuel pump is explained in FIG. 2. Reference numeral 30 is a cylindrical housing having openings at both ends, and formed with a metallic material such as iron, aluminum or the like. The housing 30 has a pump part P provided at a lower end thereof, a discharge part T provided at an upper end thereof, and a motor part M provided at a middle part thereof.
The pump part P has a pump chamber 33 formed with a pump casing 31 and a pump cover 32, and a regenerative pump type impeller 34 is rotatably provided in the pump chamber 33.
Further, the pump cover 32 has a pump suction passage 35 a, which is formed to open downward and extend into the pump chamber 33. The pump casing 31 has the pump discharge passage 35 b opening into the pump chamber 30 from the pump chamber 33.
As mentioned above, the lower end opening of the housing 30 is closed with the pump casing 31 and the pump cover 32, and the pump part P is formed at this closed portion.
The motor part M comprises an armature 36 and a field magnet 37. A lower end of a rotary shaft 38 provided at a center of the armature 36 is rotatably supported by the pump casing 31 through a bearing 39 a. An upper end of the rotary shaft 38 is rotatably supported by a bearing holding member 40 through a bearing 39 b.
Then, the lower end of the rotary shaft 38 is engaged in an engaging hole 34 a of the impeller 34, and the rotation of the rotary shaft 38 is transmitted to the impeller 34.
Further, the upper end opening of the housing 30 is closed with the bearing holding member 40 and a housing cover 41, which is provided on the upper side of the bearing holding member 40. A vertical hole 40 a of the bearing holding member 40 has a brush 42 provided movably upward and downward. A lower end 42 a of the brush 42 is pressed by a spring 43, and is elastically energized onto a planar commutator 36 a of the armature 36.
The brush is electrically connected with a terminal rod 44 projected upwardly from the housing cover 41 through a choke coil 45, a brush presser plate 46 and a pig tail 47.
Further, 48 is a discharge passage, which is projected from the housing cover 41 to open upwardly. The discharge passage 48 has a check valve 49 for preventing downward fuel flowing.
Thereby, electric current is supplied to the armature 36 from the terminal rod 44 through the choke coil 45, the brush presser plate 46, the pig tail 47, the brush 42 and the planar commutator 36 a, to thereby rotate the armature 36 in the housing 30, and the rotation of the armature 36 is transmitted to impeller 34 through the rotary shaft 38.
Further, the impeller 34 is rotated in the pump chamber 33, to thereby generate a pressure difference in the front and the rear of a blade groove on an outer circumference of the impeller. Such the pressure difference is repeatedly generated in multiple blade grooves, to thereby suck the fuel into the pump chamber 33 from the pump suction passage 35 a, and the fuel pressurized in the pump chamber 33 is discharged into the housing 30 from the pump discharge passage 35 b. Further, the discharged fuel is passed around the motor part M and discharged to a fuel pipe extending to the outside through the discharge passage 48.

SUMMARY OF THE INVENTION

Such a conventional electric fuel pump is used as the fuel supply device of an engine for marine use, such as an engine for outboard motor, an engine for inboard motor or the like. Thus, sea water may be entered into a gasoline fuel to be used in such the engine for marine use.
When the fuel containing the sea water is discharged into the housing 30 from the pump chamber 33 and contacted with a part between electrodes of the motor part M, the fuel is bonded with a metal ion such as calcium, magnesium or the like, which is dissolved in the sea water, to thereby generate calcium or the like, and the generated impurities are supplied toward the fuel injection valve from the discharge passage 48 through the fuel pipe.
On the other hand, the fuel pipe has a filter for removing such impurities. However, when calcium or the like is generated to be discharged, it is necessary to increase the maintenance work frequency for the filter.
Further, when the fuel containing a sea water is contacted with an inner conductive wire of the pig tail 47 or the like in the housing 30, electric current flows between positive and negative to thereby generate an electrolysis reaction. Then, the inner conductive wire containing a positive terminal is dissolved to promote corrosion.
Further, in the engine stopping state, the planar commutator 36 a other than a contacting part between the planar commutator 36 a and the lower end 42 a of the brush 42 is directly exposed in the fuel containing the sea water. Thus, in preservation of the engine for a long period, an oxide film is formed on the planar commutator 36 a other than the contacting part, and when the engine is started after stopping for a long time, trouble may be caused to the starting of the motor part M.
Furthermore, it is a tendency that alcohol is blended in the gasoline as an oxygen-containing fuel to be used from the viewpoint of an environment issue in recent years. In such fuel, the mixing of the gasoline and the sea water is promoted by alcohol, and the above problems are also promoted, so that it is not preferable.
Then, in order to solve the above problems, the structure illustrated in FIG. 3 is considered, wherein the fuel discharged from the pump part is not contacted with a part of the motor part by shutting off the pump part provided in the housing from the motor part.
In this structure, an inner end plate 51, a spacer 52 and an outer end plate 53 are stacked and provided at the lower end of a housing 50. An inner rotor 54 is provided in a spacer 52, and a pump P is a trochoid pump.
The inner space of the housing 50 on the upper side of the inside end plate 51 is divided to an inner chamber 50 a and an outer chamber 50 b by a cylindrical seal member 55.
Further, the outer chamber 50 b has a stator 57 with a winding 56, and the inner chamber 50 a has a rotor 60 having a magnet 59 provided on an outer circumference of a yoke 58. The rotor is rotatably provided at a shaft 61 through bearings 62 a and 62 b, wherein the shaft 61 is fixed uprightly on the outer end plate 53.
Further, the rotation of the rotor is transmitted to an inner rotor 54 through a transmission member 63, and the inner rotor 54 and the rotor 60 are synchronously rotated.
In addition, 64 is a through hole for inducing a part of the fuel in the pump part P into the inner chamber 50 a, and this through hole 64 is bored at the inner end plate 51.
According to such an electric fuel pump, electric current is supplied to the winding 56 of the stator 57, to thereby make a rotational magnetic field at the stator 57. The rotor 60 having the magnet 59 and the yoke 58 are rotated by the rotational magnetic field, and the rotation of the rotor 60 is transmitted to the inner rotor 54 of the pump part P through the transmission member 63, to thereby rotate the inner rotor 54. Thereby, the fuel is sucked into the pump part P from a suction hole 65 bored at the outer end plate 53 and pressurized by the rotation of the inner rotor 54. Then, the pressurized fuel is discharged from a discharge hole 66 bored at the outer end plate 53.
On the other hand, a part of the fuel in the pump part P is supplied into the inner chamber 50 a through the through hole 64 and filled in the inner chamber 50 a.
According to the above electric fuel pump, the rotor 60 comprising the magnet 59 and the yoke 58 is provided in the inner chamber 50 a, and the fuel is filled in the inner chamber 50 a. Thus, there is a problem that rust is generated at the rotor 60, and when the electric fuel pump is used for a long time, trouble may be caused to the rotation of the rotor 60 by the rust.
In addition, since the fuel does not flow positively in the inner chamber 50 a, the rust may be accumulated.
Further, it is necessary to provide the seal member 55 with sufficient air tightness so as not to flow the fuel into the outer chamber 50 b dividedly provided at the inner side of the housing 50. At this time, since the fuel pressurized to about 300 kpa is supplied into the inner chamber 50 a, it is especially necessary to take careful attention for controlling a dimension and assembling of the seal member 33.
Further, the winding 56 of the stator 57 is provided in the air in the outer chamber 50 b. When current is supplied to the winding 56, the winding 56 cannot efficiently radiate heat generated by an eddy current as compared with the radiation by a fuel circulation.
The electric fuel pump according to the present invention is made to solve the above-mentioned problems, and one objective of the present invention is to provide an electric fuel pump structured such that a pump part is provided at one end of a housing, a motor part is housed in the housing, and fuel pressurized in the pump part is passed through the surrounding of the motor part in the housing and discharged toward the outside, wherein, even when fuel mixed with sea water is sucked into the pump part, an impurity such as calcium or the like is not generated at a winding part of the motor part, generation of rust in a rotor part is prevented, and fuel can be supplied stably for a long period of time, so that the electric fuel pump is suitably used to an engine especially for marine use.
According to a first aspect of the electric fuel pump of the present invention, an electric fuel pump comprises a motor part housed in a housing and a pump part provided at an end part of the housing, in which the motor part is a brushless motor comprising a stator wound a winding and a rotor having a magnet fixedly provided at a yoke, and fuel pressurized by the pump part driven by the motor part is supplied into the housing and discharged toward the outside from a discharge passage at an end part of the housing through the surrounding of the brushless motor, wherein the yoke and the magnet of the rotor is subjected to a rustproof treatment such as plating, resin molding or the like, and the winding of the stator is resin-molded.
According to a second aspect of the present invention in addition to the above first aspect, an inner conductive wire, which is for supplying electric current to the winding of the stator and is provided in the housing, is resin-molded.
According to a third aspect of the present invention in addition to the above first aspect, the housing forming a motor housing chamber is made from aluminum or iron, and the inner circumference face thereof is subjected to the rustproof treatment.
According the first aspect of the present invention, the yoke and the magnet of the rotor is coated by plating or resin molding, so that the fuel containing sea water is not directly contacted with the yoke and the magnet. Thus, the rust does not generate to the yoke and the magnet.
Further, the winding of the stator is coated by resin molding, and fuel containing sea water is not directly contacted with the winding. Thus, the metal ions of calcium and magnesium solved in the sea water are not bonded to thereby precipitate calcium.
Therefore, first, the rotation of the rotor can be stably kept for a long time, so that the discharge performance of the pump can be made stable.
Further, second, since calcium and rust cannot be generated, fuel is discharged toward the outside from the housing through the discharge passage without mixing with calcium and rust. Thus, the maintenance work frequency of a filter, which is provided in a discharge pipe toward a fuel injection valve from the discharge passage, can be decreased.
Further, the fuel discharged from the pump part is continuously delivered from the discharge passage through the inside of the housing around the outer circumference of the motor part. Thus, the heat generated by eddy current can be efficiently radiated.
Further, the fuel is passed through the inside of the housing, and the opening of the discharge passage can be opened at the housing end part on the opposite side of the pump part like the conventional one. Thus, it is not necessary especially to change a piping layout of the discharge pipe.
Further, according to the second aspect of the present invention, the inner conductive wire in the housing is coated by resin molding, so that the inner conductive wire is not directly contacted with sea water. Thus, it can be prevented to corrode the inner conductive wire by an electrolysis reaction.
Further, according to the third aspect of the present invention, the inner circumference face of the motor housing chamber of the housing is subjected to the rustproof treatment. Thus, fuel containing sea water in the motor housing chamber is not directly contacted with the inner circumference face of the motor housing chamber, so that it can be prevented to generate the rust at this inner circumference face.
More particularly, since the motor housing chamber is formed with a long length along the yoke of the rotor, it is effective to prevent the rust generation at this part.

BRIEF EXPLANATION OF DRAWINGS

FIG. 1 is a longitudinal sectional view illustrating one example of an electric fuel pump according to the present invention.
FIG. 2 is a longitudinal sectional view illustrating a first example of a conventional electric fuel pump.
FIG. 3 is a longitudinal sectional view illustrating a second example of a conventional electric fuel pump.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

Hereinafter, one example of the electric fuel pump of the present invention is explained with FIG. 1.
Reference numeral 1 is a cylindrical housing having openings at both ends, and is formed with aluminum or iron.
The housing 1 comprises a pump part P provided at a lower end thereof, a discharge part T provided at an upper end thereof, and a motor M provided in a middle part thereof.
The pump P is a regenerative pump, where an impeller 4 is rotatably provided in a pump chamber 3 formed by a lower bottom part 1 a of the housing 1 and a pump cover 2 closing a lower end opening of the housing 1.
Further, the pump chamber 3 has a pump housing passage 2 a opened downwardly and a pump discharge passage 1 b which is opened to be extended upwardly. The pump discharge passage 1 b is bored at the lower bottom part la of the housing 1, and opened to the inside of the housing 1.
Further, an upper end opening of the housing 1 is closed by a housing cover 5, and a stator 6 for constituting the motor part M is fixedly provided at a lower end of the housing cover 5.
The stator 6 is located at a center of the housing 1, and has a cylinder part 6 a downwardly extended toward the inside of the housing 1. A winding 7 is wound around an outer circumference of the cylinder part 6 a. 8 is a rotary shaft, in which an upper part is rotatably supported by an upper flanged portion 6 b of the stator 6 through a bearing 9 a, and a lower part is rotatably supported by the lower bottom part 1 a of the housing 1 through a bearing 9 b. The rotary shaft 8 is provided at the inside of the cylinder part 6 a of the stator 6.
Further, a lower end of the rotary shaft 8 is projected into the pump chamber 3, and the projection part is engaged with the engaging hole 4 a of the impeller 4. For example, the shape of the engaging hole 4 a is formed to have an incomplete circular shape.
Then, the rotation of the rotary shaft 8 is transmitted to the impeller 4, and the impeller 4 is rotated synchronously with the rotary shaft 8.
A rotor 10 comprises a bottomed cup-shaped yoke 11 formed with a magnetic material and a magnet 12 fixedly provided at the inside of the yoke 11. A bottom part 11 a of the yoke 11 is fixedly provided at the rotary shaft 8.
The rotor 10 is rotated synchronously with the rotary shaft 8 in the housing 1. A space is formed between an inner circumference part of the magnet 12 and an outer circumference part of the winding 7, and a space is formed between an outer circumference part of the yoke 11 and an inner circumference face 1 c of the housing 1.
As mentioned above, the motor part M comprises the stator 6 where the winding 7 is wound, and the rotor 10 having the yoke 11 and the magnet 12.
The housing cover 5 is explained again. A lead 15 connected with an external power source such as a battery or the like, (not illustrated in the drawings) is provided to enter into the housing cover 5, and an inner conductive wire 15 a extended into the housing 1 from the lead 15 is connected with the winding 7 in the housing 1.
Further, a discharge passage 13 is upwardly opened toward the outside from the inside of the housing 1, and a check valve 14 is provided in the discharge passage 13.
The discharge part T comprises the discharge passage 13 and the check valve 14 and is provided at the upper end of the housing 1.
When electric current is supplied to the winding 7 from the lead 15 through the inner conductive wire 15 a, a magnetic field is formed at the stator 6, and the rotor 10 having the magnet 12 and the yoke 11 is rotationally driven by the magnetic field. With the rotation of the yoke 11, the rotary shaft 8 is synchronously rotated.
Further, the impeller 4 is rotated through the engaging hole 4 a by the rotation of the rotary shaft 8. By the rotation of the impeller 4, fuel is sucked into the pump chamber 3 from the pump suction passage 2 a, pressurized in the pump chamber 3 and supplied into the housing 1 through the pump discharge passage 1 b.
Further, the fuel supplied into the housing 1 is filled in the housing 1 and thereafter, discharged to the outside through the discharge passage 13. This fuel is supplied to the fuel injection valve through the discharge pipe which is not illustrated in the drawings.
In addition, the electric fuel pump according to the present invention must be constituted as follows in order to obtain the above objective.
First, the yoke 11 and the magnet 12 for the rotor 10 are subjected to a plating treatment.
Or the yoke 11 and the magnet 12 are resin-molded with a synthetic resin material, and the outer circumferences of those are coated with the synthetic resin material.
Second, the winding 7 is resin-molded with the synthetic resin material and coated with the synthetic resin material.
Then, even when fuel mixed with the sea water is supplied into the housing 1 from the pump part P, the rust is not generated on the yoke 11 and the magnet 12 since these are coated with the plating or the synthetic resin material.
Further, as for the winding 7, the outer circumference is coated with the synthetic resin material. Thus, when the winding 7 is energized, calcium is not generated by bonding of metal ions.
As mentioned above, it can be prevented to generate rust on the rotor 10 and calcium on the winding 7. As a result of this, the rust and calcium are not discharged into the discharge pipe through the discharge passage 13. Thus, the maintenance frequency of the filter, the fuel injection valve or the like can be decreased.
Further, since generation and accumulation of the rust are prevented, the spaces on the inner and outer circumferences of the yoke 11 can be maintained to be constant. Thereby, the stable rotational magnetic field can be kept, so that the rotation of the motor part can be kept stable for a long period of time.
Further, since the constitution of the electric fuel pump is same as the conventional one, it is not necessary to increase the number of parts or to make a change in assembling, so that the production cost is not remarkably increased.
Further, the fuel discharged from the pump part P can be discharged toward the discharge passage 13 through the inside of the housing. Then, the temperature rise of the winding 7 can be controlled at the same level as that of the conventional one, and it is not necessary to change the opening position of the discharge passage 13. Thus, the conventional discharge pipe can be used as it is.
Further, the inner conductive wire 15 a connecting the winding 7 and the lead 15 in the housing 1 is resin-molded with the synthetic resin material. Then, the problem that the inner conductive wire 15 a is corroded by electrolyzation can be solved, so that the electrical connection of the lead can be preferably kept for a long period of time.
Further, the inner conductive wire 15 a can be resin-molded together with the winding 7.
Furthermore, the inner circumference face 1 c of the housing 1 where the motor part M is housed is subjected to the rustproof treatment. Then, it can be prevented to generate the rust like the above.
In this structure, the inner circumference face 1 c of the housing 1 is formed with a large diameter and a long length in the vertical direction. Then, since generation of rust at the inner circumference face 1 c is prevented, the bad influence of the rust can be remarkably decreased.
In addition, the other parts provided in the housing 1 where the motor part M is housed, for example, the rotary shaft 8, the lower end face of the housing cover 5, the lower bottom part 1 a of the housing 1 or the like may be subjected to the rustproof treatment.

Claims

1. The electric fuel pump comprising a motor part housed in a housing, and a pump part provided at an end part of the housing,

said motor part being a brushless motor comprising a stator where a winding is wound, and a rotor having a magnet fixedly provided at a yoke, and fuel pressurized by the pump part driven by the motor part being supplied into the housing and discharged toward an outside from a discharge passage of the end part of the housing through the surrounding of the brushless motor,

wherein a yoke and a magnet of a rotor are subjected to a rustproof treatment such as plating, resin molding or the like, and a winding of a stator is resin-molded.

2. The electric fuel pump as claimed in claim 1, wherein an inner conductive wire, which is for supplying electric current to the winding of said stator and is provided in the housing, is resin-molded.

3. The electric fuel pump as claimed in claim 1, wherein the housing forming a motor housing chamber of said housing is made from aluminum or iron, and an inner circumference face of the housing is subjected to the rustproof treatment.