Patent Publication Number: US-2007122300-A1

Title: Electric fuel pump

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.