Patent Publication Number: US-2012038240-A1

Title: Fuel pump and method of making the same

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is based on and incorporates herein by reference Japanese Patent Application No. 2010-181758 filed on Aug. 16, 2010, and Japanese Patent Application No. 2011-75098 filed on Mar. 30, 2011. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a fuel pump that drives its pump part by driving force of its motor part to pressure-feed suctioned fuel. 
     2. Description of Related Art 
     A fuel pump that supplies fuel in a fuel tank to an internal combustion engine is widely known. The fuel pump pressurizes the fuel which is suctioned from the fuel tank at its pump part, and supplies the fuel to the engine. A motor part of the fuel pump includes a commutator made up of segments, and carries out a supply or cuffing off of an electric current to the commutator as a result of a sliding contact of a brush, which is energized, with the commutator. In JP-A-2007-023784, an urging member presses a brush on a commutator with the brush leaned toward the rear in a rotation direction of the commutator, so that generation of electric discharge between the commutator and the brush is curbed, and abnormal wear of the commutator and the brush are reduced. 
     In the fuel pump described in JP-A-2007-023784, an electrical connection to the brush is ensured by means of a pigtail which is obtained by bundling together linear conductive members. If the pigtail is connected to the brush from the front in the rotation direction of the commutator, the brush is also urged toward the front in the rotation direction of the commutator by resilient force of the pigtail. Consequently, when the contact between the commutator rotating and the brush at the front in the rotation direction of the commutator is released, the electric discharge by surge voltage between the commutator and the brush is easily generated. When an electrical current is discharged between the commutator and the brush, the commutator and the brush readily cause unusual wear. 
     SUMMARY OF THE INVENTION 
     The present invention addresses at least one of the above disadvantages. 
     According to the present invention, there is provided a fuel pump comprising a pump part, a motor part, two brushes, two pigtails, and an urging member. The pump part includes an impeller and is configured to suction and pressurize fuel. The motor part includes a rotor, a commutator, and a motor casing. The rotor is coupled with a rotating shaft of the impeller to be capable of rotating the impeller. The commutator is rotated together with the rotor to rectify an electric current supplied to the rotor. The motor casing accommodates the rotor and the commutator. Each of the two brushes includes a side surface and one axial end face that slides on the commutator to be electrically connectable to the commutator, and the two brushes are accommodated in the motor casing movably in an axial direction thereof. Each of the two pigtails is made of a linear conductive member and includes one end portion that is electrically and mechanically connected to a corresponding one of the two brushes. The urging member includes one end which is engaged with the motor casing, and the other end which is configured to press and urge each of the two brushes against the commutator from the other axial end face of the each of the two brushes. The other axial end face of each of the two brushes, with which the other end of the urging member is in contact, includes an inclined surface. A distance between the inclined surface and a sliding surface of the commutator, on which the one axial end face of each of the two brushes slides, in an axial direction of the each of the two brushes becomes longer toward a rear side of the each of the two brushes in a rotation direction of the commutator. The motor casing includes two brush accommodating chambers, each of which accommodates a corresponding one of the two brushes. The side surface and an inner wall of the motor casing, which defines each of the two brush accommodating chambers, define a clearance therebetween. Each of the two pigtails includes art extension portion extending from the one end portion thereof toward the rear side in the rotation direction of the commutator. 
     According to the present invention, there is also provided a method for making the fuel pump. According to the method, a first connecting process is performed. In performing the first connecting process, the one end portion of each of the two pigtails is connected to a corresponding one of the two brushes. Furthermore, a second connecting process is performed. In performing the second connecting process, the other end portion of each of the two pigtails is electrically and mechanically connected to a corresponding one of two brush terminals configured to supply electric power to the each of the two pigtails. Then, a flexural formation process is performed after the first and second connecting processes. In performing the flexural formation process, each of the two brushes and a corresponding one of the two brush terminals are brought close to each other, with each of the two pigtails connected to a corresponding one of the two brushes and to a corresponding one of the two brush terminals, so as to shorten a distance between the one end portion and the other end portion of the each of the two pigtails and thereby to provide a flexure for the each of the two pigtails. Subsequently, a first extension portion formation process is performed after the flexural formation process. In performing the first extension portion formation process, the extension portion is provided for each of the two pigtails. The extension portion extends toward the rear side in the rotation direction of the commutator. 
     According to the present invention, there is further provided a method for making the fuel pump. According to the method, an attachment process is performed. In performing the attachment process, the two brushes and two brush terminals are attached to the motor casing, each of the two brush terminals being configured to supply electric power to a corresponding one of the two pigtails. Furthermore, a third connecting process is performed. In performing the third connecting process, the one end portion of each of the two pigtails is connected to a corresponding one of the two brushes. In addition, a fourth connecting process is performed. In performing the fourth connecting process, the other end portion of each of the two pigtails is connected to a corresponding one of the two brush terminals. Then, a second extension portion formation process is performed after the attachment process and the third and fourth connecting processes. In performing the second extension portion formation process, the extension portion is provided for each of the two pigtails with the two brushes and the two brush terminals attached to the motor casing. The extension portion extends toward the rear side in the rotation direction of the commutator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention, together with additional objectives, features and advantages thereof, will be best understood from the following description, the appended claims and the accompanying drawings in which: 
         FIG. 1  is a sectional view generally illustrating a fuel pump in accordance with a first embodiment of the invention; 
         FIG. 2  is a sectional view taken along a line II-II in  FIG. 1  and is an enlarged view illustrating vicinity of a brush; 
         FIG. 3  is a diagram roughly illustrating configuration of the vicinity of the brush of the fuel pump in accordance with the first embodiment with the vicinity viewed from a direction of an arrow III in  FIG. 2 ; 
         FIG. 4  is a schematic view illustrating electric configuration of a coil in the fuel pump in accordance with the first embodiment; 
         FIG. 5A  is a bottom view illustrating a motor casing in the fuel pump in accordance with the first embodiment; 
         FIG. 5B  is a sectional view taken along a line VB-VB in  FIG. 5A ; 
         FIG. 5C  is a sectional view taken along a line VC-VC in  FIG. 5A ; 
         FIG. 6  is a schematic view illustrating a method of making the fuel pump in accordance with the first embodiment; 
         FIG. 7A  is a schematic view illustrating a process following  FIG. 6  in the method of making the fuel pump in accordance with the first embodiment; 
         FIG. 7B  is a sectional view taken along a line VIIB-VIIB in  FIG. 7A ; 
         FIG. 8A  is a schematic view illustrating a process following  FIGS. 7A and 7B  in the method of making the fuel pump in accordance with the first embodiment; 
         FIG. 8B  is a sectional view taken along a line VIIIB-VIIIB in  FIG. 8A ; 
         FIG. 9  is a schematic view illustrating a relationship between an electric current flowing between the brush and a commutator in the fuel pump and surge voltage in accordance with the first embodiment; 
         FIG. 10  is a schematic view illustrating a positional relationship between a pigtail and the brush in the fuel pump in accordance with the first embodiment; 
         FIG. 11  is an enlarged view showing XI in  FIG. 5A  and illustrating a forming angle of the pigtail in accordance with the first embodiment; 
         FIG. 12  is a schematic view illustrating a relationship of the forming angle of the pigtail, and the amount of sparks generated between the commutator and the brush, in the fuel pump in accordance with the first embodiment; 
         FIG. 13A  is a schematic view illustrating a method of making a fuel pump in accordance with a second embodiment of the invention; and 
         FIG. 13B  is a schematic view illustrating the method of making the fuel pump in accordance with the second embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the invention will be described below in reference to the accompanying drawings. 
     First Embodiment 
     A fuel pump  10  in accordance with a first embodiment of the invention is an in-tank pump that is disposed in a fuel tank of a vehicle, for example. The fuel pump  10  supplies fuel inside the fuel tank to an engine. The fuel pump  10  includes a pump part  12  that pressurizes the suctioned fuel, and a motor part  14  that drives the pump part  12 . The motor part  14  is a direct-current motor with a brush. The fuel pump  10  includes a housing  16  having a generally cylindrical shape. A permanent magnet  18  is disposed annularly in the circumferential direction on an inner wall surface of the housing  16 . A rotor  20  is disposed radially inward of the permanent magnet  18  concentrically with the annular permanent magnet  18 . 
     The pump part  12  includes a casing main body  31 , a casing cover  32 , and an impeller  33  which is a rotation member. The casing main body  31  and the casing cover  32  define a generally C-shaped pump passage  34 . The impeller  33  is accommodated rotatably between the casing main body  31  and the casing cover  32 . The casing main body  31  and the casing cover  32  are formed by, for example, die casting of aluminum. The casing main body  31  is fixed in one end side of the housing  16  in an axial direction thereof by press fitting. A bearing  35  that rotatably supports a shaft  21 , which is connected to the impeller  33 , is disposed at a central part of the casing main body  31 . 
     The casing cover  32  is fixed to one end portion of the housing  16  by calking, for example, with the casing main body  31  covered in the cover  32 . A thrust bearing  36  that limits axial displacement of the shaft  21  is fixed at a central part of the casing cover  32 . The casing cover  32  has a fuel inlet  38 . 
     A motor casing  41  and a fuel discharge cover  42  are disposed at the other end portion of the housing  16 , i.e., on the opposite side of the housing  16  from the casing main body  31  and the casing cover  32 . The motor casing  41  is located between the fuel discharge cover  42  and the housing  16 . The fuel discharge cover  42  is fixed to the housing  16  by calking. The motor casing  41  includes a connecting passage  44  that connects a pump chamber  22  and a fuel passage  43  of the fuel discharge cover  42 . The motor casing  41  defines a brush accommodating chamber  45  which accommodates a brush  50  such that the brush  50  can be reciprocated in its axial direction, as illustrated in  FIG. 2 . The motor casing  41  is a housing that defines the brush accommodating chamber  45 , in which the brush  50  is accommodated. The motor casing  41  accommodates the brush  50 , and a compression spring  60  serving as an urging member in its brush accommodating chamber  45 . 
     The fuel discharge cover  42  includes a fuel discharge part  46  and an electric connector part  47  radially outward of the shaft  21 , as illustrated in  FIG. 1 . The fuel discharge part  46  includes the fuel passage  43  and a pressure regulating valve  48 . The fuel passage  43  is opened or closed by a valve member  49  of the pressure regulating valve  48 . When the pressure of fuel inside the fuel pump  10  becomes larger than a predetermined value, the valve member  49  opens the fuel passage  43 . The fuel discharge cover  42  may correspond to a “motor casing”. 
     The electric connector part  47 , which is connected to the outside of the fuel pump  10 , includes a terminal  471 . The terminal  471  is electrically connected to a pigtail  51  through a choking coil  55  and a brush terminal  56 , as illustrated in  FIG. 2 . The pigtail  51  is electrically connected to a side surface  54  of the surfaces constituting the brush  50  that is located on the opposite side from a rotation center of a commutator  70 . 
     The rotor  20  is accommodated rotatably in the housing  16 , as illustrated in  FIG. 1 . One end portion of the shaft  21  of the rotor  20  is rotatably supported by the bearing  35  in its radial direction; and the other end portion of the shaft  21  of the rotor  20  is rotatably supported by the bearing  37  in the radial direction. A winding wire that constitutes a coil  23  is wound around an outer peripheral surface of the core  25 , which is fixed to the shaft  21 . As illustrated in  FIG. 2 , the commutator  70  is formed in the shape of a circular disk, and disposed above the rotor  20 . More specifically, the commutator  70  is located at an end portion of the rotor  20  on its opposite side from the pump part  12 . 
     Next, the brush  50  will be described in detail. The brush  50  is accommodated in the brush accommodating chamber  45  of the motor casing  41  as illustrated in  FIG. 3 . The brush  50  is guided by the brush accommodating chamber  45  defined by an inner wall  412  of the motor casing  41 , to reciprocate in its axial direction. The brush accommodating chamber  45  includes an opening  411  on its part in the circumferential direction, as illustrated in  FIG. 3 . The pigtail  51 , which is connected to the brush  50 , is taken out from the opening  411  of the brush accommodating chamber  45 . Accordingly, in the case of reciprocation movement of the brush  50  in its axial direction along the inner wall  412  of the motor casing  41 , the pigtail  51  connected to the brush  50  moves in the axial direction, following the brush  50 . 
     The brush accommodating chamber  45  of the motor casing  41  is formed to be slightly larger on its interior side than the brush  50 . Accordingly, a slight clearance  451  is formed between the brush  50  and the inner wall  412  of the motor casing  41 . In  FIG. 3 , the clearance  451  is overdrawn in order to describe the clearance  451  between the brush  50  and the motor casing  41  in a straightforward manner. 
     The brush  50  is in contact with the compression spring  60  on its one inclined surface  53  in the axial direction. The other end portion of the compression spring  60  is in contact with an upper part  452  of the brush accommodating chamber  45 . The compression spring  60  has extending force. Consequently, an end face  52  of the brush  50  is pressed on a sliding surface  71  of the commutator  70 . 
     The commutator  70  is constituted of segments  72 , which are divided in its circumferential direction. The segments  72  are connected respectively to the winding wires of the coils  23 , as illustrated in  FIG. 4 . As a result of a repeated contact between the brush  50  and each segment  72  of the commutator  70 , an electric current supplied to the coil  23  is rectified. The commutator  70  rotates together with the rotor  20  (see  FIG. 2 ) in a direction of an arrow R indicated in  FIGS. 3 and 4 . Therefore, in  FIGS. 3 and 4 , the front in a rotation direction of the commutator  70  is located on the right-hand side; and the rear in the rotation direction of the commutator  70  is located on the left-hand side. 
     In the first embodiment, as illustrated in  FIGS. 5A to 5C , one end portion of the pigtail  51  is connected to the brush  50 , and the other end portion of the pigtail  51  is connected to the brush terminal  56 . The rotation direction of the commutator  70  is the clockwise direction, as illustrated in  FIG. 5A . The pigtail  51 , which is connected mechanically and electrically to the side surface  54  of the brush  50 , is pulled out in the opposite direction from the rotation center of the commutator  70  through the opening  411  of the motor casing  41 . The pigtail  51 , which is drawn out up to an outer wall  453  of the brush accommodating chamber  45 , includes an extension portion  515  extending on its rear side in the rotation direction of the commutator  70  toward a contact surface of the commutator  70  and the brush  50 , as illustrated in  FIG. 58 . After that, the pigtail  51  changes its extending direction at a generally intermediate portion of the pigtail  51 , and extends to its front in the rotation direction of the commutator  70  toward a direction of the inclined surface  53 . Lastly, the other end of the pigtail  51  is connected to the brush terminal  56  provided for the fuel discharge cover  42  on a generally lateral side of the brush  50 . 
     A production method for the fuel pump  10  will be described. A formation process for the extension portion  515  of the pigtail  51  in the fuel pump  10  will be explained in reference to  FIGS. 6 to 8B . The process for forming the extension portion  515  includes mainly the following processes. Firstly, as illustrated in  FIG. 6 , the terminal  471 , the choking coil  55 , the brush terminal  56 , the pigtail  51 , and the brush  50  are attached to component attachment pallets  90   a ,  90   b ,  90   c . Meanwhile, the brush  50  is accommodated in an accommodating hole that is formed in the attachment pallet  90   a  along the attachment pallet  90   b . One end portion of the pigtail  51  is connected to the brush  50 . The other end portion of the pigtail  51  is connected to the brush terminal  56 . The pigtail  51  has a generally linear shape, since the brush  50  and the brush terminal  56 , which are connected to the pigtail  51 , are attached to the component attachment pallets  90   a ,  90   b ,  90   c  separately from each other. 
     Next, in a flexural formation process, the brush  50  accommodated in the attachment pallet  90   a  is displaced toward the brush terminal  56 , as illustrated in  FIG. 7A . More specifically, a distance between one end portion of the pigtail  51 , which is connected to the brush  50 , and the other end portion of the pigtail  51 , which is connected to the brush terminal  56 , is shortened. Accordingly, the pigtail  51  has a flexure toward the reader through a plane of paper in  FIG. 7A . 
     After the above-described flexural formation process, as illustrated in  FIGS. 8A and 8B , the extension portion  515  is formed by means of an extension portion formation jig  100  such that a flexure shape of the pigtail  51  is parallel to the side surface  54  of the brush  50 . Because the two pigtails  51  respectively have the extension portions  515  extending toward their rear sides in the rotation direction of the commutator  70 , the pigtail  51  on the left-hand side in  FIG. 8B  includes the extension portion  515  in a direction away from the coil  55 . On the other hand, the pigtail  51  on the right-hand side in  FIG. 8B  includes the extension portion  515  in a direction toward the coil  55 . 
     Operation of the fuel pump  10  will be described. The electric current, which is supplied to the terminal  471  from a power source (not shown), is fed to the commutator  70  through the brush terminal  56 , the pigtail  51 , and the brush  50 . The electric current, which is fed into the commutator  70 , is supplied to the coil  23  of the rotor  20 . When the rotor  20  is rotated by the electric current supplied to the coil  23 , the impeller  33  rotates together with the rotor  20  and the shaft  21 . When the impeller  33  rotates, fuel is suctioned from the fuel inlet  38  into the pump passage  34 . The fuel drawn into the pump passage  34  is discharged from the pump passage  34  into the pump chamber  22  as a result of the application of kinetic energy thereto by each blade groove of the impeller  33 . The fuel discharged into the pump room  22  is supplied to the outside of the fuel pump  10  through a surrounding area of the rotor  20  and the fuel passage  43 . 
     The brush  50 , which supplies an electric current to the commutator  70 , is brought into contact with the commutator  70 , with the brush  50  inclined toward its rear side in the rotation direction of the commutator  70 , as illustrated in  FIG. 10 , by urging force of the compression spring  60 , which is in contact with the inclined surface  53 . The pigtail  51 , which is connected to the brush  50  from the rear side in the rotation direction of the commutator  70 , pulls the brush  50  to the rear side in the rotation direction of the commutator  70 . 
     In the case of the rotor  20  having the coil  23 , to which a “star connection” is applied, as illustrated in  FIG. 4 , one end portion of each coil  23  is connected to a connection part  24 ; and the other end portion of each coil  23  is connected to its corresponding segment  72  of the commutator  70 . For this reason, when the contact between the brush  50  and each segment  72  of the commutator  70  is released, a residual current “di” changes rapidly during a short time “dt”, as illustrated in  FIG. 9 . As a result, electric energy stored in the coil  23  is released between the brush  50  and the commutator  70 ; and a surge voltage Vs is generated between the brush  50  and the commutator  70 . Accordingly, a spark discharge is created between the brush  50  and the commutator  70 . The spark discharge between the brush  50  and the commutator  70  causes electric wear of the brush  50  and the commutator  70 . 
     Effects of the fuel pump  10  of the first embodiment of the invention will be described. As illustrated in  FIG. 10 , pressing force F 1  by the compression spring  60  and tension F 2  by the pigtail  51  are applied to the brush  50 . More specifically, the pressing force F 1  is force whereby the sliding surface  52  of the brush  50  is pressed against the commutator  70  due to the compression spring  60  acting on the inclined surface  53  of the brush  50 . On the other hand, the tension F 2  is force whereby the pigtail  51 , which is connected to the brush  50  from its rear side in the rotation direction of the commutator  70 , pulls the brush  50  to its rear side in the rotation direction of the commutator  70 . 
     The brush  50  slides on the commutator  70  with its inclined surface  53  inclined to the rear side in the rotation direction of the commutator  70 . Accordingly, the pressing force of the brush  50  on the commutator  70  becomes larger further in a direction in which the brush  50  inclines, i.e., toward the rear in the rotation direction of the commutator  70 . The pressing force of the brush  50  against the commutator  70  becomes smaller further on the front side in the rotation direction of the commutator  70 . 
     Ease of flowing of the electric current between the commutator  70  and the brush  50  is determined by a contact state between a rectification surface  71  of the commutator  70  and the sliding surface  52  of the brush  50 . When there are fewer foreign substances and the rectification surface  71  and the sliding surface  52  are more closely-attached to each other, contact resistance between the commutator  70  and the brush  50  becomes smaller, and the electric current thereby more easily flows. Thus, the contact resistance becomes smaller on the rear side in the rotation direction of the commutator  70 . On the front side in the rotation direction of the commutator  70 , on the other hand, the electric current does not easily flow between the commutator  70  and the brush  50  as compared with the rear side in the rotation direction of the commutator  70 , and an occurrence of electric discharge is accordingly limited. As a consequence, abnormal wear of the commutator  70  and the brush  50  due to the electric discharge caused when the contact of the commutator  70  and the brush  50  is released can be reduced. 
     In the conventional technology, the pigtail, which is connected from the front side in the rotation direction of the commutator, urges the brush to the front in the rotation direction of the commutator. Accordingly, the pressing force is applied to the brush on the rear side in the rotation direction of the commutator by the compression spring, whereas tension is applied to the brush on the front side in the rotation direction of the commutator. Hence, the direction of the pressing force of the brush against the commutator is not concentrated on the rear side in the rotation direction of the commutator, so that the magnitude of the pressing force is not stable. 
     In comparison to this conventional technology, in the fuel pump  10  of the first embodiment of the invention, the pigtail  51  is formed to urge the brush  50  on the rear side in the rotation direction of the commutator  70 . In consequence, the brush  50  becomes stable with the load applied to the rear side of the brush  50  in the rotation direction of the commutator  70 , and the direction of pressing of the brush  50  against the commutator  70  is also stabilized. As a result, when the contact between the rotating commutator  70  and the brush  50  is released, not only does the amount of generated sparks become small, variation in the spark amount can also be reduced. Therefore, the abnormal wear of the commutator  70  and the brush  50  due to the electric discharge can be reduced, and variation in the amount of abnormal wear can also be limited. 
     In order to investigate a relationship between an extending direction of the pigtail  50  and the amount of sparks generated, an angle made by the extending pigtail  50  is defined as in  FIG. 11 . A point, at which an outer wall surface of the motor casing  41  in its outer peripheral direction and the pigtail  51  extending out from the opening  411  intersect with each other, is referred to as an origin point  511 . A straight line passing through the origin point  511  and extending outwardly in a direction of the normal line of the side surface  54  of the brush  50  is referred to as an X-axis  512 . A plane that is horizontal relative to the fuel pump  10  and includes the X-axis  512  is referred to as a horizontal plane  513  (see  FIG. 5B ). When the extension portion  515  of the pigtail  51  extending out of the side surface  54  of the brush  50  passes through the origin point  511 , to extend toward the rear or front in the rotation direction of the commutator  70 , the extension portion  515 , the extension portion  515  is projected on the horizontal plane  513 . In such a case, an angle between a shadow of the projected extension portion  515  and the X-axis  512  is referred to as a forming angle  80 . When viewed from the X-axis  512 , if the forming angle  80  is made on the rear side in the rotation direction of the commutator  70 , the forming angle  80  takes a positive value; and if the forming angle  80  is made on the front side in the rotation direction of the commutator  70 , the forming angle  80  takes a negative value. 
     As illustrated in  FIG. 12 , by the forming angle  80  taking a positive value, the amount of sparks becomes small, and variation in the amount of sparks also becomes small. 
     In addition, in the present embodiment, the extension portion  515  of the pigtail  51  connected to the side surface  54  of the brush  50  is pulled out in the opposite direction from the rotation center of the commutator  70 . Then, the extension portion  515  extends toward the rear in the rotation direction of the commutator  70 . Accordingly, an interference of the pigtail  51  with its peripheral components can be prevented with the above-described tension F 2  by the pigtail  51  maintained. 
     Second Embodiment 
     A second embodiment of the invention will be described with reference to  FIGS. 13A and 13B . The second embodiment is different from the first embodiment in the method for forming the extension portion of the pigtail. The same numerals are used for indicating substantially the same components as the first embodiment, and their descriptions are omitted. 
     A method for making an extension portion  515  of a pigtail  51  in a fuel pump  10  of the second embodiment includes mainly the following processes. A brush terminal  56  and a brush  50  are attached to a fuel discharge cover  42  and a motor casing  41 . Then, one end portion of the pigtail  51  is connected to the attached brush  50 . Moreover, the other end portion of the pigtail  51  is connected to the attached brush terminal  56 . 
     Next, force F is applied to the pigtail  51 , which is connected to the brush  50  and the brush terminal  56 . To the pigtail  51  on the right-hand side in  FIG. 13A , the force F is applied upward on a plane of paper of  FIGS. 13A and 13B . As well, to the pigtail  51  on the left-hand side in  FIG. 13A , the force F is given downward on the plane of paper of  FIGS. 13A and 13B . Accordingly, the pigtail  51  has the extension portion  515  as illustrated in  FIG. 13B . 
     By the production method for the fuel pump  10  of the second embodiment, the extension portion  515  of the pigtail  51  can be formed even after the attachment of the components to the fuel discharge cover  42  and the motor casing  41 . 
     Modifications of the above embodiments will be described. In the above-described embodiments, the pigtail  51  extends to the rear in the rotation direction of the commutator  70 , and then, the pigtail  51  changes its direction to the front in the rotation direction of the commutator  70  at the generally intermediate portion of the pigtail  51  so as to be connected to the brush terminal  56 . Alternatively, the point, at which to change the shape and extending direction of the pigtail  51  after its generally intermediate portion, is not necessarily limited to this. As a result of this, the fuel pump  10  has an advantage owing to a high degree of flexibility in design of a positional relationship between the brush  50  and the brush terminal  56 . 
     In the above-described embodiments, the pigtail  51  has the urging force by resilience due to its resilient deformation, which is applied to the brush  50 . Alternatively, a deformed state of the pigtail  51  is not necessarily limited to the resilient deformation. For example, even if the pigtail  51  is plastically deformed, the pigtail  51  may be employed as long as the pigtail  51  can apply the urging force toward the rear side in the rotation direction of the commutator  70  by its restoring force to the brush  50 . 
     As above, the invention is not by any means limited to the above embodiments, and may be embodied in various modes without departing from the scope of the invention. 
     To sum up, the fuel pump  10  and the method for making the fuel pump  10  in accordance with the above embodiments may be described as follows. 
     The fuel pump  10  includes a pump part  12 , a motor part  14 , two brushes  50 , two pigtails  51 , and an urging member  60 . The pump part  12  includes an impeller  33  and is configured to suction and pressurize fuel. The motor part  14  includes a rotor  20 , a commutator  70 , and a motor casing  41 . The rotor  20  is coupled with a rotating shaft  21  of the impeller  33  to be capable of rotating the impeller  33 . The commutator  70  is rotated together with the rotor  20  to rectify an electric current supplied to the rotor  20 . The motor casing  41  accommodates the rotor  20  and the commutator  70 . Each of the two brushes  50  includes a side surface  54  and one axial end face  52  that slides on the commutator  70  to be electrically connectable to the commutator  70 , and the two brushes  50  are accommodated in the motor casing  41  movably in an axial direction thereof. Each of the two pigtails  51  is made of a linear conductive member and includes one end portion that is electrically and mechanically connected to a corresponding one of the two brushes  50 . The urging member  60  includes one end which is engaged with the motor casing  41 , and the other end which is configured to press and urge each of the two brushes  50  against the commutator  70  from the other axial end face  53  of the each of the two brushes  50 . The other axial end face  53  of each of the two brushes  50 , with which the other end of the urging member  60  is in contact, includes an inclined surface  53 . A distance between the inclined surface  53  and a sliding surface  71  of the commutator  70 , on which the one axial end face  52  of each of the two brushes  50  slides, in an axial direction of the each of the two brushes  50  becomes longer toward a rear side of the each of the two brushes  50  in a rotation direction of the commutator  70 . The motor casing  41  includes two brush accommodating chambers  45 , each of which accommodates a corresponding one of the two brushes  50 . The side surface  54  and an inner wall  412  of the motor casing  41 , which defines each of the two brush accommodating chambers  45 , define a clearance  451  therebetween. Each of the two pigtails  51  includes an extension portion  515  extending from the one end portion thereof toward the rear side in the rotation direction of the commutator  70 . 
     Accordingly, when urging force toward the commutator  70  is applied by the urging member  60  to the brush  50 , the end face of the brush  50  that is in contact with the urging member  60  is inclined backward in the rotation direction of the commutator  70 . Therefore, on the contact surface between the commutator  70  and the brush  50 , the pressing force of the brush  50  against the commutator  70  becomes larger further backward in the rotation direction of the commutator  70 . Furthermore, the pigtail  51  applies the force, which pulls the brush  50  backward in the rotation direction of the commutator  70 , to the brush  50 , which is connected to the pigtail  51 . As a result of the above-described configuration of the fuel pump  10 , the brush  50  that slides on the commutator  70  is pushed on the commutator  70  by the force that becomes larger further backward in the rotation direction of the commutator  70 , maintaining a state in which the end face of the brush  50  that is in contact with the urging member  60  is inclined backward in the rotation direction of the commutator  70 . 
     Fuel flowing through the pumping device  10  exists at the sliding surfaces  52 ,  71  between the brush  50  and the commutator  70 . In this case, as the pressing force of the brush  50  against the commutator  70  is larger, the fuel existing at the sliding surfaces  52 ,  71  between the commutator  70  and the brush  50  can be further removed, and contact resistance between the commutator  70  and the brush  50  can be made smaller. Therefore, the contact resistance between the commutator  70  and the brush  50  becomes smaller further on the rear side in the rotation direction of the commutator  70 . Accordingly, at the sliding surfaces  52 ,  71  between the brush  50  and the commutator  70 , an electric current easily flows on the rear side in the rotation direction of the commutator  70 . On the other hand, because the contact resistance is great on the front side in the rotation direction of the commutator  70 , an electric current does not easily flow. As a result, electric discharge is not easily produced on the front side in the rotation direction of the commutator  70 , on which the contact between the rotating commutator  70  and the brush  50  is released. Thus, the development of abnormal wear of the commutator  70  and the brush  50  caused by the electric discharge can be limited. 
     The extension portion  515  may extend from the one end portion of each of the two pigtails  51  in an opposite direction from a rotation center of the commutator  70 . 
     In this case, the pigtail  51  has a shape that is pulled out from the brush  50  in the opposite direction from the rotation center of the commutator  70  and that extends backward in the rotation direction of the commutator  70 . Accordingly, with the pigtail  51  maintaining the force that pulls the brush  50  backward in the rotation direction of the commutator  70 , an interference between peripheral components of the brush  50 , such as the motor casing  41 , and the pigtail  51 , can be eliminated. 
     The extension portion  515  may extend from the one end portion of each of the two pigtails  51  in an opposite direction from a rotation center of the commutator  70  as well as toward the rear side in the rotation direction of the commutator  70 . 
     Similar to the above, the interference with peripheral components of the brush  50  can be eliminated with the urging force, which is applied to the brush  50  by the pigtail  51 , maintained. 
     Each of the two pigtails  51  may be resiliently deformable. 
     Accordingly, the pigtail  51 , which is formed on the rear side in the rotation direction of the commutator  70 , can pull the brush  50  with even larger force backward in the rotation direction of the commutator  70  using its resilient force. 
     The fuel pump  10  may further include two brush terminals  56 , each of which is configured to supply electric power to a corresponding one of the two pigtails  51 . Each of the two pigtails  51  may include the other end portion that is connected to a corresponding one of the two brush terminals  56 . The motor casing  41  and the two brush terminals  56  may be integrally formed. The one end portion of each of the two pigtails  51  may be connected to a corresponding one of the side surfaces  54  of the two brushes  50 . 
     Accordingly, the brush  50  and the brush terminal  56 , which are connected by the pigtail  51 , are located close to each other, and as a result, the pigtail  51  becomes short. In the case of the short pigtail  51 , the urging force due to the bending of the pigtail  51  is made large, and therefore, urging force in an unintended direction may be applied to the brush  50 . In the fuel pump  10 , the pigtail  51  is formed to extend backward in the rotation direction of the commutator  70 , so that the urging force in an unintended direction applied to the brush  50  is eliminated, and the development of electric discharge between the brush  50  and the commutator  70  is thereby curbed. Consequently, the development of abnormal wear of the commutator  70  and the brush  50  caused by the electric discharge can be limited. 
     According to the method for making the fuel pump  10 , a first connecting process is performed. In the first connecting process, the one end portion of each of the two pigtails  51  is connected to a corresponding one of the two brushes  50 . Furthermore, a second connecting process is performed. In the second connecting process, the other end portion of each of the two pigtails  51  is electrically and mechanically connected to a corresponding one of two brush terminals  56  configured to supply electric power to the each of the two pigtails  51 . Then, a flexural formation process is performed after the first and second connecting processes. In the flexural formation process, each of the two brushes  50  and a corresponding one of the two brush terminals  56  are brought close to each other, with each of the two pigtails  51  connected to a corresponding one of the two brushes  50  and to a corresponding one of the two brush terminals  56 , so as to shorten a distance between the one end portion and the other end portion of the each of the two pigtails  51  and thereby to provide a flexure for the each of the two pigtails  51 . Subsequently, a first extension portion formation process is performed after the flexural formation process. In the first extension portion formation process, the extension portion  515  is provided for each of the two pigtails  51 . The extension portion  515  extends toward the rear side in the rotation direction of the commutator  70 . 
     A fuel pump  10  made by this production method produces similar effects to the above-described fuel pump  10 . 
     According to the method for making the fuel pump  10 , an attachment process is performed. In performing the attachment process, the two brushes  50  and two brush terminals  56  are attached to the motor casing  41 , each of the two brush terminals  56  being configured to supply electric power to a corresponding one of the two pigtails  51 . Furthermore, a third connecting process is performed. In performing the third connecting process, the one end portion of each of the two pigtails  51  is connected to a corresponding one of the two brushes  50 . In addition, a fourth connecting process is performed. In performing the fourth connecting process, the other end portion of each of the two pigtails  51  is connected to a corresponding one of the two brush terminals  56 . Then, a second extension portion formation process is performed after the attachment process and the third and fourth connecting processes. In performing the second extension portion formation process, the extension portion  515  is provided for each of the two pigtails  51  with the two brushes  50  and the two brush terminals  56  attached to the motor casing  41 . The extension portion ( 515 ) extends toward the rear side in the rotation direction of the commutator  70 . 
     A fuel pump  10  made by this production method produces similar effects to the above-described fuel pump  10 . 
     Additional advantages and modifications will readily occur to those skilled in the art. The invention in its broader terms is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described.