FUEL PUMP

Abstract

A fuel pump includes a pump cover on one side of a housing, a cover end portion on the other side of the housing, a stator inside the housing, a rotor inside the stator, a shaft rotatable with the rotor, an impeller rotatable with the shaft to pressurize fuel inside the housing, a bearing portion provided in the cover end portion on its center axis to slidably support an end part of the shaft, and a relief valve capable of reducing a fuel pressure inside the housing. The cover end portion has an end surface located on its side opposite from the pump cover, and the relief valve includes a valve seat located on an opposite side of the end surface of the cover end portion from the pump cover.

Description

CROSS REFERENCE TO RELATED APPLICATION

This application is based on and incorporates herein by reference Japanese Patent Application No. 2012-127810 filed on Jun. 5, 2012.

TECHNICAL FIELD

The present disclosure relates to a fuel pump which supplies fuel to a fuel-supplied object.

BACKGROUND

Conventionally, a fuel pump is known which draws a fuel through a suction portion and discharges the drawn fuel through a discharge portion by rotating an impeller with use of an inner-rotor motor (see, for example, Patent Document 1: JP 2012-31807 A). Discharge performance of the fuel pump, such as an amount and a pressure of fuel discharged from the discharge portion, depend on rotation of the motor. Thus, it is necessary to keep accuracy high in processing of an inner wall of a bearing portion that supports a shaft of the motor.

A fuel pump of Patent Document 1 includes a relief valve. The relief valve is capable of reducing a fuel pressure in a space provided between a pump cover and a cover end in a housing by separating a valve member from a valve seat when the fuel pressure becomes higher than or equal to a predetermined value. Accordingly, it is limited that, for example, the fuel pump or a supply pipe conveying fuel to a fuel-supplied object is damaged due to excess pressure increase in the housing. In this case, the cover end has an end surface on its side opposite from the pump cover, and the valve seat of the relief valve is located in the cover end, i.e., on a near side of the end surface of the cover end to the pump cover. In other words, the valve seat is located at a position near to a bearing portion that slidably supports a shaft. When the valve seat is formed by, for example, heat forming or cutting in a manufacturing process of the fuel pump, an inner wall of the bearing portion may be deformed due to the forming of the valve seat. Additionally, in the fuel pump of Patent Document 1, a press-fit part is provided in an outer rim of the cover end that has a circular plate shape, and the press-fit part is press-fitted to an inner side of an end part of the housing. The press-fit part may also be deformed due to the forming of the valve seat. When the inner wall of the bearing portion or the press-fit part is deformed, support of the shaft by the bearing portion may become unstable in use of the fuel pump. Therefore, rotation of the shaft and an impeller may be destabilized, and a fuel discharge capacity of the fuel pump may become unstable.

SUMMARY

It is an objective of the present disclosure to provide a fuel pump capable of limiting deformation of a component due to forming of a valve seat of a relief valve.

According to an aspect of the present disclosure, a fuel pump includes a housing, a pump cover, a cover end portion, a stator, a rotor, a shaft, an impeller, a bearing portion, a discharge portion and a relief valve. The housing has a hollow cylindrical shape, and the pump cover closes an end opening of the housing on a first side of the housing in an axial direction of the housing. The pump cover includes a suction portion. The cover end portion has a circular plate shape to close the other end opening of the housing on a second side of the housing in the axial direction of the housing, and the cover end portion includes a press-fit part that is located on an outer rim of the cover end portion to be press-fitted to an inner side of the housing. The stator has a hollow cylindrical shape, and the stator is accommodated inside the housing and includes a plurality of wound wires. The rotor is rotatably provided inside the stator, and the shaft is provided coaxially with the rotor to rotate together with the rotor. The impeller is connected to one end of the shaft, and the impeller rotates together with the shaft to draw a fuel through the suction portion and pressurize the drawn fuel. The bearing portion is provided in the cover end portion on a center axis of the cover end portion to slidably support the other end of the shaft. The discharge portion is provided in the cover end portion to be used as a port through which the fuel pressurized by the impeller is discharged. The relief valve is capable of reducing a fuel pressure in a space that is located between the pump cover and the cover end portion inside the housing when the fuel pressure in the space becomes higher than or equal to a predetermined value. The relief valve includes a cylindrical portion, a valve seat, a valve member and an urging member. The cylindrical portion is integrated with the cover end portion to protrude outward from an end surface of the cover end portion on the second side of the housing. The valve seat is provided inside the cylindrical portion, and the valve member is capable of contacting the valve seat. The urging member has an end part contacting the valve member to urge the valve member toward the valve seat. The valve member is separated from the valve seat when the relief valve reduces the fuel pressure in the space, and the valve seat is located outside the cover end portion on the second side of the housing.

Accordingly, the end surface of the cover end portion is located on a side of the cover end portion opposite from the pump cover, and the valve seat is located on an opposite side of the end surface of the cover end portion from the pump cover. In other words, the valve seat is located on an opposite side of the cover end portion from the bearing portion and outside the cover end portion. Hence, although the valve seat is formed by, for example, thermal forming or cutting in a manufacturing process of the fuel pump, deformation of an inner wall of the bearing portion or the press-fit part due to the forming of the valve seat can be restricted. Therefore, rotation of the shaft and the impeller can be stabilized, and fuel discharge performance of the fuel pump can be made to be stable.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure, 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 partially sectional view, taken along a line I-I in FIG. 2, showing a fuel pump according to an exemplar embodiment of the present disclosure;

FIG. 2 is a sectional view taken along a line II-II in FIG. 1;

FIG. 3 is a view showing the fuel pump viewed in a direction of an arrow III in FIG. 1; and

FIG. 4 is a schematic diagram showing a cutting process of a cover end portion of the fuel pump according to the exemplar embodiment.

DETAILED DESCRIPTION

An exemplar embodiment of the present disclosure will be described hereinafter referring to FIGS. 1 to 3. A fuel pump 1 draws a fuel from a fuel tank to discharge and supply the fuel to an internal combustion engine that is a fuel-supplied object to which a fuel is supplied. As shown in FIGS. 1 and 2, the fuel pump 1 includes a housing 10, a pump cover 20, a cover end portion 30, a stator 40, a rotor 50, a shaft 52, an impeller 55, a discharge portion 36 and a relief valve 90.

The housing 10 is made of metal such as iron to have a cylindrical hollow shape. An outer periphery of the housing 10 is coated with zinc or tin, for example. The pump cover 20 is made of metal such as aluminum to have an approximately circular plate shape, and is located on one end of the housing 10 in an axial direction of the housing 10 to close an opening of the housing 10. The pump cover 20 is fixed to an inside of the one end of the housing 10 by crimping the one end of the housing 10 radially inward, so that the pump cover 20 is prevented from being detached from the housing 10 in the axial direction. As shown in FIG. 1, the pump cover 20 includes a suction portion 21 having a cylindrical shape. The suction portion 21 has a suction passage 211 that extends through the pump cover 20 in a plate thickness direction of the pump cover 20.

The cover end portion 30 is made, for example, of resin to have a circular plate shape. The cover end portion 30 is located on the other end of the housing 10 in the axial direction of the housing 10 to close another opening of the housing 10. The cover end portion 30 includes a press-fit part 31 on an outer rim of the cover end portion 30, and the press-fit part 31 is press-fitted to an inside of the other end of the housing 10. The cover end portion 30 is fixed to the inside of the other end of the housing 10 by crimping the other end of the housing 10 radially inward, so that the cover end portion 30 is prevented from being detached from the housing 10 in the axial direction.

The stator 40 includes sets of a core 41, an insulator 42 and a winding wire 43. The core 41 is made of a laminated core in which magnetic thin plates are laminated. The insulator 42 has a hollow cylindrical shape, and is fitted to an outer circumference of the core 41. The winding wire 43 is wound around the insulator 42. The sets of the core 41, the insulator 42 and the winding wire 43 are arranged in a circumferential direction of the housing 10 on an inner side of the housing 10. In the present embodiment, six sets of the core 41, the insulator 42 and the winding wire 43 are arranged in the circumferential direction of the housing 10 at predetermined intervals. The stator 40 and the rotor 50 are used as a three-phase (U-V-W phase) brushless motor. Two winding wires 43 configure one phase such that three phases of winding wires 43 are provided, and the three phases correspond to a U phase, a V phase and a W phase of the three-phase brushless motor respectively.

As shown in FIGS. 1 and 2, the core 41, the insulator 42 and the winding wire 43 of the stator 40 are connected to each other by molding of resin that is used as a material of the cover end portion 30. The stator 40 is integrated with the cover end portion 30 by resin molding. The stator 40 is formed in an approximately hollow cylindrical shape by the resin molding of the core 41, the insulator 42 and the winding wire 43. The stator 40 is accommodated in the housing 10 coaxially with the housing 10. The core 41 is covered by the resin or the insulator 42 except for a surface of the core 41 opposed to a center axis of the stator 40.

The rotor 50 is made of, for example, a magnetic material such as a bond magnet to have a cylindrical shape. The rotor 50 is provided on a radially inner side of the stator 40. The rotor 50 is magnetized such that north poles and south poles are arranged alternately in a circumferential direction of the rotor 50. The rotor 50 has a shaft hole 51 provided on a center axis of the rotor 50. The shaft 52 is made of metal to have a pole shape, and is press-fitted to the shaft hole 51. The shaft 52 is rotatable together with the rotor 50.

A pump casing 60 is provided between the pump cover 20 and the stator 40. The pump casing 60 is made of, for example, metal such as aluminum to have an approximately circular plate shape. The pump casing 60 has a hole portion 61 in a center part of the pump casing 60, and the hole portion 61 extends through the pump casing 60 in a plate thickness direction of the pump casing 60. A bearing member 62 is fitted into the hole portion 61 of the pump casing 60. The bearing member 62 is made of, for example, a copper-based sintered metal to have a hollow cylindrical shape.

The cover end portion 30 has a recess part 32 located on a near side of the cover end portion 30 to the rotor 50, and the recess part 32 of the cover end portion 30 concaves toward an opposite side of the cover end portion 30 from the rotor 50. The recess part 32 is located at a center part of a surface of the cover end portion 30 opposed to the rotor 50. The cover end portion 30 further includes a shaft cylindrical part 33 that is provided at a center of the recess part 32 to protrude cylindrically toward the rotor 50. A center axis of the shaft cylindrical part 33 is coincident with a center axis Ax1 of the cover end portion 30. A bearing member 34 is fitted into an inner side of the shaft cylindrical part 33. Similar to the bearing member 62, the bearing member 34 is made of, for example, a copper-based sintered metal to have a cylindrical shape.

The hole portion 61 supports one end side of the shaft 52 via the bearing member 62, and the shaft cylindrical part 33 supports the other end side of the shaft 52 via the bearing member 34. Accordingly, the rotor 50 and the shaft 52 are supported rotatably by the pump casing 60 and the cover end portion 30 via the bearing member 62, the hole portion 61, the bearing member 34 and the shaft cylindrical part 33. The shaft cylindrical part 33 of the cover end portion 30 may be used as an example of a bearing portion that supports the other end of the shaft 52.

The impeller 55 is made of resin to have an approximately circular plate shape. The impeller 55 is accommodated in a pump chamber 63 provided between the pump cover 20 and the pump casing 60. The pump chamber 63 has an approximately circular plate shape. One end of the shaft 52 is located in the pump chamber 63, and is chamfered to have a flat surface on its side wall. The impeller 55 has a hole 56 having a shape corresponding to a shape of the chamfered one end of the shaft 52. The hole 56 is located at a center part of the impeller 55. The one end of the shaft 52 is fitted into the hole 56 of the impeller 55. Therefore, the impeller 55 rotates in the pump chamber 63 when the shaft 52 rotates.

The pump cover 20 has a groove 22 on its surface located on a near side of the pump cover 20 to the impeller 55. The groove 22 has an approximately C-shape when the groove 22 is viewed in the center axis Ax1. The groove 22 communicates with the suction passage 211. The pump casing 60 has a groove 64 on its surface located on a near side of the pump casing 60 to the impeller 55. The groove 64 has an approximately C-shape when the groove 64 is viewed in the center axis Ax1. The pump casing 60 further has a through passage 65 that extends through the pump casing 60 in a plate thickness direction of the pump casing 60 to communicate with the groove 64 as shown in FIG. 1. The impeller 57 includes a blade portion 57 at a position corresponding to positions of the grooves 22 and 64.

The discharge portion 36 is made of resin to be integrated with the cover end portion 30, and protrudes cylindrically from an end surface 35 of the cover end portion 30. The end surface 35 of the cover end portion 30 is located on an opposite side of the cover end portion 30 from the pump cover 20. In the present embodiment, the discharge portion 36 is located at a position distant from the center axis Ax1 of the cover end portion 30 by a predetermined distance. The discharge portion 36 has a discharge passage 37 therein, and the discharge passage 37 communicates with a space 11 that is provided inside the housing 10 between the pump cover 20 and the cover end portion 30.

As shown in FIG. 1, the discharge portion 36 is connected to one end of a supply pipe 2. The other end of the supply pipe 2 is connected to the fuel-supplied object (internal combustion engine). Accordingly, a fuel pressurized in the space 11 due to rotation of the impeller 55 is discharged from the discharge portion 36 through the discharge passage 37 to be supplied to the fuel-supplied object via the supply pipe 2. In the present embodiment, multiple terminals 44 are provided in the cover end portion 30, and the terminals 44 are made of metal to have a long platy shape. Ends of the terminals 44 on one side in its longitudinal direction are electrically connected to the winding wires 43, and ends of the terminals 44 on the other side in its longitudinal direction protrude from the end surface 35 of the cover end portion 30 to be exposed to an outside of the fuel pump 1. In the present embodiment, the number of the terminals 44 is three, and the ends of the three terminals 44 on the one side are electrically connected respectively to the U-phase, the V-phase and the W-phase of the winding wires 43. As shown in FIG. 3, the terminals 44 are arranged adjacent to the outer rim of the end cover portion 30 at intervals of approximately 60 degrees in angle in a circumferential direction of the cover end portion 30.

The ends of the terminals 44 on the other side in its longitudinal direction are to be connected to a wire harness. When an electric power is supplied to the winding wire 43 via the wire harness, a rotating magnetic field is produced in the stator 40. Accordingly, the rotor 50 rotates, and the impeller 55 thereby rotates together with the shaft 52. As a result, fuel inside the fuel tank is drawn into the space 11 through the suction portion 21 to be pressurized by the impeller 55, thereby being discharged from the discharge portion 36.

In the present embodiment, the fuel pump 1 further includes terminal support portions 71, 72 and 73 which are made of resin to be integrated with the cover end portion 30. The terminal support portions 71, 72 and 73 protrude from the end surface 35 that is located on the opposite side of the cover end portion 30 from the pump cover 20. The terminal support portions 71, 72 and 73 supports the three terminals 44 respectively, as shown in FIG. 3. In the present embodiment, the terminal support portions 71, 72 and 73 are arranged in vicinity to an outer rim of the end surface 35 of the cover end portion 30 at intervals of approximately 60 degrees in angle in the circumferential direction of the cover end portion 30. The fuel pump 1 further includes connection portions 74. One of the connection portions 74 is located between the terminal support portion 71 and the terminal support portion 72 to connect the terminal support portions 71 and 72. Another of the connection portions 74 is located between the terminal support portion 72 and the terminal support portion 73 to connect the terminal support portions 72 and 73. The connection portions 74 are made of resin to be integrated with the terminal support portions 71, 72, 73 and the cover end portion 30. As shown in FIG. 3, the terminal support portions 71, 72, 73 and the connection portions 74 have a circular arc shape as a whole when viewed in the center axis Ax1 of the end cover portion 30. In other words, the terminal support portions 71, 72, 73 and the connection portions 74 are shaped like a part of a hollow cylinder cut off.

In the present embodiment, the fuel pump 1 further includes a stopper 81 (first stopper) that is made of resin to be integrated with the cover end portion 30. The stopper 81 protrudes from the end surface 35 in contact with an outer wall of the discharge portion 36 as shown in FIGS. 1 and 2. In the present embodiment, the fuel pump 1 further includes two subsidiary stoppers 82 (second stoppers) located on an opposite side of the discharge portion 36 from the stopper 81 as shown in FIGS. 1 and 2. The subsidiary stoppers 82 are made of resin to be integrated to the cover end portion 30. The subsidiary stoppers 82 protrude from the end surface 35 in contact with the outer wall of the discharge portion 36, similar to the stopper 81. The stopper 81 has an upper surface 83 (first surface) on an opposite side of the stopper 81 from the end surface 35, and each of the subsidiary stoppers 82 has an upper surface 84 (second surface) on an opposite side of the subsidiary stopper 82 from the end surface 35. The upper surface 83 of the stopper 81 is coplanar with the upper surfaces 84 of the subsidiary stoppers 82. Moreover, the terminal support portions 71, 72 and 73 have an upper surface 75 (third surface) on their sides opposite from the end surface 35. The upper surface 75 is coplanar with the upper surface 83 of the stopper 81 and the upper surfaces 84 of the subsidiary stoppers 82. When the supply pipe 2 is connected to the discharge portion 36, the discharge portion 36 is inserted into the supply pipe 2 until an end part of the supply pipe 2 contacts the upper surface 83 of the stopper 81 and the upper surfaces 84 of the subsidiary stoppers 82. Because the stopper 81 and the subsidiary stoppers 82 are in contact with the end part of the supply pipe 2, a motion of the supply pipe 2 toward the cover end portion 30 is restricted.

As shown in FIG. 3, the stopper 81 is arranged at a position adjacent to the outer rim of the end surface 35 of the cover end portion 30. The position of the stopper 81 is distant from the terminal support portion 71 and the terminal support portion 73 in the circumferential direction of the end cover portion 30 by approximately 120 degrees in angle. In other words, the terminal support portion 71, the stopper 81 and the terminal support portion 73 are arranged in an area adjacent to the outer rim of the cover end portion 30 at intervals of approximately 120 degrees in angle in the circumferential direction of the cover end portion 30. When a circular area of the end surface 35 is separated into two semicircular areas by an imaginary line L1 that is perpendicular to the center axis Ax1 of the cover end portion 30, as shown in FIG. 3, the stopper 81 can be located within one of the two semicircular area, and the terminal support portions 71, 72 and 73 can be located within the other one of the two semicircular area. Additionally, the stopper 81 and the terminal support portions 71, 72 and 73 are arranged on an imaginary circle C1 in the end surface 35 of the cover end portion 30 as shown in FIG. 3. The imaginary circle C1 has its center at a point located on the center axis Ax1.

In the present embodiment, the respective terminal support portions 71, 72 and 73 have outer walls 76 coincident with parts of a surface S1 of an imaginary cylinder as shown in FIG. 3. The imaginary cylinder is drawn by using the center axis Ax1 as its center axis. The stopper 81 also has an outer wall 85 coincident with a part of the surface S1 of the imaginary cylinder. The fuel pump 1 of the present embodiment further includes convex portions 38 located on outer sides of the terminal support portion 71, the terminal support portion 73 and the stopper 81 in a radial direction of the end surface 35. The convex portions 38 are made of resin to be integrated with the cover end portion 30, and protrude from the end surface 35. Specifically, the number of the convex portions 38 is three, and the three convex portions 38 are adjacent to the terminal support portion 71, the terminal support portion 73 and the stopper 81 respectively. Upper surfaces 39 of the three convex portions 38 located on their sides opposite from the end surface 35 are coplanar with each other.

As shown in FIG. 2, the relief valve 90 includes a cylindrical portion 91, a valve seat 92, a valve member 93, an urging member 94 and a stop member 95. The cylindrical portion 91 is made of resin to be integrated to the cover end portion 30, and protrudes from the end surface 35 of the cover end portion 30. The cylindrical portion 91 is provided a predetermined distance away from the center axis Ax1 of the cover end portion 30. The valve seat 92 is located inside the cylindrical portion 91. The valve member 93 has a ball shape, for example, and is capable of contacting the valve seat 92. The urging member 94 is a coil spring, for example, and its one end is in contact with the valve member 93. The stop member 95 is provided inside an end part 96 of the cylindrical portion 91 located on an opposite side of the cylindrical portion 91 from the end surface 35. The stop member 95 is engaged with the other end of the urging member 94 to fix the other end of the urging member 94 in a state where the urging member 94 is compressed in its axial direction. Thus, the urging member 94 continuously urges the valve member 93 toward the valve seat 92. In the present embodiment, the relief valve 90 is provided a predetermined distance away from the center axis Ax1 of the cover end portion 30. The end surface 35 is located on the opposite side of the cover end portion 30 from the pump cover 20, and the valve seat 92 is located on an opposite side of the end surface 35 from the pump cover 20.

The relief valve 90 is capable of reducing a fuel pressure in the space 11 between the pump cover 20 and the cover end portion 30 inside the housing 10, when the fuel pressure in the space 11 becomes higher than or equal to a predetermined value. When the relief valve 90 reduces the fuel pressure in the space 11, the valve member 93 is separated from the valve seat 92. Accordingly, it can be avoided that the fuel pump 1 or the supply pipe 2 is damaged due to an excessive increase in fuel pressure in the space 11.

A processing of the cover end portion 30 performed in a manufacturing process of the fuel pump 1 according to the present embodiment will be described with reference to FIG. 4.

(Holding Process)

Firstly, the cover end portion 30 integrated with the terminal support portion 71, the terminal support portion 73 and the stopper 81 is held by using three claw portions 101 of a chuck 100. When the chuck 100 holds the cover end portion 30, end surfaces of the three claw portions 101 tightly contact the outer wall 76 of the terminal support portion 71, the outer wall 76 of the terminal support portion 73 and the outer wall 85 of the stopper 81 from outside in the radial direction of the cover end portion 30, respectively.

(Rotation Process)

The chuck 100 rotates the claw portions 101 in a state where the terminal support portion 71, the terminal support portion 73 and the stopper 81 are held via the claw portions 101. Accordingly, the cover end portion 30 is rotated, and an axis of the rotation is coincident with the center axis Ax1 of the cover end portion 30. In the present embodiment, when the cover end portion 30 is rotated, the cover end portion 30 is continuously pressed toward the claw portions 101 in its axial direction by using a non-shown jig. Hence, the upper surfaces 39 of the three convex portions 38 contacts the three claw portions 101, respectively. In this case, when the claw portions 101 rotate relatively to the cover end portion 30, and when the claw portions 101 are displaced from the upper surfaces 39 of the convex portions 38, the claw portions 101 clash the end surface 35 due to the applied force via the jig. Therefore, it can be detected that there is a failure in the holding of the cover end portion 30 via the claw portions 101, in other words, it can be detected that holding positions of the claw portions 101 are displaced.

(Cutting Process)

In a cutting process, the press-fit part 31 is cut by using, for example, a cutting tool 102 in a state where the cover end portion 30 is held by the chuck 100 and is rotated. Additionally, an inner wall of the shaft cylindrical part 33 that is an example of the bearing portion is also cut in the cutting process. In the present embodiment, the terminal support portion 71, the terminal support portion 73 and the stopper 81 are held by the chuck 100, and the press-fit part 31 and the inner wall of the shaft cylindrical part 33 are cut without stopping the holding by the chuck 100 on the way of the cutting process. Therefore, the press-fit part 31 and the inner wall of the shaft cylindrical part 33 can be processed with a high degree of accuracy so as to be coaxial with each other.

In the present embodiment, the valve seat 92 of the relief valve 90 is formed after the above-described cutting process. For example, the valve seat 92 can be formed by pressing a shaping jig against a step surface inside the cylindrical portion 91 in a state where the shaping jig is heated to have a predetermined temperature or more. The shaping jig has a ball-shaped end part same as the valve member 93 in shape. Accordingly, the valve seat 92 having a curved surface capable of contacting the valve member 93 tightly can be formed. In the present embodiment, the valve member 93 and the urging member 94, for example, are inserted into an inside of the cylindrical portion 91 after the forming of the valve seat 92. Subsequently, the stop member 95 is made to contact the end of the urging member 94 opposite from the valve member 93, and the stop member 95 is pressed into the end part 96 of the cylindrical portion 91 such that the urging member 94 is compressed. Additionally, the end part 96 is melted by heat and is deformed by pressing. When the end part 96 is then cooled to be hard, the stop member 95 is fixed to the end part 96 of the cylindrical portion 91.

As described above, in the present embodiment, the cover end portion 30 is formed into the circular plate shape, and includes the press-fit part 31 in the outer rim of the cover end portion 30. The press-fit part 31 is press-fitted to the inside of the housing 10, and the cover end portion 30 is located on the other end of the housing 10 in its axial direction to close the opening of the housing 10. The shaft cylindrical part 33 that is an example of the bearing portion is provided on the center axis Ax1 of the cover end portion 30 to support the other end side of the shaft 52. The relief valve 90 includes the cylindrical portion 91 integrated with the cover end portion 30 to protrude from the end surface 35 on the opposite side of the cover end portion 30 from the pump cover 20, the valve seat 92 formed inside the cylindrical portion 91, the valve member 93 contactable with the valve seat 92, and the urging member 94 urging the valve member 93 toward the valve seat 92. The relief valve 90 is capable of reducing the fuel pressure in the space 11 positioned between the pump cover 20 and the cover end portion 30 inside the housing 10 when the fuel pressure becomes higher than or equal to a predetermined value. When the relief valve 90 reduces the fuel pressure, the valve member 93 is separated from the valve seat 92.

In the present embodiment, the end surface 35 is located on the opposite side of the cover end potion 30 from the pump cover 20, and the valve seat 92 is located on the opposite side of the end surface 35 from the pump cover 20. In other words, the valve seat 92 is located on the opposite side of the cover end portion 30 from the shaft cylindrical part 33, and is located outside the cover end portion 30. Accordingly, when the valve seat 92 is formed, for example, by heat forming or cutting in the manufacturing process of the fuel pump 1, deformation of the press-fit part 31 or the inner wall of the shaft cylindrical part 33 due to the forming of the valve seat 92 can be restricted. Therefore, when the fuel pump 1 is used, rotation of the shaft 52 and the impeller 55 is stabilized, and a fuel discharge capacity can be thereby stabilized. Furthermore, the end surface 35 is located on the opposite side of the cover end potion 30 from the pump cover 20, and the valve seat 92 is located on the opposite side of the end surface 35 from the pump cover 20. Therefore, as an additional effect, a metallic die for forming the cover end portion 30 of the present embodiment can be used as a metallic die for forming another cover end portion that does not include a relief valve (valve seat).

In the present embodiment, the relief valve 90 is provided a predetermined distance away from the center axis Ax1 of the cover end portion 30. In other words, the valve seat 92 is provided a predetermined distance away from the shaft cylindrical part 33 located on the center axis Ax1 of the cover end portion 30. Therefore, when the valve seat 92 is formed by, for example, heat forming or cutting in the manufacturing process of the fuel pump 1, the deformation of the inner wall of the shaft cylindrical part 33 due to the forming of the valve seat 92 can be restricted certainly.

Furthermore, in the present embodiment, the relief valve 90 includes the stop member 95 provided inside the end part 96 of the cylindrical portion 91 to fix the end part of the urging member 94 that is located on its side opposite from the valve member 93. The end part 96 of the cylindrical portion 91 is melted by heat and is deformed by pressing, and the end part 96 is then cooled to be hard such that the stop member 95 is fixed to the cylindrical portion 91. The relief valve 90 is provided a predetermined distance away from the center axis Ax1 of the cover end portion 30. Therefore, in the manufacturing process of the fuel pump 1, deformation of the inner wall of the shaft cylindrical part 33 due to heat and pressure utilized in the fixation of the stop member 95 to the end part 96 of the cylindrical portion 91 can be restricted.

Although the present disclosure has been fully described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications described below will become apparent to those skilled in the art. The relief valve 90 may be provided to be adjacent to the center axis Ax1 of the cover end portion 30. The valve seat 92 of the relief valve 90 may be formed by cutting. The terminal support portions 71 to 73, the stopper 81 and the subsidiary stopper 82 may be omitted. The convex portions 38 also may be omitted.

The bearing member 34 fitted into the inner side of the shaft cylindrical part 33 and the bearing member 62 fitted into the hole portion 61 of the pump casing 60 may be omitted, and the shaft 52 may be supported directly by the inner wall of the shaft cylindrical part 33 of the cover end portion 30 and by the inner wall of the hole portion 61 of the pump casing 60. The cover end portion 30 may be separated from the stator 40.

The material of the whole rotor 50 is not limited to the bond magnet. For example, the rotor 50 may be obtained by attaching a magnet, such as a bond magnet or a sintered ferrite magnet, to an outer wall of a cylindrical rotor core. The motor part including the stator 40, the rotor 50 and the shaft 52 has an inner rotor structure in which a rotor is located inside a stator. When the motor part has the inner rotor structure, the motor part is not limited to the above-described three-phase motor. Therefore, the motor part may be driven by using multiple phases other than three phases. Furthermore, the motor part may be structured as a brushed motor.

The fuel-supplied object is not limited to the internal combustion engine, and the fuel-supplied object may be thereby another device that requires supply of fuel. The fuel pump of the present disclosure is not limited to use for fuel, and thus may introduce therein and discharge other fluid such as liquid or gas. The present disclosure is not limited to the above-described embodiment, and is feasible in various embodiments without departing from the scope of the present disclosure. Additional advantages and modifications will readily occur to those skilled in the art. The disclosure in its broader terms is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described.

Claims

1. A fuel pump comprising:

a housing having a hollow cylindrical shape;

a pump cover closing an end opening of the housing on a first side of the housing in an axial direction of the housing, the pump cover including a suction portion;

a cover end portion having a circular plate shape to close the other end opening of the housing on a second side of the housing in the axial direction of the housing, the cover end portion including a press-fit part that is located on an outer rim of the cover end portion to be press-fitted to an inner side of the housing;

a stator having a hollow cylindrical shape, the stator being accommodated inside the housing and including a plurality of wound wires;

a rotor rotatably provided inside the stator;

a shaft provided coaxially with the rotor to rotate together with the rotor;

an impeller connected to one end of the shaft, wherein the impeller rotates together with the shaft to draw a fuel through the suction portion and pressurize the drawn fuel;

a bearing portion provided in the cover end portion on a center axis of the cover end portion to slidably support the other end of the shaft;

a discharge portion provided in the cover end portion to be used as a port through which the fuel pressurized by the impeller is discharged; and

a relief valve capable of reducing a fuel pressure in a space provided between the pump cover and the cover end portion in the housing when the fuel pressure in the space becomes higher than or equal to a predetermined value, wherein the relief valve includes:

a cylindrical portion integrated with the cover end portion to protrude outward from an end surface of the cover end portion on the second side of the housing;

a valve seat provided inside the cylindrical portion;

a valve member capable of contacting the valve seat; and

an urging member having an end part contacting the valve member to urge the valve member toward the valve seat,

the valve member is separated from the valve seat when the relief valve reduces the fuel pressure in the space, and

the valve seat is located outside the cover end portion on the second side of the housing.

2. The fuel pump according to claim 1, wherein the relief valve is located a predetermined distance away from the center axis of the cover end portion.

3. The fuel pump according to claim 2, wherein

the relief valve further includes a stop member that is provided inside an end part of the cylindrical portion to fix another end part of the urging member on an opposite side of the urging member from the valve member, and

the end part of the cylindrical portion extends radially inward of the cylindrical portion to fix the stop member inside the cylindrical portion.

4. The fuel pump according to claim 3, wherein the end part of the cylindrical portion is deformed by thermal melting, pressing and subsequent cooling to extend radially inward of the cylindrical portion.