Rotor

Abstract

Rotor used for a motor (17) that rotates an impeller (16) of a fuel pump (10), comprising: a cylindrically bound magnet (41, 63) forming a plurality of magnetic poles; an inner core (42, 62) which is a cylindrical component provided inwards from the bound magnet (41, 63), and in which both axial end surfaces (43, 44) are exposed to an exterior; and a rotating shaft (38) having a connecting end (39) having a pair of mutually parallel flat surfaces (45) fitted to the impeller (16) and designed to pass inwards through the inner core (42, 62), wherein a cross-section of the connecting end (39) has a center of gravity (G) that coincides with an axis of rotation (AX), wherein the inner core (42, 62) has an engaged part (46, 64) which is radially recessed inwards or radially projecting outwards in a section parallel to an axial direction of the inner core (42, 62); the bound magnet (41, 63) has an engaging part (47, 65) which engages with the engaged part (46, 64) in the axial direction; the engaged part (46, 64) of a plurality of engaged parts (46, 64) in a circumferential direction of the inner core (42, 62); the inner core (42, 62) comprises a plurality of metal plates (48, 66, 49, 67) stacked in the axial direction; and the majority of metal plates (48, 66, 49, 67) exhibit the following characteristics: first metal plates (48, 66) forming the engaged part (46, 64), each of the first metal plates (48, 66) having the following features: a plurality of first exterior wall surfaces (55, 71), each corresponding to the plurality of parts involved (46, 64); and a plurality of second exterior wall surfaces (56, 72), each of which is located between its adjacent two of the plurality of first exterior wall surfaces (55, 71); and second metal plates (49, 67) which are provided in the axial direction on both sides of the first metal plates (48, 66), each of the second metal plates (49, 67) having the following features: a plurality of third outer wall surfaces (57, 73), each located radially outward or radially inward from the plurality of first outer wall surfaces (55, 71); and a plurality of fourth outer wall surfaces (58, 74) which are each on the same plane or on the same curved surface as the plurality of second outer wall surfaces (56, 72).

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a rotor used in a motor that drives an impeller of a fuel pump. BACKGROUND TECHNOLOGY

[0002] In a known fuel pump, an impeller within a shell is rotationally driven by a motor to supply fuel under pressure. In a fuel pump disclosed in Patent Document 1, a rotor of a motor is composed of a rotating shaft, an inner core for fitting to the rotating shaft, and a bonded magnet covering the periphery of the inner core. The bonded magnet comprises, for example, a bonded neodymium magnet and has a cylindrical portion, a top plate closing two ends of the cylindrical portion, and a bottom plate. While a D-shape of a cross-section of one end of the rotating shaft may be accompanied by a loss of dynamic balance, such a loss of dynamic balance is corrected by a recess or protrusion of both the top plate and the bottom plate. STATE OF THE ART PATENT DOCUMENT

[0003] Patent Document 1: JP 2015-50805A

[0004] In Patent Document 1, the volume of the bonded magnet is reduced by providing the inner core. This reduces the amount of a material, such as a rare earth element, used to form the bonded magnet. On the other hand, the rarity of such a material has increased with the recent increase in demand, and thus, a further reduction in the volume of the bonded magnet is required to minimize the amount of material used.

[0005] On the other hand, since the cylindrical portion forming a magnetic pole of the rotor cannot be reduced, the top plate and bottom plate are likely to be reduced. However, if the top plate and bottom plate are reduced, the dynamic balance cannot be corrected. If a recess or the like is provided at the end of the cylindrical portion to correct the dynamic balance, the thickness of the cylindrical portion must be increased, as opposed to reducing the volume of the bonded magnet.

[0006] JP 2002-305847 A discloses a motor comprising a rotating shaft, a yoke member mounted on the rotating shaft, and a rotor with a permanent magnet mounted on the outer periphery of the yoke member. The yoke member is formed by laminating a plurality of sheet metal bodies, the outer periphery of which is provided with a recessed engaging portion that engages the axial and peripheral directions of the permanent magnet and the rotating shaft. The permanent magnet is provided with a protruding engaging portion that engages the recessed engaging portion of the yoke member.

[0007] JP 2005-295775 A discloses a motor rotor in which plastic magnets of an S-pole and an N-pole are arranged on the outer peripheral side of a rotor. The plastic magnet of each pole has a substantially semicircular cross-sectional shape on the inner peripheral side. The plastic magnets of the poles are coupled in a ring shape, and a recess 1 corresponding to the plastic magnet of each pole is formed in the outer peripheral part of a rotor core.

[0008] DE 10 2011 105 867 A1 discloses a rotor for permanent-magnet excited electrical machines. The rotor comprises a multipole, anisotropic rotor magnet, which is injection-molded onto a rotor body from plastic-bonded permanent magnet material, for example, in an injection-molding process. The rotor body has a number of radially outwardly projecting, tapered projections corresponding to the number of magnetic poles, on which the pole transitions between the magnetic poles are aligned. The rotor body has a ferromagnetic guide plate, which serves as a concentrator for the magnetic field of an alignment magnet embedded in the injection-molding tool during the injection-molding production of the anisotropic rotor magnet.

[0009] DE 10 2012 219 349 A1 discloses a rotor for an electric machine in which a plastic ring is arranged around a base body, in which particles of magnetic or magnetizable material are embedded. For reliable torque transmission between the ring and the base body, radially projecting teeth, for example in the form of longitudinal edges, are formed on the base body, which engage positively and non-positively in complementary notches on the ring. Since the base body and the surrounding ring can be made of different materials, temperature fluctuations can lead to thermally induced mechanical stresses within the ring, resulting in cracks in the ring.It is proposed to design the base body and the complementary ring in such a way that cracks are induced preferentially on the magnetically neutral fibers of the ring, where they have the least negative impact on the ring's magnetic properties. Such targeted crack formation can be achieved, for example, through the notch effect of particularly sharp-edged teeth and / or the formation of predetermined breaking points with locally reduced mechanical stability in the ring. SUMMARY OF THE INVENTION

[0010] The present disclosure addresses the above problems. Therefore, an object of the present disclosure is to provide a rotor in which a volume of a bonded magnet is reduced while preventing a loss of dynamic balance.

[0011] The object is achieved by a rotor having the features of claim 1. Further advantageous developments and embodiments of the invention are the subject of the subsequent claims.

[0012] In one aspect of the present disclosure, a rotor for a motor that rotates an impeller of a fuel pump is used. The rotor includes a cylindrical bonded magnet forming a plurality of magnetic poles, a cylindrical inner core provided inwardly of the bonded magnet, and a rotating shaft provided to pass through the inner core inwardly thereof. The inner core has both axial end surfaces exposed to the outside. The rotating shaft has a connecting end fitted to the impeller. The connecting end has a pair of mutually parallel flat surfaces, and a cross section of the connecting end has a center of gravity that coincides with a rotation axis.

[0013] The center of gravity of the cross section of the connecting end of the rotary shaft coincides with the rotation axis, preventing the rotor from losing its dynamic balance due to the connecting end. Therefore, it is not necessary to provide a recess or the like to correct the dynamic balance at the end of the bonded magnet, and the bonded magnet can thus be composed of only the cylindrical portion. The bonded magnet, which has only the cylindrical portion, has a small volume due to the absence of the top plate and bottom plate, compared to the existing magnet comprising the cylindrical portion, top plate, and bottom plate. Therefore, it is possible to reduce the volume of the bonded magnet while preventing the dynamic balance from being lost. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The foregoing and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description made with reference to the accompanying drawings, in which: Fig. 1 is a longitudinal sectional view of a fuel pump using a rotor of a first embodiment; Fig. 2 a sectional view along a line II-II in Fig. 1; Fig. 3 an impeller in Fig. 1; Fig. 4 the rotor in Fig. 1; Fig. 5 a sectional view along a line VV in Fig. 4; Fig. 6 a sectional view along a line VI-VI in Fig. 4; Fig. 7 an enlarged view of a section VII in Fig. 4; Fig. 8 a cross-sectional view of a rotor of a second embodiment according to Fig. 5 in the first embodiment; and Fig. 9 a cross-sectional view of the rotor of the second embodiment according to Fig. 6 in the first embodiment. EMBODIMENTS FOR CARRYING OUT THE INVENTION

[0015] Some embodiments will be described below with reference to the drawings. A substantially similar configuration between the embodiments is denoted by the same reference numeral, and duplicate descriptions are omitted. (First embodiment)

[0016] A fuel pump using a rotor of a first embodiment is an in-tank pump installed in a fuel tank of a vehicle, in which a fuel is drawn from a suction passage 22 formed on a lower side of Fig. 1, is pulled and pressurized and through a discharge channel 27 which is on an upper side of Fig. 1 is unloaded into a machine not shown.

[0017] A configuration of a fuel pump 10 will now be described with reference to Fig. 1 to 3. The fuel pump 10 includes a cylindrical housing 11, a suction side cover 12 provided at one end of the housing 11, a discharge side cover 13 provided at the other end of the housing 11, a bottomed cylindrical shell 15 defining a pump chamber 14 between the shell 15 and the suction side cover 12 in the housing 11, an impeller 16 provided in the pump chamber 14, and a motor 17 provided in the housing 11 and rotatingly rubbing the impeller 16.

[0018] The suction side cover 12 has a suction side pressurization channel 21 and a suction channel 22. The suction side pressurization channel 21 is provided in a wall opposite the impeller 16, among inner walls defining the pump chamber 14. The suction side pressurization channel 21 is a C-shaped groove extending in a circumferential direction. The suction channel 22 is provided to penetrate from the upstream end of the suction side pressurization channel 21 to the exterior.

[0019] The casing 15 has a discharge-side pressurization channel 23 and a discharge hole 24. The discharge-side pressurization channel 23 is provided in a wall opposite the impeller 16 among the inner walls defining the pump chamber 14. The discharge-side pressurization channel 23 is a C-shaped groove extending in the circumferential direction. The discharge hole 24 is provided to penetrate from the downstream end of the discharge-side pressurization channel 23 to one side of the motor 17. A bearing 25 is provided in a central portion of the casing 15.

[0020] The discharge side cover 13 forms a cylindrical portion 26 that protrudes toward the exterior. The cylindrical portion 26 has a discharge channel 27 that penetrates from the interior of the housing 11 to the exterior. A bearing 28 is provided in a central portion of the discharge side cover 13. The impeller 16 is a disc-shaped impeller. A fitting hole 29 is provided in a central portion of the impeller 16. The fitting hole 29 has a cross-sectional shape similar to that of a connecting end 39, as described later, and is slightly larger than the connecting end 39.

[0021] The motor 17 includes a stator 31 fixed to the housing 11 and a rotor 32 provided inside the stator 31. The stator 31 has a stator core 33, an insulator 34, a winding 35, and a terminal 36. A fuel passage 37 is defined between the housing 11 and the stator 31. The fuel passage 37 communicates with the discharge passage 27 through a fuel passage and the like (not shown). A rotary shaft 38 of the rotor 32 is rotatably supported by the bearings 25 and 28. The connecting end 39 of the rotary shaft 38 is fitted into the fitting hole 29 of the impeller 16. The rotary shaft 38 is connected to the impeller 16 in a rotationally transmittable manner.

[0022] In the fuel pump 10 configured as above, when the motor 17 is driven to rotate the impeller 16, fuel is sucked from, for example, a fuel tank into the pump chamber 14 through the suction passage 22. Fuel in the pump chamber 14 flows to spiral between the impeller 16 and each of the pressurization passages 21 and 23 and is pressurized from the suction passage 22 to the discharge hole 24. The pressurized fuel is discharged from the discharge passage 27 to the outside through the discharge hole 24, the fuel port 37, and the like.

[0023] A configuration of the rotor 32 will now be described in detail with reference to Fig. 3 to 7. The rotor 32 includes a cylindrical bonded magnet 41 forming a plurality of magnetic poles, a cylindrical inner core 42 provided inside the bonded magnet 41, and the rotating shaft 38 provided to penetrate the interior of the inner core 42. The magnetic poles are provided such that the polarity on the radially outer side alternates in the circumferential direction. A portion of the rotor 32 exposed to the internal space of the housing 11 is exposed to the fuel during operation of the fuel pump 10.

[0024] The bonded magnet 41 is composed of only one cylindrical section and does not cover both end surfaces 43 and 44 of the inner core 42. Specifically, the first end surface 43 and the second end surface 44 of the inner core 42 are exposed to the exterior. The connecting end 39 of the rotating shaft 38 has a cross-section with a center of gravity G that coincides with the rotation axis AX, while having a pair of mutually parallel flat surfaces 45.

[0025] The inner core 42 has recesses 46 that are recessed radially inward in a cross-section parallel to the axial direction. The bonded magnet 41 has projections 47 that each project into the recess 46 and engage with the recess 46 in the axial direction. Engagement of the respective projections 47 with the recesses 46 suppresses disengagement of the bonded magnet 41 from the inner core 42. The recess 46 corresponds to an "engaged part." The projection 47 corresponds to an "engaging part."

[0026] The recesses 46 are provided at a plurality of positions in the circumferential direction. In the first embodiment, the inner core 42 has a quadrilateral cross-section. The recesses 46 are provided at four positions corresponding to corners of the quadrilateral. The inner core 42 is composed of a plurality of metal plates stacked in the axial direction. The plurality of metal plates includes first metal plates 48 forming the bottoms of the recesses 46 and second metal plates 49 provided on both sides in the axial direction with respect to the first metal plates 48. In other words, the inner core 42 is composed of a combination of a laminate of a plurality of second metal plates 49, a laminate of a plurality of first metal plates 48, and a laminate of a plurality of second metal plates 49.

[0027] The first end surface 43 of the inner core 42 lies on the same plane as a first end surface 52 of the bonded magnet 41. The second end surface 44 of the inner core 42 lies on the same plane as a second end surface 54 of the bonded magnet 41. As in Fig. As shown in Figure 5, the first metal plate 48 has four first outer wall surfaces 55 corresponding to the bottoms of the recesses 46 and four second outer wall surfaces 56 located between the first outer wall surfaces 55. In the first embodiment, each first outer wall surface 55 is a curved surface corresponding to a corner of the quadrilateral. Each second outer wall surface 56 is a plane corresponding to a side of the quadrilateral.

[0028] As in Fig. 6, the second metal plate 49 has four third outer wall surfaces 57 located radially outward with respect to the first outer wall surfaces 55, and four fourth outer wall surfaces 58 located on a same plane as a second outer wall surface 56. In the first embodiment, each third outer wall surface 57 is a curved surface corresponding to a corner of the quadrilateral. Each fourth outer wall surface 58 is a plane corresponding to one side of the quadrilateral. The second outer wall surfaces 56 are provided at equal intervals in the circumferential direction. Each second outer wall surface 56 and a fourth outer wall surface 58 on the same plane are used as a reference for press-fitting the rotary shaft 38 into the stacked metal plates 48 and 49.

[0029] The effects of the first embodiment will be described below. As described above, in the first embodiment, two end surfaces 43 and 44 are exposed in the axial direction of the inner core 42 to the outside. The rotating shaft 38 requires the connecting end 39 to fit into the impeller 16. The connecting end 39 has a cross section with the center of gravity G coincident with the rotation axis AX, while the pair of flat surfaces 45 are parallel to each other.

[0030] The center of gravity G of the cross section of the connecting end 39 of the rotary shaft 38 coincides with the rotation axis AX, preventing the dynamic balance of the rotor 32 from being lost due to the connecting end 39. Therefore, it is not necessary to provide a recess or the like to correct the dynamic balance at the end of the bonded magnet 41, and thus the bonded magnet 41 can be composed of only the cylindrical portion. The bonded magnet 41, which has only the cylindrical portion, has a small volume due to the absence of the top plate and the bottom plate, compared to the existing magnet having the cylindrical portion, the top plate, and the bottom plate. Therefore, it is possible to reduce the volume of the bonded magnet 41 while preventing the dynamic balance from being lost.

[0031] In the first embodiment, the inner core 42 has recesses 46 recessed radially inward in cross-section parallel to the axial direction. The bonded magnet 41 has protrusions 47 that each engage with the recess 46 in the axial direction. Therefore, even if the bonding force between the bonded magnet 41 and the inner core 42 becomes weak, the engagement of the protrusions 47 with the recesses 46 can prevent the bonded magnet 41 from moving in the axial direction with respect to the inner core 42.

[0032] In the first embodiment, the recesses 46 are provided at the positions in the circumferential direction. The inner core 42 is composed of the plurality of metal plates stacked in the axial direction. The metal plates include the first metal plates 48 forming the bottoms of the recesses 46, and the second metal plates 49 provided on both sides of the first metal plates 48 in the axial direction. Each first metal plate 48 has a plurality of first outer wall surfaces 55 corresponding to the bottoms of the recesses 46 and a plurality of second outer wall surfaces 56 located between the first outer wall surfaces 55.Each second metal plate 49 has a plurality of third outer wall surfaces 57 located radially outward with respect to the first outer wall surfaces 55, and a plurality of fourth outer wall surfaces 58, each located on the same plane as a second outer wall surface 56. Therefore, it is possible to use the second outer wall surfaces 56 of the first metal plate 48 and the fourth outer wall surfaces 58 of the second metal plate 49 as a reference for press-fitting the rotary shaft 38 into the stacked metal plates 48 and 49.

[0033] In the first embodiment, the number of second outer wall surfaces 56 is four. The second outer wall surfaces 56 are provided at equal intervals in the circumferential direction. Therefore, when the rotary shaft 38 is press-fitted into the stacked metal plates 48 and 49, movement of the first metal plate 48 can be reliably restricted by holding the four second outer wall surfaces 56.

[0034] In the first embodiment, the first end surface 43 of the inner core 42 is on the same plane as the first end surface 52 of the bonded magnet 41. The second end surface 44 of the inner core 42 is on the same plane as the second end surface 54 of the bonded magnet 41. Therefore, it is possible to prevent fuel from seeping into the interior of the inner core 42, that is, into a space between the metal plates, and thus to suppress corrosion of the inner core 42. (Second embodiment)

[0035] In the second embodiment, as shown in Fig. 8 and Fig. As shown in Figure 9, a rotor 61 includes a rotating shaft 38, an inner core 62, and a bonded magnet 63. The inner core 62 has recesses 64 and projections 65. In the second embodiment, the inner core 62 has a hexagonal cross section. The recesses 64 are provided at six positions corresponding to the corners of a hexagon. The inner core 62 is composed of first metal plates 66 forming the bottoms of the recesses 64 and second metal plates 67 provided on both sides of the first metal plates 66 in the axial direction.

[0036] As in Fig. As shown in Figure 8, the first metal plate 66 has six first outer wall surfaces 71 corresponding to the bottoms of the recesses 64 and six second outer wall surfaces 72 located between the first outer wall surfaces 71. In the second embodiment, each first outer wall surface 71 corresponds to a corner of the hexagon. Each second outer wall surface 72 corresponds to a side of the hexagon.

[0037] As in Fig. As shown in Figure 9, each second metal plate 67 has six third outer wall surfaces 73 located radially outwardly of the first outer wall surfaces 71, and six fourth outer wall surfaces 74, each located on a same plane as a second outer wall surface 72. In the second embodiment, each third outer wall surface 73 corresponds to a corner of the hexagon. Each fourth outer wall surface 74 corresponds to a side of the hexagon.

[0038] The second outer wall surfaces 72 are provided at equal intervals in the circumferential direction. Each second outer wall surface 72 and a fourth outer wall surface 74 on the same plane are used as a reference for press-fitting the rotary shaft 38 into the stacked metal plates 66 and 67. As described in the second embodiment, the inner core 62 may have a hexagonal cross-sectional shape. The cross-sectional shape of the inner core 62 may be appropriately varied in accordance with the number of poles of the bonded magnet 63.

[0039] Modifications of the first or second embodiment will be described below. In one modification, the engaged part of the inner core may be a projection projecting radially outward in a cross section parallel to the axial direction. In addition, the engaged part of the bonded magnet may be a recess recessed radially outward. In one modification, when the inner core has a polygonal cross section, the engaged part of the inner core may be provided at a position corresponding to one side of a polygon. In one modification, the number of engaged portions of the inner core should be two or more.

[0040] In one modification, both the first outer wall surface of the first metal plate and the third outer wall surface of the second metal plate may be a planar surface. In one modification, the second outer wall surface of the first metal plate may be a curved surface. In addition, the fourth outer wall surface of the second metal plate may be a curved surface located on the same curved surface as the second outer wall surface. In one modification, the second outer wall surfaces of the first metal plate may not be provided at equal intervals in the circumferential direction.

[0041] In one modification, the end surface of the inner core may not be provided on the same plane as the end surface of the bonded magnet. In one modification, the inner core may be composed not only of a laminate of a plurality of metal plates, but also of a single component. The present disclosure is not limited to the embodiments described above and may be embodied in various ways within the scope of the present disclosure without departing from the essence of the present disclosure.

Claims

[1] Rotor used for a motor (17) rotating an impeller (16) of a fuel pump (10), comprising: a cylindrical bonded magnet (41, 63) forming a plurality of magnetic poles; an inner core (42, 62) which is a cylindrical component provided inwardly of the bonded magnet (41, 63) and having both axial end surfaces (43, 44) exposed to an exterior; and a rotary shaft (38) having a connecting end (39) having a pair of mutually parallel flat surfaces (45) and fitted to the impeller (16) and being provided to pass through the inner core (42, 62) inwardly thereof, a cross section of the connecting end (39) having a center of gravity (G) coinciding with a rotation axis (AX), wherein the inner core (42, 62) has an engaged part (46, 64) which is recessed radially inward or protrudes radially outward in a portion parallel to an axial direction of the inner core (42, 62); the bonded magnet (41, 63) has an engaging part (47, 65) which is engaged with the engaged part (46, 64) in the axial direction; the engaged part (46, 64) is one of a plurality of engaged parts (46, 64) in a circumferential direction of the inner core (42, 62); the inner core (42, 62) comprises a plurality of metal plates (48, 66, 49, 67) stacked in the axial direction; and the plurality of metal plates (48, 66, 49, 67) has the following features: first metal plates (48, 66) forming the engaged part (46, 64), each of the first metal plates (48, 66) having the following features: a plurality of first outer wall surfaces (55, 71) each corresponding to the plurality of engaged parts (46, 64); and a plurality of second outer wall surfaces (56, 72), each of which is located between its adjacent two of the plurality of first outer wall surfaces (55, 71); and second metal plates (49, 67) provided in the axial direction on both sides of the first metal plates (48, 66), each of the second metal plates (49, 67) having the following features: a plurality of third outer wall surfaces (57, 73) each located radially outward or radially inward from the plurality of first outer wall surfaces (55, 71); and a plurality of fourth outer wall surfaces (58, 74) each located on a same plane or on a same curved surface as the plurality of second outer wall surfaces (56, 72). [2] Rotor according to claim 1, wherein a number of the plurality of second outer wall surfaces (56, 72) is three or more; and the plurality of second outer wall surfaces (56, 72) are provided at equal intervals in the circumferential direction. [3] Rotor according to claim 1 or 2, in which one (43) of the axial end surfaces (43, 44) of the inner core (42) is on a same plane as an end surface (52) of the bonded magnet (41); and the other (44) of the axial end surfaces (43, 44) of the inner core (42) is on a same plane as the other end surface (54) of the bonded magnet (41).

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