Brushless motor

Abstract

Brushless micromotor comprising a stator and a rotor rotatably mounted on the stator, wherein the rotor (30) comprises a shaft (31), a rotor core (32) attached to the shaft (31) and magnets (33) attached to the rotor core (32), wherein two covers (34, 35) are attached to respective ends of the rotor core (32), wherein one of the two covers (34, 35) covers one end of the rotor core (32) and at least a part of the radially outer circumferential surface of the rotor core (32), wherein the other of the two covers (34, 35) covers at least the other end of the rotor core (32), wherein the stand comprises a housing (60), a stand core (50) attached to the stand and a plurality of openings (61, 62) formed in two ends of the housing (60), and wherein a plurality of vanes (40) are formed in at least one of the covers (34, 35) to generate an airflow when the rotor (30) is rotating, wherein the airflow flows along an air passage which includes the openings (61) formed in one end of the housing (60), gaps within the motor and the openings (62) formed in the other end of the housing (60).

Description

FIELD OF THE INVENTION

[0001] This invention relates to a brushless motor, and more particularly to a brushless micromotor. The term "brushless micromotor," as used in this specification and the appended claims, is intended to refer to a brushless motor that is small in size and has a power range from a few watts to several hundred watts. BACKGROUND OF THE INVENTION

[0002] DE 20 2008 002 092 U1 discloses a motor in the form of a synchronous motor with a stator and a rotor, in which the rotor is partially surrounded by a thermoplastic injection-molded part on which lamellae are formed as axial webs that protrude from a base body of the thermoplastic injection-molded part. To manufacture the rotor, a number of laminations are assembled to form a rotor core, then magnets are bonded to the outer surface of the rotor core. Subsequently, the rotor core is overmolded by injection molding, with the injection-molded part of a predetermined thickness surrounding the outer surface and an outer region of the end face, i.e., the end of the rotor core.

[0003] DE 101 10 660 A1 discloses a motor rotor for use in automotive servomotors. The rotor has a cylindrical magnet covering the peripheral surface of a yoke of the rotor and a magnet protective cover made of a heat-shrinkable tube that covers only the outer surface of the magnet.

[0004] DE 10 2008 012 628 A1 discloses a rotor of an electrical machine comprising several magnetic poles formed from permanent magnets bonded to a rotor iron core. A non-magnetic ring made of stainless steel covers the outer peripheral surfaces of the magnets.

[0005] DE 39 22 123 A1 discloses a rotor for a dynamoelectric machine with a rotor magnet arrangement formed from several permanent magnet segments. A non-magnetic support element is in contact with the outer surface of the segments.

[0006] From WO 2007 / 074 036 A1, a rotor for an electric motor with permanent magnet segments is known, which are attached to a rotor core by means of L-shaped cantilevers.

[0007] JP 2001 - 25 192 A discloses a permanent magnet motor in which permanent magnets are mounted in outer slots of the rotor core. A comparable mounting is disclosed in US Pat. No. 4,954,736 A.

[0008] A rotor 20 of a conventional brushless motor is in Fig. 11. The rotor 20 comprises a shaft 21, a rotor core mounted on the shaft 21, magnets 23 mounted on the radial outer surface of the rotor core, and a retaining ring 26 for retaining the magnets 23 on the rotor core against centrifugal force. The retaining ring 26 is usually made of stainless steel and must be very thin, for example, less than 0.2 mm thick; otherwise, the motor's performance will be significantly reduced. Consequently, tooling is required, tolerance control must be very strict, and production costs are high.

[0009] Additional metal discs 24 and 25 are provided on each end of the rotor core, and the rotor 20 is balanced through holes 27 drilled in the discs. The discs are usually made of copper, which is very expensive.

[0010] There is a need for a brushless, more cost-effective micromotor that is at least as reliable even in harsh environmental conditions. PRESENTATION OF THE INVENTION

[0011] For this purpose, the invention proposes a brushless micromotor according to claim 1. Advantageous embodiments of the invention are the subject of the subclaims.

[0012] Accordingly, in one aspect thereof, the present invention provides a brushless motor comprising a stator and a rotor rotatably mounted on the stator, the rotor comprising a shaft, a rotor core fixed to the shaft, and magnets fixed to the rotor core; wherein two covers are mounted on respective ends of the rotor core, one of the two covers covering one end of the rotor core and at least a portion of the radially outer peripheral surface of the rotor core, and the other of the two covers covering at least the other end and the other portion of the peripheral surface of the rotor core. The stator includes a housing, a stator core fixed to the stator, and a plurality of openings formed in two ends of the housing. Further, a plurality of fins for generating airflow when the rotor rotates are formed in at least one of the covers.The air flow flows along an air passage which includes the openings formed in one end of the housing, gaps within the motor and the openings formed in the other end of the housing.

[0013] Preferably, a plurality of axially extending grooves are formed in the radially outer peripheral surface of the rotor core, and a plurality of armatures are formed on an inner surface of the two covers and engage in the grooves.

[0014] Preferably, the magnets are mounted on the circumferential surface of the rotor core, and each slot is arranged between two adjacent magnets.

[0015] Preferably, a plurality of axially extending ribs are formed on the circumferential surface of the rotor core, each rib being arranged between two adjacent magnets.

[0016] Preferably, the two covers firmly grip the shaft, and the entire circumferential surface of the rotor core is substantially covered by the two covers, and the interface between the two covers is sealed by adhesive.

[0017] Preferably, each cover has an opposing surface forming the interface between the covers, and the opposing surfaces have a surface inclined in the axial direction of the shaft to increase the contact area for the adhesive seal.

[0018] Preferably, a locking mechanism is formed between the two covers to lock the two covers together.

[0019] Preferably, a ring is formed integrally with the slats.

[0020] Preferably, the stator core comprises a yoke, a plurality of teeth extending inwardly from the yoke, and stator windings wound around the teeth; wherein the air passage includes the gaps between the field windings.

[0021] Preferably, at least one balancing element for balancing the rotor is attached to the slats.

[0022] Alternatively, a plurality of holes are formed in the two covers and balancing elements are attached to the holes to balance the rotor. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Preferred embodiments of the present invention will now be described, by way of example only, with reference to the figures of the accompanying drawings. In the figures, identical structures, elements, or parts shown in more than one figure are designated by the same reference numerals. Dimensions of components and features shown in the figures have generally been chosen for clarity and convenience of illustration and are not necessarily drawn to scale. The figures are listed below. Fig. 1 is an exploded view of a rotor of a brushless micromotor according to a first embodiment of the present invention; Fig. 2 is a cross-sectional view of the rotor of the Fig. 1; Fig. 3 is an isometric view of the runner of the Fig. 1; Fig. 4 illustrates a stator of a brushless micromotor; Fig. Figure 5 is a partial sectional view of an assembled brushless micromotor, including the rotor of Fig. 1 and the stand Fig. 4; Fig. 6 illustrates a rotor for a brushless motor according to a second embodiment of the present invention; Fig. 7 is an exploded view of a rotor for a brushless motor according to a third embodiment of the present invention; Fig. 8 is an assembly view of the rotor of the Fig. 7; Fig. 9 is a cross-sectional view of a rotor of a brushless micromotor according to a fourth embodiment of the present invention; Fig. 10 is an exploded view of a rotor of a brushless motor according to a fifth embodiment of the present invention; and Fig. 11 is a rotor of a conventional brushless micromotor. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] Fig. 1 to 10 illustrate preferred embodiments of the present invention. Fig. 1 and Fig. 3 illustrate a rotor 30 according to a first embodiment and Fig. 2 illustrates a cross-section of the rotor 30.

[0025] The rotor 30 includes a shaft 31, a rotor core 32 fixed to the shaft 31, and a plurality of magnets 33 mounted on the rotor core 32. Two plastic covers 34, 35 are press-fitted to respective ends of the rotor core 32. In this embodiment, the magnets 33 are mounted on the radially outer peripheral surface of the rotor core by adhesive, and the magnets 33 are circumferentially arranged around the rotor 30. A plurality of axially extending grooves 37 are formed in the surface of the rotor core 32, and each groove 37 is arranged between two adjacent magnets 33. That is, the magnets 33 and the grooves 37 are arranged alternately. Every two adjacent grooves 37 define an area where one of the magnets 33 is mounted. The grooves 37 are also used to engage the two covers 34, 35, as described later.

[0026] A plurality of armatures 36 are formed on the inner surface of the two covers 34, 35. When the covers are mounted on the rotor core 32, the armatures 36 are first aligned along the corresponding grooves 37, and then the covers are pressed onto the rotor core 32. The cover 34 covers one end of the rotor core 32 and part of the peripheral surface of the rotor core 32. Likewise, the cover 35 covers the other end of the rotor core 32 and the other part of the peripheral surface of the rotor core 32. The grooves 37 can be filled with adhesive in advance to ensure that the covers 34, 35 are firmly fixed to the rotor core 32.

[0027] As in Fig. As shown in Figure 3, the covers 34, 35 are press-fitted to the rotor core 32 and the shaft 31, and the entire circumferential surface of the rotor core 32 is substantially covered by the two covers 34, 35. The interface between the two covers 34, 35 can be sealed with an adhesive, so that the rotor core 32 and the magnets 33 are insulated and there is no risk of rust forming on the rotor core 32 or the magnets 33. The covers 34, 35 are preferably made of anti-rust plastic material, such as PPS (polyphenylene sulfide) or POM (polyformaldehyde). The magnets 33 are preferably rare earth magnets. The covers 34, 35 preferably have identical structures.

[0028] In this embodiment, a plurality of fins 40 are formed at the ends of each of the two covers 34, 35 and arranged around the shaft 31. Although each fin 40 may extend in the radial direction of the motor, the fins may optionally extend in a direction offset from the radial direction of the motor, for example, offset from the radial direction along a clockwise direction. This is useful for motors that operate primarily in one direction. Optionally, each fin 40 may be inclined toward the axial direction of the rotor. An air flow is generated by the fins as the rotor 30 rotates. The air flow is directed through an air passage from one end of the motor to the other end of the motor to cool the motor. The air passage is described further below. In addition, balancing elements 42 for balancing the rotor may be mounted on the fins 40. The balancing element 42 may, as shown in Fig. 3, are in the form of a metal clip. Compared to the conventional balancing method of drilling holes in the engine, the installation of balancing elements according to the present invention is simpler.

[0029] To increase the mechanical strength of the slats 40, a ring 41 is formed integrally with the slats 40. Preferably, the ring 41 is formed at the radially outer ends of the slats 40 to prevent the mounted balancing elements 42 from slipping from the grooves under the influence of centrifugal force.

[0030] Fig. Figure 4 illustrates a stator core 50 of the brushless micromotor. The stator core 50 includes an annular yoke 54 with a plurality of teeth 53 extending radially inward from the yoke to form the stator poles. Stator windings 52 are wound around the teeth 53. A plurality of axially extending grooves 51 are formed in the radially outer surface of the stator core 50 to assist in cooling the stator by providing an air passage.

[0031] Fig. Figure 5 illustrates the assembled motor with a portion of the motor housing cut away to expose the stator and rotor 30. The stator comprises a housing, the stator core 50 secured to the housing, and field windings 52 wound around the teeth 53 of the stator core 50. The housing is provided with two terminals connected to the extensions of the stator core (in Fig. 4 not shown) bolted bearing blocks or end caps 60. Alternatively, the housing may be a deep-drawn can or the like into which the stator core 50 is pressed or otherwise secured. The rotor 30 is inserted into bearings 64 supported by the housing. A plurality of openings 61 and 62 are formed in the respective ends of the housing. As the rotor 30 rotates, air is drawn into the motor through the fins 40 formed on the cover 34 from the openings 61 formed in one end cap and then blown out of the motor via the openings 62 formed in the other end cap through the fins 40 formed on the cover 35. That is, the air passage through the motor includes the openings 61, gaps within the motor, and the openings 62.

[0032] The air passage encompasses the gaps between the field windings 52, allowing heat generated by the field windings 52 and / or the teeth 53 to be dissipated into the airflow. Additionally, air can flow along the plurality of slots 51 formed in the stator core 50. Therefore, the slots 51 are part of the air passage.

[0033] Compared to a conventional brushless motor, as used in Fig. As shown in Figure 11, the brushless motor according to the preferred embodiment does not require a stainless steel retaining ring or metal covers, thus reducing costs. Additionally, the brushless motor according to the preferred embodiment has a simple structure.

[0034] Fig. Figure 6 illustrates a rotor 30 of a brushless motor according to a second embodiment of the present invention. The main difference between the rotor 30 shown in Fig. 3 reproduced runner 30 and the one in Fig. 6 is that in this embodiment, the ring 41, which is formed integrally with the slats 40, is arranged at the radially inner ends of the slats 40. Molding this cover is easier because the ring 41, which is located at the radially inner ends of the slats 40, does not require any windows between the slats and the ring for air to pass through.

[0035] Fig. Figure 7 is an exploded view of a rotor 30 of a brushless motor according to a third embodiment of the present invention. The brushless motor is preferably used in a fuel pump. Fig. Figure 8 is a view of the assembled rotor 30. Instead of the laminations 40 and the ring 41, a plurality of holes 43 are formed in the two covers 34, 35. The holes 43 are formed during the molding of the cover. Balancing elements can be attached to the holes 43 to balance the rotor. A locking mechanism 39 is formed in the two covers 34, 35 for locking the covers together. In this embodiment, the locking mechanism 39 includes a locking part formed in one cover 34 that engages a locking part formed in the other cover 35 to hold both covers 34, 35 together when the two covers 34, 35 are attached to the rotor core 32.Each of the locking members has a rearwardly directed shoulder, and at least one of the locking members of each pair of opposing locking members has an axially extending tongue-like projection having a widened end forming the shoulder. In the engaged position, the shoulders abut each other to prevent separation of the covers 34, 35. The locking members are molded integrally with the covers. Gaps between the opposing sides 38 of the two covers 34, 35 can be sealed with adhesive. Preferably, the opposing sides 38 are chamfered or inclined in the axial direction to increase the contact area for the adhesive.

[0036] Fig. Figure 9 illustrates a cross section of a rotor 30 of a brushless motor according to the fourth embodiment of the present invention. The main difference between the rotor 30 shown in Fig. 9 shown runner 30 and the one in Fig. A feature of the rotor 30 shown in Figure 2 is that, in this embodiment, a plurality of grooves 37 and a plurality of ribs 44 are formed on the radially outer peripheral surface of the rotor core 32. The grooves 37 and the ribs 44 are arranged alternately. Each of the ribs 44 extends axially and is used as a delimiter between two adjacent magnets 33. That is, each rib 44 and one of its adjacent grooves 37 define a region where a magnet 33 is mounted.

[0037] Fig. Figure 10 illustrates another rotor 30 of a brushless motor according to a fifth embodiment of the present invention. The main difference between the rotor 30 shown in Fig. 1 reproduced runner 30 and the one in Fig. A feature of the rotor 30 shown in Figure 10 is that, in this embodiment, the cover 34 has a longer axial length than the cover 35. The cover 34 covers one end of the rotor core 32 and the entire circumferential surface of the rotor core 32, while the cover 35 covers only the other end of the rotor core 32. Two rings 41, which respectively connect the radially inner ends and the radially outer ends of the laminations 40, are integrally formed with each cover 34, 35. For example, in the cover 35, one ring 41 is integrally formed with the radially inner ends of the laminations 40, and the other ring 41 is integrally formed with the radially outer ends of the laminations 40.

[0038] As an alternative embodiment, the two covers 34 and 35 of the rotor, as shown in Fig. 3, Fig. 6 or Fig. 8, have different axial lengths.

[0039] In the description and claims of the present invention, each of the verbs "comprise," "comprise," "include," and "have," and variations thereof, is used in an inclusive sense to specify the presence of the named element and not to exclude the presence of other elements.

[0040] Although the invention is described with reference to one or more embodiments, it should be appreciated by those skilled in the art that various modifications are possible. Accordingly, the scope of the invention is determined by the following claims.

Claims

[1] A brushless micromotor comprising a stator and a rotor rotatably mounted on the stator, the rotor (30) comprising a shaft (31), a rotor core (32) fixed to the shaft (31) and magnets (33) fixed to the rotor core (32), wherein two covers (34, 35) are attached to respective ends of the rotor core (32), wherein one of the two covers (34, 35) covers one end of the rotor core (32) and at least a part of the radially outer peripheral surface of the rotor core (32), wherein the other of the two covers (34, 35) covers at least the other end of the rotor core (32), wherein the stator comprises a housing (60), a stator core (50) fixed to the stator, and a plurality of openings (61, 62) formed in two ends of the housing (60), and wherein a plurality of fins (40) for generating an air flow when the rotor (30) is rotating are formed in at least one of the covers (34, 35), the air flow flowing along an air passage which includes the openings (61) formed in one end of the housing (60), gaps within the motor and the openings (62) formed in the other end of the housing (60). [2] A brushless motor according to claim 1, wherein a plurality of radially extending grooves (37) are formed in the radially outer peripheral surface of the rotor core (32), wherein a plurality of armatures (36) are formed on an inner surface of the two covers (34, 35) and engage in the grooves (37), and wherein the magnets (33) are mounted on the peripheral surfaces of the rotor core (32), and wherein each groove (37) is arranged between two adjacent magnets (33). [3] A brushless motor according to claim 2, wherein a plurality of axially extending ribs (44) are formed on the peripheral surface of the rotor core (32), each rib (44) being arranged between two adjacent magnets (33). [4] A brushless motor according to claim 1, 2 or 3, wherein the two covers (34, 35) firmly grip the shaft (31), the entire peripheral surface of the rotor core (32) is substantially covered by the two covers, and the interface between the two covers is sealed by adhesive. [5] A brushless motor according to claim 4, wherein each cover (34, 35) has an opposing surface (38) forming the interface between the covers (34, 35), and the opposing surfaces (38) have a surface inclined in the axial direction of the shaft (31) to increase the contact areas for the adhesive seal. [6] A brushless motor according to any one of the preceding claims, wherein a locking mechanism (39) is formed between the two covers (34, 35) to lock the two covers together. [7] A brushless motor according to claim 1, wherein a ring (41) is integrally formed with the fins (40). [8] Brushless motor according to claim 1 or 7, wherein at least one balancing element (42) is attached to the laminations (40) for balancing the rotor (30). [9] A brushless motor according to any one of claims 1 to 8, wherein a plurality of holes (43) are formed in the covers (34, 35) and balancing elements are attached to the holes (43) to balance the rotor (30).

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