electric motor

Abstract

An outer rotor for use with a brushless DC electric motor includes a rotor body, a shaft coupled to co-rotate with the rotor body and defining an axis of rotation, a cover surrounding at least a portion of the rotor body, and a fan formed unitarily and integrally with the cover, the fan including a plurality of blades extending radially outwardly of the cover and configured to direct airflow along an outer surface of the cover in a direction parallel to the axis of rotation.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to co-pending U.S. Provisional Patent Application No. 63 / 245,361, filed September 17, 2021, and co-pending U.S. Provisional Patent Application No. 63 / 235,235, filed August 20, 2021, the entire contents of both of which are incorporated herein by reference.

[0002] The present invention relates to electric motors, and more particularly to external rotor brushless DC electric motors. [Background technology]

[0003] A brushless DC electric motor includes at least a stator and a rotor. A plurality of permanent magnets are supported by the rotor, and torque is received as a result of interaction between the magnets and the magnetic field produced by the stator, causing the rotor to rotate. In some cases, a brushless DC electric motor will also include a fan coupled to co-rotate with the rotor. Summary of the Invention [Means for solving the problem]

[0004] In one aspect, the present invention provides an outer rotor for use with a brushless DC electric motor. The outer rotor includes a rotor body, a shaft coupled to the rotor body for co-rotation and defining an axis of rotation, a cover surrounding at least a portion of the rotor body, and a fan formed integrally with the cover as a single unit. The fan includes a plurality of blades extending radially outward from the cover and configured to direct airflow along an outer surface of the cover in a direction parallel to the axis of rotation.

[0005] In another aspect, the present invention provides a brushless DC electric motor including a stator and an outer rotor surrounding the stator. The outer rotor includes a rotor body, a shaft coupled for co-rotation with the rotor body, the shaft defining an axis of rotation, a cover surrounding at least a portion of the rotor body, and a fan formed unitarily and integrally with the cover. The fan includes a plurality of blades extending radially outward from the cover and configured to direct airflow along an outer surface of the cover in a direction parallel to the axis of rotation.

[0006] In yet another aspect, the present invention provides a brushless DC electric motor including a stator and an outer rotor surrounding the stator. The outer rotor includes a ring magnet defining an axis of rotation, a cover surrounding at least a portion of the ring magnet, and a fan formed integrally with the cover as a single unit. The fan includes a plurality of blades extending radially outward from the cover and configured to direct airflow along an outer surface of the cover in a direction parallel to the axis of rotation.

[0007] Other features and aspects of the present invention will become apparent upon consideration of the following detailed description and accompanying drawings. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a perspective view of a brushless DC electric motor according to one embodiment of the present invention; [Figure 2] FIG. 2 is a rear view of the electric motor of FIG. 1. [Figure 3] 3 is a cross-sectional view of the electric motor of FIG. 1 taken along section line 3-3 of FIG. 1. [Figure 4] FIG. 2 is a front view of the electric motor of FIG. 1. [Figure 5] FIG. 2 is a perspective view of a brushless DC electric motor according to another embodiment of the present invention. [Figure 6] 6 is a cross-sectional view of the electric motor of FIG. 5 taken along section line 6-6 of FIG. 5. [Figure 7]FIG. 6 is a perspective view of an alternative embodiment of a fan for use with the motor of FIG. 5. [Figure 8] FIG. 6 is a side view of a power tool utilizing the electric motor of FIG. 1 or FIG. 5. [Figure 9] 9 is a cross-sectional view of the power tool of FIG. 8 taken along section line 9-9 of FIG. 8. DETAILED DESCRIPTION OF THE INVENTION

[0009] Before describing embodiments of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting.

[0010] 1-4 illustrate an electric motor 10 according to one embodiment of the present disclosure. The electric motor 10 is a brushless DC (BLDC) electric motor 10 including an internal stator 14 and an external rotor, or outer rotor 18. The rotor 18 is supported to circumferentially surround at least a portion of the stator 14 and extends along the motor axis A. Referring to FIGS. 1-3, the stator 14 includes a stator body 22 made of a ferromagnetic material and is surrounded by the rotor 18. The stator body 22 includes a plurality of fingers 24 extending radially outward, with a plurality of windings 30 wound around each finger 24. The outer rotor 18 in the illustrated embodiment is generally cylindrical in shape and extends longitudinally along the motor axis A, such that the outer rotor 18 and the stator 14 are coaxial about the motor axis A.

[0011] The rotor 18 includes a rotor body 20 and a shaft 26 coupled for co-rotation with the rotor body 20. The shaft 26 is rotatable about the motor axis A and, in some embodiments, is supported for rotation by the stator 14. For example, as shown in FIG. 6 , the shaft 26 may be supported by a first bearing 28 within the stator body 22 and a second bearing 32 within the rotor body 20. The rotor 18 also includes a ring magnet 48 having a plurality of equally spaced magnetic poles disposed around the inner circumference of the rotor body 20 in facing relation to the stator 14. The ring magnet 48 extends longitudinally along the length of the rotor body 20. In some embodiments, the ring magnet 48 may be replaced with a plurality of separate permanent magnets having a rectangular cross-sectional shape in a plane oriented perpendicular to the motor axis A.

[0012] 1-3 , the rotor 18 further includes a plastic cover 34 that surrounds the rotor body 20. The cover 34 extends longitudinally along the length of the rotor 18 and includes a first open end 38 and a second closed end 42. The rotor 18 also includes an axial fan 46 located at the closed end 42 of the cover 34. The plastic cover 34 and fan 46 are secured to the rotor 18 for co-rotation therewith, such that rotation of the outer rotor 18 results in rotation of the fan 46, which in turn induces an axial airflow F along the outer surface 36 of the cover 34 in a direction parallel to the motor axis A. In other embodiments of the motor 10, the fan 46 can be configured as a radial flow fan or a centrifugal fan that induces an axial airflow in a direction parallel to the motor axis A and can redirect the airflow radially outward.

[0013] 3 and 4, the fan 46 includes a central hub 50 coupled to the cover 34 and a plurality of blades 54 extending radially outward from the hub 50 (i.e., perpendicular to the motor axis A) and beyond the outer surface 36 of the cover 34. In the illustrated embodiment of the motor 10, the tips of the fan blades 54 extend to a radius R1 (relative to the motor axis A) that is greater than the radius R2 of the cover 34. In some embodiments, the radius R1 is at least 1.1 times the radius R2. In other embodiments, the radius R1 is at least 1.3 times the radius R2. The hub 50 is integrally formed with both the fan 46 and the cover 34. In other words, the cover 34, the hub 50, and the fan 46 are formed as a single, monolithic component.

[0014] 3 and 4, the plastic cover 34 is coupled to the rotor body 20 for co-rotation therewith. In the illustrated embodiment, the cover 34 is overmolded onto the outer surface of the rotor body 20. The fan 46 is also integrally formed during the process of overmolding the cover 34 onto the outer surface of the rotor body 20. In some embodiments, the shaft 26 is also overmolded with a portion of the central hub 50 during the overmolding process, thereby rotatably uniting the shaft 26 (via the central hub 50 and the cover 34) with the rotor body 20. The ring magnet 48 can be press-fit within the cover 34 after the cover 34 is molded.

[0015] 5 and 6 illustrate another embodiment of fan 46, in which like components have like reference numbers plus the letter "b," with the following differences described below. Rather than including a separate rotor body 20 as in fan 46, fan 46b includes a ring magnet 48b that is press-fit within cover 34b after fan 46b is formed (e.g., by an injection molding process). Also, rather than extending from a hub 50b, multiple fan blades 54b extend radially outward (i.e., perpendicular to motor axis A) from outer surface 36b of cover 34b; in the illustrated embodiment, each of multiple fan blades 54 spans the length of cover 34b.

[0016] 7 illustrates another embodiment of fan 46, 46b, where like components have like reference numbers plus the letter "c," with the following differences described below. Rather than press-fitting ring magnet 48c into cover 34c during a post-manufacturing assembly process, ring magnet 48c is overmolded with cover 34c during the injection molding process to create fan 46c. In the embodiment of FIG. 7, rotor body 20 is also omitted.

[0017] During operation of electric motor 10 (or motor 10b in the case of fan 46b or fan 46c), cover 34 and fan 46 co-rotate with rotor body 20 as a result of being rotatably united therewith during the process of overmolding cover 34 and fan 46 to rotor body 20. Fan blades 54 induce an axial airflow F around outer surface 36 of cover 34 to cool motor 10 and other electronics associated with motor 10 within the path of the cooling airflow. In some applications in which motor 10 may be used, the airflow induced by fan 46 can be used for purposes other than cooling. For example, the induced airflow may be used to transport debris or particles in a rotary hammer dust collector or vacuum.

[0018] The motor 10 may also be used in a blower that emits an airflow from a nozzle to dissipate debris from a work surface. As shown in Figures 8 and 9, the blower includes a housing 58 in which the motor 10 is disposed. The housing 58 includes a handle 62 and a longitudinally extending nozzle 66 through which the high-velocity airflow generated by the motor 10 is directed. In operation, the fan 46 is rotatably mounted to the rotor body 20 of the electric motor 10, thereby generating a high-velocity airflow. The high-velocity airflow cools the electric motor 10 and functions as the airflow emitted from the blower nozzle 66.

[0019] Although the invention has been described in detail with reference to certain preferred embodiments, variations and modifications exist within the scope and spirit of one or more independent aspects of the invention described.

[0020] Various features and aspects of the invention are set forth in the following claims.

Claims

1. 1. An outer rotor for use with a brushless DC electric motor, comprising: A rotor body; a shaft coupled for co-rotation with the rotor body, the shaft defining an axis of rotation; a cover surrounding at least a portion of the rotor body, the cover being overmolded to and in direct contact with the radially outer surface of the rotor body; a fan positioned at an axial end of the cover and formed unitarily and integrally with the cover, the fan including a central hub adjacent the axial end of the cover and a plurality of blades extending radially outward from the central hub and configured to direct airflow in a direction parallel to the axis of rotation; Outer rotor.

2. The outer rotor of claim 1 , wherein each of the blades extends farther from the rotational axis than the cover.

3. The outer rotor of claim 1 , wherein the cover and the fan are formed from plastic.

4. The outer rotor of claim 1 , further comprising a magnet positioned on an inner surface of the rotor body, the magnet coupled for co-rotation with the rotor body and the cover.

5. The outer rotor of claim 1 , wherein the cover spans the length of the rotor body.

6. 1. A brushless DC electric motor, comprising: a stator; An outer rotor surrounding the stator, A rotor body; a shaft coupled for co-rotation with the rotor body, the shaft defining an axis of rotation; a cover surrounding at least a portion of the rotor body, the cover being overmolded to and in direct contact with the radially outer surface of the rotor body; a fan positioned at an axial end of the cover and formed unitarily and integrally with the cover, the fan including a central hub adjacent the axial end of the cover and a plurality of blades extending radially outward from the central hub and configured to direct airflow in a direction parallel to the axis of rotation; an outer rotor; Brushless DC electric motor.

7. 7. The brushless DC electric motor of claim 6, wherein each of said blades extends farther from said shaft than said cover.

8. 7. The brushless DC electric motor of claim 6, wherein the fan is configured as an axial fan.

9. 1. A brushless DC electric motor, comprising: a stator; An outer rotor surrounding the stator, a ring magnet defining an axis of rotation; a cover surrounding at least a portion of the ring magnet, the cover being overmolded onto and in direct contact with the radially outer surface of the ring magnet; a fan formed as a single unit integral with the cover, the fan including a plurality of blades extending radially outward from the cover and configured to direct airflow along an outer surface of the cover in a direction parallel to the axis of rotation; an outer rotor; Brushless DC electric motor.

10. 10. The brushless DC electric motor of claim 9, wherein the blades extend radially outward from the outer surface of the cover, each blade extending along the length of the cover.

11. 10. The brushless DC electric motor of claim 9, wherein the fan is configured as an axial fan.

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