CN211239471U

CN211239471U - Rotor, brushless DC motor and power tool

Info

Publication number: CN211239471U
Application number: CN201921676732.7U
Authority: CN
Inventors: 黄伟梁; 何剑维; 徐勇辉
Original assignee: Techtronic Cordless GP
Current assignee: Techtronic Cordless GP
Priority date: 2019-10-08
Filing date: 2019-10-08
Publication date: 2020-08-11
Anticipated expiration: 2029-10-08

Abstract

A rotor for a brushless dc motor, the rotor comprising: a first body portion defining a hollow interior for receiving a stator and defining a longitudinal axis; and a second body portion configured to support the first body portion for rotation about the longitudinal axis; wherein the first body portion is formed from a sheet of magnetically permeable material that has been rolled to form a tube, and a brushless dc motor and power tool employing the rotor.

Description

Rotor, brushless DC motor and power tool

Technical Field

The utility model relates to a rotor; in particular for a rotor of a brushless dc motor.

Background

Brushless dc motors typically include a stator having a plurality of electrical windings arranged about an axis, and one or more permanent magnets supported for rotation relative to the stator. During use, the electrical windings are selectively activated to generate a magnetic field that moves the permanent magnet rotor. In some types of brushless dc motors, the stator is generally tubular and defines a cylindrical rotor cavity for receiving the rotor, which is supported for rotation relative to the stator within the rotor cavity. In other types of brushless dc motors, the rotor is tubular and defines a hollow interior for receiving the stator, the rotor being supported for rotation about the circumference of the stator.

In the latter type of brushless dc motor, the permanent magnets are typically supported on a rotor body that includes webs or spokes that connect the rotor body to a rotating output shaft. As a result, the shape of the rotor is generally large and hollow, and thus such rotors are often difficult and expensive to manufacture. It is therefore an object of the present invention to provide a rotor for a brushless dc motor which can be manufactured more easily and cheaper. It is another object of the present invention to provide an improved or alternative rotor for a brushless dc motor.

SUMMERY OF THE UTILITY MODEL

According to a first aspect, there is provided a rotor for a brushless dc motor, the rotor comprising: a first body portion defining a hollow interior for receiving a stator and defining a longitudinal axis; and a second body portion configured to support the first body portion for rotation about the longitudinal axis; wherein the first body portion is formed from a sheet of magnetically permeable material that has been rolled to form the tube.

According to a second aspect, there is provided a brushless dc motor comprising: a rotor according to the first aspect; and a stator received within the hollow interior of the rotor.

According to a third aspect, there is provided a power tool comprising the brushless dc motor according to the second aspect.

According to a fourth aspect, there is provided a method of manufacturing a rotor of a brushless dc motor, the method comprising: providing a flat sheet of magnetically permeable material; rolling the flat sheet into a tube to form a first body portion; and supporting the first body portion for rotation about the longitudinal axis using the second body portion. Optionally, the flat sheet may define a first end having a projection and a second end having a correspondingly shaped groove, and after or during the rolling step, the method may further comprise receiving the projection within the groove. The method of the third aspect may comprise any optional feature of the rotor of the first aspect or the brushless dc motor of the second aspect.

Drawings

The description of the invention is provided below with reference to the accompanying drawings, in which:

FIG. 1 is a schematic perspective view of a rotor;

FIG. 2 is a schematic perspective view of a first body portion of the rotor of FIG. 1;

FIG. 3 is a schematic perspective view of an insert of the rotor of FIG. 1; and

fig. 4 is a schematic perspective view of a portion of the rotor of fig. 1.

Detailed Description

Fig. 1 shows a rotor 2 for a brushless dc motor. The rotor 2 comprises a first body part 4 and a second body part 6. The first body portion 4 defines a hollow interior 8 defining a longitudinal axis 10. The hollow interior 8 is configured to receive a stator of a dc motor. The second body portion 6 is configured to support the first body portion 4 for rotation about a longitudinal axis 10. The first body portion 4 is formed from a sheet of magnetically permeable material, such as steel, which has been rolled to form a tube. Because the first body portion 4 is formed from a flat sheet rolled into a tube, the first body portion 4 is relatively easy and inexpensive to manufacture.

Referring to fig. 2, the first body portion 4 defines a first end 12 and a second end 14. The first end 12 is a flat plate opposite end from the second end 14. First end 12 defines a tab 16, and tab 16 is matingly received within a corresponding recess 18 of second end 14 such that when the flat sheet is rolled into a tube, first end 12 abuts second end 14 to form the tube. This ensures that the two

ends

12, 14 of the plate are aligned in the correct position to form the tube, as the projection 16 is received in the recess 18.

The tab 16 includes an enlarged portion and the groove 18 is correspondingly shaped to receive the tab 16. Because the groove 18 is correspondingly shaped to receive the projection 16, the engagement between the groove 18 and the projection 16 prevents the projection 16 from disengaging from the groove 18, and thus the connection between the first end 12 and the second end 14 is more secure.

The rotor further comprises an insert 22, the insert 22 being configured to mount the second body portion 6 to the shaft in order to transfer torque from the rotor to the shaft. As shown in FIG. 3, the insert 22 is generally tubular and defines a through bore 24 for receiving a shaft. The insert includes a plurality of longitudinally extending splines 26, the splines 26 being formed on a radially outer surface 27 of the insert 3. The splines 26 are configured to grip the second body portion 6 to prevent relative rotation between the insert 22 and the second body portion 6. In some embodiments, the second body portion 6 is molded onto the radially outer surface 27 of the insert 22. The insert 22 comprises metal and is formed by sintering.

The first body portion 4 defines a radially outer surface 20. Referring to fig. 1 and 4, the second body portion 6 comprises a polymeric material molded onto the radially outer surface 20 of the first body portion 4. The second body portion 6 also includes a plurality of radially extending and circumferentially spaced spokes 28, the spokes 28 connecting the insert 22 to the first body portion 4. The spokes 28 align the insert 22 with the longitudinal axis 10 such that the first body portion is supported for rotation about the longitudinal axis 10. The spokes 28 define one or more fan blades 30 for drawing air through the interior 8 of the rotor 2 to help cool the stator of the motor.

Referring to fig. 1, the rotor 2 further comprises permanent magnets 32, the permanent magnets 32 being received within the interior 8 of the first body portion 4. The permanent magnet 32 is tubular and is held within the interior 8 of the first body portion 4 by a push fit and may be otherwise secured using an adhesive. In other embodiments, the permanent magnet 32 need not be tubular, and may comprise a plurality of individual tile or sheet magnets arranged around the inner circumference of the first body portion 4.

The rotor 2 may be part of a brushless dc motor and the stator may be received within the interior 8.

The flat plate may be manufactured by stamping. Stamping is a highly repeatable process that ensures that the dimensions of the plate are always the same. In addition, since the projection 16 is received in the groove 18, this ensures that the circumference of the first body part 4 is always the same size, so that the first body part 4 can be manufactured accurately and with high capacity. To ensure that the rotor 2 is rotationally balanced, the second body portion 6 can be easily and inexpensively machined to remove material.

Claims

1. A rotor for a brushless dc motor, the rotor comprising:

a first body portion defining a hollow interior for receiving a stator and defining a longitudinal axis; and

a second body portion configured to support the first body portion for rotation about the longitudinal axis;

wherein the first body portion is formed from a sheet of magnetically permeable material that has been rolled to form a tube.

2. The rotor of claim 1, wherein the first body portion defines a first end and a second end, and wherein the first end defines a protrusion that is matingly received within a corresponding groove of the second end such that the first end abuts the second end.

3. The rotor of claim 2, wherein the protrusion includes an enlarged portion, and wherein the groove is correspondingly shaped to receive the protrusion.

4. The rotor of claim 3, wherein the first body portion defines a radially outer surface, and wherein the second body portion comprises a polymeric material molded on the radially outer surface of the first body portion.

5. The rotor of claim 4, further comprising an insert configured to mount the second body portion to a shaft for transferring torque from the rotor to the shaft.

6. The rotor of claim 5 wherein the insert is generally tubular and defines a through bore for receiving the shaft.

7. The rotor of claim 6 wherein the insert includes one or more longitudinally extending splines for preventing relative rotation between the insert and the second body portion.

8. The rotor of claim 7, wherein the second body portion includes one or more spokes connecting the insert to the first body portion.

9. The rotor of claim 8, wherein the one or more spokes define one or more fan blades for drawing air through the interior of the rotor.

10. The rotor of claim 9 wherein the second body portion is molded onto a radially outer surface of the insert.

11. The rotor of claim 10, further comprising a permanent magnet received within the interior of the first body portion.

12. The rotor of claim 11, wherein the magnet is tubular and is retained within the interior of the first body portion by a push-fit.

13. The rotor of claim 12 wherein the insert comprises metal and is formed by sintering.

14. A brushless dc motor, comprising:

a rotor according to the preceding claim; and

a stator received within the hollow interior.

15. A power tool comprising the brushless dc motor according to claim 14.