CN111712997B

CN111712997B - Brushless DC motor with improved grounding structure

Info

Publication number: CN111712997B
Application number: CN201980013120.6A
Authority: CN
Inventors: 李京柱; 梁玹诚; 姜玟硕
Original assignee: New Motech Co Ltd
Current assignee: New Motech Co Ltd
Priority date: 2018-04-30
Filing date: 2019-03-14
Publication date: 2022-11-11
Anticipated expiration: 2039-03-14
Also published as: WO2019212141A1; CN111712997A; KR102041045B1

Abstract

The brushless DC motor of the present invention comprises: a housing (10) containing a stator (15) therein and having a hollow portion (11), a rotor (20) coupled to a shaft (21) being located at a middle portion of the hollow portion (11); an upper bearing (22) coupled to an output side of the shaft (21) to rotatably support the shaft; an upper bearing cover (31) that houses the upper bearing (22) and covers the hollow portion (11); a lower bearing (23) coupled to a lower end of the shaft (21) to rotatably support the shaft; a lower bearing housing (32) accommodating the lower bearing (23) and coupled to a middle-lower portion of the housing (10); a first grounding member (50) having an upper end portion (50 a) bent to be coupled to an outer portion of the upper bearing cap (31) and a lower end portion (50 b) coupled to a middle portion of the lower bearing housing (32) such that the upper bearing cap (31) and the lower bearing housing (32) are equipotential.

Description

Brushless DC motor with improved grounding structure

Technical Field

The present invention relates to a grounding structure of an electric machine. More particularly, the present invention relates to a motor having a ground structure, which can more effectively prevent electrolytic corrosion of bearings by improving the ground structure, improve performance and durability, and have characteristics of small vibration and low noise.

Background

Generally, an electric machine includes a stator and a rotor. The rotor rotates under the influence of the magnetic field formed by the stator. A shaft coupled to and rotating with the rotor has bearings for supporting rotation of the shaft mounted on the upper and lower portions of the rotor.

Typically, such motors are controlled by a drive circuit. When the driving circuit is operated, electrolytic corrosion of the bearings occurs due to a potential difference between the upper and lower bearings or an axial current generated due to another cause. When the motor operates under electrolytic corrosion, noise and vibration are generated, which seriously affect the performance and durability of the motor.

In order to prevent electrolytic corrosion of a bearing, korean patent laid-open publication No. 10-2008-0109168 discloses a technique for preventing electrolytic corrosion of a bearing, in which an output side bracket surrounding an upper bearing and an opposite output side bracket surrounding a lower bearing are connected by a conductive cloth tape, and potentials at both sides are equalized. However, the member for fixing the end of the conductive cloth tape is structurally weak, and thus there may be a problem in maintaining the allelism.

Meanwhile, korean patent No. 10-1562736 discloses a structure in which a metal member for grounding is installed outside a motor case so that the upper and lower ends of the metal member for grounding are directly connected to an upper bearing cap and a lower bearing cap. In the prior art, an effective ground connection is made between the upper and lower bearing caps, but since it has a structure in which the bearings are inserted to the outside of the upper and lower bearing caps, the two bearings are easily exposed to the outside. In particular, due to the structure in which one end of the metal member for grounding is in light contact with the lower bearing cap, the grounding member is likely to be isolated, and thus there may be a problem that electrolytic corrosion of the bearing cannot be effectively prevented.

In this respect, in order to solve the above-mentioned problems, the present inventors have proposed a motor having an improved grounding structure not proposed in the prior art.

Disclosure of Invention

Technical problem

It is an object of the present invention to provide an electric machine with an improved grounding structure.

Another object of the present invention is to provide a motor capable of more effectively preventing electrolytic corrosion of a bearing by effectively maintaining allelism between an upper bearing and a lower bearing by simultaneously contacting a lower bearing cover and a grounding member structure of the bearing.

The above objects and other inherent objects of the present invention can be easily achieved by the present invention as hereinafter explained.

Technical scheme

The brushless DC motor of the present invention comprises:

a housing 10 having a stator 15 therein and having a hollow 11, wherein a rotor 20 coupled to a shaft 21 is positioned at a middle portion of the hollow 11;

an upper bearing 22 coupled to an output side of the shaft 21 to rotatably support the shaft;

an upper bearing cover 31 for accommodating the upper bearing 22 and covering the hollow portion 11;

a lower bearing 23 coupled to a lower end of the shaft 21 to rotatably support the shaft;

a lower bearing housing 32 accommodating the lower bearing 23 and coupled to a middle lower portion of the housing 10; and

the first grounding member 50 has an upper end portion 50a bent to be coupled to the outside of the upper bearing cap 31 and a lower end portion 50b coupled to a middle portion of the lower bearing housing 32, so that the upper bearing cap 31 and the lower bearing housing 32 are equipotential.

In the present invention, the first grounding member 50 may be disposed on the first recess 13, and the first recess 13 may be formed to connect the upper surface, the side surface and the bottom surface of the housing 10.

In the present invention, the brushless dc motor may further include a first ground member 50 on a side surface of the housing 10; and a second ground member 51 electrically contacted with the core of the stator 15 through a side surface of the first ground member 50.

In the present invention, it is preferable that the lower end portion 50b has a curved shape, and the end portion of the curved shape is interposed between the lower bearing 23 and the lower bearing housing 32.

In the present invention, it is preferable that the lower bearing housing 32 is coupled to an inner side of the lower protruding portion 14, and the lower protruding portion 14 protrudes downward toward the housing 10.

In the present invention, it is preferable that the lower end portion 50b of the first ground member 50 is guided to the second groove 14a, and the second groove 14a is formed on the lower protrusion 14.

In the present invention, it is preferable that the lower end portion 50b of the first ground member 50 is coupled to a third groove 32a, and the third groove 32a is formed on the lower bearing housing 32.

ADVANTAGEOUS EFFECTS OF INVENTION

The invention has the advantages that the allelism between the upper bearing and the lower bearing is effectively maintained through the novel structure of the grounding component which simultaneously contacts the lower bearing cover and the bearing, thereby more effectively preventing the electrolytic corrosion of the bearing.

Drawings

Fig. 1 is an exploded view of an electric machine according to the present invention;

FIG. 2 is an exploded schematic view of a motor according to the present invention;

FIG. 3 is a bottom exploded schematic view of a motor according to the present invention;

FIG. 4 is a bottom exploded view of the motor according to the present invention;

fig. 5 is an exploded schematic view of a grounding structure of a lower bearing cap of the motor according to the present invention; and is

Fig. 6 isbase:Sub>A cross-sectional view taken along linebase:Sub>A-base:Sub>A' of fig. 1.

The present invention will be described in detail below with reference to the accompanying drawings.

Detailed Description

Fig. 1 is an exploded view of the above-described motor 100 according to the present invention; fig. 2 is an exploded view of the motor 100 according to the present invention; fig. 3 is a bottom exploded schematic view of the motor 100 according to the present invention.

As can be seen from fig. 1 to 3, the motor 100 according to the present invention may include a housing 10, a rotor 20, an upper bearing cover 31, a lower bearing housing 32, an upper protection member 41, and a lower protection member 42.

The housing 10 has a hollow portion 11 in which a space in the middle is hollow, and an annular flange portion 12 protrudes upward along an upper portion of the hollow portion 11. A rotor 20 coupled to the shaft 21 and rotating together with the shaft 21 is located within the hollow 11. The first recess 13 is where the first ground member 50 is placed. The first groove 13 is formed by the flange portion 12 or a portion adjacent to the flange portion 12 to be connected to the upper surface, the side surface, and the bottom surface of the case 10. The lower protrusion 14 protrudes downward at the middle of the lower surface of the housing 10. The first groove 13 may be shaped to extend to the lower protrusion 14. The lower protruding portion 14 is opened with a second groove 14a for guiding a lower end portion 50b of the first grounding member 50, and a portion of the bottom surface of the lower housing 32 is exposed to the outside through a lower opening portion 14b formed on the bottom surface of the lower protruding portion 14.

The stator 15 is located inside the housing 10, and the housing 10 is located facing a side surface of the rotor 20. The stator 15 is electrically connected to the printed circuit substrate 15a, and the connector 15b and the lead 15c are mounted to supply an external power source to the printed circuit substrate 15 a. Fig. 3 shows the stator 15 and the housing 10 as separate parts. However, it is preferable that the stator 15, the printed circuit substrate 15a and the connector 15b are formed by injection molding, integrally molded with the housing 10 in an insert mold.

The rotor 20 includes a magnet positioned facing the stator. The shaft 21 is penetratingly coupled to a middle portion of the rotor 20. Thus, the rotor 20 and the shaft 21 become one unit and rotate together. A load (such as a fan) is coupled to the upper end of the shaft 21. That is, the upper end of the shaft 21 becomes the output side. An upper bearing 22 for supporting the rotation of the shaft 21 is coupled to the bottom of the upper end of the shaft 21. The lower bearing 23 is coupled to a lower end of the shaft 21 to support the rotation of the shaft 21.

The upper bearing cap 31 is coupled to cover the hollow portion 11 of the housing 10 with a conductive material. A circumferential portion of the upper bearing cap 31 is coupled to the flange portion 12 of the housing 10. The middle portion of the upper bearing cover 31 has an upward protruding shape, and the upper bearing 22 is coupled to an inner portion of the protruding shape. As shown in fig. 2, the upper bearing 22 is coupled to the lower side of the upper bearing cap 31, but the coupling shape is not limited thereto, and the protruding shape of the middle portion of the upper bearing cap 31 may be changed such that the upper bearing 22 is coupled to the upper side of the upper bearing cap 31. The upper portion of the upper bearing cap 31 is covered with an upper protection member 41 to be protected.

The lower bearing housing 32 is made of a conductive material and has a cup shape with an upper opening, and the lower bearing 23 is coupled in the space in the middle. The lower bearing housing 32 has a third groove 32a opened on a bottom surface thereof, and the third groove 32a is coupled to a lower end portion 50b of the first ground member 50. The lower bearing seat 32 has a lower opening 32b in the middle of the bottom surface thereof, and the third groove 32a and the lower opening 32b have a shape connected to each other. A bottom surface portion of the lower bearing housing 32 is exposed to the outside through the lower opening portion 14 b. The exposed portion is covered with a lower protection member 42. The lower protrusion 14 is coupled to the middle groove 42a of the lower sheathing member 42. The upper and

lower sheathing members

41 and 42 may use rubber or plastic made of an elastic material.

FIG. 4 is a bottom exploded view of the electric machine 100 according to the present invention; fig. 5 is an exploded view of the grounding structure of the lower bearing housing 32 side of the motor 100 according to the present invention; fig. 6 isbase:Sub>A cross-sectional view taken along linebase:Sub>A-base:Sub>A' of fig. 1.

Referring to fig. 4 and 6, the first ground member 50 is coupled to the first groove 13 of the housing 10. The first ground member 50 of the side surface portion of the housing 10 is opened with a ground hole 50c. The second grounding member 51 is inserted into the grounding hole 50c so as to penetrate the side surface of the housing 10 and is coupled to the core portion of the stator 15 inside the housing 10. This structure can be confirmed from fig. 6. As shown in fig. 4 and 6, the second grounding member 51 is a bolt, but the second grounding member is not necessarily limited to a bolt, but other members such as a pin or a screw may be used as long as it can be coupled to the grounding hole 50c to make the stator core and the first grounding member 50 equipotential.

The upper end portion 50a of the first ground member 50 has a curved shape, and as shown in fig. 6, the upper end portion 50a is press-fitted between the flange portion 12 of the housing 10 and the outer peripheral portion of the upper bearing cap 31 coupled thereto. The lower end portion 50b of the first grounding member 50 has a shape bent at its end into a "U" shape, and the bent portion is coupled to the third groove 32a of the lower bearing housing 32.

As shown in fig. 4, the first ground member 50 is coupled along the first groove 13, and the first ground member 50 has a curved shape while passing through the second groove 14a of the lower protrusion 14. As described above, the lower end portion 50b is "U" shaped as an end portion passing through the second groove 14a, and the lower end portion 50b is coupled to the third groove 32a opened on the lower bearing housing 32.

As shown in fig. 6, a curved portion at the end of the lower end 50b of the first grounding member 50 is in contact with the bottom surface portion 23a of the lower bearing 23. Preferably, the end of the lower end 50b of the first grounding member 50 is interposed between the lower bearing 23 and the lower bearing housing 32 so as to be in contact with both members at the same time. With this structure, the lower end portion of the first grounding member 50 is ensured to be firmly coupled and to be stably kept in electrical contact.

The description of the present invention provided above is intended only to provide examples to aid understanding of the present invention and is not intended to limit the scope of the present invention. The description of the present invention should be defined by the appended claims, and it should be noted that simple modifications or changes made to the present invention within the scope of the claims belong to the invention claimed in the present invention.

Claims

1. A brushless DC motor is provided, which comprises a motor body,

the method comprises the following steps:

a housing (10) having a stator (15) therein and having a hollow portion (11), a rotor (20) coupled to a shaft (21) being located at a middle portion of the hollow portion (11);

an upper bearing (22) coupled to an output side of the shaft (21) to rotatably support the shaft;

an upper bearing cover (31) that houses the upper bearing (22) and covers the hollow portion (11);

a lower bearing (23) coupled to a lower end of the shaft (21) to rotatably support the shaft;

a lower bearing housing (32) accommodating the lower bearing (23) and coupled to a middle lower portion of the housing (10); and

a first grounding member (50) having an upper end portion (50 a) bent to be coupled to an outer portion of the upper bearing cap (31) and a lower end portion (50 b) coupled to a middle portion of the lower bearing housing (32) such that the upper bearing cap (31) and the lower bearing housing (32) are equipotential,

the lower end part (50 b) has a curved shape, and the end part of the curved shape is placed between the lower bearing (23) and the lower bearing seat (32).

2. The brushless dc motor according to claim 1, wherein the first grounding member (50) is located in a first recess (13), and the first recess (13) is formed in the housing (10) so as to connect an upper surface, a side surface, and a bottom surface of the housing (10).

3. The brushless dc motor according to claim 1, further comprising a second ground member (51), wherein the second ground member (51) electrically contacts the core of the stator (15) through a side surface of the first ground member (50).

4. The brushless dc motor according to claim 1, wherein the lower bearing housing (32) is coupled to an inner side of a lower protrusion (14), and the lower protrusion (14) is formed to protrude downward at a middle of a lower surface of the housing (10).

5. The brushless DC motor according to claim 4, wherein the lower end (50 b) of the first grounding member (50) leads to a second groove (14 a), said second groove (14 a) being formed on said lower protrusion (14).

6. The brushless dc motor according to claim 1, wherein a lower end portion (50 b) of the first grounding member (50) is coupled to a third groove (32 a), said third groove (32 a) being formed on said lower bearing seat (32).