WO2019212141A1

WO2019212141A1 - Brushless dc motor with improved ground structure

Info

Publication number: WO2019212141A1
Application number: PCT/KR2019/002974
Authority: WO
Inventors: Kyoung Joo Lee; Hyun Sung Yang; Min Seok Kang
Original assignee: New Motech Co., Ltd.
Priority date: 2018-04-30
Filing date: 2019-03-14
Publication date: 2019-11-07
Also published as: CN111712997B; CN111712997A; KR102041045B1

Abstract

The brushless DC motor according to the present invention, comprises: a housing 10 comprising a stator 15 in the inside, and having a hollow part 11 in which a rotor 20 coupled to a shaft 21 is positioned in the middle part; an upper bearing 22 coupled to an output side of the shaft 21 to rotatably support the shaft; an upper bearing cover 31 accommodating the upper bearing 22 and covering the hollow part 11; a lower bearing 23 coupled to a lower end of the shaft 21 to rotatably support the shaft; a lower bearing holder 32 accommodating the lower bearing 23 and coupled to a middle lower part of the housing 10; and a first grounding member 50 having an upper end part 50a bendingly coupled to an outer part of the upper bearing cover 31, and a lower end part 50b coupled to a middle part of the lower bearing holder 32, so as to make the upper bearing cover 31 and the lower bearing holder 32 electrically equipotential.

Description

BRUSHLESS DC MOTOR WITH IMPROVED GROUND STRUCTURE

The present invention relates to the ground structure of the motor. More specifically, the present invention relates to a motor with a ground structure having improved performance and durability, and less vibration and noise by improving the ground structure to prevent electrolytic corrosion of the bearing more effectively.

In general, motors comprise stators and rotors. The rotor rotates being affected by the magnetic field formed by the stator. The shaft which is coupled to the rotor to rotate together with the rotor has a bearing supporting the rotation of the shaft installed at an upper part and a lower part of the rotor.

In general, such motors are controlled by a driving circuit. Electrolytic corrosion occurs to the bearing by the potential difference generated between the upper bearing and the lower bearing when the driving circuit operates, or by the axial direction current generated for another reason. When a motor operates by such electrolytic corrosion, noise and vibration occur, which badly affect the performance of the motor and the durability of the motor.

In order to prevent such electrolytic corrosion of the bearing, Korean Patent Laid-Open No. 10-2008-0109168 discloses a technology preventing electrolytic corrosion of the bearing by connecting the output side bracket enclosing the upper bearing and the opposite output side bracket enclosing the lower bearing with a conductive tape to make the potential of both sides to be equipotential. However, the structure of the part fixing the end of the conductive tape is weak, and thus there may be problems in maintaining equipotentiality.

Meanwhile, Korean Patent No. 10-1562736 discloses a structure in which a metal member for grounding is installed at an outer side of the motor housing so as to directly connect an upper end and a lower end of the metal member for grounding to an upper bearing cover and a lower bearing cover. In this prior art, ground connection is made effectively between the upper bearing cover and the lower bearing cover, but since it has a structure inserting the bearing into the outside of the upper bearing cover and the lower bearing cover, the two bearings are easily exposed to the outside. In particular, due to the structure in which an end of the metal member for grounding is slightly in contact with the lower bearing cover, it is likely that the ground member may be isolated, and accordingly there may be a problem that the electrolytic corrosion of the bearing is not prevented effectively.

In this regard, in order to solve the above problems, the present inventors suggest a motor with improved ground structure that has not been suggested in the prior art.

It is an object of the present invention to provide a motor with improved ground structure.

It is another object of the present invention to provide a motor capable of preventing electrolytic corrosion of the bearing more effectively by effectively maintaining equipotentiality between the upper bearing and the lower bearing through the structure of the ground member which contacts the lower bearing cover and the bearing simultaneously.

The above object of the present invention or other inherent objects could all be easily achieved by the present invention explained in the following.

The brushless DC motor according to the present invention, comprises:

a housing 10 comprising a stator 15 in the inside, and having a hollow part 11 in which a rotor 20 coupled to a shaft 21 is positioned in the middle part;

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

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

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

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

a first grounding member 50 having an upper end part 50a bendingly coupled to an outer part of the upper bearing cover 31, and a lower end part 50b coupled to a middle part of the lower bearing holder 32, so as to make the upper bearing cover 31 and the lower bearing holder 32 electrically equipotential.

In the present invention, the first grounding member 50 may be positioned on a first groove 13 formed to be connected to the upper surface, the side surface, and the bottom surface of the housing 10.

In the present invention, the brushless DC motor may further comprise, on the side surface of the housing 10, a first grounding member 50; and a second grounding member 51 which penetrates the side surface of the first grounding member 50 to be in electric contact with the core of the stator 15.

In the present invention, preferably, the lower end part 50b has a bent shape, and the end of the bent shape is interposed between the lower bearing 23 and the lower bearing holder 32.

In the present invention, preferably, the lower bearing holder 32 is coupled to an inner side of a lower protrusion 14 downwardly protruding to the housing 10.

In the present invention, preferably, a lower end part 50b of the first grounding member 30 is guided to a second groove 14a formed on the lower protrusion 14.

In the present invention, preferably, the lower end part 50b of the first grounding member 30 is coupled to a third groove 32a formed on the lower bearing holder 32.

The present invention has an effect of preventing the electrolytic corrosion of the bearing more effectively by effectively maintaining equipotentiality between the upper bearing and the lower bearing through the new structure of the ground member which contacts the lower bearing cover and the bearing simultaneously.

Fig. 1 is a perspective view of the motor according to the present invention;

Fig. 2 is an exploded perspective view of the motor according to the present invention;

Fig. 3 is an exploded bottom perspective view of the motor according to the present invention;

Fig. 4 is a bottom perspective view of the motor according to the present invention;

Fig. 5 is an exploded perspective view of the ground structure of the motor according to the present invention; and

Fig. 6 is a cross sectional view taken along line A-A' of Fig. 1.

Hereinafter, the present invention will be explained in more detail with reference to the accompanied drawings.

Fig. 1 is a perspective view of the motor 100 according to the present invention; Fig. 2 is an exploded perspective view of the motor 100 according to the present invention; and Fig. 3 is an exploded bottom perspective view of the motor 100 according to the present invention.

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

The housing 10 has a hollow part 11 where the space in the middle is hollow, and an annular flange part 12 upwardly protruding along an upper part of the hollow part 11. A rotor 20 coupled to a shaft 21 to rotate together therewith is positioned in the hollow part 11. A first groove 13 is a place where a first grounding member 50 is positioned. The first groove 13 is formed from the flange part 12 or a part adjacent to the flange part 12 to be connected to the upper surface, the side surface, and the bottom surface of the housing 10. A lower protrusion 14 is downwardly protruding in the middle of a lower surface of the housing 10. The first groove 13 may be formed to extend to the lower protrusion 14. A second groove 14a for guiding a lower end part 50b of the first grounding member 50 is formed on the lower protrusion 14, and part of a bottom surface of the lower bearing holder 32 is exposed to the outside through a lower opening part 14b formed on a bottom surface of the lower protrusion 14.

A stator 15 is positioned inside the housing 10 positioned to face a side surface of the rotor 20. The stator 15 is electrically connected to a printed circuit substrate 15a, and a connector 15b and a lead wire 15c are installed to supply an external power to the printed circuit substrate 15a. Fig. 3 illustrates the stator 15 and the housing 10 to be separate parts. However, preferably, the stator 15, the printed circuit substrate 15a and the connector 15b are manufactured by injecting molding to be integrally formed with the housing 10 in an insert mold.

The rotor 20 comprises a magnet positioned to face the stator. A shaft 21 is penetratingly coupled in the middle part of the rotor 20. Accordingly, the rotor 20 and the shaft 21 become one unit and rotate together. A load such as a fan is coupled to an upper end of the shaft 21. In other words, 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 a bottom part of the upper end of the shaft 21. A lower bearing 23 is coupled to a lower end of the shaft 21 to support the rotation of the shaft 21.

An upper bearing cover 31 is coupled to cover the hollow part 11 of the housing 10 with a conductive material. The circumferential part of the upper bearing cover 31 is coupled to the flange part 12 of the housing 10. The middle part of the upper bearing cover 31 has an upwardly protruding shape, and an upper bearing 22 is coupled to the inner side part of the protruding shape. Fig. 2 illustrates that the upper bearing 22 is coupled to a lower side of the upper bearing cover 31, but the coupling shape is not limited thereto, and the protruding shape of the middle part of the upper bearing cover 31 may be changed so that the upper bearing 22 is coupled to an upper side of the upper bearing cover 31. The upper part of the upper bearing cover 31 is covered by an upper protecting member 41 to be protected.

The lower bearing holder 32 is made of a conductive material and has the shape of a cup whose upper part is open, and a lower bearing 23 is coupled in the space in the middle. A third groove 32a coupled to a lower end part 50b of the first grounding member 50 is formed on a bottom surface of the lower bearing holder 32. A lower opening part 32b is formed in the middle of the bottom surface of the lower bearing holder 32, and the third groove 32a and the lower opening part 32b have a shape connected to one another. Part of the bottom surface of the lower bearing holder 32 is exposed to the outside through the lower opening part 14b. The exposed part is covered by a lower protecting member 42. A lower protrusion 14 is coupled to a middle groove 42a of the lower protecting member 42. The upper protecting member 41 and the lower protecting member 42 may have rubber or plastic of an elastic material applied thereto.

Fig. 4 is a bottom perspective view of the motor 100 according to the present invention; Fig. 5 is an exploded perspective view of the ground structure of the motor 100 according to the present invention; and Fig. 6 is a cross sectional view taken along line A-A' of Fig. 1.

Referring to Figs. 4 to 6 together, the first grounding member 50 is coupled to the first groove 13 of the housing 10. A grounding hole 50c is formed in the first grounding member 50 of a side surface part of the housing 10. A second grounding member 51 is inserted into the grounding hole 50c so as to penetrate a side surface of the housing 10 and be coupled to a core part of the stator 15 inside the housing 10. This structure can be confirmed from Fig. 6. Figs. 4 and 6 illustrate that 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 screw, etc. may be used as far as it can be coupled to the grounding hole 50c to make the stator core and the first grounding member 50 electrically equipotential.

An upper end part 50a of the first grounding member 50 has a bent shape, and as can be seen from Fig. 6, it is pressedly inserted between the flange part 12 of the housing 10 and the outer peripheral part of the upper bearing cover 31 to be coupled thereto. A lower end part 50b of the first grounding member 50 has a shape where the end thereof is bent in a "U" shape, and the bent part is coupled to a third groove 32a of the lower bearing holder 32.

As can be seen from Fig. 4, the first grounding member 50 is coupled along the first groove 13, and has a bent shape while passing through the second groove 14a of the lower protrusion 14. As explained above, the lower end part 50b, which is an end part passing through the second groove 14a, has a "U" shape and this part is coupled to the third groove 32a formed in the lower bearing holder 32.

As can be seen from Fig. 6, the bent part at an end of the lower end part 50b of the first grounding member 50 is in contact with a bottom surface part 23a of the lower bearing 23. Preferably, the end of the lower end part 50b of the first grounding member 50 is interposed between the lower bearing 23 and the lower bearing holder 32 to be in contact with both members. Through this structure, the lower end part of the first grounding member 50 is guaranteed to form a firm coupling, and to stably maintain electric contact.

The explanation in the present invention provided above was merely to provide examples to help understand the present invention, and was not intended to limit the scope of the present invention. The explanation in the present invention shall be defined by the accompanying claims, and it should be interpreted that simple modification or alternation of the present invention made within the scope of the claims belong to the protection scope of the present invention.

Claims

A brushless DC motor, comprising:

a housing 10 comprising a stator 15 in the inside, and having a hollow part 11 in which a rotor 20 coupled to a shaft 21 is positioned in the middle part;

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

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

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

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

a first grounding member 50 having an upper end part 50a bendingly coupled to an outer part of the upper bearing cover 31, and a lower end part 50b coupled to a middle part of the lower bearing holder 32, so as to make the upper bearing cover 31 and the lower bearing holder 32 electrically equipotential.
The brushless DC motor of claim 1, wherein the first grounding member 50 is positioned on a first groove 13 formed to be connected to the upper surface, the side surface, and the bottom surface of the housing 10.
The brushless DC motor of claim 1, further comprising, on the side surface of the housing, a first grounding member 50; and a second grounding member 51 which penetrates the side surface of the first grounding member 50 to be in electric contact with the core of the stator 15.
The brushless DC motor of claim 1, wherein the lower end part 50b has a bent shape, and the end of the bent shape is interposed between the lower bearing 23 and the lower bearing holder 32.
The brushless DC motor of claim 1, wherein the lower bearing holder 32 is coupled to an inner side of a lower protrusion 14 downwardly protruding to the housing 10.
The brushless DC motor of claim 5, wherein a lower end part 50b of the first grounding member 30 is guided to a second groove 14a formed on the lower protrusion 14.
The brushless DC motor of claim 1, wherein the lower end part 50b of the first grounding member 30 is coupled to a third groove 32a formed on the lower bearing holder 32.