KR101655112B1

KR101655112B1 - Brushless DC Motor

Info

Publication number: KR101655112B1
Application number: KR1020150047659A
Authority: KR
Inventors: 장정철; 이경주; 양창진
Original assignee: 뉴모텍(주)
Priority date: 2015-04-03
Filing date: 2015-04-03
Publication date: 2016-09-22

Abstract

The present invention relates to a brushless DC motor which can save time and cost in an assembling process of a motor, blocks leakage of current applied to the motor to prevent high-frequency noise from occurring and to prevent electrolytic corrosion of a bearing. The brushless DC motor comprises: a cylindrical housing which is provided with an opening portion on the upper face; a stator core which is accommodated to come in close contact with the inside of the side of the housing, and is provided with a hollow portion such that a rotor including a rotation shaft at the center rotates; and a bearing cover which opens and closes the opening portion, wherein an opened portion for exposing a part of the side of the stator core to the outside is provided on the side of the housing, and a grounding portion, which extends from the outer peripheral surface and is formed to protrude downwards to come in contact with the stator core exposed through the opened portion when the opening portion is closed, is provided.

Description

Brushless DC Motor < RTI ID = 0.0 >

The present invention relates to a brushless DC motor. More specifically, the present invention can save time and cost in the assembling process of a motor, and can prevent leakage of current applied to the motor, thereby preventing occurrence of high frequency noise, To a brushless DC motor having a structure.

A brushless DC motor includes a stator and a rotor. The rotor rotates in response to a magnetic field formed by the stator. A bearing coupled to the rotor and supporting the rotation of the rotation shaft is installed at the upper and lower portions of the rotor.

Brushless DC motors are generally controlled by a drive circuit, which causes electrical corrosion of the bearings due to the potential difference generated between the upper and lower bearings when the drive circuit operates, or due to axial currents generated for other reasons. Such electric corrosion causes noise and vibration when the motor is operated, which adversely affects the performance of the motor.

In order to prevent electrical corrosion of such bearings, Japanese Patent Application No. 10-1442414 discloses a resin-made housing having a flange protruding from a periphery of an opening formed on an upper surface thereof, and a flange portion A stator core fixed to the inside of the housing and having a plurality of teeth formed in an inner surface thereof to which the coils are wound, the stator core having one end coupled to the flange portion, And a connector made of metal which contacts the engaging groove portion of the bearing cover when the bearing cover is engaged with the upper surface of the housing and the other end contacts the stator core through the housing.

However, the prior art as described above is disadvantageous in terms of time and cost due to the addition of a complicated work process because it has a separate connector for grounding and a hole is drilled in the stator core to fix it, There is also a problem that inconvenience occurs when coupling with a device.

Further, since the ground contact area between the screw and the stator core is narrow and the screw is exposed to the outside, the ground can be released due to the screw loosening or the like, which causes a problem of reliability of the ground.

Accordingly, the present inventors intend to propose a brushless DC motor having a more improved ground structure in view of the above-mentioned problems.

An object of the present invention is to provide a brushless DC motor capable of preventing electrical corrosion of a bearing.

Another object of the present invention is to provide a brushless DC motor having a grounded area that is widened to improve grounding reliability.

Another object of the present invention is to provide a brushless DC motor in which grounding is automatically performed when only a bearing cover is press-fitted without any separate process for grounding.

It is still another object of the present invention to provide a brushless DC motor in which interference with a motor set due to grounding is eliminated.

The above and other objects of the present invention can be easily achieved by the present invention described below.

In the brushless DC motor according to the present invention,

A cylindrical housing having an opening formed on an upper surface thereof; A stator core which is held in close contact with the inside of the side surface of the housing and in which a hollow portion is formed so that a rotor including a rotating shaft can rotate; And a bearing cover for opening and closing the opening, wherein an opening portion for exposing a side portion of the stator core to the outside is provided on a side surface of the housing.

In the present invention, the bearing cover may be provided with a ground portion extending from the outer circumferential surface and protruding downward to be in contact with the stator core exposed through the opening portion when the opening portion is closed.

In the present invention, at least one ground portion is formed along the circumferential direction of the outer peripheral surface of the bearing cover, and the opening portion may be provided at the side portion of the housing corresponding to the number and position of the ground portions.

In the present invention, the housing side surface portion may be provided with a stepped portion along the periphery thereof so that the grounded portion can be seated.

In the present invention, the grounding portion may be formed with a bent portion extended in the direction of the axis of rotation, and a fastening hole may be provided on the side surface of the stator core so that the fastening portion is engaged with the fastening portion.

The brushless DC motor according to the present invention has a structure in which the bearing cover and the stator core are directly brought into contact with each other and grounded. By not using a separate connecting member for grounding such as a connector or an electric tape, And the grounding area is widened, so that the reliability of the grounding is improved and the interference with the motor set due to the grounding can be eliminated.

1 is an exploded perspective view of a brushless DC motor according to the present invention.
2 is a perspective view of a brushless DC motor according to the present invention.
3 is a sectional view taken along the line AA 'of FIG.
4 is an enlarged view of a portion B in Fig.
Hereinafter, a preferred embodiment of a brushless DC motor according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view of a brushless DC motor according to the present invention. FIG. 2 is a perspective view illustrating a brushless DC motor according to the present invention. FIG. 3 is a cross- Sectional view.

Referring to FIG. 1, a brushless DC motor according to the present invention includes a bearing cover 10, a housing 20, a stator assembly 30, and a rotor assembly 40.

The bearing cover 10 may be formed in a disk shape or the like depending on the shape of the housing 20, or may be formed by pressing a stainless steel sheet or the like with a metal material.

An upper bearing 44 is inserted into the bearing insert 11 when the bearing assembly 10 is engaged with the rotor assembly 40. Thereby, the rotor assembly 40 is rotatably supported with respect to the stator assembly 30, and the movement of the rotor assembly 40 in the direction of the rotation axis 41 is restricted. Needless to say, the bearing insert 11 may be formed in various ways depending on the structure of the upper bearing 44 and the shape of the housing 20.

The bearing cover 10 covers the upper opening 21 of the housing 20 and functions to isolate the inside of the motor from the outside. That is, the bearing cover 10 can be press-fitted into the opening 21 as in a general motor.

To this end, the bearing cover 10 may be formed with a coupling groove 12 into which a flange portion 22 formed around the opening 21 of the housing 20 is inserted. Therefore, when engaging the bearing cover 10 with the housing 20, the engaging groove 12 of the bearing cover 10 is positioned above the flange portion 22 of the housing 20 and then the bearing cover 10 So that the engaging groove 12 is inserted into the flange portion 22.

The bearing cover 10 according to the present invention not only opens and closes the opening 21 to accommodate the upper bearing 44 but also extends from the coupling groove 12 to the side surface of the housing 20 By forming the following ground portion 13, an axial current can flow through the stator core 31 to the ground terminal.

That is, the grounding portion 13 is formed to protrude downward from the outer circumferential surface of the bearing cover 10, and when the opening portion 21 is closed by the bearing cover 10, The bearing cover 10 and the stator core 31 are electrically connected to each other by being brought into contact with the stator core 31 exposed through the opening 23. [

At least one or more grounding portions 13 may be formed along the circumferential direction of the outer peripheral surface of the bearing cover 10. The number of the grounding portions 13 may be appropriately selected in consideration of the size and leakage current of the motor, And the reliability of the ground can be improved.

The grounding part 13 may be formed in various forms according to the structure of the housing 20 and the opening part 23, and a detailed description thereof will be given later with reference to FIG.

The housing 20 has an opening 21 opened and closed by a bearing cover 10 on an upper surface thereof and a flange portion 22 for engaging with the bearing cover 10 along the periphery of the opening 21, Can be formed. Such a flange portion 22 is not necessarily provided for enhancing the coupling strength when the bearing cover 10 is press-fitted into the opening portion 21 and engaged with the housing 20.

The housing 20 is made of a resin material so as to be insulated from the stator assembly 30 installed therein and is separately manufactured and assembled with the stator assembly 30 or insert injection molding using a BMC (Bulk Molding Compound) or may be integrally formed with the stator assembly 30 by an injection molding method.

At least one opening 23 corresponding to the grounding part 13 is formed on the side surface of the housing 20 and the stator core 31 is closely accommodated in the side surface of the housing 20, A part of the stator core 31 inside the housing 20 is exposed to the outside through the opening portion 23. [

As described above, when the bearing cover 10 and the housing 20 are engaged with each other, the grounding portion 13 of the bearing cover 10 is in contact with the stator core 31 to be electrically connected .

The stator assembly 30 includes a stator core 31, upper and lower insulators 32 and 33, a coil (not shown), and a printed circuit board 34.

The stator core 31 is generally formed by laminating an electrical steel sheet or the like. Though not shown, a plurality of teeth in which coils are wound on the inner surface are formed in an annular shape. A hollow portion 35 is formed at the center of the stator core 31 so that the rotor assembly 40 including the rotating shaft 41 can rotate.

Insulators (32, 33) are provided for insulation between the teeth and the stator core (31) and for facilitating the coil winding.

That is, the insulators 32 and 33 are coupled to the upper and lower portions of the stator core 31, respectively. The insulators 32 and 33 are wound around the inner surface of the stator core 31 and the winding portions of the teeth, And prevent direct contact with the inner surface and the teeth of the outer tube 31.

The upper and lower insulators 32 and 33 are made of a synthetic resin material such as polyacetal or the like and are separately manufactured and assembled to the stator core 31 or integrally formed with the stator core 31 by insert injection molding or the like It is possible.

Electronic parts for driving the motor, for example, an inverter circuit and a logic circuit when the motor is a brushless motor, are mounted on the printed circuit board 34.

Meanwhile, the coil and the printed circuit board 34 may be electrically connected to each other by using a power pin (not shown) to supply power for driving the motor, and the power pins may be formed by molding the insulators 32 and 33 It can be formed integrally.

In addition, the power supply pin may further include a dummy pin (not shown) in the same form as the power supply pin. The dummy pins are connected to the printed circuit board 34 so that the printed circuit board 34 can be more stably coupled to the stator core 31 and electrically connected to the stator core 31 So that the ground structure can be obtained through the printed circuit board 34.

The rotor assembly 40 includes a rotor core 42 positioned inside the stator assembly 30, a rotating shaft 41 fixed to the rotor core 42, magnets 43 mounted on the outer surface of the rotor core 42 The upper and lower bearings 44 and 45 are coupled to the rotary shaft 41 to support the rotary shaft 41 and facilitate the smooth rotation of the rotor core.

The rotor core 42 is provided so as to oppose the teeth to which the coil is wound, and when the coil is powered, the rotor core 42 starts to rotate, and the motor is driven by the rotation of the rotation shaft 41. Since the structure of such a rotor assembly 40 is well known, a detailed description thereof will be omitted.

Fig. 4 is an enlarged view of a portion B in Fig. 3; Fig. Hereinafter, a grounding structure of the brushless DC motor according to the present invention will be described with reference to FIG.

The ground structure of the brushless DC motor according to the present invention is such that when the bearing cover 10 is covered with the housing 20 constituting the main body of the motor, the bearing cover 10 and the stator core 31 inside the housing are brought into contact with each other , A grounding structure is formed without the necessity of separately providing a connector or an electrical tape.

In order to form such a grounding structure, firstly, an opening portion 23 should be formed on the side surface of the housing 20. The opening 23 is for exposing the stator core 31 closely contacted with the inner side surface of the housing to the outside, and may be formed on the side surface of the housing, that is, the side surface of the housing to which the stator core is closely attached.

At least one opening 23 may be formed along the side surface, and the size and shape of the opening 23 may be appropriately selected in consideration of the ground area.

On the other hand, the step portion 24 having a constant width in the circumferential direction may be formed on the side surface portion of the housing 20. The stepped portion 24 prevents the side surface portion from being bent when the bearing cover 10 is engaged with the housing 20 and at the same time facilitates the contact between the grounding portion 13 and the stator core 31 . It is preferable that the step portion 24 is formed to have a width corresponding to the thickness of the bearing cover 10. The step portion 24 and the opening portion 23 are connected to each other to form the ground portion 13 .

4, when the bearing cover 10 is pressed into the housing 20, the lower surface of the grounding portion 13 is seated on the stepped portion 24, and the inner surface of the grounding portion 13 is opened And comes into contact with the stator core 31 exposed through the portion 23.

Fig. 4 (a) shows a rectangular ground portion 13 according to a general embodiment, and Fig. 4 (b) shows another embodiment. Referring to FIG. 4 (b), the inner side surface of the grounding portion 13 may be formed with a bent portion 13a extending in the direction of the rotation axis. At this time, on the side surface of the stator core 31, a coupling groove 31a is formed corresponding to the coupling portion 13a so that the coupling portion 13a is in contact with the coupling portion 13a. By forming the engaging portion 13a and the engaging groove 31a in this way, the ground contact area between the bearing cover 10 and the stator core 31 can be increased, and a more rigid ground structure can be formed.

According to the ground structure of the brushless DC motor according to the present invention, when a motor is operated, a current generated due to a potential difference generated between the upper bearing 44 and the lower bearing 45 is transmitted to the upper bearing 44, The stator core 31, the printed circuit board 34, and the ground GND in this order, thereby solving the problem of electric corrosion of the bearing.

It is to be understood that the foregoing detailed description of the present invention has been presented for illustrative purposes only and is not intended to limit the scope of the present invention. It is intended that the scope of the invention be defined by the claims appended hereto, and that all such modifications and variations are intended to be included within the scope of the present invention.

10: bearing cover 11: bearing insertion portion
12: engaging groove portion 13:
20: housing 21: opening
22: flange portion 23:
24; Step 30: Stator assembly
31: stator core 32: upper insulator
33: lower insulator 34: printed circuit board
35: hollow part 40: rotor assembly
41: rotating shaft 42: rotor core
43: Magnet 44: Upper bearing
45: Lower bearing

Claims

A cylindrical housing having an opening formed on an upper surface thereof;
A stator core which is held in close contact with the inside of the side surface of the housing and in which a hollow portion is formed so that a rotor including a rotating shaft can rotate; And
A bearing cover for opening and closing the opening;
And,
Wherein an opening portion for exposing a side portion of the stator core to the outside is provided on a side surface of the housing,
The bearing cover includes a ground portion extending from an outer circumferential surface and protruding downward to be in contact with the stator core exposed through the opening portion when the opening portion is closed,
Wherein at least one of the grounding portions is formed along the circumferential direction of the outer circumferential surface of the bearing cover and the opening portion is provided in the housing lateral portion corresponding to the number and position of the grounding portions,
Wherein the grounding portion is formed with a bent portion extending in the direction of the axis of rotation, and a fastening hole is provided on the side surface of the stator core so that the fastening portion is engaged with the fastening hole.

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The method according to claim 1,
Wherein a stepped portion is formed along a periphery of the housing side surface portion to seat the ground portion.

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