WO2021025269A1

WO2021025269A1 - Ungrounded motor

Info

Publication number: WO2021025269A1
Application number: PCT/KR2020/006527
Authority: WO
Inventors: Jeong Cheol Jang; Kyoung Joo Lee; Hyun Sung Yang; Kwang Deok Seo
Original assignee: New Motech Co., Ltd.
Priority date: 2019-08-05
Filing date: 2020-05-19
Publication date: 2021-02-11
Also published as: KR102238237B1; CN113906654A; KR20210016753A

Abstract

The motor (100) according to the present invention comprises: a stator (1) comprising an upper insulator (11), a stator core (12) and a lower insulator (13); a rotor (2) installed opposite to the stator (1) to rotate; a shaft (20) coupled to the rotor (2) to rotate together therewith; and a printed circuit substrate (3) electrically connected to the stator (1), wherein the rotor (2) comprises a rotor main body (21) and a magnet (22) coupled to an outer circumferential surface of the rotor main body (21), and the rotor main body (21) is made of an insulating material.

Description

UNGROUNDED MOTOR

The present invention relates to a motor. More specifically, the present invention relates to a motor of a new structure capable of preventing damage caused by electric erosion of the bearing and reducing the noise produced in the motor by excluding the grounded structure of the motor and improving the motor to have an ungrounded structure.

In general, a motor comprises a stator and a rotor. A magnetic field formed by the stator causes the rotor to rotate. A shaft is coupled to the rotor to rotate together with the rotor, and a bearing which supports the rotation of the shaft is installed at an upper portion and a lower portion of the rotor.

The motor is generally controlled by a driving circuit. A potential difference generated between the bearing and the shaft when the driving circuit is operating, or an axial current generated for other reasons causes electric erosion in the bearing. Such electric erosion produces noise and vibration when the motor is operating, adversely affecting the performance of the motor and the durability of the motor.

In order to prevent electric erosion of the bearing, Korean Patent Laid-Open No. 10-2008-0109168 discloses a technique preventing electric erosion of the bearing by connecting an output bracket enclosing the upper bearing and an opposite output bracket enclosing the lower bearing with a conductive tape to establish equal electric potential at both sides. However, the structure of the part fixing the end of the conductive tape is weak, and thus there may be difficulties in maintaining the equal electric potential.

Meanwhile, Korean Patent No. 10-1562736 discloses a structure wherein a metal member for grounding is installed outside the motor housing so that the upper end and lower ends of the metal member for grounding are directly connected to the upper bearing cover and the lower bearing cover. This prior art provides grounding between the upper bearing cover and the lower bearing cover effectively, but the two bearings are easily exposed to the outside because it has a structure where the bearings are inserted to the outside of the upper bearing cover and the lower bearing cover. In particular, due to the structure where the end of the metal member for grounding slightly contacts the lower bearing cover side, the grounding member may be isolated, thereby not being able to block the generation of electric erosion in the bearing effectively.

Japanese Patent Laid-Open No. 2013-81264 discloses a structure maintaining the equal electric potential by connecting the cover enclosing the upper bearing and the cover enclosing the lower bearing with a grounding plate. Japanese Patent Laid-Open No. 2004-229429 discloses a structure connecting the bearing, the bearing cover and the stator core to maintain ground potential.

The prior art references provided above prevent the generation of a potential difference at the bearing by using an artificial grounding member, but have a problem that the use of an additional member causes the complex structure of the motor and increases manufacturing costs.

In this regard, in order to solve the above problems, the present inventors suggest a motor with a new structure which has an ungrounded structure not disclosed in prior art, capable of preventing damage to the bearing and reducing operating noise of the motor.

It is an object of the present invention to provide a motor having an ungrounded structure.

It is another object of the present invention to provide a motor capable of preventing electric erosion of the bearing through an ungrounded structure.

It is yet another object of the present invention to provide a motor capable of lowering manufacturing costs and reducing operating noise of the motor.

The objects above and other objects inferred therein can be easily achieved by the present invention explained below.

The motor 100 according to the present invention comprises: a stator 1 comprising an upper insulator 11, a stator core 12 and a lower insulator 13; a rotor 2 installed opposite to the stator 1 to rotate; a shaft 20 coupled to the rotor 2 to rotate together therewith; and a printed circuit substrate 3 electrically connected to the stator 1, wherein the rotor 2 comprises a rotor main body 21 and a magnet 22 coupled to an outer circumferential surface of the rotor main body 21, and the rotor main body 21 is made of an insulating material.

In the present invention, preferably, the rotor main body 21 is formed by injection molding having the shaft 20 and the magnet 22 placed in an insert injection mold.

In the present invention, preferably, a plurality of balance holes 21B formed to penetrate axially are formed symmetrically with respect to the shaft 20 on the rotor main body 21.

In the present invention, the shaft 20 may be enclosed with an insulating tube 20A.

In the present invention, preferably, the insulating tube 20A covers the shaft 20 from a portion coupled to an upper bearing 4 to a portion coupled to a lower bearing 7.

The present invention has an effect of providing a motor capable of preventing electric erosion of the bearing, lowering manufacturing costs and reducing operating noise of the motor with an ungrounded structure.

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

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

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

Fig. 4 is an exploded perspective view of a rotor of the motor according to the present invention;

Fig. 5 is a perspective view illustrating the coupling of the rotor, the shaft and the bearings of the motor according to the present invention;

Fig. 6 is a graph illustrating the result of measuring noise of the motor according to the present invention in comparison with the conventional motor; and

Fig. 7 is a graph illustrating the result of measuring vibration of the motor according to the present invention in comparison with the conventional motor.

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

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

As illustrated in Fig. 1 to Fig. 3, the motor 100 according to the present invention comprises a stator 1, a rotor 2 and a printed circuit substrate 3, and the stator 1 and the printed circuit substrate 3 are placed inside a housing 10.

The stator 1 comprises a stator core 12, and upper and

lower insulators

11 and 13 coupled to an upper portion and a lower portion of the stator core 12. A coil (not illustrated) winds around a portion protruding towards the inside of the stator 1, and the end of the coil is electrically connected to the printed circuit substrate 3.

The rotor 2 is placed inside the stator 1, and the rotor 2 rotates through interaction with a magnetic field changing generated in the stator 1. The rotor 2 comprises a rotor main body 21 and a magnet 22 coupled to an outer circumferential surface of the rotor main body 21. A shaft 20 is coupled to the center portion of the rotor main body 21. When the rotor 2 rotates, the shaft 20 rotates together therewith. The rotation of the upper side of the shaft 20 is supported by an upper bearing 4, and the rotation of the lower side is supported by a lower bearing 7. The upper bearing 4 is coupled to a bearing holder 5, and the bearing holder 5 is fixedly installed in an upper protrusion 102 protrudingly formed on an upper portion of the housing 10. The lower bearing 7 is coupled to the center portion of a bearing cover 8, and the bearing cover 8 covers an inner space 103 open to the lower portion of the housing 10 from the lower portion side. An upper damper 6 is coupled to the upper protrusion 102 of the housing 10, and a lower damper 9 is coupled to the bearing cover 8 to soften the vibration of the motor.

The printed circuit substrate 3 is placed on an upper portion of the upper insulator 11 of the stator 1. Preferably, the form of the housing 10 is manufactured by placing the stator 1 in an insert injection mold having the printed circuit substrate 3 placed on an upper portion of the stator 1 to form an electric connection with the coil (not illustrated), and molding by resin molding. More preferably, the housing 10 is manufactured by insert injection molding having the bearing holder 5 placed on an upper portion in the center of the stator 1.

A lead wire drawn out part 101 guiding a lead wire to electrically connect the printed circuit substrate 3 to an external power source is provided at one side of the housing 10. The upper protrusion 102 for accommodating the bearing holder 5 is formed in the center of the upper portion of the housing 10. The shaft 20 may protrude from the upper portion in the center of the upper protrusion 102. The upper bearing 4 supporting the upper portion side of the shaft 20 to be rotatable is forcibly inserted in the bearing holder 5 and installed therein, and the bearing holder 5 is installed inside the upper protrusion 102.

The inner space 103 forming the inner space of the housing 10 has a shape open to the lower portion side, and the rotor 2 coupled to the shaft 20 is placed in the inner space 103 to rotate. The portion open to the lower portion side of the inner space 103 is covered by the bearing cover 8. The lower bearing 7 supporting the lower portion of the shaft 20 is coupled to the center of the bearing cover 8.

Fig. 4 is an exploded perspective view of a rotor 2 of the motor according to the present invention. Fig. 5 is a perspective view illustrating the coupling of the rotor 2, the shaft 20 and the

bearings

4 and 7 of the motor according to the present invention. Referring to Fig. 4 and Fig. 5 together, the rotor 2 of the present invention comprises a rotor main body 21 and a magnet 22.

The rotor main body 21 is made of an insulating material such as rubber and has a cylindrical shape. Preferably, the magnet 22 is coupled to an outer circumferential side of the rotor main body 21 and has a ring shape. A shaft coupling hole 21A penetrating vertically to be coupled to the shaft 20 is formed in the center of the rotor main body 21. A plurality of balance holes 21B formed to penetrate axially may be formed around the shaft coupling hole 21A. The balance hole 21B serves the role of preventing heating inside the rotor allowing smooth rotation while the rotor rotates. The number of balance holes 21B is not particularly limited, but preferably balance holes 21B are formed symmetrically with respect to the shaft 20. Preferably, the rotor main body 21 is manufactured by insert injection molding having the shaft 20 and the magnet 22 placed in an insert injection mold.

An insulating tube 20A made of an insulating material may be coupled to an outer circumference of the shaft 20. Preferably, the insulating tube 20A may be made of the same material as the rotor main body 21, and more preferably may be manufactured integrally with the rotor main body 21 in the insert injection mold. Preferably, the insulating tube 20A is formed to cover the shaft 20 from a portion coupled to the upper bearing 4 to a portion coupled to the lower bearing 5.

As a result of comparing the motor according to the present invention manufactured as above with the conventional motor, electric erosion of the bearing may be prevented without a ground structure, and noise and vibration of the motor may be reduced. Fig. 6 and Fig. 7 illustrate experimental results comparing noise and vibration.

Fig. 6 is a graph illustrating the result of measuring noise of the motor 100 according to the present invention in comparison with the conventional motor; and Fig. 7 is a graph illustrating the result of measuring vibration.

In order to measure noise and vibration, the motor 100 according to the present invention has a rotor main body 21 made of rubber formed by insert injection mold, and an insulating tube 20A is not applied thereto. The motor according to prior art which is to be compared with the above has a rotor made of ferrite magnet. Fig. 6(a) is a graph illustrating the results measuring the noise using the motor according to the present invention, and Fig. 6(b) is a graph illustrating the results measuring the noise using the conventional motor. From the results, it can be understood that the noise of the motor according to the present invention was reduced by about 1.2 dB as compared to the conventional motor. Also, Fig. 7(a) is a graph illustrating the results measuring the vibration using the motor according to the present invention, and Fig. 7(b) is a graph illustrating the results measuring the vibration using the conventional motor. From the results, it can be understood that the vibration of the motor according to the present invention was reduced by about 16.9 um/s as compared to the conventional motor.

The detailed description of the present invention described as above simply explains examples for helping understand the present invention, but does not intend to limit the scope of the present invention. The scope of the present invention is defined by the accompanying claims. Additionally, it should be construed that simple modifications or changes of the present invention fall within the scope of the present invention.

Claims

A motor, comprising:

a stator 1 comprising an upper insulator 11, a stator core 12 and a lower insulator 13;

a rotor 2 installed opposite to the stator 1 to rotate;

a shaft 20 coupled to the rotor 2 to rotate together therewith; and

a printed circuit substrate 3 electrically connected to the stator 1,

wherein the rotor 2 comprises a rotor main body 21 and a magnet 22 coupled to an outer circumferential surface of the rotor main body 21, and

the rotor main body 21 is made of an insulating material.
The motor of claim 1, wherein the rotor main body 21 is formed by injection molding having the shaft 20 and the magnet 22 placed in an insert injection mold.
The motor of claim 1, wherein a plurality of balance holes 21B formed to penetrate axially are formed symmetrically with respect to the shaft 20 on the rotor main body 21.
The motor of claim 1, wherein the shaft 20 is enclosed with an insulating tube 20A.
The motor of claim 4, wherein the insulating tube 20A covers the shaft 20 from a portion coupled to an upper bearing 4 to a portion coupled to a lower bearing 7.