KR20110045702A - A brushless DC motor for sensorless type - Google Patents

Abstract

PURPOSE: A sensorless brushless DC motor is provided to reduce eddy currents by minimizing the leakage flux of a rotor magnet. CONSTITUTION: In a sensorless brushless DC motor, a supporting member(130) supports a shaft(110). A stator(150) is fixed to the supporting member. The stator comprises a core with a coil wounded therein. A rotor case(170) is rotated with the shaft. The rotor case comprises a rotor magnet(190) and covers the lower part of the rotor magnet.

Description

A brushless DC motor for sensorless type

The present invention relates to a sensorless brushless DC motor.

In general, a brushless DC motor (brushless DC motor) is to remove the mechanical contact such as a brush, commutator and the like provided to alternately supply the current from the DC motor, instead of having an electronic commutator, also referred to as a no-commutator motor It is called.

1 is a cross-sectional view of a brushless DC motor according to a conventional example.

As shown in FIG. 1, the brushless DC motor according to the related art is disposed near the stator 10 having the coil 14 wound around the core 12 and the outer circumference thereof, and has a rotor magnet 30 on the inner circumferential surface thereof. And a rotor case 20 for supporting the disk D. At this time, the base plate 40 between the stator 10 and the rotor magnet 30 has a Hall sensor 50 used to measure the characteristics of the motor, such as the rotational speed by recognizing a change in the magnetic flux from the rotor magnet 30 Equipped.

However, in recent years, in addition to miniaturization of brushless DC motors, a sensorless circuit in which an optical disk drive (ODD) performs a function of the hall sensor 50 without using the hall sensor 50 is used. (sensorless) type brushless DC motors have been proposed. In the senseless type, since the magnetic flux from the rotor magnet 30 toward the hall sensor 50 is only an unnecessary leakage magnetic flux, a method for preventing the occurrence of leakage magnetic flux is required. This is not being tried. Since the leakage magnetic flux generates an eddy current and lowers the rotational efficiency of the rotor case 20, a solution for this problem will be urgently required.

The present invention has been made to solve the above problems, an object of the present invention is to provide a sensorless type brushless DC motor that can reduce the leakage magnetic flux of the rotor magnet.

A sensorless brushless DC motor according to a preferred embodiment of the present invention includes a shaft, a support member rotatably supporting the shaft, a stator fixed to the support member, and a coil wound around a core, and the shaft and Rotating integrally, the rotor magnet is coupled to the inner peripheral surface to face the stator, characterized in that it comprises a rotor case formed to cover the lower portion of the rotor magnet.

Here, the rotor case, the central portion is inserted into the shaft and the disc portion extending in the outward direction of the shaft, bent downward from the end of the disc portion, the annular edge portion is coupled to the rotor magnet on the inner peripheral surface, and the And a lower shield portion which is bent inward from the end of the annular rim toward the shaft and covers the lower portion of the rotor magnet.

The rotor case may be formed by press working.

In addition, the rotor case is characterized in that formed of a magnetic or ferromagnetic material.

In addition, it characterized in that it further comprises an upper shield member for covering the upper portion of the rotor magnet.

Sensorless brushless DC motor according to another embodiment of the present invention, a shaft, a support member for rotatably supporting the shaft, a stator is fixed to the support member, the coil wound around the core, the shaft and Rotating integrally, characterized in that it comprises a rotor case coupled to the rotor magnet to face the stator on the inner circumferential surface, and a lower shield member for covering the lower portion of the rotor magnet.

Here, the rotor case, the central portion is inserted into the shaft and the disc portion extending in the outward direction of the shaft, and the bent downward from the end of the disc portion, the inner circumferential surface of the lower portion is covered by the lower shield member It characterized in that it comprises an annular edge coupled to the rotor magnet.

In addition, the lower shield member is characterized in that formed of a magnetic or ferromagnetic material.

The lower shield member may be bonded or press-fitted to the rotor case or the rotor magnet.

In addition, it characterized in that it further comprises a shield member for covering the upper and outer peripheral surface of the rotor magnet.

Sensorless type brushless DC motor according to another embodiment of the present invention, a shaft, a support member for rotatably supporting the shaft, a stator fixed to the support member, the coil wound around the core, and the shaft Rotate integrally with, but having a seating groove on the inner circumferential surface, characterized in that it comprises a rotor case is coupled to the rotor magnet to face the stator in the seating groove.

Here, the inner wall of the rotor case forming the mounting groove is characterized in that the mounting groove has a thickness corresponding to the rotor magnet so as to cover the upper and lower portions of the rotor magnet.

In addition, the rotor case is characterized in that formed of a magnetic or ferromagnetic material.

The features and advantages of the present invention will become more apparent from the following detailed description based on the accompanying drawings.

Prior to this, terms and words used in the present specification and claims should not be construed in a conventional and dictionary sense, and the inventor may appropriately define the concept of a term in order to best describe its invention The present invention should be construed in accordance with the spirit and scope of the present invention.

According to the present invention, since the rotor case includes a lower shield portion covering the lower portion of the rotor magnet, by minimizing the magnetic flux leaking from the rotor magnet, it is possible to reduce the generation of eddy currents and to prevent a decrease in rotational efficiency. At this time, since the lower shield portion is integrally formed by pressing the rotor case, no additional member is required, and the structure and the process are simplified.

In addition, according to the present invention, by providing a shield member to cover the upper and / or outer peripheral surface including the lower portion of the rotor magnet, it is possible to reduce the leakage flux and improve the concentration of magnetic flux toward the stator.

In addition, according to the present invention, since the shielding member and the magnetic flux can be formed through the shield member, the degree of freedom in selecting a material for the rotor case can be increased. For example, by forming a rotor case made of a light resin material, it is possible to achieve a light weight of a sensorless type brushless motor while reducing leakage flux compared with the conventional structure.

In addition, according to the present invention, by forming a guide groove into which the rotor magnet is coupled to the rotor case, the inner wall of the rotor case forming the guide groove can shield the magnetic flux leaking from the rotor magnet. This makes it possible to shield the leakage magnetic flux and at the same time reduce the thickness.

The objects, specific advantages and novel features of the present invention will become more apparent from the following detailed description and the preferred embodiments associated with the accompanying drawings. In the present specification, in adding reference numerals to the components of each drawing, it should be noted that the same components as possible, even if displayed on different drawings have the same number as possible. In describing the present invention, when it is determined that the detailed description of the related known technology may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

 Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a cross-sectional view of a sensorless type brushless DC motor according to a first embodiment of the present invention. Hereinafter, the sensorless type brushless DC motor 100a according to the present embodiment will be described with reference to the drawings.

As shown in FIG. 2, the sensorless brushless DC motor 100a according to the present embodiment includes a shaft 110, a support member 130, a stator 150, and a rotor magnet 190. It is configured to include a rotor case 170, the rotor case 170 is formed so as to cover the lower portion of the rotor magnet 190, proposes a structure to minimize the magnetic flux leakage from the rotor magnet 190 in the downward direction.

The shaft 110 is formed in a cylindrical shape having a predetermined diameter, and rotates by an electromagnetic force generated by the interaction of the rotor magnet 190 and the stator 150, and the rotor case 170 fixed to an upper portion thereof. Rotate integrally

The support member 130 is for supporting the components constituting the brushless DC motor 100a as a whole, including the shaft 110, and a bearing portion for rotatably supporting the shaft 110 and a support portion for supporting the shaft 110. It consists of.

 The bearing part includes a bearing 132 for supporting the shaft 110 in a radial direction and a thrust washer 134 for supporting the shaft 110 in an axial direction. Here, the bearing 132 is formed in a hollow cylindrical shape having a hollow portion in which the shaft 110 is accommodated, and rotatably supports the shaft 110 by a fluid interposed between the shaft 110. In addition, the thrust washer 134 is disposed under the shaft 110, to rotatably support the lower end of the shaft (110).

The support unit includes a bearing holder 136 for supporting the bearing 132, a support 142 for supporting the thrust washer 134, and a bearing holder 136 to form a component constituting the brushless DC motor 100a. It consists of a base plate 144 that supports as a whole.

The bearing holder 136 is formed in a hollow cylindrical shape so that the inner circumferential surface supports the outer circumferential surface of the bearing 132. At this time, the outer circumferential surface of the bearing holder 136 is engaged with a hooking part 172c provided in the disc portion 172 of the rotor case 170 to protrude to prevent injuries of the rotor case 170. 138, and is formed stepped so as to have a seating surface 140 on which the stator 150 is seated.

The support 142 is disposed under the thrust washer 134 to support the thrust washer 134, and is supported by a caking or spinning process inside the bearing holder 136.

The base plate 144 supports the components of the brushless DC motor 100a as a whole, and the brushless DC motor 100a is installed to be fixed to a device such as a hard disk drive. The bearing holder 136 The outer side of the caulking or the spun process is bonded support. Here, a circuit board (not shown) on which an electronic device such as an encoder, a connector, and a passive device is mounted is coupled to the upper portion of the base plate 144.

The stator 150 is configured to form an electric field by receiving an external power source. The stator 150 includes a core 152 and a coil 154 wound around the core 152. When a current is supplied to the coil 154, the armature magnetic flux is excited along the supplied current, and the armature magnetic flux is generated by linking with the magnetic flux generated by the rotor magnet 190, thereby causing the rotor case 170 to rotate. Done. Here, the stator 150 is fixedly coupled to the seating surface 140 of the bearing holder 136.

The rotor case 170 is a configuration in which a central portion is inserted into the shaft 110 and rotates together with the shaft 110. For example, a disc portion is inserted into the shaft 110 and extends in an outward direction of the shaft 110. 172, an annular edge portion 174 bent downward from an end of the disc portion 172, and a rotor magnet 190 coupled to an inner circumferential surface thereof, and a shaft 110 from an end of the annular edge portion 174. It is configured to include a lower shield portion 176 that is bent inwardly toward the (), and covers the lower portion of the rotor magnet 190.

The rotor case 170 having such a structure can be easily formed through a bending process by press working. In this way, by pressing the rotor case 170 without a separate additional member, it can be processed to include a lower shield portion 176 to perform the leakage flux shielding function of the rotor magnet 190.

Here, a chucking assembly 172a is provided at the center of the upper surface of the disc portion 172 to chuck the mounted disk D, and the outer surface of the disc 172 prevents slipping of the disk D. The slip preventing member 172b is provided, and the lower surface may include an engaging portion 172c and / or a suction magnet 172d for preventing an injury of the rotor case 170 during rotation. Here, the engagement portion 172c is engaged with, for example, the protrusion 138 formed in the bearing holder 136 to prevent the injuries of the rotor case 170, and the suction magnet 172d is the base plate ( The magnetic force of the bearing 132, the bearing holder 136, and / or the stator 150 fastened to the 144 may serve to prevent the injury of the rotor case 170. Meanwhile, although the disk D is mounted on the rotor case 170 in the drawing, it may be possible to separately provide a turntable for mounting a disk, which will also be included in the present invention. .

In addition, a rotor magnet 190 that generates an electromagnetic force by the action of the stator 150 is coupled to the inner circumferential surface of the annular edge portion 174. At this time, the rotor magnet 190 serves to generate a force for rotating the rotor case 170 by the action with the stator 150, and has a circular ring structure in which magnetic poles are alternately magnetized in the circumferential direction.

The lower shield portion 176 is bent inward from the end of the annular edge portion 174 toward the shaft 110 to cover the lower portion of the rotor magnet 190 so as to cover the magnetic flux leaking toward the base plate 144. By shielding, the magnetic flux directed to the stator 150 is concentrated. In order to achieve such a function, the rotor case 170 is preferably formed of a ferromagnetic substance such as an iron plate, a magnetic material such as magnetic stainless steel, or a silicon steel sheet, preferably a ferromagnetic material having a specific permeability of 1 or more. . At this time, since the lower shield portion 176 is formed to cover the lower portion of the rotor magnet 190, in addition to the leakage flux shielding function as described above, due to the magnetic attraction force of the rotor magnet 190 and the base plate 144 In addition to preventing the rotational resistance to occur, it serves to increase the bearing capacity for the rotor case 170 of the rotor magnet 190.

3 is a cross-sectional view illustrating a modification of the sensorless type brushless DC motor shown in FIG. 2. Hereinafter, the sensorless brushless DC motor 100a 'according to the present modification will be described with reference to this.

As shown in FIG. 3, the sensorless brushless DC motor 100a ′ according to the present modification leaks from the upper portion of the rotor magnet 190 in the brushless DC motor 100a according to the first embodiment. In order to minimize the magnetic flux, the upper shield member 180a is further provided on the upper portion of the rotor magnet 190. By employing such a structure, by shielding not only the magnetic flux leaking to the lower portion of the rotor magnet 190 but also the magnetic flux leaking to the top, it is possible to minimize the leakage magnetic flux. Here, in order to achieve the shielding function, the upper shield member 180a is preferably formed of a magnetic material such as magnetic stainless steel or a ferromagnetic material such as silicon steel sheet, preferably a ferromagnetic material having a specific permeability of 1 or more.

4 is a schematic cross-sectional view of a sensorless brushless DC motor according to a second preferred embodiment of the present invention. Hereinafter, the sensorless type brushless DC motor 100b according to the present embodiment will be described.

As shown in FIG. 4, the sensorless brushless DC motor 100b according to the present embodiment does not include the shield portion 176 by bending the rotor case 170 as in the first embodiment. A lower shield member 180b covering the lower portion of the rotor magnet 190 is provided separately.

Here, the lower shield member 180b is formed of a magnetic material such as magnetic stainless steel or a ferromagnetic material such as silicon steel sheet, preferably a ferromagnetic material having a specific permeability of 1 or more so as to perform a leakage magnetic flux shielding function, and the rotor magnet 190 or the rotor The lower surface of the case 170 is bonded or press-bonded using an adhesive or the like, or is attached by magnetic force of the rotor magnet 190.

On the other hand, since the lower shield member 180b is provided in the present embodiment, the rotor case 170 may not be formed of a magnetic material or a ferromagnetic material as in the first embodiment.

FIG. 5 is a cross-sectional view illustrating a modification of the sensorless brushless DC motor shown in FIG. 4. Hereinafter, the sensorless type brushless DC motor 100b 'according to the present modification will be described with reference to this.

As shown in FIG. 5, the sensorless brushless DC motor 100b ′ according to the present modification has a lower, upper, and / or lower surface except for an inner circumferential surface of the rotor magnet 190 facing the stator 150. Alternatively, the shield member 180c is provided to cover the outer circumferential surface, and the structure has a structure for minimizing the leakage magnetic flux of the rotor magnet 190. Meanwhile, although the shield member 180c is illustrated as being integrally formed in FIG. 5, it is also possible to be provided to cover each of the lower, upper, and / or outer circumferential surfaces, and may be selectively provided as necessary. something to do.

Here, the shield member 180c covering the outer circumferential surface of the rotor magnet 190 forms a magnetic path by reducing the magnetic resistance when magnetic flux from one magnetic pole of the outer circumferential surface of the rotor magnet 190 enters the other magnetic pole. Minimize leakage magnetic flux

Meanwhile, in the present embodiment, since the shield member 180c covers the lower part, the upper part, and the outer circumferential surface of the rotor magnet 190 to form a magnetic path, the material of the rotor case 170 can be freely selected. For example, it may be possible to form the rotor case 170 using a resin material which is inexpensive and lightweight.

6 is a schematic cross-sectional view of a sensorless type brushless DC motor according to a third embodiment of the present invention. Hereinafter, the brushless DC motor 100c according to the present embodiment will be described.

As shown in FIG. 6, in the sensorless brushless DC motor 100c according to the present embodiment, a guide groove 175 is formed in an annular edge portion 174 of the rotor case 170, and a rotor magnet ( 190 is characterized in that is inserted into the guide groove 175. Here, since the guide groove 175 has a size corresponding to the thickness of the rotor magnet 190, the inner wall of the annular rim portion 174 forming the guide groove 175 is a magnetic flux leaking from the rotor magnet 190 To perform the function of shielding. The guide groove 175 also prevents the thickness increase due to the rotor magnet 190 or the additional shield member, and increases the coupling force of the rotor magnet 190 to the rotor case 170.

In this case, the rotor case 170 is preferably formed of a magnetic material such as magnetic stainless steel or a ferromagnetic material such as silicon steel sheet, preferably a ferromagnetic material having a specific permeability of 1 or more so as to perform a leakage magnetic flux shielding function.

Although the present invention has been described in detail through specific embodiments, this is for explaining the present invention in detail, and the sensorless type brushless DC motor according to the present invention is not limited thereto. It will be apparent that modifications and improvements are possible by those skilled in the art.

All simple modifications and variations of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be apparent from the appended claims.

1 is a cross-sectional view of a brushless DC motor according to a conventional example.

2 is a cross-sectional view of a sensorless type brushless DC motor according to a first embodiment of the present invention.

3 is a cross-sectional view illustrating a modification of the sensorless type brushless DC motor shown in FIG. 2.

4 is a schematic cross-sectional view of a sensorless brushless DC motor according to a second preferred embodiment of the present invention.

FIG. 5 is a cross-sectional view illustrating a modification of the sensorless brushless DC motor shown in FIG. 4.

6 is a schematic cross-sectional view of a sensorless type brushless DC motor according to a third embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

110: rotating shaft 130: support member

132: bearing 134: thrust washer

136: bearing holder 142: support

144: base plate 150: stator

152: core 154: coil

170: rotor case 172: disc part

174: annular edge portion 175: seating groove

176: lower shield portion 180a, 180b, 180c: shield member

Claims (13)

shaft; A support member rotatably supporting the shaft; A stator fixed to the support member and having a coil wound around the core; And A rotor case which is integrally rotated with the shaft and coupled to a rotor magnet to face the stator on an inner circumferential surface thereof, the rotor case being configured to cover a lower portion of the rotor magnet; Sensorless type brushless DC motor comprising a. The method according to claim 1, The rotor case, A disc portion having a central portion inserted into the shaft and extending in an outward direction of the shaft; An annular edge portion bent downward from the end of the disc portion, the rotor magnet coupled to an inner circumferential surface thereof; And A lower shield portion which is bent inward from the end of the annular rim toward the shaft to cover the lower portion of the rotor magnet; Sensorless type brushless DC motor comprising a. The method according to claim 2, The rotor case is a brushless DC motor of a sensorless type, characterized in that formed by press working. The method according to claim 1, The rotor case is a brushless DC motor of a sensorless type, characterized in that formed of a magnetic body or ferromagnetic material. The method according to claim 1, The sensorless type brushless DC motor further comprises an upper shield member covering an upper portion of the rotor magnet. shaft; A support member rotatably supporting the shaft; A stator fixed to the support member and having a coil wound around the core; A rotor case rotatably integrated with the shaft, the rotor magnet being coupled to the inner circumferential surface so as to face the stator; And A lower shield member covering a lower portion of the rotor magnet; Sensorless type brushless DC motor comprising a. The method according to claim 6, The rotor case, A disc portion having a central portion inserted into the shaft and extending in an outward direction of the shaft; And An annular edge portion bent downward from an end of the disc portion, the rotor magnet coupled to a lower portion of the inner circumferential surface thereof covered by the lower shield member; Sensorless type brushless DC motor comprising a. The method according to claim 6, The lower shield member is a sensorless brushless DC motor, characterized in that formed of a magnetic body or ferromagnetic material. The method according to claim 6, And the lower shield member is bonded or press-fitted to the rotor case or the rotor magnet. The method according to claim 6, The sensorless brushless DC motor further comprises a shield member covering the upper and outer circumferential surface of the rotor magnet. shaft; A support member rotatably supporting the shaft; A stator fixed to the support member and having a coil wound around the core; And A rotor case which rotates integrally with the shaft and has a seating groove on an inner circumferential surface thereof, and a rotor magnet is inserted and coupled to face the stator in the seating groove; Sensorless type brushless DC motor comprising a. The method of claim 11, And the seating groove has a thickness corresponding to the rotor magnet so that an inner wall of the rotor case forming the seating groove covers the upper and lower portions of the rotor magnet. The method of claim 11, The rotor case is a brushless DC motor of a sensorless type, characterized in that formed of a magnetic body or ferromagnetic material.

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