JP4325559B2 - Brushless motor - Google Patents

Description

  The present invention mainly relates to a brushless motor (hereinafter abbreviated as a motor) used for driving a disk in an apparatus for recording and reproducing information such as CD-ROM (R / RW) and DVD ± (R / RW). In particular, the present invention relates to a motor bearing device.

  In recent years, a motor that rotates and drives a disk that records and reproduces information such as CD-ROM (R / RW) and DVD ± (R / RW) is oil-impregnated from a porous metal due to the demand for low cost. Metal is used as a general bearing means (see the prior art in Patent Document 1).

  FIG. 5 is a cross-sectional view showing the structure of a conventional motor. In FIG. 5, 51 is an output shaft for transmitting rotation, 52 is an oil-impregnated metal, 53 is a housing for retaining the oil-impregnated metal, 54 is a rotor, 55 is a stator, and 56 is a bracket made of a printed circuit board. The motor obtains a rotational force by a magnetic force generated sequentially between the rotor 54 and the stator 55, and an output shaft 51 fixed at the center of the rotor 54 is fixed to the oil-impregnated metal 52 and the bracket 56. It is supported rotatably by a bearing device composed of the housing 53 and transmits rotation with high accuracy to the outside.

  However, along with the increase in the speed of recording and reproducing media equipment such as CD-ROM (R / RW) and DVD ± (R / RW), the margin of long-term reliability of the bearing means is reduced, and the bearing means The necessity of the oil retaining structure of the oil-impregnated metal that constitutes the material and the countermeasures against scattering of the oil contained in the oil-impregnated metal have become important issues.

  That is, in the conventional configuration as described above, since the outer periphery of the oil-impregnated metal is hermetically sealed by the housing, the pressure applied to the end face of the oil-impregnated metal due to the pressure generated at the contact portion between the output shaft and the oil-impregnated metal when the output shaft rotates. Increases, and the oil blows out to the oil-impregnated metal end face, and particularly adheres to the inner top face on the top face side of the rotor. Furthermore, the oil adhering to the rotor diffuses in the radial direction on the inner top surface of the rotor due to centrifugal force and does not return to the oil-impregnated metal, so the oil retained in the oil-impregnated metal decreases and normal lubrication does not work. There was a problem that accurate rotation transmission was not performed.

  Therefore, the applicant provides a motor bearing device that can reduce the amount of oil blown to the oil-impregnated metal end face while maintaining cost reduction and can maintain accurate rotation transmission for a long time, and an excellent motor equipped with this device. For this purpose, the pressure on the end face of the oil-impregnated metal is reduced by providing a portion that does not seal the outer periphery of the oil-impregnated metal on the top surface side of the rotor of the press-fit portion of the oil-impregnated metal and housing. Proposed a motor with a bearing configuration that can reduce the number of blowouts and maintain accurate rotation transmission for a long time (see, for example, Patent Document 1).

  The configuration of this motor is shown in FIG. In FIG. 6, 61 is an output shaft, 62 is an oil-impregnated metal, 65 is a bracket, 63 is a housing, and 64 is a rotor. The housing 63 is formed integrally with the bracket 65, and the dimension of the oil retaining metal holding portion 66 is set to 1/2 to 4/5 of the total length of the oil retaining metal 62 on the top surface side of the rotor 64. The outer periphery of the oil retaining metal 62 on the 64 side is open. With this configuration, oil can be prevented from blowing out to the end face of the oil-impregnated metal, and the bracket and the housing are integrally formed, so that the number of motor components can be reduced.

  However, along with the drastic increase in speed of equipment such as CD-ROM (R / RW) and DVD ± (R / RW), the radial and bearing end face pressures inside the bearing due to disc imbalance are higher than expected. It became a thing. In the configuration of the second conventional example, there has been a problem that the oil flows out from the outer periphery of the oil-impregnated metal released by this pressure and the bearing end surface, making it difficult to meet the demand for longer life.

Therefore, the applicant attaches the cylindrical cover to the open portion of the oil-impregnated metal outer periphery with a gap between the end surface of the oil-impregnated metal and the outer periphery, so that the oil extruded from the end surface of the oil-impregnated metal is scattered during rotation. Even so, the cover becomes a wall for preventing oil scattering, and further, the oil of the oil-impregnated metal scattered in the cylindrical portion by the gap between the outer periphery of the oil-impregnated metal and the cylindrical portion of the cover passes through the gap. An oil recovery structure for returning to the oil-impregnated metal has been proposed (see, for example, Patent Document 2).

  The configuration of the motor of the third conventional example is shown in FIG. In FIG. 7, 71 is an output shaft, 72 is an oil-impregnated metal, 73 is a rotor, and 76 is a bracket in which a burring portion 75 and a motor mounting base portion 74 are integrally formed. An oil-impregnated metal 72 is fixed to the inner peripheral part of the burring part 75 of the bracket 76 in a state where a part of the outer periphery is released, and a stator core 77 is fixed to the outer peripheral part of the burring part 75. A cylindrical metal holder 70 (cover) comprising a cylindrical portion 70a having a gap with the end surface and outer periphery of the oil-impregnated metal 72 and an end surface portion 70b extending from the one end portion of the cylindrical portion toward the inner diameter side is provided. The end surface of the burring portion 75 of the bracket 76 and the other end surface of the cylindrical portion 70a of the metal holder 70 are press-fitted and fixed to the inner peripheral portion of the stator core 77.

  However, in the configuration of the third conventional example, it is difficult to finish each end face of the metal holder 70 (cover) and the burring portion of the bracket 76 to an ideal plane. It is inevitable that a minute gap is generated on the surface. Further, since the metal holder 70 (cover) is fixed to the inner diameter of the stator core 77 formed by the laminated iron core, oil flows out from the gap between the butted surfaces into the gap between the iron cores of the laminated iron core by capillary action. There was a fear. For this reason, there has been a problem that during operation of the motor, oil of the oil-impregnated metal gradually flows out from this gap, and it is difficult to maintain sufficient reliability for a long time.

Further, in order to rotate the disk at a high speed, the current supplied to the motor is greatly increased, and the heat generated in the coil wound around the stator core 77 is transmitted from the stator core 77 to the oil-impregnated metal 72 via the metal holder 70 (cover). Also, there has been a problem of increasing the bearing temperature and reducing the reliability of the bearing.
JP-A-9-294350 (page 2-3, FIG. 6, FIG. 7) JP 2002-262540 A (Page 4-5, FIG. 1)

  The present invention solves such a conventional problem, and a motor bearing device capable of maintaining accurate rotation transmission for a long time even at high speed rotation, and an excellent motor equipped with this device at low cost. The purpose is to provide.

  In order to solve the above-mentioned problems, the present invention forms a metal holder that covers the outer periphery and end face of the oil-impregnated metal exposed from the burring portion of the bracket, and is formed of an insulating resin integrally with the insulating portion (insulator) of the stator core, The brushless motor is configured to fix the stator core to the bracket via the metal holder.

According to the first aspect of the present invention, since the outer periphery and end face of the oil-impregnated metal exposed from the burring portion of the bracket are covered with the metal holder, oil leakage from the oil-impregnated metal can be prevented. In addition, since the metal holder is formed integrally with the insulating portion (insulator) of the stator core with an insulating resin, the metal holder can be attached easily and reliably. Furthermore, since the stator core is fixed to the bracket via a metal holder made of resin, the thermal resistance between the stator core and the bracket and between the stator core and the oil-impregnated metal is increased, and the bearing temperature rise due to heat generation of the coil wound around the stator core is suppressed. The advantageous effect that it can be obtained is obtained.
In addition, since the stator core is fixed to the step portion formed at the boundary between the metal holding portion and the enlarged diameter portion of the burring portion of the bracket via the wing portion of the metal holder, all the burring portions of the bracket are connected to the stator core. Inductive current generated in the stator core due to abrupt changes in the current supplied to the coil that is electrically insulated and wound around the stator core (for example, during PWM drive) flows into the bracket, which is harmful to the equipment on which the motor is mounted. The advantageous effect that the influence can be suppressed is obtained.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

(Embodiment 1)
1 to 3 show a first embodiment of the present invention. FIG. 1 is a sectional view showing the structure of a motor according to Embodiment 1 of the present invention. In FIG. 1, reference numeral 1 denotes a shaft for transmitting rotation. Reference numeral 2 denotes a frame, in which a ring-shaped rotor magnet 3 magnetized in the circumferential direction is press-fitted or bonded and fixed to the inner periphery of the frame 2. Then, burring is applied to the center of the frame 2 and the shaft 1 is directly press-fitted. In this way, the rotor (rotor) 10 is composed of the shaft 1, the frame 2, and the rotor magnet 3.

  The bracket 4 is made of a magnetic material and is formed by a pressing method, and has a stepped burring portion 11 in a substantially central portion. The burring portion 11 functions as a bearing housing for housing the bearing means. In the bracket 4, a burring portion 11 constituting a bearing housing and an attachment base portion 12 for attaching a motor are integrally formed. In this way, since the burring portion 11 and the mounting base portion 12 are integrally formed, the squareness of the mounting base portion 12 with respect to the burring portion 11 is formed with high accuracy. It becomes easy.

  The burring part 11 of the bracket 4 includes a metal holding part 11a into which the oil-impregnated metal 5 is press-fitted and fixed, an enlarged diameter part 11b having an outer diameter larger than the outer diameter of the metal holding part 11a, and a metal holding part 11a. A step portion 11c is formed at the boundary with the enlarged diameter portion 11b. The shaft 1 is rotatably supported by the oil-impregnated metal 5.

  On the other hand, the stator core 8 is formed by laminating silicon steel plates, and is a stator core having a plurality of salient poles 8a as shown in FIG. A hole 8 b is formed in the center of the stator core 8. 13 is a metal holder made of insulating resin, and FIG. 2 shows a perspective view thereof. A cylindrical portion 13a having an outer diameter that is the same as or slightly smaller than the inner diameter of the hole 8b of the stator core 8, an end surface portion 13b extending from the one end in the axial direction of the cylindrical portion 13a to the inner diameter side, and the other end Further, the stator core 8 includes a plurality of blade portions 13c extending in a direction perpendicular to the shaft so as to cover one end face in the axial direction of each salient pole 8a. As shown in FIG. 3, the cylindrical portion 13 a of the metal holder 13 is inserted into the central hole 8 b of the stator core 8 from the end surface portion 13 b side, and the blade portion 13 c of the metal holder 13 is inserted in the axial direction of each salient pole 8 a of the stator core 8. A part of the outer peripheral surface of the cylindrical portion 13a is fixed to the inner peripheral surface of the hole 8b of the stator core 8 by press-fitting, bonding or the like. An insulating member 14 is provided separately from the blade portion 13c so as to cover the end surface of each salient pole 8a of the stator core 8 opposite to the side covered with the blade portion 13c of the metal holder 13, and the blade portion 13c and the insulating member 14 are insulated. A stator coil (copper wire) 6 (not shown) is wound around the stator core 8 via the member 14 to form a stator winding assembly 15 (armature).

The stator winding assembly 15 assembled as described above is attached to the bracket 4 in which the oil-impregnated metal 5 is fixed to the burring portion 11. Specifically, the inner peripheral surface of the cylindrical portion 13a of the metal holder 13 is oil-impregnated in the end surface portion 13b of the metal holder 13 so as to cover the outer peripheral surface 5a from the end surface 5b side of the oil-impregnated metal 5 exposed to the outside of the burring portion 11. End face 5b of metal 5
Is inserted into the oil-impregnated metal 5 until facing each other with a slight gap, and is fixed to the outer peripheral surface 11d of the metal holding portion 11a of the burring portion 11 of the bracket 4 by press fitting, adhesion or the like.

  In the present embodiment, the stator core 8 is fixed to the step portion 11c formed in the burring portion 11 of the bracket 4 through the blade portion 13c of the metal holder 13 as described above.

  Further, a printed circuit board 7 on which at least a part of a circuit for driving and controlling the motor is mounted is fixed to the mounting base portion 12 of the bracket 4 by adhesion or the like. A winding end of the stator coil 6 of the stator winding assembly 15 is wired on the printed circuit board 7 to constitute a stator assembly 9.

  With the above configuration, since the outer periphery 5a and the end surface 5b of the oil-impregnated metal 5 exposed from the burring portion 11 of the bracket 4 are covered with the metal holder 13, oil leakage from the oil-impregnated metal 5 can be prevented. In addition, the metal holder 13 is integrally formed with an insulating resin so that the wings 13c, which are the insulating portions (insulators) of the salient poles 8a of the stator core 8, can be attached easily and reliably. It can be carried out. Furthermore, since the stator core 8 is fixed to the bracket 4 via the metal holder 13 made of resin, the thermal resistance between the stator core 8 and the bracket 4 and between the stator core 8 and the oil-impregnated metal 5 is increased, and the coil 6 wound around the stator core 8 An advantageous effect that an increase in bearing temperature due to heat generation can be suppressed is obtained.

  By the way, when speeding up a device such as a CD-ROM (R / RW) or a DVD ± (R / RW), a PWM drive method using a carrier exceeding an audible frequency is generally adopted so as not to affect the noise. Therefore, a large current having a high frequency flows through the coil 6 wound around the stator core 8. As a result, an induced current is generated in the stator core 8, and when the stator core 8 and the bracket 4 are electrically connected as in the above-described conventional example, the device on which the motor is mounted through the mounting base portion 12 of the bracket 4. There was a risk that the induced current would flow through the chassis, resulting in harmful noise. However, according to the configuration of the first embodiment of the present invention, all the burring portions 11 of the bracket 4 are electrically insulated from the stator core 8 and the current supplied to the coil 6 wound around the stator core 8 is rapidly increased. It can be suppressed that induced current generated in the stator core 8 due to a change (for example, during PWM driving) flows into the bracket 4 via the burring processing portion 11 and affects the device on which the motor is mounted as harmful noise.

  Next, the shaft 1 of the rotor 10 is inserted into the oil-impregnated metal 5 of the stator assembly 9 from the burring portion 11 side, and a ring made of a magnetic material from the tip 1a opposite to the side where the frame 2 of the shaft 1 is press-fitted. A cylindrical thrust ring 16 is fixed at a predetermined position by press fitting or the like. Then, a cup-shaped thrust cup 17 made of a magnetic material is pressed into a predetermined position on the inner periphery of the enlarged diameter portion 11b of the burring portion 11 of the bracket 4 from the direction opposite to the protruding direction of the burring portion 11. Secure to. On the bottom surface of the thrust cup 17, a thrust receiver 18 having excellent wear resistance is disposed in advance at a position in contact with the tip 1 a of the shaft 1, enabling stable rotation accuracy for a long time, and the thrust ring 16. A ring-shaped thrust attracting magnet 19 is arranged in advance at a position opposite to, and the thrust direction displacement of the rotor 10 is displaced by a magnetic attracting force acting between the thrust attracting magnet 19 and the thrust ring 16 made of a magnetic material. Stabilized. Since the thrust cup 17 is also made of a magnetic material, a magnetic loop is formed from the thrust attracting magnet 19 through the thrust ring 16 to the thrust cup 17, so that the thrust attracting magnet 19 is not an expensive rare earth sintered magnet, for example, neodymium. An inexpensive resin magnet such as a bond magnet can be used.

As described above, it is possible to provide an inexpensive motor bearing device capable of maintaining accurate rotation transmission for a long time even at high speed rotation, and an excellent motor including this device.

(Embodiment 2)
FIG. 4 is a perspective view of a metal holder according to Embodiment 2 of the present invention. 4, the configuration in which a plurality of ribs 13d having an envelope surface that is the same as or slightly larger than the inner diameter of the hole 8b of the stator core shown in FIG. 3 is formed in the cylindrical portion 13a of the metal holder 13 in the axial direction. And different. With this configuration, the cylindrical portion 13a of the metal holder 13 can be easily press-fitted into the hole 8a of the stator core. In addition, the rib 13d (protrusion) formed on the cylindrical portion 13a of the metal holder 13 creates a space between the circumferential surface of the cylindrical portion 13a and the inner circumferential surface of the hole 8b of the stator core, and the stator core 8 and the oil-impregnated metal 5 Since the air layer is formed between the two, the heat resistance is further increased, and an effect that the bearing temperature rise due to the heat generation of the coil 6 wound around the stator core 8 can be further suppressed can be obtained.

  The brushless motor having the bearing structure of the present invention is useful as a brushless motor used for driving a disk in an apparatus for recording and reproducing information such as CD-ROM (R / RW) and DVD ± (R / RW). It is.

Sectional drawing which shows the structure of the motor by Embodiment 1 of this invention The perspective view of the metal holder by Embodiment 1 of this invention FIG. 3 is an explanatory diagram of stator assembly of the motor according to the first embodiment of the present invention. The perspective view of the metal holder by Embodiment 2 of this invention Sectional drawing which shows the structure of the 1st conventional motor Sectional drawing which shows the structure of the 2nd conventional motor Sectional view showing the structure of a third conventional motor

1, 51, 61, 71 Shaft (output shaft)
2 Frame 3 Rotor magnet 4, 56, 65, 76 Bracket 5, 52, 62, 72 Oil-impregnated metal 5a Oil-impregnated metal outer periphery 5b Oil-impregnated metal end face 6 Stator coil 7 Printed circuit board 8, 55, 77 Stator core 8a Salient pole 8b Hole 9 Stator assembly 10, 54, 64, 73 Rotor
11, 53, 63, 75 Burring processing part (housing)
11a, 66 Metal holding portion 11b Expanded diameter portion 11c Stepped portion 11d Metal holding portion outer peripheral surface 12, 74 Mounting base portion 13, 70 Metal holder (cover)
13a, 70a Metal holder (cover) cylindrical part 13b, 70b End face part of metal holder (cover) 13c Metal holder wing part 13d Rib 14 Insulating member 15 Stator winding assembly (armature)
16 Thrust ring 17 Thrust cup 18 Thrust receiver 19 Thrust suction magnet

Claims (1)

A bracket made of a magnetic material in which a burring portion constituting the bearing housing in the central portion and a mounting base portion for motor mounting are integrated, and an inner side of the burring portion of the bracket. An oil-impregnated metal whose part of the entire length is press-fitted and fixed, a stator core disposed outside the burring portion of the bracket, a frame having a shaft fixed at the center, and the frame A cylindrical rotor magnet fixed to the inner circumference of the stator core and subjected to multipolar magnetization in the circumferential direction, and a cylindrical portion having an outer diameter that is the same as or slightly smaller than the inner diameter of the hole formed in the center of the stator core; A plurality of end surfaces extending in the direction perpendicular to the shaft so as to cover one end surface in the axial direction of the stator core from the other end and the end surface extending from the one end in the axial direction of the cylindrical portion to the inner diameter side. Insulation with wings A metal holder made of resin, a part of the outer peripheral surface of the cylindrical portion of the metal holder is fixed to the central hole of the stator core, and the wing portion of the metal holder and the other axial end surface of the stator core An outer periphery in which an armature is formed by winding a copper wire through an insulator provided separately from the wing portion of the metal holder, and the cylindrical portion of the metal holder is exposed to the outside of the bracket of the oil-impregnated metal And a metal holding portion for press-fitting oil-impregnated metal into the burring portion of the bracket and covering the one end surface in the axial direction. A stepped portion is formed at the boundary between the enlarged diameter portion having an outer diameter larger than the outer diameter size of the metal holding portion and the metal holding portion and the enlarged diameter portion, and the step is formed via the wing portion of the metal holder. Brushless motor, characterized in that it comprises a structure fixed to the step portion of stator core.

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