JP4353138B2 - 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. A bearing 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 bearing, 53 is a housing for retaining the oil-impregnated bearing, 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 sequentially generated 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 bearing 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 bearing constituting the oil and the countermeasures against scattering of the oil contained in the oil-impregnated bearing have become important issues.

  That is, in the conventional configuration as described above, since the outer periphery of the oil-impregnated bearing is sealed with the housing, the pressure applied to the end face of the oil-impregnated bearing is caused by the pressure generated at the contact portion between the output shaft and the oil-impregnated bearing when the output shaft rotates. Increases, and the oil blows out to the end surface of the oil-impregnated bearing, and adheres to the inner top surface particularly on the top surface 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 bearing, so the oil retained in the oil-impregnated bearing decreases and normal lubrication does not work. There was a problem that accurate rotation transmission was not performed.

  Accordingly, the applicant provides a motor bearing device capable of maintaining a precise rotation transmission for a long time by reducing the amount of oil blown to the end face of the oil-impregnated bearing while reducing the cost, and an excellent motor equipped with this device. For this purpose, the pressure on the end face of the oil-impregnated bearing is reduced by providing a portion that does not seal the outer periphery of the oil-impregnated bearing on the top surface of the rotor of the press-fit portion of the oil-impregnated bearing 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 bearing, 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-impregnated bearing holding portion 66 is set to 1/2 to 4/5 of the entire length of the oil-impregnated bearing 62 on the top surface side of the rotor 64. The outer periphery of the oil retaining bearing 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 bearing, and the number of motor components can be reduced by integrally forming the bracket and the housing.

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 is a problem that the oil flows out from the outer periphery and the end face of the oil-impregnated bearing released by this pressure, making it difficult to meet the demand for longer life.

  Therefore, the applicant attaches a cylindrical cover to the open portion of the outer periphery of the oil-impregnated bearing with a gap between the end surface and the outer periphery of the oil-impregnated bearing, so that the oil pushed out from the end surface of the oil-impregnated bearing is scattered during rotation. Even so, the cover serves as a wall for preventing oil scattering, and further, the oil in the oil-impregnated bearing that has scattered in the cylindrical portion due to the gap between the outer periphery of the oil-impregnated bearing and the cylindrical portion of the cover is passed through the gap. An oil recovery structure for returning to the oil-impregnated bearing 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 bearing, 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 bearing 72 is fixed to the inner peripheral portion of the burring portion 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 portion of the burring portion 75. A cylindrical metal holder 70 (cover) is formed of a cylindrical portion 70a having a gap from the end surface and outer periphery of the oil-impregnated bearing 72 and an end surface portion 70b extending from the one end portion of the cylindrical portion toward the inner diameter side. 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 the oil in the oil-impregnated bearing gradually flows out of the gap due to the operation of the motor, 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 bearing 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 an outer periphery and an end surface of an oil-impregnated bearing exposed from a bearing housing portion with an insulating resin (insulator) of a stator core, and forms the metal holder. Thus, the stator core is fixed to the bracket while maintaining high reliability against environmental changes.

  According to the first aspect of the present invention, since the outer periphery and end surface of the oil-impregnated bearing exposed from the bearing housing portion are covered with the metal holder, oil leakage from the oil-impregnated bearing 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 through 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 bearing is increased, and the increase in the bearing temperature due to the heat generated by the coil wound around the stator core is suppressed. The advantageous effect that it can be obtained is obtained. In addition, the stator core is directly attached to the bearing housing portion by a configuration in which a notch portion that connects the outer peripheral surface of the bearing housing portion formed in the cylindrical portion of the metal holder and the inner peripheral surface of the central hole of the stator core is filled with an adhesive. Since it can be bonded and fixed, the effect of maintaining high reliability over a long period of time against changes in temperature environment and the like can be achieved.

  According to the second aspect of the present invention, the bracket and the bearing housing portion are integrally formed by burring, and the step portion formed at the boundary between the metal holding portion and the enlarged diameter portion of the bearing housing portion is formed. Since the stator core is fixed via the wing portion of the metal holder, the structure can be simplified, and the bearing housing portion is electrically insulated from the stator core, and a rapid change in the current supplied to the coil wound around the stator core ( For example, an advantageous effect can be obtained that an induction current generated in the stator core due to PWM driving or the like flows into the bracket and can be prevented from affecting the equipment on which the motor is mounted as harmful noise.

  According to the invention of claim 3, the cylindrical portion of the metal holder can be easily press-fitted into the hole of the stator core. In addition, the protrusion formed on the cylindrical part of the metal holder creates a space between the circumferential surface of the cylindrical part and the inner peripheral surface of the hole of the stator core, and an air layer is formed between the stator core and the oil-impregnated bearing. The thermal resistance is increased, and the effect that the bearing temperature rise due to the heat generated by the coil wound around the stator core can be further suppressed can be 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.

  Reference numeral 4 denotes a bracket formed of a magnetic material by a press method. The bracket 4 has a stepped burring portion at a substantially central portion. The burring portion of the bracket 4 includes a metal holding portion 11a into which the oil-impregnated bearing 5 is press-fitted and fixed, an enlarged diameter portion 11b having an outer diameter larger than the outer diameter of the metal holding portion 11a, and a metal holding portion 11a. A step portion 11 c is formed at the boundary with the diameter portion 11 b to constitute the bearing housing portion 11. The shaft 1 is rotatably supported by the oil-impregnated bearing 5.

  In this burring portion, a bearing housing portion 11 for housing a bearing and a mounting base portion 12 for mounting a motor are integrally formed. Since the bearing housing portion 11 and the mounting base portion 12 are integrally formed in this way, it is easy to accurately form the squareness of the mounting base portion 12 with respect to the bearing housing portion 11. Become.

On the other hand, the stator core 8 is formed by laminating silicon steel plates, and has a plurality of salient poles 8 as shown in FIG.
a stator core having a. A hole 8 b is formed in the center of the stator core 8. 13 is a metal holder made of an insulating resin, and FIGS. 2A and 2B are perspective views 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 And 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 of the stator core 8, and the cylindrical portion 13a has a boundary with the blade portion 13c. A plurality of notches 13d are formed in the vicinity. 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 wing 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 wing portion 13c of the metal holder 13, and the wing 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 coil assembly 15 (armature).

  The stator coil assembly 15 assembled as described above is attached to the bracket 4 in which the oil-impregnated bearing 5 is fixed to the bearing housing 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 bearing 5 exposed to the outside of the bearing housing portion 11. The bearing 5 is inserted into the oil-impregnated bearing 5 until facing the end face 5b with a slight gap, and is fixed to the outer peripheral face 11d of the metal holding part 11a of the bearing housing part 11 of the bracket 4 by press fitting, adhesion or the like. At this time, since the notch 13d is formed in the cylindrical part 13a of the metal holder 13, the inner peripheral surface of the hole 8b of the stator core 8 and the metal of the bearing housing part 11 are filled by filling the notch 13d with an adhesive. The outer peripheral surface 11d of the holding part 11a is directly fixed with an adhesive. Thereby, the effect that the reliability of the fixing strength of the stator coil assembly 15 and the bracket 4 can be maintained over a long period against changes in temperature environment such as heat generation of the stator coil (copper wire) 6 can be achieved.

  In the present embodiment, the stator core 8 is fixed to the step portion 11 c formed in the bearing housing portion 11 of the bracket 4 through the blade portion 13 c 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. The winding end of the stator coil 6 of the stator coil assembly 15 is wired on the printed circuit board 7 to form a stator assembly 9.

  With the above configuration, since the outer periphery 5a and the end surface 5b of the oil-impregnated bearing 5 exposed from the bearing housing portion 11 of the bracket 4 are covered with the metal holder 13, oil leakage from the oil-impregnated bearing 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. Further, since the stator core 8 is fixed to the bracket 4 through 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 bearing 5 is increased, and the stator coil 6 wound around the stator core 8. An advantageous effect is obtained in that an increase in the bearing temperature due to the heat generation can be suppressed.

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, the entire bearing housing portion 11 of the bracket 4 is 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 is possible to suppress an induced current generated in the stator core 8 due to a slight change (for example, during PWM driving) from flowing into the bracket 4 via the bearing housing portion 11 and affecting the equipment on which the motor is mounted as harmful noise.

  Next, the shaft 1 of the rotor 10 is inserted into the oil-impregnated bearing 5 of the stator assembly 9 from the bearing housing portion 11 side, and a ring-shaped thrust made of a magnetic material from the tip of the shaft 1 opposite to the side where the frame 2 is press-fitted. The 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 fixed to a predetermined position on the inner periphery of the enlarged diameter portion 11b of the bearing housing portion 11 of the bracket 4 from a direction opposite to the protruding direction of the bearing housing portion 11 by press fitting or the like. To do. 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 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 disposed in advance at the opposite position, and the thrust direction displacement of the rotor 10 is stabilized by the magnetic attracting force acting between the thrust attracting magnet 19 and the thrust ring 16 made of a magnetic material. It has become. 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.

  In the present embodiment, it is not necessary to integrally form the bracket 4 and the bearing housing portion 11 as described above. Even if the bearing housing portion 11 is formed separately from the bracket 4, the above-described effects are similarly obtained. be able to.

(Embodiment 2)
4a and 4b are perspective views of a metal holder according to Embodiment 2 of the present invention. 4A and 4B, the configuration in which a plurality of ribs 13e having an envelope surface that is the same as or slightly larger than the inner diameter of the stator core hole 8b shown in FIG. 3 is formed in the cylindrical portion 13a of the metal holder 13 in the axial direction. Different from Form 1. 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, as in the first embodiment, the cylindrical portion 13a of the metal holder 13 has a plurality of cutout portions 13d near the boundary with the wing portion 13c, so that the cutout portion 13d is filled with an adhesive. As a result, the inner peripheral surface of the hole 8b of the stator core 8 and the outer peripheral surface 11d of the metal holding portion 11a of the bearing housing portion 11 are directly fixed with an adhesive. While the adhesive is cured, the stator core 8 is held by press-fitting into the metal holding part 11a of the bearing housing part 11 via the metal holder 13, so that the stator core 8 can be accurately fixed at a predetermined position. This not only improves workability, but also reliability of the fixing strength of the stator coil assembly 15 and the bracket 4 over a long period of time against changes in the temperature environment such as heat generation of the stator coil (copper wire) 6. Can be maintained. In addition, the rib 13e (projection) 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 peripheral surface of the hole 8b of the stator core, and the stator core 8 and the oil-impregnated bearing 5 Since the air layer is formed between the two, the heat resistance is further increased, and the 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 (A) Front side perspective view of a metal holder according to Embodiment 1 of the present invention, (b) Back side perspective view of a metal holder according to Embodiment 1 of the present invention FIG. 3 is an explanatory diagram of stator assembly of the motor according to the first embodiment of the present invention. (A) Front side perspective view of a metal holder according to Embodiment 2 of the present invention, (b) Back side perspective view of a metal holder according to Embodiment 2 of the present 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

Explanation of symbols

1, 51, 61, 71 Shaft (output shaft)
2 Frame 3 Rotor magnet 4, 56, 65, 76 Bracket 5, 52, 62, 72 Oil-impregnated bearing 5a Outer portion of oil-impregnated bearing 5b End surface of oil-impregnated bearing 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
DESCRIPTION OF SYMBOLS 11 Bearing housing part 11a, 66 Metal holding part 11b Expanded diameter part 11c Step part 11d Outer peripheral surface of metal holding part 12, 74 Mounting base part 13, 70 Metal holder (cover)
13a, 70a Metal holder (cover) cylindrical part 13b, 70b Metal holder (cover) end face part 13c Metal holder wing part 13d Notch part 13e Rib 14 Insulating member 15 Stator coil assembly (armature)
16 Thrust ring 17 Thrust cup 18 Thrust receiver 19 Thrust attracting magnet 53, 63, 75 Burring processing part (housing)

Claims (3)

A rotor assembly comprising a shaft, a rotor frame fixed at the center of the shaft, and a ring-shaped rotor magnet fixed to the inner periphery of the rotor frame and subjected to multipolar magnetization in the circumferential direction; An oil-impregnated bearing to be supported, a bearing housing portion that holds the oil-impregnated bearing, a bracket that fixes the bearing housing portion in the center, and a plurality of salient poles that face the rotor magnet, are disposed outside the bearing housing portion. And a stator assembly including a stator coil assembly formed by winding a stator coil around the stator core via an insulator, and a circuit board to which a terminal of the stator coil is electrically connected. In the brushless motor, the circuit board is fixed to the bracket, and the stator coil assembly is From 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 theta core, an end surface extending from the one end in the axial direction of the cylindrical portion toward the inner diameter, and the other end A metal holder made of an insulating resin having a plurality of wings extending in a direction perpendicular to the shaft so as to cover one end face in the axial direction of the stator core; The stator coil is fixed to the central hole of the stator core, and the stator coil is interposed on the other end face in the axial direction of the stator core via an insulator disposed separately from the blade portion of the metal holder and the blade portion. The cylindrical portion of the metal holder covers the outer peripheral surface exposed to the outside of the bearing housing of the oil-impregnated bearing, and the end surface portion of the metal holder is close to one end surface of the oil-impregnated bearing. Oppositely fixed to the outer peripheral surface of the bearing housing portion, the cylindrical portion of the metal holder is formed with a notch portion that communicates the outer peripheral surface of the bearing housing portion and the inner peripheral surface of the central hole of the stator core, A brushless motor characterized in that an adhesive is filled in the notch. A bearing housing part is integrally formed from a bracket by a burring process, and the bearing housing part has a metal holding part for press-fitting an oil-impregnated bearing and an enlarged diameter part having an outer diameter larger than the outer diameter of the metal holding part. A step portion is formed at a boundary between the metal holding portion and the enlarged diameter portion, and a stator core is fixed to the step portion via a wing portion of a metal holder. Brushless motor. The brushless motor according to any one of claims 1 to 2, wherein a plurality of protrusions having an envelope surface that is the same as or slightly larger than the inner diameter of the hole of the stator core are formed on the outer periphery of the cylindrical portion of the metal holder in the axial direction. .

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