JP2005137144A - Spindle motor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spindle motor that reduces the occurrence of noise, by making excitation vibrations from a stator core arising from the high-speed revolutions of a motor hardly transferred to the stator housing side, while maintaining fixing strength and easiness in assembling. <P>SOLUTION: A stator core 12 is fitted to a rotating shaft 4 with gap portions 16 provided partially between the inside circumferential surface of the stator core and the outside circumferential surface of the stator housing via adhesives 15 applied at two or more positions in the circumferential direction on the outside circumferential surface of the stator housing 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a spindle motor used for driving a disk such as a polygon mirror, FD, CD, or DVD.

  In a laser beam printer provided with a polygon mirror and disk drive devices such as FD, CD, and DVD, a spindle motor is used as a drive source for driving various disks, polygon mirrors and the like at high speed. As the spindle motor, an outer rotor type DC brushless motor is preferably used. Specifically, a cup-shaped rotor housing is supported on the rotating shaft, and a ring-shaped magnet is fixed to the inner wall surface of the rotor housing. A polygon mirror, a disk, and the like are mounted on the rotor housing. A stator housing portion is coaxially assembled to the rotating shaft via a bearing, and a stator core around which a stator coil is wound is fixed to the stator housing portion by an adhesive.

  A stator coil is wound around three phases (U-phase, V-phase, W-phase) on the magnetic pole portion projecting radially from the stator core, and the stator coil of each phase is energized to rotate the rotor. Energized. That is, the rotor rotates at high speed by repeatedly repelling and attracting the magnetic poles of the magnets facing the stator magnetic poles. At this time, electromagnetic vibration is generated by energization of the three-phase stator coil, and the vibration is transmitted from the stator core to the stator housing side to generate noise. Specifically, for example, when a polygon mirror is rotationally driven using a DC brushless motor, the stator core is often rotated at a high speed of about 15000 rpm to 30000 rpm, depending on the excitation component (for example, switching frequency component) to the stator coil. Vibrates, the electromagnetic vibration is transmitted to the stator housing side, resonates with the optical unit, and an unpleasant harmonic sound around 9.4 kHz, for example, is generated as noise.

The following techniques have been proposed to prevent the generation of noise associated with the high speed rotation of the spindle motor. For example, in a disk spindle motor, a rotor is rotatably supported on a fixed shaft via a bearing. A stepped holder is fitted coaxially on the fixed shaft, and a stator core is press-fitted into the stepped holder. By providing an air gap between the inner peripheral surface of the mounting hole of the stator core and the outer peripheral surface of the fixed shaft, the electromagnetic vibration generated on the stator side is hardly transmitted to the fixed shaft side or fixed. By providing a concave portion on the shaft side and filling the concave portion with an adhesive and bonding the stator core, it is difficult to transmit electromagnetic vibration generated on the stator side to the fixed shaft side (see Patent Document 1). Further, the stator core is bonded to the housing base so that the electromagnetic vibration generated on the stator side is difficult to be transmitted to the fixed shaft side (see Patent Document 2).
JP-A-6-335216 JP 2000-163859 A

When the stator core is bonded and fixed to the stator housing portion, the gap between the inner peripheral surface of the mounting hole and the outer peripheral surface of the stator housing portion is small, so that a buffer material that absorbs electromagnetic vibration cannot be inserted with the same shape. Further, the fixing portion between the stator core and the stator housing portion is required to have a sufficient fixing strength that can withstand the use environment such as the motor starting torque, impact, and environmental change.
In addition, when an air gap is provided between the inner peripheral surface of the stator core mounting hole and the outer peripheral surface of the fixed shaft for support, a stepped holder for supporting the stator core is required, which increases the number of parts and increases the fixed shaft. When a concave portion is provided in the concave portion and an adhesive is filled in the concave portion to bond the stator core, the number of steps such as cutting increases, so that the manufacturing cost increases. Further, when manufacturing by changing the diameter of the mounting hole of the stator core, it is necessary to change the die to be punched, and since an air gap is provided, there is a problem that it is difficult to achieve the coaxiality when the stator core is assembled.
Furthermore, when the stator core is bonded to the housing base portion, the stator housing becomes large and requires a fixed area.

  The present invention has been made to solve these problems, and an object of the present invention is to cause excitation vibration from the stator core accompanying the high-speed rotation of the motor to the stator housing side while maintaining the fixing strength and the ease of assembly. An object of the present invention is to provide a spindle motor in which generation of noise is reduced by making transmission difficult.

In order to achieve the above object, the present invention comprises the following arrangement.
A rotor having a ring-shaped magnet that is rotatably supported around a rotation axis in a rotor housing, and a spindle motor in which a stator core around which a stator coil is wound is fitted into a stator housing in which the rotor is incorporated via a bearing In
The stator core is fitted into the rotating shaft with a gap partly provided between the stator core inner peripheral surface and the stator housing outer peripheral surface via an adhesive applied to the outer peripheral surface of the stator housing at a plurality of locations in the circumferential direction. It is characterized by.
Further, the adhesive is applied along the axial direction at a position where the adhesive faces the outer peripheral surface of the stator housing into which the stator core is fitted.

If the spindle motor described above is used, the stator core is provided with a gap portion between the inner peripheral surface of the core and the outer peripheral surface of the housing via an adhesive applied to the outer peripheral surface of the stator housing at a plurality of locations in the circumferential direction. Since it is fitted coaxially, the excitation vibration from the stator core accompanying high-speed rotation of the motor can be made difficult to be transmitted to the stator housing side by the gap part where it is partially interposed. Therefore, it is possible to reduce the noise caused by the harsh harmonic sound in the vicinity of 7 kHz to 10 kHz generated by transmitting the excitation vibration of the stator core to the stator housing.
In addition, since the stator core is fixed to the outer peripheral surface of the stator housing by an adhesive applied in a plurality of locations in the circumferential direction, the manufacturing cost can be reduced without increasing the number of parts and processing steps, and the motor starting torque, impact, While maintaining sufficient fixing strength that can withstand the usage environment such as environmental changes, the degree of coaxiality with respect to the rotation axis can be easily obtained, and the assemblability can be improved.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a spindle motor according to the invention will be described with reference to the accompanying drawings. In the spindle motor of this embodiment, a stator coil is wound around a rotor having a ring-shaped magnet supported so as to be rotatable around a rotation axis in a rotor housing, and a stator housing in which the rotor is incorporated via a bearing. The present invention is widely applied to a brushless motor for high-speed rotation in which a stator is fitted. In this embodiment, a DC brushless motor for driving a polygon mirror (hereinafter referred to as “polygon mirror motor”) will be described.

The schematic configuration of the polygon mirror motor will be described with reference to FIGS.
In FIG. 1, the rotor 1 uses a cup-shaped rotor housing 2. A shaft hole 3 is bored in the rotor housing 2, and a rotating shaft 4 is integrally fixed to the shaft hole 3. A polygon mirror 5 is mounted on the upper surface of the rotor housing 2 and is pressed against the upper surface of the rotor housing 2 by a pressing spring 6. The holding spring 6 is fixed by a C-type retaining ring 8 that is fitted into a cylindrical portion 7 that is erected around the shaft hole 3. A ring-shaped magnet 9 is fixed to the inner peripheral surface of the rotor housing 2. The magnet 9 is alternately magnetized with N and S poles in the circumferential direction.

  A rotating shaft 4 is coaxially incorporated in the stator housing 11 via a dynamic pressure bearing 10. The stator housing 11 is formed by continuously forming cylindrical portions having different outer diameters, a stator core 12 is fitted into the small diameter portion, and a printed circuit board 13 is fixed to the large diameter portion.

The stator core 12 is provided with radially provided stator magnetic pole portions, and a stator coil 14 for three phases is wound around each stator magnetic pole portion. As the stator core 12, for example, a laminated core in which silicon steel plates punched by a press are laminated is used.
2 (a) and 2 (b), the stator core 12 is partially disposed between the core inner peripheral surface and the housing outer peripheral surface via the adhesive 15 applied to the outer peripheral surface of the stator housing 11 at a plurality of locations in the circumferential direction. Is provided with a gap portion 16. Specifically, the adhesive 15 is applied along the axial direction at two locations on the outer peripheral surface of the stator housing 11 into which the stator core 12 is fitted, at positions facing each other. The adhesive 15 applied in a line in the axial direction spreads when the stator core 12 is fitted into the stator housing 11 and is bonded in the circumferential direction with an adhesive area of about 30 degrees.

  The printed circuit board 13 is caulked to the stator housing 11 in a direction orthogonal to the rotation shaft 4. The printed circuit board 13 is mounted with electronic components constituting a motor drive circuit, and a magnetic pole sensor (for example, a hall sensor) 17 is provided on the same substrate so as to face the end surface of the magnet 9. The magnetic pole sensor 17 detects the magnetic pole position of the rotor 1 from the leakage flux of the magnet 9. In accordance with the rotational position of the rotor 1 detected by the magnetic pole sensor 17, the motor drive circuit switches the energization to the stator coil 14 in a direction for energizing the rotation of the rotor 1.

  An end cover 18 is fitted into the stator housing 11 using a hole diameter step from the printed circuit board 13 side. The end cover 18 is provided with a thrust receiver 19 for receiving the shaft end of the rotary shaft 4 to define the shaft end position.

Next, measurement data of noise (9.4 kHz component) measured by driving the polygon mirror motor configured as described above will be described with reference to FIG. FIG. 3A is noise data of a motor in which the stator core 12 is fitted with the adhesive 15 applied to the entire circumference of the stator housing 11, and FIG. 3B is two locations facing the outer periphery of the stator housing 11. The noise data of the motor in which the adhesive 15 is applied and fitted in the axial direction. The vertical axis represents the noise level (dB (A)), and the horizontal axis represents the number of samplings (the number of measured motors). The curve in the figure shows a normal distribution curve of noise values. The measured polygon mirror motor specification shows data when the magnet 9 has 12 poles, the stator core 12 has 9 slots, and is rotated at a rotational speed of 15748 rpm.
As a result, the average value of noise (9.4 kHz component) in the case of all-around bonding is 25.7428 dB (A), whereas the average value of noise (9.4 kHz component) in the case of bonding at two locations. It was found that the value can be reduced by about 10 dB (A), which is about 16.0776 dB (A).
FIGS. 4A and 4B are graphs showing a frequency analysis of noise at the same rotation speed of the motor. 4A is noise data of a motor in which the stator core 12 is fitted with the adhesive 15 applied to the entire circumference of the stator housing 11, and FIG. 4B is a diagram showing two positions facing the outer circumference of the stator housing 11. This is noise data of a motor in which the adhesive 15 is applied and fitted in the axial direction. The vertical axis represents the noise level (dB (A)), and the horizontal axis represents the frequency (kHz). According to this graph, it can be seen that the harmonic sound of 9.4 kHz is reduced.

  Although the said Example illustrated the case where the stator core 12 was adhere | attached partially in two places facing the stator housing 11, it is not necessarily limited to this aspect, If the fixing strength of the stator core 12 can be maintained, three places, You may adhere | attach partially in more places even if it is four places. The spindle motor is exemplified by a polygon mirror driving motor, but is not limited to this. Other applications such as a disk driving motor for FD, CD, CD-R, CD-RW, DVD, etc. This motor may be used.

It is a section explanatory view of a polygon mirror motor. It is the top view and cross-sectional explanatory drawing of the bearing housing part to which the adhesive agent was apply | coated. It is a comparison figure which shows the measurement data of the noise level at the time of apply | coating an adhesive agent to the perimeter of a bearing housing part, and a 2 case. It is a comparison figure which shows the frequency analysis of the noise in the case where the rotation speed of the motor when an adhesive agent is apply | coated to the perimeter of a bearing housing part and two places is applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotor 2 Rotor housing 3 Shaft hole 4 Rotating shaft 5 Polygon mirror 6 Holding spring 7 Cylindrical part 8 C-type retaining ring 9 Magnet 10 Dynamic pressure bearing 11 Stator housing 12 Stator core 13 Printed circuit board 14 Stator coil 15 Adhesive 16 Gap part 17 Magnetic pole Sensor 18 End cover 19 Thrust receiver

Claims (2)

A rotor having a ring-shaped magnet that is rotatably supported around a rotation axis in a rotor housing, and a spindle motor in which a stator core around which a stator coil is wound is fitted into a stator housing in which the rotor is incorporated via a bearing In
The stator core is fitted into the rotating shaft with a gap partly provided between the stator core inner peripheral surface and the stator housing outer peripheral surface via an adhesive applied to the outer peripheral surface of the stator housing at a plurality of locations in the circumferential direction. A spindle motor characterized by   2. The spindle motor according to claim 1, wherein an adhesive is applied along the axial direction at a position facing the outer peripheral surface of the stator housing into which the stator core is fitted.

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