JPH1169712A - Spindle motor, and rotating body equipment using the spindle motor as drive source for the rotating body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the occurrence of contact and sliding on the surface of thrust dynamic pressure bearing during starting. SOLUTION: In a shaft rotation type spindle motor equipped with an air dynamic pressure bearing, a metal pivot 10 is attached to the lower end of a shaft 3 and a liftable pivot receiver 11 is attached to a base plate 1. Also the liftable pivot receiver 11 is constituted with a magnetic pivot receiver 11 pushed up by a spring 12 and a magnet 14 pulling down this pivot receiver 11 during stop. By doing this, the pivot 10 and the pivot receiver 11 are separated during rated rotation and a solid contact is made during the stop.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor having an air dynamic pressure bearing having a radial dynamic pressure bearing portion and a thrust dynamic pressure bearing portion, and to rotating this spindle motor such as a magnetic disk, an optical disk or a polygon mirror. The present invention relates to a rotating body device serving as a body driving source, and more particularly, to prevention of wear due to contact sliding of a thrust dynamic pressure bearing surface at the time of startup or shortening of the life of the device.

[0002]

2. Description of the Related Art In a rotating device such as a magnetic disk device, an optical disk device or a scanner including a polygon mirror, a driving source for driving a rotating member such as a magnetic disk, an optical disk or a polygon mirror is provided with an air dynamic pressure bearing. Spindle motors are widely used. This is because the air dynamic pressure bearing has a simple structure and can be miniaturized, and because it rotates in a non-contact manner during rated rotation, there is no vibration or uneven rotation caused by the bearing, and it has excellent high-speed durability In addition, since oil and grease are not used, there is a feature that there is no contamination due to scattering of a lubricant.

However, a spindle motor having an air dynamic pressure bearing has a problem in that the dynamic pressure generating surface of the thrust bearing comes into solid contact when the rotation stops, and therefore, when it starts up, it comes into contact with the surface and wear occurs. This will be described more specifically with reference to FIG. 9, which is a conventional spindle motor having an air dynamic pressure bearing. In FIG. 9, the thrust dynamic pressure bearing is a donut disk-shaped thrust member 5 provided at the lower end of the hub 7 on the rotor side and a donut disk provided on the base plate 1 on the stator side so as to face the donut disk-shaped thrust member 5. And a thrust pressing member 6. The thrust dynamic pressure generating surface is a lower surface of the donut disk-shaped thrust member 5 provided with a thrust dynamic pressure generating groove as shown in FIG. 6 and a smooth upper surface of the donut disk-shaped thrust pressing member 6. It is a very narrow thing. At the time of rated rotation, high pressure dynamic pressure air is pushed into this narrow clearance by the pump action, so it is non-contact.However, at the time of rotation stop, the rotor including the rotating body such as the magnetic disk falls by its own weight, and the donut disk-shaped thrust The lower surface of the member 5 sits on the upper surface of the donut disk-shaped thrust holding member 6, and the dynamic pressure generating surface comes into solid contact. Then, at the time of startup, the lower surface of the donut disk-shaped thrust member 5 rotates while being in contact with the upper surface of the donut disk-shaped thrust pressing member 6, so that wear due to contact sliding occurs.

[0004] Wear due to contact sliding generated on the thrust dynamic pressure generating surface shortens the life of the air dynamic pressure bearing and therefore the life of the spindle motor. To cope with this problem, Japanese Patent Application Laid-Open No. Hei 7-259 discloses a method in which a material having high wear resistance such as ceramic is used for the components of the thrust dynamic pressure bearing.
There is a device devised in the structure disclosed in Japanese Patent No. 849. The latter will be described with reference to FIG. 9. A gap between radial dynamic pressure bearing surfaces, that is, a cylindrical member that is a smooth surface and an outer peripheral surface of a columnar member 3 having a radial dynamic pressure generating groove as shown in FIG. 4 is formed. 4 is smaller than the gap between the lower surface of the donut-shaped thrust member 5 provided with the thrust dynamic pressure generating groove and the upper surface of the donut-shaped thrust pressing member 6 which is a smooth surface. On the other hand, contact sliding on the radial dynamic pressure bearing surface is unavoidable, and only contact sliding on the thrust dynamic pressure bearing surface is prevented. In this case, a material having high wear resistance, such as ceramic, is used as a component of the radial dynamic pressure bearing. However, all of them have a problem that processing and assembly are difficult.

[0005]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a thrust hydrodynamic bearing surface at the time of startup in a spindle motor having an air dynamic pressure bearing or a rotary device using the spindle motor as a driving source of a rotary body. Is to prevent contact sliding.

[0006]

SUMMARY OF THE INVENTION In a shaft rotary type spindle motor provided with an air dynamic pressure bearing or a rotary device using a spindle motor as a driving source of a rotary body, a metal pivot is provided at a lower end of the shaft and a pivot receiver is provided. The pivot and the pivot receiver are separated from each other at the time of rated rotation and are in solid contact with each other when stopped. Further, the pivot receiver is a vertically movable pivot receiver so that the pivot and the pivot receiver are separated from each other at the time of rated rotation and are in solid contact at the time of stop. The vertically movable pivot receiver is formed of a magnetic pivot receiving member that is pushed up to a first predetermined position by a spring, and an electromagnet that pulls down the pivot receiving member to a second predetermined position when stopped.

A rotary shaft type spindle motor having a radial dynamic pressure bearing portion having a cylindrical bearing member and a cylindrical bearing member, and an air dynamic pressure bearing having a donut-shaped thrust member and a donut-shaped thrust pressing member. Alternatively, in a rotating body device using a spindle motor as a driving source of a rotating body, a metal pivot is attached to a lower end of a shaft, and a pivot receiver is attached to a base plate, respectively, and further, the interval between the pivot and the pivot receiver at the time of rated rotation is set to By making the distance between the upper surface of the donut disk-shaped thrust member and the lower surface of the donut disk-shaped thrust holding member slightly smaller, the pivot and the pivot receiver are separated at the time of rated rotation and solidly contacted at the time of stop. .

Further, in a shaft rotary spindle motor provided with an air dynamic pressure bearing or a rotary device using a spindle motor as a drive source of a rotary body, a metal pivot is mounted on a lower end of the shaft and a pivot receiver is mounted on a base plate. Pivot bearings are provided. Then, a magnetic fluid or a conductive magnetic fluid was interposed between the pivot and the pivot receiver.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is characterized in that a pivot is attached to a lower end of a shaft and a pivot receiver is attached to a base plate, respectively, and furthermore, the pivot and the pivot receiver are separated at a rated rotation and solidly contact at a stop. An embodiment of the spindle motor according to the present invention will be described.
In FIG. 1, 1 is a base plate of a stator, and 2 is a shaft of a rotor. Reference numeral 3 denotes a cylindrical member having a shaft hole, into which the shaft 2 is press-fitted and fixed. Reference numeral 4 denotes a cylindrical member erected on the base plate 1. The columnar member 3 is inserted into the cylindrical member 4 with a narrow clearance on the order of microns. Reference numeral 6 denotes a donut-shaped thrust pressing member, which is disposed close to the upper end surface of the columnar member 3 and is fixed to the upper end of the cylindrical member 4. Reference numeral 7 denotes a substantially cup-shaped hub of a rotor which is coaxially fixed to the upper end of the shaft 2 and supports a rotating body such as a medium of an HDD (hard disk drive) on an outer peripheral surface. The stator coil 8 is disposed and mounted on the outer peripheral surface of the cylindrical member 4, and the rotor magnet 9 is disposed and mounted on the inner peripheral surface of the substantially cup-shaped hub 7 at a position facing the stator coil 8.

Reference numeral 10 denotes a pivot attached to the lower end of the shaft 3, and reference numeral 11 denotes a pivot receiver which can move a magnetic body up and down.
Reference numeral 2 denotes a bearing cover having a pivot receiving and receiving portion fixed to the base plate 1. Reference numeral 13 denotes a spring disposed between the bottom surface of the pivot receiving and receiving portion of the dynamic pressure bearing cover 12 and the lower surface of the pivot receiver 11. Further, reference numeral 14 denotes an electromagnet that is disposed opposite to the vertically movable pivot receiver 11 and is housed in a concave portion provided on the inner peripheral surface of the pivot receiver housing of the bearing cover 12. The electromagnet 14 is excited from a power source 16 via SW2 as shown in FIG. 7, and the control of SW2 is performed by a controller (not shown).

In the radial dynamic pressure bearing portion composed of the columnar member 3 and the cylindrical upper member 4, a radial dynamic pressure generating groove G1 as shown in FIG. The outer peripheral surface of the shaped member 4 is a smooth surface.
Further, the cylindrical member 3 and the donut disk-shaped thrust holding member 6
6, a thrust dynamic pressure generating groove G2 as shown in FIG. 6 is formed in the annular end face at the upper end of the columnar member 3, and the lower surface of the thrust holding member 6 has a smooth surface. Have been. In the second thrust dynamic pressure bearing portion composed of the columnar member 3 and the dynamic pressure bearing cover 12, a thrust dynamic pressure generating groove G2 is formed on the annular end face at the lower end of the columnar member 3, and the dynamic pressure is increased. The annular end surface at the upper end of the bearing cover 12 is a smooth surface. The radial dynamic pressure generating groove G1 is a herringbone groove as shown in FIG. 5, and the thrust dynamic pressure generating groove is a spiral groove as shown in FIG.

In the shaft rotary type spindle motor of FIG. 1 constructed as described above, since the electromagnet 14 is not energized at the time of stop, the vertically movable pivot receiver 11 is pushed up by the spring 13 and the pivot 10 is pivoted. The upper surface of the receiver 11 is in solid contact. The spring 13
The size and strength are selected so as to hold the position of the columnar member 3 at the rated rotation or a position close to the position. Therefore, the upper end of the columnar member 3 does not contact the lower surface of the thrust holding member 6, and the lower end of the columnar member 3 does not contact the annular end surface of the upper end of the dynamic pressure bearing cover 12.
In short, in the spindle motor of FIG. 1, no solid contact occurs in the thrust dynamic pressure bearing portion when the spindle motor is stopped.

The operation at the time of starting and stopping will be described with reference to the excitation circuit diagram of FIG. 7 and the time chart of FIG. Time T
When the start switch of the motor is turned on at 1, the controller (not shown) turns on the stator coil switch SW1 to excite the stator coil 8. by this,
The motor starts to rotate. When the motor is started, the vertically movable pivot receiver 11 is still at the first predetermined position. At time T2, the controller turns on the electromagnet SW2 to energize the electromagnet 14, and lowers the magnetic pivot receiver 11, which has been at the first predetermined position, to the second predetermined position. When the pivot receiver 11 is at the first predetermined position, the pivot 10 is supported by the pivot receiver 11, and the thrust dynamic pressure bearing surface is sufficiently separated. Since the pivot receiver 11 is at the first predetermined position not only before the time T1 but also during the time from the time T1 to the time T2, no contact sliding occurs on the thrust dynamic pressure bearing surface when the motor is started.

When the motor rotates at a high speed, a radial dynamic pressure is applied to a clearance between the outer peripheral surface of the cylindrical member 3 and the inner peripheral surface of the cylindrical member 4, and at the same time, the upper end surface of the cylindrical member 3 and the thrust holding member 6 Thrust dynamic pressure is generated in the clearance between the lower surface of the cylindrical member 3 and the clearance between the lower end surface of the columnar member 3 and the upper end surface of the dynamic pressure bearing cover 12, and the motor operates smoothly by the air dynamic pressure bearing. Rotate. Since the time T2 is a time when the motor reaches the rated rotation state or a state close to the rated rotation state, the time interval from the time T1 is short.

When the motor is stopped, the controller first turns off the electromagnet switch SW2 at time T3. Then, the exciting current stops flowing through the electromagnet 14, and the pivot receiver 11 at the second predetermined position is pushed up by the spring 13 to return to the first predetermined position, and supports the pivot 10. Immediately at time T4, the controller turns off the switch SW1 for the stator coil, stops the exciting current to the stator coil 8, and stops the motor. Even if the stator coil switch SW1 is turned off, the motor continues to rotate for a while due to inertia.
Can be a very short time interval of zero or close to it.
Although the control of the excitation of the stator coil 8 and the electromagnet 14 shown in the time chart of FIG. 8 has been described as being performed by a controller (not shown), by adding a circuit element such as a timer or a delay element to the excitation circuit of FIG. Can also be realized.

FIG. 3 shows the present invention wherein the pivot is attached to the lower end of the shaft and the pivot receiver is attached to the base plate, and the pivot and the pivot receiver are separated from each other at the time of rated rotation and are in solid contact at the time of stop. 1 shows another embodiment of the spindle motor according to the present invention. The spindle motor of FIG. 3 has almost the same configuration as the spindle motor of FIG. 1, but the only difference is that the pivot receiver 11 is
Can be moved up and down, whereas in FIG. 3, it is fixed. The pivot receiver 11 in FIG. 3 is provided in the pivot receiving portion of the dynamic pressure bearing cover 12 so that the distance a between the pivot 10 and the upper surface of the pivot receiver 11 is set to the thrust distance between the upper surface of the columnar member 3 and the thrust. It is arranged and fixed so as to be smaller than the distance b with the lower surface of the holding member 6.

In the shaft rotary type spindle motor of FIG. 3 configured as described above, the rotor descends when stopped, and the pivot 10 makes solid contact with the upper surface of the pivot receiver 11. However, as described above, the pivot 10 and the pivot receiver 1
1 is smaller than the distance b between the upper surface of the columnar member 3 and the lower surface of the thrust holding member 6, the lower end of the columnar member 3 is rated at the annular end surface at the upper end of the hydrodynamic bearing cover 12. Although they are closer than when they rotate, they do not make contact because they leave a gap between b and a. At this time, the upper end of the columnar member 3 and the lower surface of the thrust holding member 6 are further separated from each other at the time of the rated rotation and are not in contact with each other. In short, even in the spindle motor of FIG. 3, solid contact does not occur in the thrust dynamic pressure bearing portion at the time of stop.

When the start switch of the motor is turned on, the rotor starts to rotate. At this time, since the thrust dynamic pressure bearing surfaces are spaced apart from each other at a very small interval, no contact sliding occurs at the time of startup. When the motor rotates at a high speed, the pivot 10 moves away from the pivot receiver 11 by the action of the radial dynamic pressure and the thrust dynamic pressure as in FIG. Therefore, at the time of rated rotation, the bearing of the spindle motor in FIG. The grounding of the rotor can be realized by interposing a conductive magnetic fluid between the pivot 10 and the pivot receiver 11, so that the spindle motor shown in FIG. Suitable for source.

FIG. 2 shows an embodiment of the spindle motor according to the present invention in which a pivot bearing having a metal pivot attached to a lower end of a shaft and a pivot receiver attached to a base plate is provided together with an air dynamic pressure bearing. The spindle motor of FIG. 2 has almost the same configuration as the spindle motor of FIG. 3, except for the pivot 10 and the pivot receiver 1.
1 is far away in FIG. 3, but is always in solid contact in FIG. In FIG. 2, a lubricant is interposed between the pivot 10 and the pivot receiver 11 as needed. In this case, a magnetic fluid is used as the lubricant. The magnetic fluid has an advantage that contamination due to scattering can be prevented. If the conductive magnetic fluid is used as a lubricant, the rotor can be reliably grounded. Therefore, the spindle motor shown in FIG. 2 is also suitable as a drive source for a rotating device such as a hard disk device in which static electricity is easily accumulated. In FIG. 2, since the rotor is supported on the stator using the air dynamic pressure bearing and the pivot bearing, no contact sliding occurs on the air dynamic pressure bearing when the motor is started.

FIG. 10 shows a hard disk drive in which a spindle motor SM according to the present invention is used as a drive source of a medium 15 which is a rotating body.

[0021]

According to a first aspect of the present invention, there is provided a shaft rotary type spindle motor having an air dynamic bearing or a rotary device using a spindle motor as a driving source of a rotary body, wherein a pivot is provided at a lower end of the shaft and a pivot receiver is provided on a base plate. And the pivot and the pivot receiver are separated from each other at the time of rated rotation and solidly contact at the time of stop. In other words, the spindle motor according to the present invention supports the rotor to the stator only by the air dynamic pressure bearing at the time of rated rotation, and supports the rotor to the stator by the touch-down pivot when stopped. Further, the second invention relates to two types of air dynamic pressure bearings and pivot bearings.
The present invention relates to a spindle motor having two bearings, or a rotating device using the spindle motor as a driving source of a rotating body. In any of the inventions, since the pivot and the pivot receiver are in solid contact at the time of stop, contact sliding does not occur in the dynamic pressure bearing, particularly in the thrust dynamic pressure bearing in the first invention, at the time of startup. Therefore, the life of the pneumatic dynamic bearing and thus the life of the device is not shortened due to the contact sliding at the time of starting. Further, an effect of reducing the load torque (friction torque) at the time of starting is also exerted. Furthermore, since the components or parts embodying the means for achieving such effects are easily available and easily processed and assembled, it is possible to avoid an increase in the size and cost of the apparatus.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an embodiment of a spindle motor provided with a dynamic pressure bearing according to the present invention, in which a pivot and a pivot receiver are separated at a rated rotation and solidly contact at a stop.

FIG. 2 is a sectional view of an embodiment of a spindle motor provided with a dynamic pressure bearing and a pivot bearing according to the present invention.

FIG. 3 is a cross-sectional view of another embodiment of the spindle motor provided with the dynamic pressure bearing according to the present invention, in which the pivot and the pivot receiver are separated at a rated rotation and solidly contact at a stop.

FIG. 4 is a diagram for explaining a relationship between a distance a between a pivot and a pivot receiver of the spindle motor shown in FIG. 3 and a distance b between thrust bearing constituent members.

FIG. 5 is a view showing an example of a radial dynamic pressure generating groove.

FIG. 6 is a diagram illustrating an example of a thrust dynamic pressure generation groove.

FIG. 7 is an excitation circuit diagram of a stator coil and an electromagnet.

FIG. 8 is a diagram illustrating a time relationship between excitation of a stator coil and an electromagnet.

FIG. 9 is a sectional view of a spindle motor provided with a conventional air dynamic pressure bearing.

FIG. 10 is a perspective view of a floppy disk drive using a spindle motor as a drive source.

[Explanation to the code]

 DESCRIPTION OF SYMBOLS 1 Base plate 2 Shaft 3 Columnar member 4 Cylindrical member 5 Thrust member 6 Upper cover or donut-shaped thrust holding member 7 Substantially cup-shaped hub 8 Stator coil 9 Rotor magnet 10 Pivot 11 Pivot receiving 12 Pivot receiving and receiving part 13 Spring 14 Electromagnet 15 Media 16 Power supply SM Spindle motor G1 Radial dynamic pressure generating groove G2 Thrust dynamic pressure generating groove SW1 Switch for stator coil SW2 Switch for electromagnet

Claims (8)

[Claims] 1. A shaft rotary type spindle motor having an air dynamic pressure bearing, wherein a pivot is attached to a lower end of a shaft and a pivot receiver is attached to a base plate, respectively.
A spindle motor, wherein the pivot and the pivot receiver are separated from each other during rated rotation and are in solid contact when stopped. 2. The pivot receiver according to claim 1, wherein the pivot receiver is a vertically movable pivot receiver, so that the pivot and the pivot receiver are separated from each other at the time of rated rotation and are in solid contact at the time of stop. Spindle motor. 3. The pivot receiver which can be raised and lowered comprises a magnetic pivot receiving member which is pushed up by a spring, and an electromagnet which pulls down the pivot receiving member when stopped. Item 2. The spindle motor according to item 2. 4. A rotary shaft type spindle motor having a radial dynamic pressure bearing portion having a cylindrical bearing member and a cylindrical bearing member, and an air dynamic pressure bearing having a donut-shaped thrust member and a donut-shaped thrust pressing member. In the above, a pivot is attached to the lower end of the shaft and a pivot receiver is attached to the base plate, and further, the distance between the pivot and the pivot receiver at the time of rated rotation is set to the upper surface of the donut-shaped thrust member and the donut-shaped thrust holding member. By making it slightly smaller than the gap with the lower surface,
A spindle motor, wherein the pivot and the pivot receiver are separated at a rated rotation and solidly contact at a stop. 5. A spindle motor provided with an air dynamic pressure bearing, wherein a pivot bearing is provided in which a metal pivot is attached to a lower end of a shaft and a pivot receiver is attached to a base plate. 6. The spindle motor according to claim 1, wherein a magnetic fluid or a conductive magnetic fluid is interposed between said pivot and said pivot receiver. 7. A rotary shaft type spindle motor provided with an air dynamic pressure bearing, wherein a pivot is attached to a lower end of a shaft and a pivot receiver is respectively attached to a base plate, and the pivot and the pivot receiver are separated at a rated rotation. A rotating body device using a spindle motor as a driving source for the rotating body, wherein the rotating body makes a solid contact when stopped. 8. A spindle motor provided with a pneumatic dynamic bearing, wherein the spindle motor is provided with a pivot bearing having a metal pivot attached to a lower end of the shaft and a pivot receiver attached to a base plate. Is a driving device of the rotating body.