JP3529869B2 - Hydrodynamic bearing means for motor - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to motors. More specifically, it relates to a hydrodynamic bearing for a motor.

[0002]

2. Description of the Related Art Up to now, for example, as shown in FIG.
Spindle motors using hydrodynamic bearings are known to those skilled in the art. In a known spindle motor 1 using a hydrodynamic bearing as shown in FIG. 8, the lower end of the shaft 4 is fixed to the boss portion 3 of the fixed base member 2, and the radius of the boss portion 3 is fixed. The stator 5 is fixed to the outside in the direction by a suitable means. A reduced diameter portion 6 is provided at the upper end of the shaft 4, and a thrust plate 7 is fitted and fixed to the reduced diameter portion 6, and the upper surface of the thrust plate 7 is also fitted to the reduced diameter portion 6. It is held by the bush 8. A cover plate 9 is arranged outside the bush 8 in the radial direction and on the upper surface of the thrust plate 7. A shaft holding member 10 is provided radially outward of the cover plate 9, and the shaft holding member 10 and the cover plate 9 are in a fixed relationship with each other. Further, a part of the shaft holding member 10 holds the thrust plate 7 and extends further downward from the thrust plate 7, and supports a dynamic pressure fluid radial bearing portion 11 formed in the middle of the shaft 4. Further, the shaft holding member 10 supports the rotor magnet 12 at a position opposed to the stator 5 radially outward of the stator 5. Furthermore, the shaft holder 10 has a hub 13 radially outward thereof, and the hub 13 holds a disk 14. Between the upper surface of the thrust plate 7 and the lower surface of the cover plate 9, the lower surface of the thrust plate 7 and the shaft holder 10
And the shaft 4 and the yoke 10 respectively have oils, which form a hydrodynamic bearing.

[0003]

In such a hydrodynamic bearing for a spin motor, however, the spindle rotates at an extremely high speed during operation, and the stopped state and the rotated state are repeated many times. Due to the large amount of air, air can often be mixed into the oil. If air is mixed in the oil, the mixed air often remains in the oil as bubbles without being discharged to the outside. When air bubbles are accumulated in the oil, for example, when the temperature of the oil rises, the air has a larger coefficient of thermal expansion than the oil, so that the air bubbles may expand and the oil may fly out from the bearing portion.

In the conventional hydrodynamic bearings of this type, there has not been a portion for holding extra oil, that is, an oil reservoir. Therefore, it is necessary to strictly measure the amount of oil present in the bearing portion, and if the amount of oil is larger than a predetermined value, there is a risk that excess oil will leak from the bearing portion to the outside.

Further, since it is not possible to hold excess oil in the bearing in advance in this way, if the bearing is used for a long time, the oil will evaporate. This may cause seizure and the like, resulting in shortening the life of the bearing.

Further, in the conventional hydrodynamic bearings of this type, there is no means for sealing and maintaining the oil in the bearing portion at the end portion of the bearing portion. Therefore, the bearing portion is concerned. There was a risk that oil would leak from the outside and other mechanical elements would be contaminated by the leaked oil.

[0007]

SUMMARY OF THE INVENTION Therefore, the present invention is intended to solve these problems, and for this purpose, the bearing portion is provided with a communication hole communicating with the outside of the bearing portion. Further, the bearing portion is provided with a portion for holding extra oil, that is, an oil reservoir. Further, means for maintaining and retaining oil in the bearing portion is provided at the end portion of the bearing portion.

[0008]

In the hydrodynamic bearing of the present invention, since the bearing portion is provided with the communicating hole communicating with the outside of the bearing portion, the air mixed in the oil escapes from the communicating hole to the outside of the bearing portion. Became possible. Also, by providing a part for holding extra oil in the bearing part, that is, an oil reservoir, it is not necessary to strictly measure the amount of oil interposed in the bearing part, and when the bearing is used for a long time, the oil Even if the oil evaporates and the oil in the bearing portion decreases, sufficient oil for preventing seizure can be held in the bearing portion in advance, so that the life of the bearing is not shortened. Further, by providing a means for sealing and holding the oil in the bearing portion at the end portion of the bearing portion, there is a risk that the oil leaks from the bearing portion to the outside and contaminates other mechanical elements with the leaked oil. Will be resolved.

[0009]

1 is a partially enlarged view of a spindle motor 20 as an example of a motor having a hydrodynamic bearing of the present invention. In the figure, reference numeral 21 is a shaft having a lower end fixedly held to a boss portion (not shown) of the fixed base member. A reduced diameter portion 22 is provided at the upper end of the shaft 21. A thrust plate 23 is fitted in and fixed to the reduced diameter portion 22, and the upper surface of the thrust plate 23 is held by a bush 24 which is also fitted in the reduced diameter portion 22. A cover plate 25 is arranged radially outward of the bush 24 and on the upper surface of the thrust plate 23. A shaft holding member 26 is attached to the cover plate 25 in the same manner as shown in FIG. The shaft holding member 26 and the cover plate 2
5 is connected to each other. A part of the holding member 26 holds the side surface of the thrust plate 23 and extends from there to below the thrust plate 23, and further, a hydrodynamic fluid radial bearing portion 27 formed in the middle of the shaft 21.
I support you. The radial bearing portion 27 includes a pair of bearing grooves 27 arranged at intervals in the axial direction.
It may be formed from a and 27b, and may be formed on the inner peripheral surface of the holding member 26 instead of the shaft 21. The boss portion of the base member (not shown) holding the shaft 21 is radially outwardly of the boss portion by a suitable means.
9 is fixedly held. As shown in FIG. 8, the holding member 26 supports a rotor magnet (not shown) at a position opposed to the stator on the outside in the radial direction of the stator 29. Further, as shown in FIG. 8, the holding member 26 has a hub (not shown) radially outward thereof, and a disk (not shown) is held by the hub. As a result, the thrust plate 23 and the cover plate 25 and the holding member 26 surrounding the upper surface, the side surface, and the lower surface of the thrust plate 23, and between the shaft 21 and the holding member 26 are respectively provided with the first plate. And a second hydrodynamic bearing, that is, a hydrodynamic bearing. In the embodiment, the first hydrodynamic bearing comprises a hydrodynamic thrust bearing portion having bearing grooves formed on the upper and lower surfaces of the thrust plate 23.

In the present invention, the reduced diameter portion 2 of the shaft 21
The thrust plate 23 attached to the No. 2 is formed by a radially inner portion 30 whose lower surface portion is scraped off and a radially outer portion 31 sandwiched by the cover plate 24 and the holding member 26. Has been done. Further, the thrust plate 2 is provided on the radially inner portion 30.
At least one communication hole 32 that communicates with the upper and lower surfaces of the metal plate 3 is formed. The radially inner portion 30 of the thrust plate 23 is scraped off in the lower surface portion, but this is for increasing the volume of the void portion described later, and is not an essential item, and a sufficient volume can be secured. At times, the entire thrust plate 23 may have the same thickness.

A passage 28 is formed between a radially inner portion 33 of the cover plate 25 and the bush 24. The lower surface of the radially inner portion 33 of the cover plate 25 is provided with a taper notch at a predetermined angle (a °) radially outward and downward from the lower surface.
As a result, the lower surface portion of the cover plate 25 inward in the radial direction, the upper surface of the thrust plate 23, and the bush 24.
A space 34 is formed between the and. An upper end of the communication hole 32 is open in the void 34. Here, the angle a is preferably 5 ° to 10 °.

As shown in FIG. 1, the thrust plate 23
Of the holding member 26 from the lower surface of the shaft to the radial bearing portion 27 of the shaft 21 at a predetermined angle (b ° and c).
The taper is cut off in the form of a taper, and a space 36 having a substantially triangular cross section is formed between the lower surface of the thrust plate 23 and the shaft 21 and the holding member 26. This void 36 provides an oil holding sump. Further, as shown clearly in FIG. 2, at least one groove 37 is formed in the corner portion 35. The groove 37 communicates the thrust bearing portion on the lower surface of the thrust plate 23 with the radial bearing portion 27 side of the shaft 21. Here, it is desirable that the angle b is larger than the angle a, for example, an angle of about 45 °. The angle c is automatically specified by specifying the angle b.

Further, at a lower portion of the holding member 26 hanging from the corner portion 35 facing the shaft 21, a predetermined angle (d °) toward the lower side of the shaft 21 and outward in the radial direction. The notch is provided. As a result, a space 38 is formed between the holding member 26 and the shaft 21. As shown in FIG. 2, the lower end of the space 38 is closed by an annular flange portion 39 that integrally extends from the holding member 26 toward the shaft 21. This flange portion 39 provides an oil retaining means, and at least one (in FIG. 2, one in FIG. 2 and two in FIG. 3) which communicates the flange portion 39 with the upper and lower sides is shown. is doing)
Groove 40 is formed. Where the angle d is the angle c
It is desirable that the angle is smaller than that, for example, 5 ° to 10 °.

As shown in FIG. 1, the first hydrodynamic bearing portion formed between the thrust plate 23, the cover plate 25, and the holding member 26 of the present invention, and between the shaft 21 and the holding member 26. The second hydrodynamic bearing portion formed in the above is filled with a predetermined oil. To prevent oil from leaking from these hydrodynamic bearings,
The portion having the angle a ° is the first sealing portion, the portion having the angle b ° is the second sealing portion, the portion having the angle c ° is the third sealing portion, and the angle d °.
Forming a fourth seal portion. As is known to those skilled in the art, the sealing force is such that the first seal portion has a second seal portion angle (a °) less than the second seal portion angle (b °). Will be larger than. Similarly, since the angle (d °) of the fourth seal portion is smaller than the angle (c °) of the third seal portion, the sealing force is larger in the fourth seal portion than in the third seal portion.

As a result, in the first hydrodynamic bearing portion, the oil flows into the void portion 3 rather than flowing out to the space 34 side.
Provides a tendency to flow to the 6 side. The thrust bearing portion is located between the first seal portion and the second seal portion, and the radial bearing portion 27 is formed between the third seal portion and the fourth seal portion. Located in between. On the other hand, in the second hydrodynamic bearing portion, the oil provides a tendency to flow into the void 36 side rather than flow into the void 38 side. This allows air bubbles to get into the oil,
Even if the pressure or temperature of oil rises and the bubbles expand,
The oil flows into the space 36 rather than out of the machine. Therefore, oil is prevented from flowing out of the machine. Further, in order to prevent the oil from flowing out of the machine if the oil flows out from the fourth seal portion, the flange portion 39 provides an oil holding means. Further, the groove 40 is formed by the oil holding means 3
The air in the oil held in 9 is separated, and only the air is allowed to escape to the outside of the machine easily.

The void 36, which provides an air chamber, communicates with the outside air through the communication hole 32, the void 34 and the passage 28. Therefore, even if air or air bubbles are mixed in the oil that has flowed from the first dynamic pressure fluid bearing portion and the second dynamic pressure fluid bearing portion into the gap portion 36, the separation of gas and liquid is not achieved in this air chamber. Is carried out, and only gas such as air is passed through these communication holes 3
It is possible to easily escape to the outside of the aircraft via 2 etc. Further, the oil contained in the first hydrodynamic bearing portion and the oil contained in the second hydrodynamic bearing portion mutually pass through the groove 37 opened in the void 36. It is in communication. For this reason, the oil in each hydrodynamic bearing moves freely and is adjusted so that the oil pressure in both hydrodynamic bearings is always the same, and the oil prevents mutual seizure of the shaft. The oil retained in the functioning voids 36 is freely supplied to each hydrodynamic bearing portion of the oil evaporated by the long-term operation of the spindle motor 20 as required, and similarly, the seizure of the shaft is caused. It provides the effect of preventing each other.

That is, in the hydrodynamic bearing of the present invention, the bearing portion has a communication hole 32 or a groove 40 communicating with the outside of the bearing portion.
Was set up. Thereby, even if air is mixed in the oil, the air can escape from the communication hole or groove to the outside of the bearing portion. Therefore, even if air is mixed into the oil of the bearing section by rotating the spindle at an extremely high speed during operation and repeating the stopped state and the rotating state many times, the mixed air is quickly Moreover, since the oil is easily discharged from the bearing portion, there is no possibility of the oil splashing out of the bearing portion even when the temperature of the oil rises.

Further, since the bearing portion is provided with a portion for holding extra oil, that is, an oil sump, it is not necessary to strictly measure the amount of oil present in the bearing portion. Even if there is more than this, excess oil is stored in the oil sump, and there is no fear of leaking to the outside from the bearing portion. That is, the amount of injected oil is expanded to a tolerance close to the volume of the air chamber. In addition, even if the oil evaporates when the bearing is used for a long time and the oil in the bearing decreases, enough oil can be retained in the bearing in advance to prevent seizure, which shortens the life of the bearing due to oil shortage. There is no fear of becoming.

Further, by providing a means for sealing and holding the oil in the bearing portion at the end portion of the bearing portion, the oil leaks from the bearing portion to the outside, and other mechanical elements are contaminated with the leaked oil. That danger has been resolved.

FIG. 4 shows a second embodiment of the present invention. The spindle motor 50 is different from the spindle motor 20 shown in FIG. 1 in that the shaft 51 and the thrust plate 52 are more reliably integrated, vibration of the thrust plate 52 is eliminated, and vibration of the entire spindle motor 50 is reduced. In order to prevent this, the shaft 51 and the thrust plate 52 are integrally molded. By forming them integrally as described above, the perpendicularity between the shaft 51 and the thrust plate 52 can be maintained. Therefore, in FIG. 4, the shaft 51 has no reduced diameter portion, and there is no bush for holding the radially inner portion of the thrust plate 52. Other parts and elements, and further the entire function and effect are the spindle motor 20 shown in FIG.
It is similar to the case of.

5 and 6 show a third embodiment of the present invention. The spindle motor 60 is different from the spindle motor 20 shown in FIG. 1 in the position of an air vent groove 40 provided in the flange portion 39 shown in FIGS. In this embodiment, a groove 64 having a length equal to or larger than the thickness dimension of the flange portion 3 is formed on the surface of the holding member 62 facing the flange portion 63 of the holding member 62. The groove 64 is formed in the space 6 formed by the flange portion 63.
5 is connected to the outside of the machine, and has a function of discharging the air in the oil flowing into the space 65 to the outside of the machine. Other parts and elements, and further the whole function and effect are the same as those of the spindle motor shown in FIG.

FIG. 7 shows a fourth embodiment of the present invention. The spindle motor 70 is different from the spindle motor 20 shown in FIG. 1 in that the space 38 shown in FIGS.
And the flange portion 39 and the air vent groove 40 provided in the flange portion 39. In the example of FIG.
The space 7 provided in the lower part of the second hydrodynamic bearing portion 73 formed between the shaft 71 and the holding member 72.
4, the flange portion 75 as an oil holding means for holding the oil flowing out into the void 74, and the air vent groove 76 for guiding the air out of the oil accumulated in the flange portion 75 to the outside of the machine are all provided on the shaft 71 itself. It is provided in. On the other hand, the surface of the holding member 72 that supports the shaft 71 has a straight surface, which makes the processing of the holding member 72 extremely easy. Here the flange part 7
The position of the oil holding surface of No. 5 is the lower edge portion 77 of the holding member 72.
Higher than. Further, the groove 76 needs to extend below the lower edge 77. This is because it becomes possible to properly retain oil and release air. Other parts and elements, and further the whole function and effect are the same as those of the spindle motor shown in FIG.

In these embodiments, the thrust plate does not need to be thinly shaved on the lower surface side of the inner portion of the radius method as shown in the respective drawings, and the entire thickness may be the same. On the street.

[0024]

In the hydrodynamic bearing of the present invention, since the bearing portion is provided with the communication hole 32 or the groove 40 which communicates with the outside of the bearing portion, even if air is mixed in the oil, the air will not be discharged. It can escape to the outside of the bearing through the passage. Therefore, even if air is mixed in the oil of the bearing section by rotating the spindle at an extremely high speed during operation and repeating the stopped state and the rotated state many times, the mixed air is swift. And easily discharged from the bearing portion. So, for example, even if the oil temperature rises,
There is no longer a risk of oil spattering from the bearing.

Since the bearing portion is provided with a portion for holding extra oil, that is, an oil reservoir, it is not necessary to strictly measure the amount of oil present in the bearing portion. Further, even if the oil supply amount is larger than the required amount, excess oil is accommodated in the oil reservoir, and there is no fear of leaking from the bearing portion to the outside. Further, even if the oil evaporates when the bearing is used for a long time and the oil in the bearing portion decreases, sufficient oil can be held in the bearing portion in advance to prevent seizure. Therefore, there is no fear that the life of the bearing will be shortened.

Further, by providing a means for sealing and holding the oil in the bearing portion at the end portion of the bearing portion, the oil leaks from the bearing portion to the outside and contaminates other machine elements with the leaked oil. That danger has been resolved.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing a first embodiment of the present invention.

FIG. 2 is a partial perspective view showing the holding member of FIG.

FIG. 3 is a sectional view taken along line XX in FIG.

FIG. 4 is a sectional view of a main part similar to FIG. 1, showing a second embodiment of the present invention.

FIG. 5 is a cross-sectional view of a main part similar to FIG. 1, showing a third embodiment of the present invention.

6 is a cross-sectional view taken along the line YY of FIG.

FIG. 7 is a cross-sectional view of an essential part similar to FIG. 1, showing a fourth embodiment of the present invention.

FIG. 8 is a cross-sectional view showing an example of a spindle motor including a known hydrodynamic bearing.

[Explanation of symbols]

21 shaft 23 Thrust plate 26 Holding member 27 Radial bearing 32 communication holes 35 corners 36 Void 39 Flange part

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Claims (14)

(57) [Claims] 1. A shaft, a shaft holding member holding the shaft as a bearing, and a thrust plate attached to the shaft, wherein the thrust plate portion has a first dynamic pressure fluid bearing means. Second on the shaft
Is a hydrodynamic bearing means for a spindle motor in which a hydrodynamic bearing means is interposed between the shaft and the lower surface of the thrust plate. A fluid dynamic bearing means for a motor, characterized in that a communication hole for connection is provided in the thrust plate. 2. The first hydrodynamic bearing means has a first seal portion on the upper surface of the thrust plate, a second seal portion on the lower surface of the thrust plate, and the second seal portion is the above-mentioned. 2. A fluid dynamic bearing means for a motor according to claim 1, wherein the fluid dynamic bearing means is open in the space. 3. The dynamic pressure bearing means for a motor according to claim 2, wherein the sealing force of the first seal portion is larger than the sealing force of the second seal portion. 4. A second hydrodynamic bearing means is provided with a third hydrodynamic bearing means at one end.
And a fourth seal portion at the other end,
2. The dynamic pressure fluid bearing means for a motor according to claim 1, wherein said seal portion is open to said space. 5. The fluid dynamic bearing means for a motor according to claim 4, wherein the sealing force of the fourth seal portion is larger than that of the third seal portion. 6. A hydrodynamic bearing for a motor according to claim 4, wherein an oil holding flange portion for holding oil leaking from the seal portion is provided outside the fourth seal portion. means. 7. The fluid dynamic bearing means for a motor according to claim 6, wherein the flange portion is provided on either the shaft or the shaft holding member. 8. A dynamic pressure fluid bearing means for a motor according to claim 7, wherein an air vent groove is provided in the flange portion. 9. An oil flow groove for allowing oil to flow between the first dynamic pressure fluid bearing means and the second dynamic pressure fluid bearing means is provided in the void portion. The dynamic pressure fluid bearing means of the motor according to any one of claims 1 to 8. 10. The hydrodynamic bearing means for the motor according to claim 3 or 5, wherein the magnitude of the sealing force is adjusted by the notch angle of the seal portion. 11. The notch angle of the first seal portion and the fourth seal portion is 5 to 10 °, and the notch angle of the second seal portion and the third seal portion is about 45 °. A fluid dynamic bearing means for a motor according to claim 10. 12. A shaft, a shaft holding member that holds the shaft as a bearing, a dynamic pressure fluid radial bearing means interposed between the shaft and the shaft holding member, and an outside of the radial bearing means. A fluid dynamic bearing means for a motor comprising: a seal means; and an oil holding flange for holding oil leaking from the seal portion outside the seal means. A hydrodynamic bearing means for a motor, characterized in that a portion is provided. 13. The fluid dynamic bearing means for a motor according to claim 12, wherein the flange portion is provided on the shaft holding member. 14. The fluid dynamic bearing means for a motor according to claim 12, wherein an air vent groove is provided in said flange portion.