JPH08163820A - Motor with dynamic fluid bearing means - Google Patents

Abstract

PURPOSE: To obtain a motor equipped with a dynamic pressure fluid bearing means for preventing oil leakage effectively and seizure due to deficiency of oil. CONSTITUTION: The motor comprises a shaft 21, shaft holding members 25, 26, and a thrust plate 23 carried on the shaft 21 where a thrust dynamic pressure fluid bearing means is interposed between the thrust plate 23 and the shaft holding members 25, 26 while a radial dynamic pressure fluid bearing means 27 is interposed between the shaft holding members 25, 26 and the shaft 21. An oil sump 40 and an air chamber 41 are disposed between the thrust plate 23 and the shaft holding members 25, 26 and the oil sump 40 is coupled with a channel 40 for feeding oil to the thrust dynamic pressure fluid bearing means while the air chamber 41 is coupled with a channel 42 communicating the atmosphere.

Description

Detailed Description of the Invention

[0001]

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

[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. 4, 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 similarly 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 sleeve member 10 is provided on the outer side of the cover plate 9 in the radial direction, and the cover plate 9 and the sleeve member 10 are fixed to each other, and these constitute a shaft holding member. In addition, a part of the sleeve member 10 holds the thrust plate 7 and extends from there below the thrust plate,
1 bears a radial hydrodynamic bearing means 12 formed in the middle of the shaft 4. Further, the sleeve member 1
Reference numeral 0 supports the rotor magnet 13 at a position opposed to the stator 5 radially outward of the stator 5. Furthermore, the sleeve member 10 has a hub 14 radially outward thereof, and the hub 14 holds a disk (not shown). Oil is interposed between the upper surface of the thrust plate 7 and the lower surface of the cover plate 9 and between the lower surface of the thrust plate 7 and the sleeve member 10 to form thrust hydrodynamic bearing means, and the shaft 4
Oil is interposed between the and the yoke 10 to form a radial dynamic pressure fluid bearing means.

[0003]

In such a spinned motor, however, it often rotates at an extremely high speed during operation, and the stopped state and the rotated state are repeated many times, so that it is often submerged in oil. Air may be mixed in. 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.

Further, in the conventional motor provided with this type of hydrodynamic bearing means, there is no reservoir for holding extra oil, that is, a so-called 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. In addition, since it is not possible to retain excess oil in the bearing in advance in this way, if the bearing is used for a long time, the oil evaporates, but in such a case, the oil in the bearing decreases, This may cause seizure or the like, resulting in shortening the life of the bearing.

The present invention solves the above-mentioned problems and provides a motor having a hydrodynamic bearing means capable of effectively preventing oil leakage and preventing seizure due to insufficient oil supply. It is to be.

[0006]

A motor according to the present invention has a shaft, a shaft holding member that holds the shaft as a bearing, and a thrust plate provided on the shaft. The thrust plate and the shaft holding member are provided. And thrust dynamic fluid bearing means, and radial dynamic fluid bearing means is provided between the shaft holding member and the shaft. An oil reservoir containing oil and an air chamber containing air are provided between the outer peripheral surface of the thrust plate and the shaft holding member, and the oil in the reservoir is thrust-moved in the oil reservoir. An oil supply passage for supplying the pressure fluid bearing means is communicated with the air chamber, and an air passage for communicating the air chamber with the atmosphere is communicated with the air chamber.

[0007]

In the motor of the present invention, the oil reservoir and the air chamber are provided between the outer peripheral surface of the thrust plate and the shaft holding member. The oil reservoir is connected to an oil supply passage for supplying the oil in the reservoir to the thrust hydrodynamic bearing means. Therefore, in the thrust hydrodynamic bearing means, the oil tends to flow outward in the radial direction due to the centrifugal force generated by the rotation of the rotor. The oil is supplied to the thrust dynamic pressure fluid bearing means through the supply passage, and the oil shortage in the thrust dynamic pressure fluid bearing means is eliminated. Also, in the air chamber,
Since the air passage for communicating the air chamber with the atmosphere is communicated, the air collected from the oil in the air chamber is discharged to the atmosphere through the air passage, and the adverse effect of the air can be avoided. By providing an oil reservoir and an air chamber that has the function of adjusting the amount of oil, it is not necessary to strictly measure the amount of oil present in the bearing means, and the oil will evaporate when the bearing is used for a long time. Even if the oil in the bearing means decreases, sufficient oil can be held in advance to prevent seizure.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the essential part of an embodiment of a motor of the present invention. In FIG. 1, the illustrated motor includes a shaft 21 whose lower end is fixedly held by a boss (not shown) of a fixed base member. A reduced diameter portion 22 is provided at the upper end of the shaft 21. A thrust plate 23 is attached to the reduced diameter portion 22.
3 is fixed to the reduced diameter portion 22 by a bush 24, as in the prior art. A cover plate 25 is disposed on the outer surface of the bush 24 in the radial direction and on the upper surface of the thrust plate 23. This cover plate 2
5, a sleeve member 26 is attached, as in FIG. Also in this example, the cover plate 23 and the sleeve member 26 are fixed to each other to form a shaft holding member. A part of the sleeve member 26 holds the peripheral side surface of the thrust plate 23 and extends from there to below the thrust plate 23, and further supports the radial dynamic pressure fluid bearing means 27 provided in the middle of the shaft 21. . The radial dynamic pressure fluid bearing means 27 includes a pair of bearing grooves 2 formed on the shaft 21 at intervals in the axial direction.
8 and 29, the inner peripheral surface of the sleeve member 26 may be formed instead of the shaft 21. A boss portion of the base member (not shown) holding the shaft 21 has a stator (not shown) fixedly held radially outward thereof by a suitable means. As shown in FIG.
The sleeve member 26 supports a rotor magnet (not shown) at a position opposed to the stator radially outward of the stator. Further, the sleeve member 2
As shown in FIG. 4, 6 has a hub (not shown) radially outward thereof, and a magnetic disk (not shown) is attached to this hub.
Is held. As a result, the thrust plate 23
And a thrust dynamic fluid bearing means between the cover plate 25 and the sleeve member 26 surrounding the upper surface, side surface and lower surface of the thrust plate 23, and between the shaft 21 and the sleeve member 26. , Radial dynamic pressure fluid bearing means are provided. In the embodiment, the thrust hydrodynamic bearing means is the thrust plate 2
3 is composed of bearing grooves formed on the upper and lower surfaces. The bearing groove of this thrust dynamic pressure fluid bearing means is replaced by the cover plate 25 instead of the thrust plate.
It can also be formed on the sleeve member 26.

In the motor of the embodiment, the sleeve member 2 facing the corners of the thrust plate 23 and the shaft 21.
A part of the facing portion of 6 is scraped off in a triangular shape, and by scraping off, the air chamber 30 (second
Which constitutes the air chamber). This air chamber 3
In order to increase the volume of 0, a part of the thrust plate 23 may be cut out.

The radial dynamic pressure bearing means and the thrust dynamic pressure fluid bearing means 27 are further configured as follows. That is, an atmosphere passage 31 that communicates with the outside of the motor, that is, the atmosphere, is defined between the radially inner portion 31 of the cover plate 25 and the bush 24. On the lower surface of the radially inner portion of the cover plate 25, there is provided a taper portion 32 (constituting a first sealing means) that is inclined upward inward at a predetermined angle (a °) from the inside. It is provided. As a result, a space 33 is formed between the lower surface portion of the cover plate 25 radially inward, the upper surface of the thrust plate 23, and the bush 24. The angle a here is preferably 5 ° to 10 °.

As shown in FIG. 1, the thrust plate 23
From the bottom surface of the shaft to the radial dynamic pressure fluid bearing means 2 of the shaft 21
7 is a predetermined angle (b °,
The taper portion 34 (angle b) is attached to the lower thrust hydrodynamic bearing means.
°) (constituting the second sealing means) and the taper portion 35 (angle c °) following the radial dynamic pressure fluid bearing means 27 (the third).
Which constitutes the sealing means). 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 the angle b
Is automatically specified.

Further, the lower portion of the sleeve member 26 hanging from the corners defining the tapered portions 34 and 35 facing the shaft 21 is radially outward toward the lower side of the shaft 21. Is provided with a taper portion 37 (which constitutes a fourth sealing means) inclined at a predetermined angle (d °). Here, the angle d is preferably, for example, 5 ° to 10 °.

As shown in FIG. 1, the thrust hydrodynamic bearing means formed between the thrust plate 23, the cover plate 25 and the sleeve member 26 of the present invention, and formed between the shaft 21 and the sleeve member 26. The radial dynamic pressure hydrodynamic bearing means 27 is filled with oil. In order to prevent oil from leaking from these hydrodynamic bearing means, in the embodiment, the maximum gap between the tapered portion 32 (first sealing means) and the tapered portion 37 (fourth sealing means) is the thrust plate 23. It is set to be larger than the gap between the sleeve member 26 and the sleeve member 26, which makes it difficult for oil to flow out from the tapered portions 32 and 37.

Further in connection with the thrust plate 23,
It is configured as follows. Referring to FIG. 2 together with FIG. 1,
In the first embodiment, the outer circumferential surface of the thrust plate 23 is formed with a tapered groove 38 in the circumferential direction. This groove 38
1 has the smallest depth in the left peripheral portion in FIGS. 1 and 2 (substantially does not exist in the embodiment), and FIG.
Is the largest on the right side (eg 0.2 to 1 mm)
The degree is good). The cross section of the groove 38 may be, for example, a substantially V shape or a substantially trapezoidal shape. In the embodiment, the tapered groove 38 is formed such that the bottom surface thereof is slightly eccentric to the left side in FIGS. 1 and 2 with respect to the circular thrust plate 23, and thus the thrust groove 23 of the thrust plate 23 is formed. It is configured such that the space between the sleeve member 26 and the sleeve member 26 is minimized at one circumferential portion, and that the space between the sleeve member 26 and the other circumferential portion of the thrust plate 23 is maximized. By forming the groove 38 in the thrust plate 23, the oil existing between the outer peripheral surface of the thrust plate 23 and the inner peripheral surface of the sleeve member 26 has a smaller gap along the bottom surface of the groove 38. That is, the force acting to move to the left in FIG. 1 and FIG. 2 acts, and this oil collects on the left side of the groove 38 of the thrust plate 23 as shown in FIG.
8 (the portion located on the left side of the thrust plate 23) functions as an oil reservoir 40, while the oil-free space between the outer peripheral surface of the thrust plate 23 and the sleeve member 26, that is, the groove 38. On the right side (the portion located on the right side of the thrust plate 23) functions as an air chamber 41 in which air exists. In the outer peripheral surface of the thrust plate 23, a region where the groove 38 does not exist and the sleeve member 26 are provided.
As will be easily understood, oil is interposed in the space with the inner peripheral surface of the, and the broken line 44 in FIG. 2 indicates the oil boundary surface in the concave groove 38.

The thrust plate 23 is further provided with an air passage 42 and an oil supply passage 43. Airway 4
The reference numeral 2 extends linearly to the right in FIGS. 1 and 2 in the radial direction of the thrust plate 23, and its one end opening is open to the air chamber 41. The other end of the air passage 42 is branched upward and downward, and the upper opening is opened to the void 33 (specifically, a region substantially outside the tapered portion 32 and where no oil is present), and the lower side. The opening is open to the air chamber 30. Therefore, when air or air bubbles are mixed in the oil, gas-liquid is separated in the air chambers 30 and / or 41, and only gas such as air is discharged to the outside of the machine through the air passage 42.
In addition, when gas-liquid separation can be performed only in one air chamber 41 and sufficient oil can be held in the oil reservoir 40,
The air chamber 30 existing between the radial dynamic pressure fluid bearing means 27 and the thrust dynamic pressure fluid bearing means can be omitted.

The oil supply passage 43 extends linearly to the left in FIGS. 1 and 2 in the radial direction of the thrust plate 23, and one end of the oil supply passage 43 opens to the oil reservoir 40. The other end of the oil supply passage 43 is branched upward and downward, and the upper opening is located in the upper thrust hydrodynamic bearing means (specifically, inside the upper thrust bearing groove where oil is present). Open, the lower opening is the lower thrust hydrodynamic bearing means (specifically, the area inside the lower thrust bearing groove where oil is present)
It is open to. Therefore, when the oil in the thrust dynamic pressure fluid bearing means is reduced to some extent, the oil from the oil reservoir 40 is supplied to the thrust dynamic pressure fluid bearing means (both the upper side and the lower side) through the oil supply passage 43, and the thrust dynamic pressure is reduced. It is possible to reliably prevent seizure and the like due to the reduction of oil in the fluid bearing means. The oil reservoir 40 functions as an oil amount adjusting space for accommodating the spare oil together with the air chamber 30, and therefore the amount of oil interposed in the thrust dynamic pressure fluid bearing means and the radial dynamic pressure fluid bearing means is strictly controlled. Therefore, even if the oil in the bearing means is reduced due to evaporation of the oil when used for a long period of time, sufficient oil can be held in advance to prevent seizure.

FIG. 3 shows a main part of a modified example of the motor, and the same members as those of the embodiments of FIGS. 1 and 2 are designated by the same reference numerals. Referring to FIG. 3, the outer peripheral surface of thrust plate 23 is provided with recessed grooves 52 having substantially the same depth except a part thereof (the left portion in FIG. 3). The cross section of the groove 52 may be, for example, substantially V-shaped or substantially trapezoidal, as in the above-described example. By forming the concave groove 52, the gap between the thrust plate 23 and the sleeve member 26 at one circumferential portion (the left circumferential portion in FIG. 3) becomes small, and the other circumferential portion (a portion other than the one circumferential portion) is formed. In, the distance from the sleeve member 26 becomes large. Therefore, the oil interposed between the outer peripheral surface of the thrust plate 23 and the inner peripheral surface of the sleeve member 26 exists in the region excluding the groove 52, and tends to collect at both ends of the groove 52.
Therefore, the oil collects on the left peripheral surface portion of the thrust plate 23, and this portion functions as the oil reservoir 40, while the outer peripheral surface of the thrust plate 23 and the sleeve member 26.
And a space where no oil exists, that is, an intermediate portion of the groove 52 (a portion located on the right side of the thrust plate 23) functions as an air chamber 41 in which air exists, and the air chamber 41 is an oil amount adjusting space. Acts as. The broken line 53 is
The oil boundary surface in the groove 52 is shown.

The thrust plate 23 has a structure shown in FIGS.
An air passage 42 and an oil supply passage 43 are provided as in the embodiment of FIG. The air passage 42 extends straight to the right in FIG. 3, and one end of the air passage 42 opens to the air chamber 41. The other end of the air passage 42 is similar to the above-mentioned embodiment.
It branches upward and downward and opens into the space 33 and the air chamber 30 (see FIG. 1). The oil supply passage 43 linearly extends to the left in FIG. 3, one end of which opens into the oil reservoir 40, and the other end of the oil supply passage 43 branches upward and downward to form an upper side and a lower side. Of the thrust dynamic pressure fluid bearing means.

The other structure of this modification is substantially the same as that of the embodiment shown in FIGS. 1 and 2, and as can be easily understood, this modification also has substantially the same operation as that of the above embodiment. The effect is achieved.

In the above-mentioned embodiment, the description has been made by applying to the shaft fixed type motor, but it can also be applied to the shaft rotating type motor.

[0021]

In the motor of the present invention, the oil reservoir 40 and the air chamber 41 are provided between the outer peripheral surface of the thrust plate 23 and the shaft holding member. The oil reservoir 40 is connected to an oil supply passage 43 for supplying the oil in the reservoir 40 to the thrust hydrodynamic bearing means. Therefore, in the thrust hydrodynamic bearing means, the oil tends to flow outward in the radial direction due to the centrifugal force generated by the rotation of the motor. Even if such a tendency occurs, the oil from the oil reservoir 40 is Oil is supplied to the thrust dynamic pressure fluid bearing means through the oil supply passage 43, and the lack of oil in this thrust dynamic pressure fluid bearing means is eliminated. In addition, the air chamber 41 includes the air chamber 4
Since the air passage 42 for communicating 1 with the atmosphere is communicated, the air collected from the oil in the air chamber 41 is discharged to the atmosphere through the air passage 42, and the adverse effect of air can be avoided. . Since the oil reservoir 40 and the air chamber 41 for adjusting the amount of oil are provided, it is not necessary to strictly measure the amount of oil interposed in the bearing means, and even if the amount of oil evaporates and the amount of oil decreases. Since it will be replenished, seizure at the bearing means can be prevented.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of essential parts showing a first embodiment of a motor according to the present invention.

2 is a cross-sectional view showing a thrust plate of the motor of FIG. 1 and its vicinity.

FIG. 3 is a sectional view showing a main part of a modified example of the motor of the present invention.

FIG. 4 is a sectional view showing an example of a known motor.

[Explanation of symbols]

 21 shaft 23 thrust plate 25 cover plate 26 sleeve member 27 radial dynamic pressure fluid bearing means 30 air chamber 38 concave groove 40 oil reservoir 41 air chamber 42 air passage 43 oil supply passage 44 oil boundary surface 52 inner surface 53 oil boundary surface

Claims (10)

[Claims] 1. A shaft, a shaft holding member which holds the shaft as a bearing, and a thrust plate which is provided on the shaft, and between the thrust plate and the shaft holding member. A motor having thrust dynamic pressure fluid bearing means interposed, and radial dynamic pressure fluid bearing means interposed between the shaft holding member and the shaft, wherein the motor is provided between an outer peripheral surface of the thrust plate and the shaft holding member. Is provided with an oil reservoir in which oil is present and an air chamber in which air is present. The oil reservoir is for supplying the oil in the reservoir to the thrust dynamic pressure fluid bearing means. The oil supply path is in communication with the air chamber,
A motor is characterized in that an air path for communicating this air chamber with the atmosphere is communicated. 2. The motor according to claim 1, wherein the oil supply passage and the air passage are provided in a thrust plate. 3. The outer peripheral surface of the thrust plate is provided with a tapered groove having the smallest distance from the shaft holding member at one end and the largest distance from the shaft holding member at the other end. A space that is formed and has a small gap between the thrust plate and the shaft holding member functions as the oil reservoir, and a space that has a large gap between the thrust plate and the shaft holding member functions as the air chamber. The motor according to item 1 or 2. 4. The motor according to claim 3, wherein the tapered groove is formed such that a bottom surface of the tapered groove is slightly eccentric to the oil reservoir side. 5. The outer peripheral surface of the thrust plate is formed with a concave groove in the circumferential direction except a part thereof, and in the part, a first space having a small distance from the shaft holding member is defined. In the groove, a second space having a large distance from the shaft holding member is defined, and the first space and a part of the second space function as the oil reservoir, and the second space The motor according to claim 1 or 2, wherein the remainder of the space functions as the air chamber. 6. The motor according to claim 3, wherein the groove has a substantially V-shaped cross section. 7. The motor according to claim 1, wherein a second air chamber is provided between the thrust dynamic pressure fluid bearing means and the radial dynamic pressure fluid bearing means. 8. A taper portion is provided at a facing portion of the shaft holding member that faces a corner portion of the shaft and the thrust plate, and the taper portion defines the second air chamber. The motor according to claim 7. 9. The motor according to claim 7, wherein one end of the air passage is opened to the air chamber, and the other end of the air passage is opened to the second air chamber and the atmosphere. 10. The thrust hydrodynamic bearing means is provided on the upper side and the lower side of the thrust plate, one end of the oil supply passage opens to the oil reservoir, and the other end of the oil supply passage extends. The motor according to any one of claims 1 to 9, wherein the motor is opened to an upper surface and a lower surface of the thrust plate and supplies the oil to the upper and lower thrust hydrodynamic bearing means.