JPH08163819A - Motor with dynamic fluid bearing means - Google Patents

Abstract

PURPOSE: To obtain a motor equipped with a dynamic pressure fluid bearing means for preventing seizure due to deficiency of oil. CONSTITUTION: The motor comprises a shaft 21, a shaft holding member, 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 member while a radial dynamic pressure fluid bearing means 27 is interposed between the shaft holding member and the shaft 21. A first space having relatively small gap and a second space having relatively large gap are provided between the outer circumferential face of the thrust plate 23 and the inner circumferential face of the shaft holding member. The first space functions as an oil sump 40 while the second space functions as an air chamber 41 and the thrust plate 23 is provided with a channel 43 for feeding oil from the first space to the thrust dynamic pressure fluid bearing means.

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 portion 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 further fixed. Stator 5 outward in the direction
Is stuck. 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. The bushing 8 is held. 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. Further, a part of the sleeve member 10 holds the thrust plate 7 and extends from there to below the thrust plate 7, and this sleeve portion 11 is formed in the middle of the shaft 4 to provide radial dynamic fluid bearing means 1.
2 is supported. Further, the sleeve member 10 supports the rotor magnet 13 at a position facing the stator 5 radially outward of the stator 5. Furthermore, the sleeve member 10 has a hub 14 radially outwardly thereof, and the hub 14 holds a magnetic 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 and the sleeve. Oil is interposed between the member 10 and the radial dynamic pressure fluid bearing means.

[0003]

However, in such a spinned motor, since it rotates at an extremely high speed during operation, oil flows radially outward in the thrust hydrodynamic bearing means due to centrifugal force, The oil in the thrust hydrodynamic bearing means tends to run short. If the thrust hydrodynamic bearing means is deficient in oil, the thrust plate and the sleeve member may come into metal contact with each other, and seizure may occur in the bearing means.

Further, in this type of motor, there is no reservoir for holding excess 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, The bearing life may be shortened.

An object of the present invention is to solve the above problems and to provide a motor provided with a hydrodynamic bearing means capable of preventing seizure due to insufficient oil for a long period of time.

[0006]

A motor of the present invention includes 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 A thrust dynamic fluid bearing means is interposed between a holding member, and a radial dynamic fluid bearing means is interposed between a shaft holding member and a shaft. A first space portion having a relatively small distance between them and a second space portion having a relatively large distance between them is provided between the inner peripheral surface and the first space portion. It functions as a reservoir, the second space functions as an air chamber in which air exists, and the thrust plate supplies the oil in the first space to the thrust hydrodynamic bearing means. Oil supply passage is provided for.

[0007]

In the motor of the present invention, the first space portion functioning as an oil reservoir and the second space portion functioning as an air chamber are provided between the outer peripheral surface of the thrust plate and the shaft holding member. ing. The thrust plate is also provided with an oil supply path for supplying the oil in the oil 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 motor. 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.

[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 facing 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 shaft holding member (cover plate 25 that surrounds the upper surface, the side surface, and the lower surface of the thrust plate 23).
And a sleeve member 26) and a thrust dynamic pressure fluid bearing means 50 (FIG. 2) is provided between the shaft 21 and the sleeve member 26, and a radial dynamic pressure fluid bearing means 27 is provided between the shaft 21 and the sleeve member 26. . In the embodiment, the thrust hydrodynamic bearing means is composed of bearing grooves 51 formed on the upper surface and the lower surface of the thrust plate 23 (only one provided on the upper surface of the thrust plate 23 is shown in FIG. 2). There is. The bearing groove 51 of the thrust hydrodynamic bearing means 50 may be formed in the cover plate 25 and / or the sleeve member 26 instead of the thrust plate 23.

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. By scraping off, the first air chamber 30
Is specified. The air chamber 30 may be formed by cutting out a part of the thrust plate 23 in order to increase the volume thereof.

The radial dynamic pressure bearing means 27 and the thrust dynamic pressure fluid bearing means 50 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 which is inclined upward inward in the radial direction at a predetermined angle (a °). As a result, a space 33 is formed between 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.
Are formed. 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 °) following the thrust dynamic pressure fluid bearing means 50 on the lower side and the taper portion 35 (angle c) following the radial dynamic pressure fluid bearing means 27. °) and are provided. 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, the lower portion of the sleeve member 26 facing the shaft 21 is provided with a taper portion 37 which is inclined radially outward toward the lower side of the shaft 21 at a predetermined angle (d °). is there. Here, the angle d is preferably smaller than the angle c, for example, 5 ° to 10 °.

As shown in FIG. 1, the thrust dynamic pressure fluid bearing means 50 and the radial dynamic pressure fluid bearing means 27 are filled with oil. In order to prevent oil from leaking from the hydrodynamic bearing means 27 and 50, in the embodiment, the maximum distance between the tapered portions 32 and 37 is set to the shaft 2
It is set larger than the distance between the shaft holding member 1 and the shaft holding member, which makes it difficult for the 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 eccentric to the left side in FIGS. 1 and 2 with respect to the circular thrust plate 23. In order to minimize the gap between the sleeve member 26 at one circumferential portion (the left circumferential portion in FIGS. 1 and 2), the other circumferential portion (FIGS. 1 and 2) of the thrust plate 23.
In the right peripheral portion), the distance from the sleeve member 26 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 interval along the bottom surface of the groove 38. That is, the force that moves 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. (The portion located on the left side of the thrust plate 23) is the oil reservoir portion 4 as the first space portion.
0, while the space between the outer peripheral surface of the thrust plate 23 and the sleeve member 26 is free of oil,
That is, the right part of the groove 38 (the part located on the right part of the thrust plate 23) functions as an air chamber 41 in which air exists as the second space. 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 between the inner peripheral surface of the groove and the inner peripheral surface of the groove, and the broken line 44 in FIG.

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 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 50 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 path 43 is branched upward and downward, and the upper opening and the lower opening have upper and lower thrust hydrodynamic bearing means 50 (specifically, upper and lower thrust bearing grooves 51). Area (ie, Figure 2
At a region radially inner than the region between the two-dot chain lines 53 and 54) in which oil is present). Therefore, when the oil in the thrust dynamic pressure fluid bearing means 50 decreases 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 It is possible to reliably prevent the seizure and the like due to the decrease in the oil of the pressure fluid bearing means 50. The air chambers 30 and 41 act as an oil amount adjusting space for accommodating the spare oil, and therefore the amount of oil present in the thrust dynamic pressure fluid bearing means 50 and the radial dynamic pressure fluid bearing means 27 is strictly measured. No longer needed
Further, it is possible to prevent seizure from occurring due to oil evaporation due to long-term use.

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 shape of the thrust plate 23 is circular, but the thrust plate 23 is attached to the shaft (only the reduced diameter portion 22 of the shaft is shown in FIG. 3) with some eccentricity to the left side in FIG. Has been. With such a configuration, the sleeve member 2 is provided at one circumferential portion of the thrust plate 23 (the circumferential portion on the left side in FIG. 3).
6 is the smallest, and the other peripheral portion (the right peripheral portion in FIG. 3) is the largest distance from the sleeve member 26. Therefore, the oil interposed between the outer peripheral surface of the thrust plate 23 and the inner peripheral surface of the sleeve member 26 has the smallest space in the space, that is, FIG.
In, the thrust plate 23 tends to gather on the left peripheral portion. Therefore, oil collects on the left peripheral surface portion of the thrust plate 23, this portion functions as the oil reservoir 56 as the first space portion, and the right peripheral portion thereof is the air chamber where the air exists as the second space portion. It functions as 58 parts and this second
The space portion (air chamber 58) serves as a space for adjusting the amount of oil. The solid line 57 in FIG. 3 indicates the oil boundary surface.

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 is open to the air chamber 58 (second space portion). The other end of the air passage 42 is branched upward and downward to open to the space 33 and the air chamber 30 (see FIG. 1), as in the above embodiment. The oil supply path 43 extends linearly to the left in FIG. 3, and one end of the oil supply path 43 opens to the oil reservoir 56 (first space),
The other end of the oil supply path 43 is branched upward and downward to form upper and lower thrust dynamic pressure fluid bearing means 50 (specifically, an area where the upper and lower thrust bearing grooves 51 are present (that is, FIG. 2). At a region radially inner than the region between the two-dot chain lines 53 and 54) in which oil is present).

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.

[0020]

In the motor of the present invention, the first space portion functioning as the oil reservoir 40 (56) is provided between the outer peripheral surface of the thrust plate 23 and the shaft holding member, and the air chamber 4 is provided.
A second space portion that functions as 1 (58) is provided. The thrust plate 23 also has an oil reservoir 40
An oil supply passage 43 for supplying the oil of (56) to the thrust hydrodynamic bearing means 50 is provided. Therefore, in the thrust hydrodynamic bearing means 50, the oil tends to flow radially outward due to the centrifugal force generated by the rotation of the motor, but even if such a tendency occurs, the oil reservoir 40 (56) Oil is supplied to the thrust dynamic pressure fluid bearing means 50 through the oil supply passage 43, the lack of oil in the thrust dynamic pressure fluid bearing means 50 is eliminated, and seizure of the bearing means is prevented. In addition, the air chamber 42 (58) acts as an oil amount adjustment space, and it is possible to hold a sufficient amount of oil by utilizing this space.

[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 Fluid Bearing Means 28, 29 Radial Bearing Groove 30 Air Chamber 38 Groove 40, 56 Oil Reservoir 41, 58 Air Chamber 42 Air Channel 43 Oil Supply Channel 50 Thrust Motion Pressure fluid bearing means 51 Thrust bearing groove

Claims (7)

[Claims] 1. A shaft, a shaft holding member holding the shaft as a bearing, and a thrust plate provided on the shaft, wherein a thrust motion is provided between the thrust plate and the shaft holding member. In a motor in which a pressure fluid bearing means is interposed, an opening of an oil supply passage for supplying oil to the thrust dynamic pressure fluid bearing means is arranged on an upper surface and / or a lower surface of the thrust plate. A motor characterized by. 2. An oil reservoir containing oil and an air chamber containing air are provided between the outer peripheral surface of the thrust plate and the inner peripheral surface of the shaft holding member. The motor according to claim 1, wherein one end is opened to the oil reservoir and the other end is opened to the upper surface and / or the lower surface of the thrust plate. 3. A thrust dynamic fluid bearing means is interposed between the shaft holding member and the upper surface and the lower surface of the thrust plate, and a radial dynamic fluid is provided between the shaft and the shaft holding member. 4. The motor according to claim 3, wherein a bearing means is interposed, and the other end of the oil supply passage is opened to the upper surface and the lower surface of the thrust plate. 4. A first space having a relatively small distance between the outer peripheral surface of the thrust plate and the inner peripheral surface of the shaft holding member, and a second space having a relatively large distance therebetween. 4. The motor according to claim 2, wherein the space portion is provided, the first space portion functions as an oil reservoir, and the second space portion functions as an air chamber. 5. A circumferential groove having a predetermined width in the axial direction is formed on the outer peripheral surface of the thrust plate, and a part of the groove has the smallest distance from the shaft holding member. In the other part, it is composed of a tapered groove having the largest distance from the shaft holding member, and the part near the small distance between the thrust plate and the shaft holding member acts as the first space, The motor according to claim 4, wherein the vicinity of the other portion where the distance between the plate and the shaft holding member is large acts as the second space portion. 6. The thrust plate is eccentrically mounted on the shaft in a predetermined direction, and a space portion between the thrust plate and the shaft holding member is a first space portion having a small distance in the predetermined eccentric direction. The motor according to claim 4, wherein the motor acts as a second space having a large gap in a direction opposite to the predetermined direction. 7. The oil supply path according to claim 1, wherein the other end of the oil supply path is opened radially inward of a bearing groove of the thrust hydrodynamic bearing means and in an area where oil is present. The motor described in.