JP2001078388A - Motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a motor that has high electrical efficiency, and at the same time can maintain stable rotation over a long time. SOLUTION: In this motor, that is equipped with disk-shaped thrust plates 4a and 4b stuck to the end part of a shaft 4, and thrust dynamic pressure bearings 16 and 18 where lubricating oil is maintained between at least one axial direction surface of the thrust plate and the thrust surface of a sleeve member 6b, when the thrust plate is set to low temperature, extremely small gap deformation results, so that the internal pressure of the lubricating oil being maintained at the thrust dynamic bearing part becomes low. When the thrust plate is set to high temperature, extremely small gap deformation results so that the internal pressure of the lubricating oil being maintained at the thrust dynamic bearing part becomes high, thus generating specific dynamic pressure at the thrust dynamic bearing part, maintaining required bearing stiffness, and hence maintaining stable rotation of the motor for a long time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor for rotating a recording disk such as a hard disk, and more particularly to a motor having a fluid dynamic bearing using lubricating oil as a working fluid.

[0002]

2. Description of the Related Art As a bearing means for rotatably supporting a rotor on a shaft, for example, a thrust plate is arranged on a shaft, and lubricating oil (between an axial surface of the thrust plate and a surface facing the axial direction) is provided. Oil), forming a dynamic pressure generating groove for generating a dynamic pressure in the lubricating oil by the rotation of the rotor to form a thrust dynamic pressure bearing portion to support a load in the thrust direction of the motor. A lubricating oil is held between the outer peripheral surface of the shaft and the inner peripheral surface of the rotor radially opposed to the shaft, and a dynamic pressure generating groove for generating a dynamic pressure in the lubricating oil by rotation of the rotor is formed. 2. Description of the Related Art A motor provided with a fluid dynamic bearing that forms a radial dynamic pressure bearing portion to support a radial load of the motor is conventionally known.

[0003]

However, when a motor provided with such a fluid dynamic pressure bearing using a lubricating oil as a working fluid is used in a wide temperature range (for example, 0 to 100 ° C.), heat generation of the motor and the like occur. The oil that can maintain a predetermined viscosity even at high temperatures due to the oil viscosity has temperature characteristics, so at low temperatures the viscosity is too high and the viscous resistance of the bearings increases, so the rotational load of the motor increases, The electrical efficiency decreases. For this reason, using low viscosity oil improves the electrical efficiency of the motor,
If the oil is of the same material type, low-viscosity oils generally have a low molecular weight, and at high temperatures, the viscosity of the oil decreases to increase fluidity and decrease bearing rigidity, so it is difficult to obtain stable rotation of the motor. At the same time, the evaporation rate is high and the oil easily evaporates due to the heat generated by the motor, so that the oil held in the bearing portion is depleted at an early stage, thereby deteriorating the durability and reliability of the motor.

That is, the contradictory problems of improving the electric efficiency of the motor and maintaining the viscosity of the oil at high temperatures and suppressing the evaporation are difficult to solve by improving only the oil. Also, the structure needs to be improved.

It is an object of the present invention to provide a motor having high electric efficiency and capable of maintaining stable rotation for a long period of time.

[0006]

In order to solve the above-mentioned problems, the present invention provides a disk-shaped thrust plate fixed to an end of a shaft, and a radially opposed radially opposed surface of the shaft with a small radial gap. A sleeve member having an inner peripheral surface and a thrust surface opposed to the axial surface of the thrust plate via a small thrust gap; and the thrust plate for supporting the shaft and the sleeve member relatively rotatably relative to each other. A thrust dynamic pressure bearing which holds lubricating oil between at least one axial direction surface and a thrust surface of the sleeve member, and a lubricating oil between an outer peripheral surface of the shaft and a radial inner peripheral surface of the sleeve member. And a radial dynamic pressure bearing portion holding the thrust plate, wherein the thrust plate is provided with the thrust minute gap according to a temperature change. Characterized by deformation to change.

In this configuration, the thrust plate is
When the temperature is low, the internal pressure of the lubricating oil (oil) held in the thrust dynamic pressure bearing is reduced, and when the temperature is high, the internal pressure of the lubricating oil held in the thrust dynamic pressure is increased, By changing the dynamic pressure generated in the thrust dynamic pressure bearing in response to temperature changes, the viscous resistance of the lubricating oil generated in the bearing at low temperatures can be suppressed even at low temperatures. Efficiency is improved, and at a high temperature, a predetermined dynamic pressure is generated in the thrust dynamic pressure bearing portion, so that necessary bearing rigidity can be maintained.
In addition, since the viscosity resistance of the lubricating oil at low temperatures can be reduced, lubricating oil with a somewhat high viscosity can be used. Stable rotation can be maintained for a long time.

In this case, the outer peripheral end of the thrust plate moves in the axial direction in accordance with the temperature change, and the axial dimension of the thrust micro-gap of the thrust dynamic pressure bearing portion is such that, at low temperatures, the vicinity of the outer peripheral end of the thrust plate is inward. The above-mentioned effect can be obtained by making the thrust plate larger than the vicinity of the peripheral end portion and making the vicinity of the outer peripheral short portion and the vicinity of the inner peripheral end portion of the thrust plate almost equal at high temperature.

The axial dimension of the thrust micro-gap of the thrust dynamic pressure bearing is such that the internal pressure of the lubricating oil held by the thrust dynamic pressure bearing is low at low temperatures and high at high temperatures. In the vicinity of the portion, the temperature changes so as to expand at low temperature and to shrink at high temperature.

In such a thrust dynamic pressure bearing portion, the thrust plate can be formed by, for example, laminating two or more members having different coefficients of thermal expansion in the axial direction.

By disposing a member having a low coefficient of thermal expansion on the side of the axial direction constituting the thrust dynamic pressure bearing of the thrust plate and a member having a high coefficient of thermal expansion on the opposite side, the so-called bimetal effect reduces the temperature. Accordingly, the member arranged on the opposite side having a high thermal expansion coefficient expands more than the member arranged on the thrust dynamic pressure bearing portion side having a low thermal expansion coefficient. The thrust micro-gap moves so as to be close to the thrust surface of the sleeve member constituting the dynamic pressure bearing portion, and has substantially the same axial dimension over the entire region from the inner peripheral end to the outer peripheral end of the thrust dynamic pressure bearing portion. Becomes

Further, by using a shape memory alloy for a part of the thrust plate, the shape of the thrust plate changes at a predetermined temperature and the axial dimension of the thrust minute gap can be changed.

In addition, a pair of thrust plates are provided at both ends of the shaft, and spiral grooves are formed as dynamic pressure generating means for pressing the lubricating oil inward in the radial direction so that the pair of thrust plates face each other. A thrust dynamic pressure bearing portion is formed on the surface side, an air interposed portion is formed in the radial minute gap and communicates with the outside of the motor, and air is interposed. Lubricating oil is pumped toward the thrust dynamic pressure bearing portion as a dynamic pressure generating means. A herringbone-shaped groove having an unbalanced shape in the axial direction is formed to form a pair of radial dynamic pressure bearing portions adjacent to the air interposition portion and the pair of thrust dynamic pressure bearing portions, and the lubricating oil is moved to the adjacent thrust dynamic pressure bearing portion. By continuously holding between the pressure bearing part and the radial dynamic pressure bearing part, the thrust minute gap is wide at low temperatures and the internal pressure of the lubricating oil held by the thrust dynamic pressure bearing part is reduced. Also, since the pumping force for the generated lubricating oil is reduced, the lubricating oil held in the thrust dynamic pressure bearing portion is pressed radially outward by centrifugal force due to the rotation of the motor, and accordingly, the radial dynamic pressure bearing portion The lubricating oil retained in the oil is sent to the thrust hydrodynamic bearing part side more by the action of the unbalanced herringbone groove and centrifugal force, and the interface with the gas interposed part facing the outside air moves to the outside in the axial direction and the ring A substantial part of the lower spiral groove constituting the bone-shaped groove, for example, about half of the axial dimension of the lower spiral groove is exposed to air, and the generated dynamic pressure is reduced. The efficiency is further improved.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of a motor according to the present invention will be described with reference to FIGS. 1 to 3 by taking as an example a case where the motor is used as a recording disk drive motor. However, the present invention is not limited to the embodiments shown in FIGS.

FIG. 1 is a longitudinal sectional view schematically showing a schematic structure of a motor according to an embodiment of the present invention. FIGS. 2A and 2B show a thrust caused by a temperature change of the motor shown in FIG. It is a fragmentary sectional view showing typically change of the direction of an axis of a thrust minute gap of a dynamic pressure bearing part. Also, FIG.
It is a top view which shows typically the schematic structure of the thrust plate of another embodiment motor of this invention.

In FIG. 1, the recording disk drive motor 1 includes a bracket 2, a shaft 4 having one end externally fixed in a central opening 2 a of the bracket 2,
A rotor 6 rotatable relative to the shaft 4; The rotor 6 has a rotor hub 6 a on which a recording disk D is mounted on an outer peripheral portion, and a sleeve member which is located on the inner peripheral side of the rotor hub 6 a and is axially supported by the shaft 4 via a minute gap in which lubricating oil 8 is held. 6b. A rotor magnet 10 is fixed to the inner peripheral portion of the rotor hub 6a by bonding or the like.
2 is installed.

At a substantially central portion of the sleeve member 6b, a through hole 6c passing through the sleeve member 6b in the axial direction so as to form a minute gap between the inner peripheral surface and the outer peripheral surface of the shaft 4 for holding the lubricating oil 8. Are formed. A disk-shaped upper thrust plate 4a and a lower thrust plate 4b projecting radially outward are attached to the upper and lower portions of the shaft 4, respectively, and correspond to the upper thrust plate 4a and the lower thrust plate 4b of the through hole 6c. An upper opening 6d and a lower opening 6e having a diameter larger than the outer diameter of each of the thrust plates 4a and 4b are formed in the portion. The upper opening 6d and the lower opening 6e are ring-shaped upper and lower counter plates 7a and 7b having openings 7a2 and 7b2 through which the shaft 4 is inserted at the center.
b.

A small amount of lubricating oil 8 is held between the upper thrust surface 6f extending from the inner peripheral portion of the through hole 6c to the outer peripheral portion of the upper opening 6d and the lower surface (axially inner side surface) of the upper thrust plate 4a. A gap is formed, and a group of spiral grooves 14 for generating dynamic pressure in the lubricating oil 8 with the rotation of the rotor 6 are formed in parallel on the upper thrust surface 6f, and the upper thrust dynamic pressure bearing portion is formed. 16 are constituted. A lower thrust surface 6g extending from an inner peripheral portion of the through hole 6c to an outer peripheral portion of the lower opening 6e;
A small gap for holding the lubricating oil 8 is formed between the upper thrust surface (the inner side surface in the axial direction) and the lower thrust surface 6.
In g, a group of spiral grooves 14 for generating a dynamic pressure in the lubricating oil 8 with the rotation of the rotor 6 is formed in parallel to form a lower thrust dynamic pressure bearing portion 18. The spiral grooves 14 formed in the upper and lower thrust dynamic pressure bearing portions 16 and 18 have a shape in which the generated dynamic pressure is directed radially inward so as to pump the lubricating oil 8 radially inward. Have.

The upper thrust plate 4a and the lower thrust plate 4b are composed of first members 4a1, 4b1 located on the surface side of the upper thrust dynamic pressure bearing portion 16 and the lower thrust dynamic pressure bearing portion 18, and the first member 4a1. , 4b1
And the second members 4a2 and 4b2 are laminated and bonded in the axial direction. The second members 4a2 and 4b2 are the first members.
It has a higher coefficient of thermal expansion than the members 4a1, 4b1,
For example, the first members 4a1, 4a1 are formed from iron-based stainless steel, and the second members 4a2, 4b2 are formed from a copper alloy. In this case, the shaft 4 and the upper thrust plate 4a and the lower thrust plate 4b are
First members 4a1, 4 having higher member strength than a2, 4b2
When the fastening is performed on the b1 side, structural stability can be achieved in terms of fastening strength and accuracy. The change in the axial dimension of the minute gap formed between the lower surface of the upper thrust plate 4a and the upper thrust surface 6f constituting the upper thrust dynamic pressure bearing portion 16 due to the temperature change will be described later with reference to FIG. This will be described in detail with reference to FIGS.

Outer peripheral surface 4a3 of upper thrust plate 4a
Is formed in a tapered shape so that the gap between the inner circumferential surface of the upper opening 6d of the rotor 6 and the radially opposed upper surface is enlarged toward the outside in the axial direction. The held lubricating oil 8 forms a boundary surface 8a with the atmosphere in a gap between the outer peripheral surface 4a1 of the upper thrust plate 4a and the inner peripheral surface of the upper opening 6d of the rotor 6 when the motor 1 is stationary. ing. Similarly, the outer peripheral surface 4b3 of the lower thrust plate 4b is formed in a tapered shape so that the gap between the outer peripheral surface 4b3 and the inner peripheral surface of the lower opening 6e of the rotor 6 which faces radially increases toward the axial direction. The lubricating oil 8 held by the lower thrust dynamic pressure bearing portion 18 keeps the outer peripheral surface 4 b 1 of the lower thrust plate 4 b and the lower opening 6
A boundary surface with the atmosphere is formed in a gap between the inner peripheral surface of e and the inner peripheral surface.

Upper and lower thrust dynamic pressure bearing portions 16, 1
The gap between the outer peripheral surfaces 4a3 and 4b3 of the upper and lower thrust plates 4a and 4b and the inner peripheral surfaces of the upper opening 6d and the lower opening 6e of the rotor 6 radially opposed to the lubricating oil 8 held by the upper and lower thrust plates 4a and 4b. By holding the inside so as to form a boundary surface with the atmosphere, even when the lubricating oil 8 is pressed and moved outward in the radial direction by the centrifugal force during rotation of the motor 1, the inner circumference of the upper opening 6d and the lower opening 6e is moved. The surface prevents further movement. Further, the lubricating oil 8 diffused to the surfaces of the upper and lower thrust plates 4a, 4b and the rotor 6 due to the oil migration phenomenon is moved radially outward by the action of centrifugal force and moves from the boundary surface with the atmosphere. The lubricating oil 8 is returned to the oil 8 and is prevented from leaking to the outside of the motor 1.

In this case, the gap between the outer peripheral surfaces of the upper and lower thrust plates 4a and 4b and the inner peripheral surfaces of the upper openings 6d and 6e of the rotor 6 radially opposed to each other increases toward the outside in the axial direction. With this configuration, the upper first tapered seal portion 17a and the lower first tapered seal portion 19b are formed, and the surface tension of the lubricating oil 8 and the atmospheric pressure are maintained in a balanced state.

Lower surface 7a1 of upper counter plate 7a
Is formed in a tapered shape in which the gap in the axial direction between the upper surface (axially outer surface) of the upper thrust plate 4a increases radially inward, and an upper second tapered seal portion 17b is formed. . The upper tapered seal portion 17b communicates with the outside air through a gap between the opening 7a2 and the outer peripheral surface of the shaft 4, and is opened when the motor 1 rotates.
At 7b, a boundary surface with the outside air is formed and held. The upper surface 7b1 of the lower counter plate 7b is
Lower thrust plate 4 inward in the radial direction
The lower second tapered seal portion 19b is formed in a tapered shape such that an axial gap between the lower surface (b) and the lower surface (axial outer surface) of the b is increased. Similarly, the lower second tapered seal portion 19b is opened to communicate with the outside air through a gap between the opening 7b2 and the outer peripheral surface of the shaft 4, and when the motor 1 rotates, the lubricating oil 8 The tapered seal portion 19b forms and holds a boundary surface with the outside air.

Thus, when the motor 1 is rotating,
Since the boundary surface of the lubricating oil 8 is located in each of the second tapered seal portions 17b and 19b facing inward in the radial direction, the lubricating oil 8 is diffused by an oil migration phenomenon due to centrifugal force acting on the lubricating oil 8 when the motor 1 rotates. The lubricating oil 8 is pressed radially outward, and each of the second tapered seal portions 17b,
The oil is returned to the lubricating oil 8 held in the motor 19b, thereby preventing the motor 1 from leaking to the outside.

The upper and lower thrust dynamic pressure bearing portions 16, 1
The spiral groove 14 of FIG. 8 has a shape in which the generated dynamic pressure feeds the lubricating oil 8 inward in the radial direction so that each thrust dynamic pressure bearing portion 1 can be filled when the lubricating oil 8 is filled.
Bubbles generated in the lubricating oil 8 retained in the lubricating oil 6 and 18 move from the high-pressure bearing portion to the boundary surface of the low-pressure lubricating oil 8 and are released to the atmosphere.

An annular recess 4c is formed substantially at the center of the outer peripheral surface of the shaft 4 so as to increase the gap between the shaft 4 and the inner peripheral surface of the through hole 6c.
A communication hole 20 communicating with the outside air formed therein is opened, and the outside air taken into the minute gap from this opening is formed in the concave portion 4c.
An annular gas intervening portion 22 is formed between the gas passage and the inner peripheral surface of the through hole 6c. The lubricating oil 8 held in the minute gap between the outer peripheral surface of the shaft 4 and the inner peripheral surface of the through hole 6c by the gas intervening portion 22 is divided vertically in the axial direction. Through hole 2c
Lubricating oil 8 divided and held above and below the inner peripheral surface of
A group of herringbone-shaped grooves 24 for generating a dynamic pressure in the lubricating oil 8 with the rotation of the rotor 6 is formed in parallel at a portion corresponding to the upper radial dynamic pressure bearing 26 and the lower radial dynamic pressure. A bearing 28 is configured. The herringbone-shaped grooves 24 formed in the upper and lower radial dynamic pressure bearing portions 26 and 28 are formed by connecting spiral grooves in opposite directions to each other. Appear to be biased toward
The spiral groove located outside in the axial direction is shorter than the spiral groove located inside in the axial direction.

In this configuration, since the dynamic pressure generating means formed in each of the thrust dynamic pressure bearing portions 16 and 18 is a spiral groove, it cannot generate the necessary load supporting pressure by itself. Dynamic pressure bearings 26, 28
Of the herringbone-shaped groove 24, the pressure peak of the generated dynamic pressure is axially outside (each thrust dynamic pressure bearing portion 16, 18).
Side), a dynamic pressure required for the thrust portion is generated by cooperation of the two bearing portions to support the load. In this case, when the motor 1 rotates, the boundary between the end portions of the lubricating oil 8 near the gas dynamic portion 22 near the radial dynamic pressure bearing portions 26 and 28 moves into the radial dynamic pressure bearing portions 26 and 28 to form an unbalanced herringbone shape. The groove specifications are set so that a part of the groove 24 is exposed to the atmosphere to balance the dynamic pressure of the thrust dynamic pressure bearing portions 16 and 18.

The lubricating oil 8 is continuously held between the radial dynamic pressure bearing portions 26 and 28 and the adjacent thrust dynamic pressure bearing portions 16 and 18, and the boundary surface (gas intervening) of one of the lubricating oils 8 is held. From the boundary surface with the outside air held in the portion 22 to the boundary surface of the other lubricating oil 8 (second tapered seal portions 17b, 17b,
9b, the dynamic pressure reaches a local maximum only at one point, and there is no minimum point. Therefore, even if the lubricating oil 8 contains air bubbles, the dynamic pressure automatically increases. A configuration in which the pressure is eliminated to the atmosphere where the pressure is minimized can be adopted.

As described above, the air bubbles generated in the lubricating oil 8 held in each bearing portion sequentially move to the low pressure side, and each lubricating oil 8
Are released into the atmosphere from the boundary of the lubricating oil 8
This prevents the lubricating oil 8 from leaking out of the bearing due to thermal expansion of bubbles when the temperature of the motor 1 rises.

Upper and lower counter plates 7a, 7b
By setting the radial gap between the inner peripheral surfaces 7a2 and 7b2 of the shaft 4 and the outer peripheral surface of the shaft 4 as small as possible, a labyrinth sealing effect is generated, and steam (oil) generated by vaporizing the lubricating oil 8 is generated. The resistance of the mist to the outside of the motor 1 can be increased to keep the vapor pressure near the boundary surface of the lubricating oil 8 high, so that further evaporation of the lubricating oil 8 can be prevented. The above effect can be further enhanced by applying an oil repellent made of, for example, a fluorine-based material to each of these surfaces.

The dynamic pressure generating means of each of the thrust dynamic pressure bearing portions 16 and 18 is formed as a spiral groove 14 and the lubricating oil 8 held in the adjacent radial dynamic pressure bearing portions 26 and 28 continuously. Since there is no point where the dynamic pressure is minimized, the outside air and the vicinity of the joint between the shaft 4 and each of the thrust plates 4a and 4b at the boundary between the thrust bearings 16 and 18 and the radial bearings 26 and 28 are separated. Communicate,
For example, since it is not necessary to provide a breathing hole or the like in the thrust plate, the outer diameter of the thrust plate can be reduced, so that the peripheral speed decreases, and the bearing loss due to the viscous resistance of the lubricating oil 8 is thereby reduced. Is suppressed and the motor 1
Not only can the electrical efficiency of the motor be improved and the power consumption can be suppressed, but also the effect of the lower thrust dynamic pressure bearing portion 18 on the magnetic circuit portion composed of the rotor magnet 10 and the stator 12 can be reduced. Drive torque can be obtained.

Here, with reference to FIGS. 2 (a) and 2 (b), a description will be given of the change in the axial dimension of the minute gap formed in the thrust dynamic pressure bearing portion due to the temperature change.
In (a) and (b), each member is shown in a somewhat exaggerated manner for easy understanding. 2A and 2B, only the upper thrust dynamic pressure bearing portion 16 will be described as an example, but the first member 4b1 and the second member 4b1 that constitute the lower thrust dynamic pressure bearing portion 18 and the lower thrust plate 4b will be described. The same applies to the member 4b2. In this case, the second members 4a2 and 4b2 having a high coefficient of thermal expansion are made of a copper alloy (coefficient of thermal expansion:
18.0 × 10 ⁻⁶ or more), and the first member 4a having a lower coefficient of thermal expansion than the second members 4a2 and 4b2.
1, 4b1 is an iron-based stainless steel (coefficient of thermal expansion: 10.4)
× 10 ⁻⁶ or less).

FIG. 2A schematically shows a state of the upper thrust dynamic pressure bearing portion 16 and the upper radial dynamic pressure bearing portion 26 at a low temperature.

At a low temperature, neither the first member 4a1 nor the second member 4a2, which are laminated in the axial direction and constitute the upper thrust plate 4a, thermally expands, so that the upper thrust plate 4a is Are curved outward in the axial direction, in other words, in a direction away from the upper thrust surface 6f of the sleeve member 6b. That is,
The upper thrust dynamic pressure bearing portion 16 is in a state where the axial dimension increases as the minute gap formed between the lower surface of the upper thrust plate 4a and the upper thrust surface 6f goes radially outward.

As described above, the upper thrust dynamic pressure bearing portion 16
Of the lubricating oil 9 held in the upper thrust dynamic pressure bearing portion 16 is reduced, and the spiral groove 14 pressurizes the lubricating oil 8 (see FIG. 1). Pumping pressure) is suppressed. As the pumping pressure of the upper thrust dynamic pressure bearing portion 16 against the lubricating oil 8 decreases, the lubricating oil 8 held by the upper thrust dynamic pressure bearing portion 16 is pressed radially outward by centrifugal force due to the rotation of the rotor 6. As a result, the pressure peak of the dynamic pressure originally generated is shifted toward the upper thrust dynamic pressure bearing portion 16 side, and the pumping pressure of the unbalanced herringbone-shaped groove 24 and the centrifugal force act on the upper portion. The lubricating oil 8 held in the radial dynamic pressure bearing portion 26 is dragged toward the upper thrust dynamic pressure bearing portion 16, and the interface between the gas interposition portion 22 and the gas bearing portion 22 is pulled outward in the axial direction, so that a considerable amount of the herringbone groove 24 is formed. part,
For example, about half of the lower spiral groove constituting the herringbone groove 24 is exposed to air in the axial direction, and the portion functioning as a bearing is reduced, and the generated dynamic pressure is reduced.

As described above, at the time of low temperature, the axial dimension of the minute gap of the upper thrust dynamic pressure bearing 16 increases, and the internal pressure of the lubricating oil 8 held by the upper thrust dynamic pressure bearing 16 decreases. The dynamic efficiency of the spiral groove 14 and the herringbone-shaped groove 24 formed as dynamic pressure generating grooves in each bearing portion is suppressed, and the electrical efficiency of the motor 1 is reduced by suppressing the viscous resistance of the lubricating oil 8. Be improved.
At low temperatures, since the viscosity of the lubricating oil 8 is high and the fluidity is low, even if the dynamic pressure of each bearing portion is reduced as described above, it is possible to obtain a bearing rigidity that does not hinder practical use. .

Further, even at a low temperature where the viscosity of the lubricating oil 8 becomes a problem, the viscous resistance of each bearing portion is suppressed, and the motor 1
Since the electrical efficiency of the lubricating oil is prevented from lowering, it is possible to use a lubricating oil with a certain degree of viscosity. Is prevented.

The lubricating oil 8 that has moved from the upper radial dynamic pressure bearing portion 26 to the upper thrust dynamic pressure bearing portion 16 by the action of the herringbone-shaped groove 24 with centrifugal force and unbalance.
Is held in the upper first taper seal portion 17a and the upper second taper seal portion 17b which are gaps larger than the minute gap of the upper thrust dynamic pressure bearing portion 16, so that bearing loss is minimized. .

FIG. 2B schematically shows a state of the upper thrust dynamic pressure bearing portion 16 and the upper radial dynamic pressure bearing portion 26 at a high temperature.

At a high temperature, both the second member 4a2 and the first member 4a1 located on the lower surface of the upper thrust plate 4a having a lower coefficient of thermal expansion than the second member 4a2 thermally expand. Since the two members 4a2 are formed from members having a higher coefficient of thermal expansion than the first member 4a1,
The upper thrust plate 4a has its outer peripheral end gradually approaching inward in the axial direction, in other words, approaching the upper thrust surface 6f of the sleeve member 6b due to a bimetal effect caused by bonding metals having different coefficients of thermal expansion according to the temperature rise. The lower surface of the upper thrust plate 4a and the upper thrust surface 6f face each other in the axial direction while being substantially parallel to each other.

As described above, the upper thrust dynamic pressure bearing portion 16
The lower surface of the upper thrust plate 4a and the upper thrust surface 6f face each other in a substantially parallel state, and the axial dimension of the minute gap of the upper thrust dynamic pressure bearing portion 16 is substantially the same as the entire upper thrust dynamic pressure bearing portion 16. In the upper thrust dynamic pressure bearing portion 16, the internal pressure of the held lubricating oil 8 increases, and the spiral groove 1
4, the lubricating oil 8 is fed radially inward at a predetermined pumping pressure at a predetermined pumping pressure, and accordingly, the interface of the lubricating oil 8 held by the upper radial dynamic pressure bearing portion 26 on the gas intervening portion 22 side is also increased. The herringbone-shaped groove 24 is located substantially in the lubricating oil 8 at a position closer to the inner side in the axial direction than that at the time of low temperature, in other words, closer to the concave portion 4 c forming the gas intervening portion 22. The upper radial dynamic pressure bearing portion 26 also generates a predetermined dynamic pressure.

As described above, at low temperatures when the viscosity of the lubricating oil 8 is high, the minute gap of the upper thrust dynamic pressure bearing portion 16 expands radially outward, thereby suppressing the viscous resistance of the lubricating oil 8. Therefore, a somewhat viscous lubricating oil 8
Can be used. Thus, even at a high temperature, a decrease in bearing stiffness and evaporation due to a decrease in the viscosity of the lubricating oil 8 are suppressed, and stable rotation of the motor 1 can be maintained for a long period of time.

Although one embodiment of the motor according to the present invention has been described above, the present invention is not limited to such an embodiment, and various changes and modifications can be made without departing from the scope of the present invention. .

For example, in the above-described embodiment, a pair of thrust plates 4a and 4b are provided at the upper and lower portions of the shaft 4, and a pair of thrust dynamic pressure bearing portions 16 and 18 are formed on surfaces facing each other in the axial direction. Although the motor 1 has been described, a motor in which a thrust plate is arranged only on one end side of a shaft and a thrust dynamic pressure bearing portion is formed only on one of upper and lower surfaces in the axial direction of the thrust plate. Applicable.

In this case, by applying a magnetic force to the rotor in a direction opposite to the direction of action of the dynamic pressure generated in the thrust dynamic pressure bearing portion, the dynamic pressure and the magnetic force are balanced and the rotation of the rotor is stabilized. It becomes possible to support. Further, by providing only one thrust dynamic pressure bearing portion, the viscous resistance of the lubricating oil can be further reduced, and the electric efficiency of the motor can be greatly improved.

The thrust plate 4 shown in FIG.
As shown at d, a slit 4d1 extending radially inward from the outer peripheral portion of the thrust plate 4d and penetrating in the axial direction is formed. When the temperature is low, the slit 4d1 is opened and formed by the spiral groove 14. The pumping pressure generated in the thrust dynamic pressure bearing portion is suppressed, and at a high temperature, the thrust plate 4d thermally expands in the circumferential direction to close the slit 4d1, and the thrust dynamic pressure bearing portion performs predetermined pumping by the spiral groove 14. By configuring so that pressure is generated, it is also possible to obtain the same operation and effects as those of the above-described embodiments of the present invention. FIG. 3 shows a configuration in which the above-described slit 4d1 is formed at two locations on the outer peripheral portion of the thrust plate 4d.
It is possible to form the number and size of the slits 4d1 necessary for improving the electric efficiency of the motor, such as one or two or more.

[0047]

According to the motor of the present invention, the thrust plate is deformed so that the internal pressure of the lubricating oil (oil) held in the thrust dynamic pressure bearing becomes low at a low temperature, and the thrust dynamic pressure bearing at a high temperature. The internal pressure of the lubricating oil is deformed to increase, and the dynamic pressure generated in the thrust dynamic pressure bearing changes according to the temperature change. The viscous resistance of the lubricating oil generated in the bearing portion can be suppressed, and the electric efficiency of the motor is improved. At the time of high temperature, a predetermined dynamic pressure is generated in the thrust dynamic pressure bearing portion, so that necessary bearing rigidity can be maintained. In addition, since the viscosity resistance of the lubricating oil at low temperatures can be reduced, lubricating oil with a certain degree of viscosity can be used, and even at high temperatures, early depletion of lubricating oil due to viscosity reduction and evaporation can be prevented, and motor Stable rotation can be maintained for a long time.

In addition, the outer peripheral end of the thrust plate moves in the axial direction in response to the temperature change, and the axial dimension of the thrust minute gap of the thrust dynamic pressure bearing portion is such that, at low temperatures, the vicinity of the outer peripheral end of the thrust plate is the inner periphery. By making the thrust plate larger than the vicinity of the end portion and making the vicinity of the outer peripheral short portion of the thrust plate nearly equal to the vicinity of the inner peripheral end portion at a high temperature, the bearing portion can be made even at a low temperature when the lubricating oil has a high viscosity at a low temperature. The viscous resistance of the lubricating oil generated by the thrust can be suppressed, the electric efficiency of the motor is improved, and at high temperatures, the thrust plate is deformed so that the internal pressure of the lubricating oil held in the thrust dynamic pressure bearing part increases, and the thrust dynamic pressure A predetermined dynamic pressure can be generated in the bearing portion, and required bearing rigidity can be maintained. In addition, since the viscosity resistance of the lubricating oil at low temperatures can be reduced, lubricating oil with a certain degree of viscosity can be used, and even at high temperatures, early depletion of lubricating oil due to viscosity reduction and evaporation can be prevented, and motor Stable rotation can be maintained for a long time.

In addition, a pair of thrust plates are provided at both ends of the shaft, and spiral grooves are formed as dynamic pressure generating means for pressing the lubricating oil inward in the radial direction so that the pair of thrust plates face each other. A thrust dynamic pressure bearing portion is formed on the surface side, an air interposed portion is formed in the radial minute gap and communicates with the outside of the motor, and air is interposed. Lubricating oil is pumped toward the thrust dynamic pressure bearing portion as a dynamic pressure generating means. A herringbone-shaped groove having an unbalanced shape in the axial direction is formed to form a pair of radial dynamic pressure bearing portions adjacent to the air interposition portion and the pair of thrust dynamic pressure bearing portions, and the lubricating oil is moved to the adjacent thrust dynamic pressure bearing portion. By continuously holding between the pressure bearing part and the radial dynamic pressure bearing part, the thrust minute gap is wide at low temperatures and the internal pressure of the lubricating oil held by the thrust dynamic pressure bearing part is reduced. Also, since the pumping force for the generated lubricating oil is reduced, the lubricating oil held in the thrust dynamic pressure bearing portion is pressed radially outward by centrifugal force due to the rotation of the motor, and accordingly, the radial dynamic pressure bearing portion The lubricating oil retained in the oil is sent to the thrust hydrodynamic bearing part side more by the action of the unbalanced herringbone groove and centrifugal force, and the interface with the gas interposed part facing the outside air moves to the outside in the axial direction and the ring A considerable part of the lower spiral groove constituting the bone-shaped groove, for example, about half of the axial dimension of the lower spiral groove is exposed to air, and the generated dynamic pressure is reduced. The efficiency is further improved.

In addition, by automatically removing air bubbles contained in the lubricating oil into the atmosphere from the bearing end where the pressure is minimized, for example, a radial dynamic pressure bearing portion and a thrust dynamic pressure bearing adjacent thereto are provided. The breathing holes formed in the thrust plate are no longer necessary to communicate the boundary between the thrust plate and the outside air, making it easy to process the thrust plate and reducing the cost of the motor. In this way, the accuracy required for fixing the thrust plate to the shaft, such as the squareness, can be somewhat reduced, and the peripheral speed decreases, and the viscosity resistance of the lubricating oil can be suppressed. The efficiency of the project can be improved.

[0051]

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view schematically showing a schematic configuration of a motor according to an embodiment of the present invention.

FIG. 2 is a partial cross-sectional view schematically showing a change in axial dimension of a small thrust gap of a thrust dynamic pressure bearing portion due to a temperature change of the motor shown in FIG.

FIG. 3 is a plan view schematically showing a thrust plate of a motor according to another embodiment of the present invention.

[Explanation of symbols]

 4 Shaft 4a, 4b, 4d Thrust plate 6b Sleeve member 16, 18 Thrust dynamic pressure bearing 26, 28 Radial dynamic pressure bearing

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 3J011 AA08 BA03 BA09 CA02 DA01 JA02 SB01 3J102 AA07 BA19 CA03 EA29 FA01 5H605 BB19 CC04 EB03 EB06 EB28 FF00 FF03 FF04 5H607 AA00 BB01 BB09 BB17 CC03 GG12 GG15 KK15 KK15 KK15 KK15 KK15 QQ04 RR00 UA01

Claims (8)

[Claims] 1. A disk-shaped thrust plate fixed to an end of a shaft, a radial inner peripheral surface opposed to an outer peripheral surface of the shaft via a radial minute clearance, and a thrust minute clearance on an axial surface of the thrust plate. A sleeve member having a thrust surface opposed thereto, and at least one axial direction surface of the thrust plate and a thrust surface of the sleeve member for supporting the shaft and the sleeve member so as to be relatively rotatable relative to each other. A thrust dynamic pressure bearing holding lubricating oil, and a radial dynamic pressure bearing portion holding lubricating oil between an outer peripheral surface of the shaft and a radial inner peripheral surface of the sleeve member. The motor, wherein the thrust plate is deformed so that the thrust minute gap changes according to a temperature change. 2. The motor according to claim 1, wherein the thrust minute gap changes by moving an outer peripheral end of the thrust plate in an axial direction according to a temperature change. 3. The thrust minute gap according to claim 1, wherein the axial dimension near the outer peripheral portion of the thrust plate increases at a low temperature and decreases at a high temperature.
A motor according to claim 1. 4. The axial small dimension of the gap near the inner peripheral end of the thrust plate in a predetermined temperature range in the thrust dynamic pressure bearing portion when the axial dimension of the gap near the outer peripheral portion of the thrust plate is within a predetermined temperature range. The motor according to claim 1, wherein the motor is maintained in an enlarged state. 5. The thrust plate is formed by laminating at least two members having different coefficients of thermal expansion in the axial direction, and the members constituting the thrust plate expand based on the respective coefficients of thermal expansion in response to a rise in temperature. 5. The motor according to claim 1, wherein the axial direction dimension of the thrust minute gap in the thrust dynamic pressure bearing portion changes. 6. The thrust dynamic pressure bearing portion is formed between an axial inner surface of the thrust plate and a thrust surface of the sleeve member axially opposed to the thrust plate, and the thrust plate has an axial lower surface. 6. The motor according to claim 5, wherein a member having a low coefficient of thermal expansion is laminated on a side of the thrust plate, and a member having a high coefficient of thermal expansion is positioned on an upper surface side in the axial direction of the thrust plate. 7. The motor according to claim 1, wherein a shape memory alloy is used for at least a part of the thrust plate. 8. The thrust plate is provided in a pair at both ends of the shaft, and the thrust dynamic pressure bearing portion has a spiral groove shaped as a dynamic pressure generating means for pressing the lubricating oil inward in the radial direction. And a pair of thrust plates, which are formed on opposing surfaces of the pair of thrust plates, respectively, and an air interposed portion through which air is communicated with the outside of the motor is formed in the radial minute gap, and the radial dynamic pressure bearing portion is formed. As a dynamic pressure generating means, a herringbone-shaped groove having an unbalanced shape in the axial direction is formed so that lubricating oil is pumped in the direction of the thrust dynamic pressure bearing portion, and is formed in the air interposed portion and the pair of thrust dynamic pressure bearing portions. The lubricating oil is formed as a pair adjacent to each other, and the lubricating oil is continuously held between the adjacent thrust dynamic pressure bearing portion and the radial dynamic pressure bearing portion. A motor according to claim 1.