JPH10285877A - Cooling structure of motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide long-term continuos use for the cooling structure of a motor by forming a shaft member into a sealed hollow shape, sealing working fluid in it under a vaccum-deaerated condition, and forming the shaft into a member serving as heat pipe. SOLUTION: A shaft 19 is a pipe whose cross section is circular, and its upper end part is closed by a rectangular Cu plate 20 which serves as a heat slinger and its lower end part is closed by a circular end plate. Pure water is sealed as working fluid W in a shaft 19 under a vaccum-deaerated condition to form it into a member serving as heat pipe. By forming the shaft 19 itself into a member serving as heat pipe, the heat at a heated position is carried to a case 16 positively and is discharged to the outside of the case by the second heat pipe 33. Therefore, it is possible to prevent noise and vibration of a ball bearing 28 resulting from heating, thereby providing long-term continuos driving for a spindle motor 18.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to cooling of a motor bearing.

[0002]

2. Description of the Related Art FIGS. 7 and 8 are schematic views showing a spindle motor provided in a hard disk drive (hereinafter, referred to as HDD). A plurality of hard disks 3 (only one is shown), a spindle motor 4 for rotating them, a read / write head 5, and a stepper for driving the hard disks 3 (only one is shown) are provided inside a case 2 of the HDD 1 made of a plastic hollow flat container. A motor 6 and the like are provided.

As the spindle motor 4, for example, a direct drive DC brushless motor is employed, and the spindle motor 4 is provided on the bottom of the case 2 with its shaft 7 oriented vertically in FIG. This shaft 19
Is a pipe having a circular cross section made of SUS304 as an example, and the upper end thereof is fixed to the inner wall surface on the upper side of the case 2.

On the other hand, the lower end of the shaft 7 is fixed to the lower inner wall surface of the case 2. That is, the upper surface and the lower surface of the case 2 are supported by the shaft 7. An iron core 9 around which a winding 8 is wound is provided at an outer peripheral portion substantially at the center in the length direction of the shaft 7. Further, the shaft 7 is provided with an outer rotor 10 that covers the upper side and the side of the iron core 9.

[0005] The outer rotor 10 comprises a substantially bottomed cylindrical body 11 and a flange 12 protruding from a lower portion of the outer peripheral surface of the body 11 in the radial direction in FIG. . A ball bearing 13 is provided on the inner edge of the body 11, and the ball bearing 13 rotatably supports the outer rotor 10 with respect to the shaft 7. Also, the core 9 of the inner peripheral surface of the body 11
The permanent magnet 14 is attached to a position facing the. On the other hand, a plurality of hard disks 3 are provided on the flange portion 12 in a stacked state. Although not shown, the outer rotor 1 is attached to the spindle motor 4.
A drive circuit for rotating 0 at a constant speed is provided.

[0006]

By the way, in the field of personal computers, multi-functions and processing speeds have been steadily increasing, and in connection with this, for example, an increase in the number of hard disks 3 installed and An increase in the number of revolutions of the spindle motor 4 is desired for the HDD 1.

However, in the above-mentioned conventional spindle motor 4, when the hard disk 13 is driven continuously for a long period of time with the number of hard disks 13 increased or the rotational speed increased, for example, The grease overheated and deteriorated, possibly causing abnormal vibration and noise.

This is because most of the frictional heat generated in the ball bearing 13 when the outer rotor 10 is rotated is released from the ball bearing 13 itself to the atmosphere inside the case 2 or the shaft 7 and the case 2
And is only released from those wall surfaces, for example, by being transmitted to the heat generating portion. In other words, the cooling of the heat generating portion is caused by natural air cooling.

The present invention has been made in view of the above circumstances, and has as its object to provide a motor cooling structure that can be used continuously for a long period of time.

[0010]

In order to achieve the above object, the present invention is directed to a motor having a rotating body which rotates about a center axis of a shaft member. The shaft member is formed in a hermetically sealed hollow shape, and a working fluid is sealed in the inside thereof in a vacuum degassed state, so that the shaft member is formed into a heat pipe.

Therefore, according to the first aspect of the present invention, when only the rotating body rotates, heat is generated at the sliding portion between them, whereas when the rotating body rotates together with the shaft member, In addition, heat is generated in the bearing supporting the shaft member. In either case, the generated heat is transferred to the working fluid inside the shaft member through the shaft member, and evaporates it.

The steam of the working fluid flows toward a location where both the temperature and the internal pressure are low in the internal space of the shaft member, where heat such as air is taken away and condensed. That is, heat is released to the outside. As described above, since the heat of the heat generating portion is transferred to the outside by the working fluid, overheating of the portion is prevented from occurring.

According to a second aspect of the present invention, there is provided a motor having a rotating body that rotates about a central axis of a shaft member, wherein the shaft member is formed in a hollow shape,
A heat transfer member made of a material having higher thermal conductivity than the shaft member is provided in a hollow portion of the shaft member.

According to the second aspect of the present invention, when only the rotating body rotates, heat is generated at the sliding portion between the two. On the other hand, when the rotating body rotates together with the shaft member, the shaft member is rotated. Heat is generated in the bearing that supports the motor. In any case, the generated heat is transmitted to the heat transfer member inside through the shaft member, and is conducted to the inside and released to the outside. As a result, the heat generating part is cooled. In this case, since the heat transfer member has better thermal conductivity than the shaft member, the cooling capacity is improved as compared with the related art.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment according to the first aspect of the present invention will be described below with reference to FIGS. In this specific example, a spindle motor built in an HDD will be described as an example of a cooling target. The case 16 of the HDD 15 is a plastic hollow flat container, in which a plurality of hard disks 17 (only one is shown), a spindle motor 18 for rotating them, a read / write head and And a stepping motor (both not shown) for driving the motor.

As an example, the spindle motor 18 is a direct drive DC brushless motor, and is provided on the bottom of the case 16 with its shaft 19 oriented vertically in FIG. The shaft 19 corresponding to the shaft member of the present invention is, for example, SUS304.
, The upper end of which is closed by a rectangular Cu plate 20 also serving as a heat radiating plate, which will be described later, and the lower end thereof is closed by a circular end plate.

Further, inside the shaft 19, pure water is sealed as a working fluid W in a vacuum degassed state to form a heat pipe. In other words, the shaft 19 itself is formed as a heat pipe container, and a wick (not shown) made of metal mesh is laid on the side surface of the inner wall surface. The shaft 19 is a first heat pipe 21.

Further, the lower end of the shaft 19 is
6 is fixed to the lower inner wall surface via an E-shaped wheel stopper 22, whereas the upper end of the shaft 19 is provided with a Cu plate 20 in a concave portion 23 formed in the upper surface of the case 16. It is fixed to the case 16 by being fitted. That is, the shaft 19 is disposed so as to support the upper surface and the lower surface of the case 16 with the Cu plate 20 exposed from the case 16.

An iron core 25 around which a winding 24 is wound is provided at an outer peripheral portion substantially at the center in the length direction of the shaft 19. Further, the shaft 19 is provided with an outer rotor 26 that covers the upper side and the side of the iron core 25.

The outer rotor 26 corresponds to the rotating body of the present invention, and has a substantially bottomed cylindrical body 26a.
And a flange portion 26b protruding in a radial direction in FIG. 2 from a lower portion of the outer peripheral surface of the body portion 26a. The outer rotor 26 is connected to the trunk 26
two ball bearings 2 attached to the inner periphery of
8 rotatably attached to the outer peripheral surface of the shaft 19. These ball bearings 28 are arranged so as to be shifted vertically in FIG.

A permanent magnet 29 is attached to a portion of the inner peripheral surface of the body portion 26a of the outer rotor 26 which faces the iron core 25. On the other hand, a plurality of hard disks 17 are provided on the flange portion 26b in a stacked state.

On the other hand, a heat radiating plate 31 made of the Cu plate 20 is exposed on the upper surface of the case 16. A mounting groove 32 for fixing a second heat pipe 33 to be described later is formed on the upper surface of the radiator plate 31, and one end of the second heat pipe 33 is brought into close contact with the mounting groove 32. It is fitted.

As an example, as the second heat pipe 33, a flat plate heat pipe in which pure water is used as a working fluid W in a Cu container having a rectangular cross section is employed. Fixed. Note that a wick (not shown) that generates capillary pressure is provided inside the second heat pipe 33. Thus, the first heat pipe 21 and the second heat pipe 33 are configured to be able to exchange heat via the heat sink 31. Although not shown, the spindle motor 18 has a drive circuit for rotating the outer rotor 10 at a constant speed.

Next, the operation of the spindle motor 18 configured as described above will be described. When the HDD 15 is not driven, the first heat pipe 21 is in a state where the working fluid is supplied to almost the entire area of the container side wall surface by the capillary pressure of the wick. On the other hand, also in this specific example, when the HDD 15 is driven, the outer rotor 26 holding the hard disk 17 rotates around the outer periphery of the shaft 19. Thereby, friction heat is generated in each of the two ball bearings 28. This heat is transmitted to the working fluid W inside through the wall surface of the shaft 19.

At this point, since a temperature difference occurs at both ends of the shaft 19, the operation of the first heat pipe 21 is automatically started. That is, the liquid-phase working fluid W is heated and evaporated in the vicinity of the location corresponding to each ball bearing 28 in the container, and the vapor flows toward the upper end of the container where the internal pressure is low, and the case 16 The heat is taken away by the heat sink 31 and the container of the second heat pipe 33 which are exposed to the outside, and the heat is condensed.

In this case, in addition to the heat radiation plate 31 having better thermal conductivity than the case 16, the heat pipe on the heat receiving side is disposed in surface contact with the upper surface of the heat radiation plate 31 on the heat radiation side. Therefore, heat transfer between the first heat pipe 21 and the second heat pipe 33 is favorably performed. The working fluid W of the first heat pipe 21 that has been radiated and liquefied flows toward the end disposed on the bottom side of the case 16 due to the capillary pressure of the wick or gravity, and a part thereof is positioned upward. Evaporates again due to the heat of the ball bearing 28, and the remaining portion evaporates again due to the heat of the ball bearing 28 located below.

On the other hand, when the heat is transmitted from the first heat pipe 21, the operation of the second heat pipe 33 is started.
The vapor of the working fluid W generated inside the container flows toward the end disposed obliquely to the upper right in FIG. 1, where it is deprived of heat by the air and the upper surface of the case 16 and condensed. In other words, almost the entire upper surface of the case 16 including the heat radiating plate 31 functions as a heat sink.

The working fluid W that has returned to the liquid phase by releasing heat
Is returned toward the end arranged on the heat sink 31 by the capillary action of the wick, and is evaporated again by the heat of the ball bearing 2 carried by the working fluid of the first heat pipe 21. Thereafter, the same cycle is continued, and as a result, the contact point between the shaft 19 and the ball bearing 28 is cooled.

As described above, since the shaft 19 itself is formed into a heat pipe, the heat of the heat generating portion is actively transferred to the case 16 and this heat is released to the outside of the case by the second heat pipe 33. Noise and vibration of the ball bearing 28 can be prevented.
Thus, long-term continuous driving of the spindle motor 18 becomes possible. The first heat pipe 21 is a heat pipe formed from the existing shaft 19, and the second heat pipe 33 is a thin flat plate. And almost the same.

Next, another embodiment according to the first aspect of the present invention will be described with reference to FIGS. The example shown here is the second heat pipe 33 in the first specific example.
Is omitted. The detailed description of the same configuration as the above specific example is omitted.

A spindle motor 18 is accommodated in the case 16 with the shaft 19 oriented vertically in FIG. The shaft 19 of the spindle motor 18
Is a pipe having a circular cross section in which the upper end is closed by a rectangular Cu plate 20 also serving as a heat sink 31 and the lower end is closed by a circular end plate, and the inside of which is vacuum degassed. Pure water is working fluid W in the state
And is formed as a heat pipe 27. A wick (not shown) made of metal mesh is laid on the side surface of the inner wall surface of the shaft 19.

The heat radiating plate 31 is provided so as to be exposed on the upper surface of the case 16. It is made of this flat Cu plate 20, and has a surface area about four times that of the first specific example.

Next, the operation of the spindle motor 18 configured as described above will be described. Also in this specific example, when the HDD 15 is driven,
The outer rotor 26 holding the outer circumference of the shaft 19 rotates. As a result, heat is generated in each ball bearing 28. This heat is transmitted to the internal liquid-phase working fluid W via the wall surface of the shaft 19. Then, the working fluid W becomes
As it evaporates, it rises toward the end provided with the heat radiating plate 31, and the heat outside the case 16 takes heat through the heat radiating plate 31 to condense. That is, heat is released from the surface of the heat sink 31 to the outside.

It should be noted that the heat pipe 27 that has liquefied by releasing heat
The working fluid W flows downward along the wick toward the end disposed on the bottom side of the case 16 and evaporates again at locations respectively corresponding to the two ball bearings 28. Thereafter, a similar cycle is continued,
As a result, the contact point between each ball bearing 28 and the shaft 19 is cooled.

As described above, the heat generated in the ball bearing 28 is positively discharged to the outside of the case 16 by the heat pipe shaft 19 and the heat radiating plate 31 integrated with the upper end thereof and exposed from the case 16. Thus, overheating during long-term continuous driving can be reliably prevented as in the above specific example. Further, since the heat sink 31 having a large surface area is provided instead of the second heat pipe 33 in the first specific example, the initial cost is further reduced.

Further, referring to FIGS.
A specific example according to the present invention will be described. The example shown here is a configuration in which the first heat pipe 21 in the first specific example is omitted. The detailed description of the same configuration as any of the above specific examples is omitted.

The spindle motor 18 has its shaft 1
9 is accommodated in the case 16 of the HDD 15 in a posture in which it is oriented in the vertical direction in FIG. A pair of sleeves 35 facing up and down is formed on the inner wall surface of the case 16. These sleeves 35 are in the form of pipes protruding from the inner wall surface of the case 16 in opposite directions, and the inner and outer diameters thereof are set equal to the shaft 19 of the spindle motor 18.

Between the upper and lower sleeves 35, a shaft 19 made of a pipe having a circular cross section is disposed coaxially with the two sleeves 35. In other words, the upper sleeve 3
5 and the upper end surface of the shaft 19 are connected in close contact with each other, and the end surface of the lower sleeve 35 and the lower end surface of the shaft 19 are held in close contact with each other. Further, a set screw 36 is inserted into the lower sleeve 35 and the shaft 19 from the bottom side of the case 16, thereby fixing the shaft 19 to the case 16.

A rod-shaped heat transfer member 37 having an outer diameter equal to the inner diameter of the shaft 19 is provided inside the shaft 19. The upper end surface of the heat transfer member 37 extends to the bottom surface of the heat radiating plate 31 fitted into the concave portion 32 of the upper surface of the case 16 and is in close contact therewith. As an example, the heat transfer member 37 is made of Cu whose thermal conductivity is about twice as high as that of SUS 304 which is a material of the shaft 19.

As described above, the heat radiating plate 31 is provided on the upper surface of the case 16 so as to be exposed. A mounting groove 32 is formed on the upper surface of the heat sink 31.
As an example, a flat heat pipe 38 in which pure water is sealed in a Cu container having a rectangular cross section is fitted into and fixed to the mounting groove 32 in a close contact state. That is, the heat transfer member 37 and the heat pipe 38 are connected via the heat radiating plate 31 so as to be able to exchange heat.

Next, the operation of the spindle motor 18 configured as described above will be described. When the outer rotor 26 holding the hard disk 17 rotates around the outer periphery of the shaft 19 as the HDD 15 is driven, heat is generated in each ball bearing 28. This heat is transferred to shaft 1
9 is transmitted to the heat transfer member 37 via the side wall surface, is transmitted through the inside thereof, is transmitted from the upper end to the bottom surface of the heat transfer plate 31, and is further transmitted to one end of the heat pipe 38. . In this case, the heat pipe 38 on the heat receiving side is disposed above the heat transfer member 37 on the heat radiating side, and furthermore, is in surface contact with each other, so that heat transfer between the two can be performed well.

When heat is transferred to the heat pipe 38, a working fluid vapor is generated inside the container, and the above-mentioned fluid flows toward the upper right end in FIG. Heat is deprived of the part and condenses. Therefore, the upper surface of the case 16 acts as a heat sink for the heat transfer member 37 and the heat pipe 38, and each ball bearing 28 is cooled.

As described above, by disposing the heat transfer member 37 having a higher thermal conductivity than the shaft 19 itself in the shaft 19, the heat generated in the ball bearing 28 is smoothly transmitted to the radiator plate 31, and from there. Since heat is removed and released by the heat pipe 38, overheating of the heat-generating portion can be reliably prevented, whereby the spindle motor 18 can be driven continuously for a long period of time. Further, since this specific example has a simple configuration in which a solid Cu material is attached to the existing shaft 19, there is an advantage that the cost is lower than that of the first specific example in which the shaft 19 itself is formed into a heat pipe.

In each of the above embodiments, the spindle motor for the HDD has been exemplified. However, the present invention is not limited to the above embodiment. For example, a spindle motor provided in a CD player or an FDD (floppy disk drive), It can be applied to a general DC motor or the like in which the shaft rotates together with the winding.

[0045]

As is apparent from the above description, in any of the first and second aspects of the present invention, the heat transfer capability of the shaft member is improved, so that the connection between the shaft member and the bearing supporting the shaft member is improved. Overheating of the sliding part or the sliding part between the rotating body and the shaft member can be prevented, thereby enabling long-term continuous driving.

[Brief description of the drawings]

FIG. 1 is a schematic view showing the appearance of an HDD spindle motor according to the first embodiment of the present invention.

FIG. 2 is a sectional view showing a configuration of the spindle motor and a case.

FIG. 3 is a schematic diagram showing another specific example according to the invention of claim 1;

FIG. 4 is a cross-sectional view showing a configuration of the spindle motor and a case.

FIG. 5 is a schematic view showing the appearance of a spindle motor for an HDD according to the invention of claim 2;

FIG. 6 is a cross-sectional view showing a configuration of the spindle motor and a case.

FIG. 7 is a schematic view showing a conventional HDD spindle motor.

FIG. 8 is a sectional view showing a configuration of the spindle motor and a case.

[Explanation of symbols]

15: HDD, 16: Case, 17: Hard Disk, 18: Spindle Motor, 19: Shaft,
21: first heat pipe, 24: winding, 26: outer rotor, 28: ball bearing, 31: heat sink, 35: sleeve, 37: heat transfer member, 38: heat pipe.

 ────────────────────────────────────────────────── ─── Continued on front page (72) Inventor Kazuhiko Goto 1-5-1, Kiba, Koto-ku, Tokyo Inside Fujikura Co., Ltd.

Claims (2)

[Claims] 1. A motor having a rotating body that rotates about a central axis of a shaft member, wherein the shaft member is formed in a hermetically sealed hollow shape, and a working fluid is sealed in the inside thereof in a vacuum-degassed state. Wherein the shaft member is a heat pipe. 2. A motor having a rotating body that rotates about a central axis of a shaft member, wherein the shaft member is formed in a hollow shape, and heat transfer made of a material having higher thermal conductivity than the shaft member. A cooling structure for a motor, wherein the member is provided in a hollow portion of a shaft member.