Motor

A motor is disclosed. The motor in accordance with an embodiment of the present invention can include: a shaft; a bearing supporting the shaft to rotate; a thrust plate supporting a lower end of the shaft a boss joined to the shaft and having a ring-shaped groove on a side facing the bearing; and a rotor joined to the boss.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Korean Patent Application No. 10-2008-0092827, filed with the Korean Intellectual Property Office on Sep. 22, 2008, the disclosure of which is incorporated herein by reference in its entirety.

BACKGROUND

1. Technical Field

The present invention relates to a motor.

2. Description of the Related Art

A spindle motor, which is used in a driving device of a large-capacity memory storage device such as an optical disk, an ODD slim and a Half height driving set, uses an oil-impregnated bearing to help a shaft to rotate. The oil-impregnated bearing is a kind of a sliding bearing, and is made of a porous material that can contain lubricating oil. The porous material commonly consists of a sintered body.

The oil-impregnated bearing is joined to the shaft such that there exists a constant gap therebetween. The gap is filled with lubricating oil leaked from the oil-impregnated bearing due to the rotation of the shaft. The oil-impregnated bearing can hereby support the shaft to be rotatable.

However, the lubricating oil contained in the oil-impregnated bearing can be leaked not only to the gap between the shaft and the bearing but also to the upper part of the oil-impregnated bearing. When the lubricating oil of the oil-impregnated bearing is lost, the lubrication of the oil-impregnated bearing is deteriorated and a friction between the shaft and the oil-impregnated bearing is increased.

Accordingly, more power is required for driving the spindle motor, and noise and vibration and the like may occur when the motor rotates at a high speed. Besides, some parts of the bearing may be also worn out due to the friction between the shaft and the oil-impregnated bearing, thereby causing a shorter life span of the spindle motor.

SUMMARY

An aspect of the present invention provides a motor capable of preventing lubricating oil of a bearing from being lost through the upper part of the bearing.

One aspect of the invention provides a motor. The motor in accordance with an embodiment of the present invention can include: a shaft; a bearing supporting the shaft to rotate; a thrust plate supporting a lower end of the shaft a boss joined to the shaft and having a ring-shaped groove on a side facing the bearing; and a rotor joined to the boss.

There can be a plurality of the ring-shaped grooves.

A receiving part can be formed on a side of the boss facing the bearing such that an upper side of the bearing can be received. An inner circumferential surface of a side wall of the receiving part can be formed at an angle to an outer circumferential surface of the bearing. A sealing material can be interposed between the receiving part and the bearing.

Meanwhile, the shaft further can include a cylinder part extended downward from an edge of a lower end of the shaft in correspondence to the length of the bearing. A receiving groove can be formed on the thrust plate, the receiving groove receiving a lower end of the cylinder part. The receiving groove can receive even the lower end of the bearing. A supporting protrusion can be formed on the thrust plate. The supporting protrusion protrudes upward such that the lower end of the shaft is supported.

A burring part is formed in the center of the rotor. The burring part protrudes upward and receives the boss. The boss can be extended outward such that an upper side of the bearing can be received by the burring part.

A hollow part can be formed inside the shaft.

DETAILED DESCRIPTION

A motor according to certain embodiments of the invention will be described below in more detail with reference to the accompanying drawings, in which those components are rendered the same reference number that are the same or are in correspondence, regardless of the figure number, and redundant explanations are omitted. Also, the basic principles will first be described before discussing the preferred embodiments of the invention.

Hereinafter, an embodiment of the motor according to the present invention will be described in more detail with reference to the accompanying drawings.

A characteristic and an advantage of the present invention will be clear with the following drawings and detailed description of the present invention.

Hereinafter, embodiments of a motor in accordance with the present invention will be described in detail with reference to the accompanying drawings. In description with reference to accompanying drawings, the same reference numerals will be assigned to the same or corresponding elements, and repetitive descriptions thereof will be omitted.

FIG. 1is a cross sectional view showing a disk driver1000according to an embodiment of the present invention. As shown inFIG. 1, a spindle motor used in the disk drive1000according to an embodiment of the present invention includes a shaft500, a bearing502supporting the shaft500to be rotatable, a thrust plate508supporting the lower end of the shaft500, a boss700joined to the shaft500and having a ring-shaped groove702on a side thereof facing the bearing502, and a rotor300joined to the boss700. The ring-shaped groove702interrupts the lubricating oil flowing out from the bearing502, so that it is possible to prevent the lubricating oil from flowing to the outside of the bearing502.

The disk drive1000can include a chucking part100and a spindle motor200.

The chucking part100can join a disk to the spindle motor200such that the disk can be mounted to and demounted from the spindle motor200. The chucking part100can include a housing102, a chuck-pin104and an elastic member106. The housing102can house the chuck-pin104and the elastic member106, and can be joined to the rotor300. The chuck-pin104can be received by the housing102such that the chuck-pin104is protruded to the outside of the housing102. The elastic member106can elastically support the chuck-pin104.

When the chucking part100is inserted into a through hole formed in the center of the disk, the chuck-pin104can move backward and then forward. Once the disk is seated on the rotor300, the chuck-pin104can compress the inner circumferential surface of the disk, allowing the chucking part100to join the disk to the spindle motor200such that the disk can be mounted to and demounted from the spindle motor.

The bearing can support the shaft500to be rotatable. The bearing may be an oil-impregnated bearing502containing lubricating oil. There may be a constant gap such that the lubricating oil soaked from the oil-impregnated bearing502is interposed between the shaft500and the oil-impregnated bearing502.

A holder504can support the oil-impregnated bearing502. The holder504can fix the bearing502on a base plate600by surrounding the outer circumferential surface of the oil-impregnated bearing502. Additionally, a stator400can be joined to the outer circumferential surface of the holder504.

The stator400can include a stator core410, which includes both teeth414and a ring-shaped body412, and a coil420, which is wound on the teeth414. The teeth414can be extended to the outside of the ring-shaped body412.

The ring-shaped body412can be fixed to the holder504by joining the inner circumferential surface of the ring-shaped body412to the outer circumferential surface of the holder504. When electricity is supplied to the coil420, the teeth414is magnetized. Then, the rotor300can be rotated by the electromagnetic interaction between the teeth414and the drive magnet306.

The thrust plate508can be joined to the lower part of the holder504so as to support the lower end of the shaft500. A washer506is joined to the upper side of the thrust plate508so that the shaft500can smoothly rotate.

The rotor300includes a rotor case302, the drive magnet306and a friction member308. The rotor case302can include a burring part302a, an expansion part302band an extension part302c. The burring part302amay have a cylinder shape protruding upward in the center of the rotor case302, and may be formed by bending the central part of the rotor case302. The boss700can be joined to the shaft500by being inserted within the burring part302a.

The expansion part302bis radially extended from the lower end of the burring part302aand can cover the stator400. The basal surface of the disk on which the chucking part100is seated can be supported by joining a ring-shaped friction member308to the upper side of the expansion part302. The extension part302cis extended downward from the lower end of the expansion part302band the drive magnet306can be joined to the inner circumferential surface of the extension part302c.

The boss700can be interposed between the shaft500and the burring part302a. The boss700has a ring shape. The inner circumferential surface of the boss700can be joined to the shaft500and the outer circumferential surface of the boss700can be joined to the burring part302a. The thickness t2of the boss700can be smaller than the thickness t1of the burring part302a. The boss700can be inserted and fixed to the burring part302asuch that the upper surface of the boss700is aligned with the upper surface of the burring part302a.

The boss700can be extended to the outside thereof in order that the upper part of the oil-impregnated bearing502can be received by the burring part302a. That is, as the outside diameter of the boss700and the inside diameter of the burring part302aare formed to be larger than the outside diameter of the oil-impregnated bearing502, the upper part of the oil-impregnated bearing502can be received by the burring part302a.

Since the upper part of the oil-impregnated bearing502is received by the burring part302a, the entire length of the oil-impregnated bearing502may be increased as long as a part of the oil-impregnated bearing502is inserted into the burring part302a. As a result, it is possible that the bearing working length of the oil-impregnated bearing502for supporting the shaft500is increased.

In case the shaft is supported by use of the oil-impregnated bearing, there may be a gap between the shaft and the oil-impregnated bearing, causing the shaft to rotate in an angle with respect to the oil-impregnated bearing.

In this case, the shaft is supported by both symmetrical ends of the oil-impregnated bearing. Mutual friction between the both ends causes the life span of the oil-impregnated bearing to be reduced, and then the life span of the spindle motor is eventually shortened.

Accordingly, the shaft500can be more stably supported by the oil-impregnated bearing502through increase of the bearing working length of the oil-impregnated bearing502for supporting the shaft500, and then such a problem can be solved. Besides, since the shaft500is more stably supported by the oil-impregnated bearing502, it is also possible to reduce unnecessary noise and vibration caused by the vibration of the shaft500.

Meanwhile, because the bearing working length of the oil-impregnated bearing502for supporting the shaft500can be increased as much as a thickness difference between the boss700and the burring part302aby inserting the boss into the burring part302aof a simple shape, an additional manufacturing cost of the rotor case302can be prevented.

As the disk drive1000which uses the spindle motor200obtaining structural stability of the shaft500is able to ensure the stable driving of the disk and to stably perform reading/writing.

In the meantime, since the burring part302areceives the upper part of the oil-impregnated bearing502, the expansion part302band the extension part302ccoving the stator400can be, as a whole, closer to the base plate600. This signifies that the spindle motor200is ensured to be thinner.

As the extension part302cof the rotor case is closer to the base plate600, the drive magnet306is also able to be closer to the base plate600. Therefore, the magnetic core of the stator400is guaranteed to be identical to the magnetic core of the drive magnet306, acoustic noise can be reduced.

The ring-shaped groove702can be formed on a side of the boss700, which faces the bearing502, that is, the basal surface of the boss700.FIG. 2is a plan view showing a disk driver1000according to an embodiment of the present invention.

As shown inFIG. 2, there may be a plurality of the ring-shaped grooves702. The centers of the plurality of the ring-shaped grooves702can be identical to the center of the shaft500. The ring-shaped groove702is formed on the path of the lubricating oil flowing out from the oil-impregnated bearing502, and interrupts the flow of the lubricating oil by receiving the flowing lubricating oil. Consequently, it is possible to prevent the lubricating oil from flowing out from the oil-impregnated bearing502.

FIG. 3is a cross sectional view showing a part of a disk driver1000according to an embodiment of the present invention. As shown inFIG. 3, if the shaft500rotates, due to air flow around the rotor300, the pressure between the oil-impregnated bearing502and the boss700may be lower than that between the oil-impregnated bearing502and the shaft500.

Here, owing to the rotation of the shaft500, the lubricating oil111leaked between the shaft500and the oil-impregnated bearing502may rise along the outer circumferential surface of the shaft500. The lubrication oil111, having risen, can move to the outside of the boss700along the basal surface of the boss700due to centrifugal force and viscosity between the lubricating oil111and the basal surface of the boss700.

The lubricating oil111moving along the basal surface of the boss700can be received by the ring-shaped groove702. While the lubricating oil111received by the ring-shaped grooves702′ and702″ is constantly subjected to the centrifugal force, the side wall702aof the ring-shaped groove restricts the flow of the lubricating oil against the centrifugal force. Therefore, the lubricating oil111is not allowed to move to the outside of the boss700any more.

Even though the flow of the lubricating oil111continues to increase so that the lubricating oil111overflows the ring-shaped groove702′ of the inside of the boss700, the ring-shaped groove702″ of the outside of the boss700can prevent the flow of the lubricating oil111by the same operation as that of the ring-shaped groove702′ of the inside of the boss700. It shall be evident that the number of the ring-shaped groove702can be controlled by taking the amount of the flow of the lubricating oil and the size of the boss700into consideration.

FIG. 4is a cross sectional view showing a disk driver2000according to another embodiment of the present invention.FIG. 5is a cross sectional view showing a boss710of a disk driver2000according to another embodiment of the present invention.

As shown inFIGS. 4 and 5, the boss710of the disk driver2000according to another embodiment of the present invention can have a receiving part713formed on a side of the boss710facing the oil-impregnated bearing502in order that the upper part of the oil-impregnated bearing502can be received. The formed receiving part713allows the oil-impregnated bearing502to further enter the boss710. Consequently, the bearing working length of the oil-impregnated bearing502for supporting the shaft510can be increased.

The width in thickness direction of the outer circumferential surface of the boss710, which comes in contact with the inner circumferential surface of the burring part302a, may not be reduced regardless of the bearing working length of the oil-impregnated bearing502for supporting the shaft510. As a result, the bearing working length of the oil-impregnated bearing502for supporting the shaft510can be increased while the boss710and the rotor300are more securely joined.

As shown inFIG. 5, a protruding part716is formed in the middle of the lower part of the boss710and can be inserted into the shaft510. The protruding part716can be integrally formed with the boss710or can be separately manufactured to be joined to the boss710.

The inside of the shaft510can have a hole for receiving the protruding part716of the boss710. The hole may be deeper than the length of the protruding part716. Therefore, although the boss710is joined to the shaft510, the hole in the middle of the shaft510cannot be completely filled with the protruding part716of the boss710so that a hollow part512may be formed inside the shaft510.

The rotating parts in the disk drive2000can be the chucking part100, the rotor300, the shaft510and the boss710. As the hollow part512is formed inside the shaft510among them, a moment of inertia as well as the weight of the rotating parts can be reduced. Accordingly, it is possible to reduce the electric power required for driving the spindle motor200.

FIG. 6is a cross sectional view showing a part of a disk driver2000according to another embodiment of the present invention. As shown inFIG. 6, a sealing material718can be interposed between the boss710and the oil-impregnated bearing502.

The sealing material718can prevent the lubricating oil from flowing out from the oil-impregnated bearing502by sealing the space between the oil-impregnated bearing502and the boss710. The sealing material718is made of a material, such as grease, having viscosity higher than that of the lubricating oil.

The inner circumferential surface715of the receiving part side wall714can be formed at an angle to the outer circumferential surface of the oil-impregnated bearing502. The receiving part713can be formed such that the inside diameter, which the inner circumferential surface715of the receiving part side wall714forms, increases more toward a farther lower part of the receiving part. As a result, a distance between the inner circumferential surface715of the receiving part side wall714and the outer circumferential surface of the oil-impregnated bearing502can be more increased toward a farther lower part of the receiving part.

Even if the sealing material718is not interposed between the oil-impregnated bearing502and the boss710, a taper-shaped gap “A” formed between the inner circumferential surface715of the side wall714and the outer circumferential surface of the oil-impregnated bearing502can prevent the lubricating oil from flowing out by means of the surface tension effects of the flowing lubricating oil.

Eventually, the taper-shaped gap “A” formed between the inner circumferential surface715of the receiving part side wall714and the outer circumferential surface of the oil-impregnated bearing502can be designed for self-sealing.

FIG. 7is a cross sectional view showing a disk driver3000according to yet another embodiment of the present invention. As shown inFIG. 7, a shaft520of the a disk driver3000according to yet another embodiment of the present invention can further include a cylinder part522extending downward from the edge of the lower end of the shaft520.

In other words, the cylinder part522is formed to be extended downward from the edge of the lower end of the shaft520in order that a bearing working length of the oil-impregnated bearing502for supporting the shaft520is increased by extending the outer circumferential surface of the shaft520in the direction of length thereof.

The cylinder part522can have a cylinder shape surrounding the outer circumferential surface of the shaft520and can be extended to have the same length as that of the inner circumferential surface of the oil-impregnated bearing502. Additionally, the cylinder part522can be also integrally formed with the shaft520unlike the embodiment of the present invention.

FIG. 8is a cross sectional view showing a part of a disk driver3000according to yet another embodiment of the present invention. As shown inFIG. 8, the cylinder part522forms an additional surface for contact with the oil-impregnated bearing502on the outer circumferential surface of the shaft520, thereby extending the bearing working length of the oil-impregnated bearing502for supporting the shaft520(by as long as “L” ofFIG. 8) as compared with that of a conventional technology (dotted lines ofFIG. 8).

A rounding treatment is performed on the lower end of the shaft520so as to minimize the friction of the lower end of the shaft520. The length of the cylinder-shaped outer circumferential surface of the shaft520is hereby reduced so that the bearing working length of the oil-impregnated bearing502for supporting the shaft520may be reduced. With regard to this matter, it is possible to supplement the length of the oil-impregnated bearing502for supporting the shaft520by forming the cylinder part522. The cylinder part522is therefore able to supply the lower end of the shaft520with an additional length as long as “L” ofFIG. 8of the oil-impregnated bearing502for supporting the shaft520.

Both a supporting protrusion518aprotruding upward for supporting the lower end524of the shaft520and a receiving groove518creceiving the lower end of the cylinder part522can be formed on the thrust plate518.

As described above, the cylinder part522, i.e., a part extending downward from the edge of the lower end of the shaft520, can extend the length of the outer circumferential surface of the shaft520. In correspondence to this, the supporting protrusion518acan protrude upward on the upper side of the thrust plate518in order to prevent the cylinder part522from coming into contact with the upper side of the thrust plate518.

The washer506may be joined to the upper side of the supporting protrusion518ain order to reduce the friction between the lower end of the shaft520and the supporting protrusion518a. If the washer506is joined, a groove518bhaving a thickness the same as that of the washer506is formed in the supporting protrusion518a, so that the upper side of the supporting protrusion518acan have the same height as that of the upper side of the washer.

The receiving groove518creceiving the lower end of the cylinder part522can be formed on the upper side of the thrust plate518adjacently to the supporting protrusion518a. The receiving groove518ccan be formed of a ring-shaped groove adjacently to the supporting protrusion518a.

The receiving groove518ccan extend the bearing working length of the oil-impregnated bearing502for supporting the shaft520by receiving the lower end of the cylinder part522having an extended-length that is longer than the length of the shaft520.

The receiving groove518ccan receive even the lower end of the oil-impregnated bearing502. In order to increase the bearing working length of the oil-impregnated bearing502for supporting the shaft520, the oil-impregnated bearing502can be extended such that the length of the oil-impregnated bearing502is longer than that of the shaft520. In correspondence to this, the length of the cylinder part522can be also extended.

With the view of receiving both the cylinder part522having an extended-length that is longer than the length of the shaft520and the lower end of the oil-impregnated bearing502, the receiving groove518ccan be extended to the outside such that the outside diameter thereof is more than the outside diameter of the oil-impregnated bearing502.

Consequently, it is possible to increase the bearing working length of the oil-impregnated bearing502for supporting the shaft520without increasing the overall height of the spindle motor200.

While the present invention has been described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modification in forms and details may be made without departing from the spirit and scope of the present invention as defined by the appended claims.