Aerodynamic bearing assembly for spindle motor for hard disk drives

Disclosed is an aerodynamic bearing assembly for a spindle motor for hard disk drives, in which a hub of the spindle motor is pivoted in both radial and thrust directions by the ball bearing, which directly contacts the center of the hub, to perform rotation according to the rotational principle of a whirligig, and is subject to the thrust load through the aerodynamic bearing assembly with air groove(s) without being in contact with it, so that the hub maintains a rotational center without mechanical contact resulting in noise and starting failure of the assembly during an initial starting (low-speed rotation). The assembly includes air grooves, the air groove generating aerodynamic pressure between the hub and the aerodynamic bearing while the hub rotates.

FIELD OF INVENTION

The present invention relates to a spindle motor for hard disk drives. More particularly, the present invention relates to an aerodynamic bearing assembly for a spindle motor for hard disk drives capable of pivoting a lower portion of a hub in both radial and thrust directions through use of a ball bearing, which comes into direct contact with the lower portion of the hub, so that a rotational center of the hub can be maintained without mechanical contact resulting in noise and starting problems of the aerodynamic bearing assembly during an initial starting (during low-speed rotation).

BACKGROUND ART

Generally, a hard disk drive functions as an auxiliary memory unit of a computer, and is comprised of a platter, a head, a spindle motor, a head arm and a printed circuit board. The hard disk drive helps to operate the system of a computer either by reading out and regenerating information stored at the platter through the head or by writing new information on the platter through the head.

In the construction of the above-mentioned hard disk drive, the platter is a metallic circular plate coated with magnetic material, functioning to write various data. The platter is stacked in layers and rotates about a rotatable shaft. This rotatable shaft is named a spindle shaft. A motor for rotating the spindle shaft is named a spindle motor.

The head for reading/writing data stored at the platter is connected to the head arm so as to access desired information addresses. This head arm is driven by a head actuator, which is called a voice coil motor (VCM). A conventional spindle motor will be described below.

FIG. 1is an exploded perspective view of a conventional spindle motor for hard disk drives employing at least one ball bearing, andFIG. 2is a cross sectional view of the spindle motor ofFIG. 1.

As shown inFIGS. 1 and 2, the conventional spindle motor10for hard disk drives employing at least one ball bearing comprises a base11serving for a lower portion of the spindle motor; a spindle shaft12fitted at a center of the base in a vertical direction; a first ball bearing13fitted on a lower portion of the spindle shaft12positioned on the upper side of the base11; a stator14fitted around the first ball bearing13and constructed in such a manner that a coil14bis wound around a core14aof the stator; a second ball bearing15fitted on an upper portion of the spindle shaft12; a hub16, being rotatable about the first and second ball bearings13and15, for covering the upper portion of the base11; and an annular permanent magnet17fitted on an inner circumferential surface of a lower portion of the hub16and generating driving force for rotating the hub16through use of the magnetic field produced in cooperation with the coil14b.

In the conventional spindle motor10for hard disk drives constructed as mentioned above, when power is supplied to the coil14bof the stator14, a magnetic field (not shown) is established between the coil14band the permanent magnet17. The magnetic field between the coil14band the permanent magnet17allows the hub16to be rotated in one direction.

However, the construction wherein the hub16rotates using the first and second ball bearings13and15makes it impossible to drive at a high speed with a strict rotational precision, which results in generating noise and vibration when the ball bearing rotates at a high speed. The following description will be made regarding the construction of an aerodynamic bearing shown inFIG. 3.

FIG. 3is a cross-sectional view of a conventional spindle motor for hard disk drives employing at least one aerodynamic bearing.

The conventional spindle motor20for hard disk drives employing at least one aerodynamic bearing shown inFIG. 3includes a base21formed as a lower portion of the spindle motor, a first ball bearing22fitted on an upper central portion of the base21, a stator23fitted around the first ball bearing22and constructed in such a manner that a coil23bis wound around a core23aof the stator, a spindle shaft24fitted on an upper central portion in a vertical direction, a second bearing25fitted on an upper portion of the spindle shaft24, a supported hub26that is rotatable about the spindle shaft24and constructed to cover the upper portion of the base21, first and second aerodynamic bearings27and28fitted on an inner upper portion of the hub26for generating aerodynamic pressure for smoothly rotating the hub26about the spindle shaft24, and a permanent magnet27fitted on an inner circumferential surface of a lower portion of the hub16for generating driving force for rotating the hub26through use of the magnetic field produced in cooperation with the coil23b.

In the conventional spindle motor20for hard disk drives employing at least one aerodynamic bearing constructed as mentioned above, when power is supplied to the coil23bof the stator23, a magnetic field (not shown) is established between the coil23band the permanent magnet27. The magnetic field between the coil23band the permanent magnet27allows the hub26to be rotated in one direction.

Once the hub26rotates, air begins to flow on the inner surfaces of the first and second aerodynamic bearings27and28. The faster the hub26rotates, the stronger the air flows. As a result, the flow of air is changed into a layer of air having a predetermined rigidity between the first and second aerodynamic bearings27and28, the spindle shaft24, the first bearing25, and the second bearing22in proportion to the rotational speed of the hub26. Therefore, the hub26with a mounted platter (not shown) rotates about the spindle shaft24while overcoming the imposed load and disturbance from the air layer acting as a bearing between the spindle shaft24and the hub26.

However, the conventional spindle motor for hard disk drives employing at least one aerodynamic bearing, constructed as mentioned above, enables rigidity of the air layer to be improved at a low-speed rotation, but rigidity of the air layer is maintained almost constantly without an increase in proportion to the rotational speed when the motor rotates beyond a fixed speed.

Further, the conventional spindle motor for hard disk drives employing at least one aerodynamic bearing constructed as mentioned above is designed so that the base is assembled with the first ball bearing, but the spindle shaft is assembled with the second bearing, so that the assembled two sets maintain a predetermined size of air gap with respect to the aerodynamic bearings. Therefore, there are problems in that the spindle motor has a reduced assembly capability and has a difficulty in constantly maintaining a constant thickness of the air gap. Moreover, the spindle motor is designed so that the hub is supported around the spindle shaft via the air gap without putting the hub into direct contact with the spindle shaft. Therefore, during initial starting, the spindle motor is subjected to malfunction, attrition losses of the aerodynamic bearings as well as the first and second ball bearings, noise and vibration, all of which are caused by friction.

SUMMARY OF THE INVENTION

Therefore, the present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide an aerodynamic bearing assembly for a spindle motor for hard disk drives, in which a rotatable hub of the spindle motor for hard disk drives is adapted not only to be pivoted in both radial and thrust directions by the ball bearing coming into direct contact with the center of the hub so as to perform rotation according to the rotational principle of the whirligig, but also to be subjected to the thrust load through the aerodynamic bearing assembly with the air groove(s) without being in contact with it, so that the hub can maintain a rotational center without mechanical contact resulting in noise and starting failure of the aerodynamic bearing assembly during an initial starting (during low-speed rotation).

It is another object of the present invention to provide an aerodynamic bearing assembly for a spindle motor for hard disk drives, in which a hub, which is designed to have a conical structure like a whirligig and a rotatable point-contact supporting structure through the ball bearing, is combined with the aerodynamic bearing having at least one air groove, which is formed on at least one of the upper horizontal surface of the main bearing body of the aerodynamic bearing, the outer circumferential surface of the main bearing body of the aerodynamic bearing, the lower horizontal surface of the hub and the inner circumferential surface of the cylindrical section of the hub, so that rotational rigidity of the bearing against disturbance during high-speed rotation rather than during low-speed rotation as well as the capability of rotating without a slant are improved, and thus an excellent rotational precision can be obtained.

It is yet another object of the present invention to provide an aerodynamic bearing assembly for a spindle motor for hard disk drives, in which a hub is designed to have a conical structure like a whirligig and a rotatable point-contact supporting structure through the ball bearing, so that even though static electricity is generated by friction between the air caused by a high-speed rotation and the platter, the static electricity can be discharged through the ball bearing, thus improving a structural safety of the spindle motor.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In order to accomplish the above-mentioned objects, there is provided an aerodynamic bearing assembly employed in a spindle motor for hard disk drives, the spindle motor including a base, a hub, a stator and a permanent magnet, the base serving as a lower portion of the spindle motor, the hub being rotatably fitted on the base and able to fixedly mount a platter, the stator being formed with a plurality of cores wound around by one or more coils along an outer circumference of the stator and being formed with an open press-fit portion at the center of the stator. The permanent magnet is fitted on an inner circumferential surface of the hub and generates a magnetic field in cooperation with the coil. The aerodynamic bearing assembly comprises an aerodynamic bearing including a main bearing body formed in a concentric disk shape to serve as an upper portion of the aerodynamic bearing, and an auxiliary bearing body integrally formed on a lower portion of the main bearing body and press-fitted into the open press-fit portion of the stator to fixedly mount the stator on an outer circumferential surface of the auxiliary bearing body, the aerodynamic bearing being fixedly installed in a space between the base and the hub; and a ball bearing for rotatably pivoting a center of the hub in both radial and thrust directions at a center of the aerodynamic bearing, wherein at least one of an upper horizontal surface of the main bearing body of the aerodynamic bearing, an outer circumferential surface of the main bearing body of the aerodynamic bearing, a lower horizontal surface of the hub and a lower inner circumferential surface of the hub, is provided with at least one air groove having a predetermined depth. The air groove generates aerodynamic pressure between the hub and the aerodynamic bearing while the hub rotates.

In the above-mentioned construction, the air groove may be formed on the upper horizontal surface of the main bearing body of the aerodynamic bearing, or on the outer circumferential surface of the main bearing body of the aerodynamic bearing, or both on the upper horizontal surface of the main bearing body of the aerodynamic bearing and on the outer circumferential surface of the main bearing body of the aerodynamic bearing.

Meanwhile, the air groove may be formed on the lower horizontal surface of the hub, or on the lower inner circumferential surface of the hub, or both on the lower horizontal surface of the hub and on the lower inner circumferential surface of the hub.

Further, the air groove may be formed both on the upper horizontal surface of the main bearing body of the aerodynamic bearing and on the lower inner circumferential surface of the hub, or both on the outer circumferential surface of the main bearing body of the aerodynamic bearing and on the lower horizontal surface of the hub.

In the above-mentioned constructions, the upper horizontal surface of the main bearing body of the aerodynamic bearing may be further provided with at least one oilless bearing in a ring shape. Here, one or more air groove is formed in a predetermined depth on an upper surface of the oilless bearing.

Further, the oilless bearing may be mounted on the lower horizontal surface of the hub in a ring shape. Here, one or more air groove is formed in a predetermined depth on a lower surface of the oilless bearing.

On the other hand, at least one pair of oilless bearings opposite to each other may be formed on the upper horizontal surface of the main bearing body of the aerodynamic bearing and on the lower horizontal surface of the hub in a ring shape. Here, of the opposite oilless bearings, one, which is mounted on the upper horizontal surface of the main bearing body of the aerodynamic bearing, may be provided with an air groove on an upper surface thereof, while the other, which is mounted on the lower horizontal surface of the hub, may be provided with an air groove on a lower surface thereof.

According to the present invention, as mentioned above, the ball bearing for rotatably supporting the hub is arranged at a rotational center of the aerodynamic bearing to be at a lower position than an upper horizontal plane of the main bearing body of the aerodynamic bearing, so that the ball bearing has a rotatable supporting point at the lower position than the upper horizontal plane of the main bearing body of the aerodynamic bearing.

Alternatively, the ball bearing for rotatably supporting the hub may be arranged at a rotational center of the aerodynamic bearing to be flush with an upper horizontal plane of the main bearing body of the aerodynamic bearing, so that the ball bearing has a rotatable supporting point flush with the upper horizontal plane of the main bearing body of the aerodynamic bearing.

Further, the ball bearing for rotatably supporting the hub may be arranged at a rotational center of the aerodynamic bearing to be at a higher position than an upper horizontal plane of the main bearing body of the aerodynamic bearing, so that the ball bearing has a rotatable supporting point at the higher position than the upper horizontal plane of the main bearing body of the aerodynamic bearing.

Hereinafter, the preferred embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 4is an exploded perspective view of a spindle motor for hard disk drives with a pivot structure according to the present invention,FIG. 5is a partially sectional perspective top view of a spindle motor for hard disk drives with a pivot structure according to the present invention,FIG. 6is a partially sectional perspective bottom view of a spindle motor for hard disk drives with a pivot structure according to the present invention,FIG. 7is a cross-sectional view of an assembled spindle motor for hard disk drives with a pivot structure according to the present invention,FIG. 8is a perspective view of a first embodiment of an aerodynamic bearing assembly of a spindle motor for hard disk drives with a pivot structure according to the present invention.

As shown inFIGS. 4 to 8, a spindle motor100for a hard disk drive according to the present invention is designed to allow a center on a lower side of a hub120to be pivoted in both radial and thrust directions through a ball bearing150coming into direct contact with the lower portion of the hub, so that the hub can be rotated while maintaining a rotational center without mechanical contact between the hub120and an aerodynamic bearing140resulting in noise and starting failure caused by rotation of the hub120during an initial starting (or low-speed rotation) of the spindle motor100.

That is, the spindle motor100for hard disk drives according to the present invention is designed so that the hub120is supported in a point-contact manner as a whirligig and operates on the principle of rotation of the whirligig (The faster a whirligig rotates, the more rotational inertia increases. Therefore, a whirligig rotating at a high speed tends to rotate more easily than that at a low speed. This phenomenon is derived from the law of conservation of angular momentum.), thus improving rotational rigidity of the bearing against disturbance as well as its capability of rotating without a slant. The spindle motor100can thus obtain a high rotation precision.

Further, the spindle motor100for hard disk drives according to the present invention is designed so that when the hub120rotates at a high speed, aerodynamic pressure is established between the aerodynamic bearing140in which a main bearing body142is provided with at least one air groove142a, and the hub120, thus coping with thrust load of the hub120and not causing the hub120to be in contact with the main bearing body142while the hub120is rotating at a high speed.

As mentioned above, the spindle motor100for hard disk drives according to the present invention is characterized by a construction combining the aerodynamic bearing140with the ball bearing150, and by a construction causing the hub120to be supported in a point-contact manner the same as a whirligig in rotation.

The spindle motor100for hard disk drives according to the present invention, comprises a base110; a hub120fitted rotatably on the base110and having a platter (not shown) mounted on the hub; a stator130constructed in such a manner that an open press-fit portion132is provided at a center portion thereof and that at least one coil136is wound around a plurality of cores134, which are formed at the same angular distance along an outer circumference of the stator; an aerodynamic bearing140including a disk-shaped main bearing body142formed with at least one air groove142aso as to generate aerodynamic pressure in cooperation with the hub120, and an auxiliary bearing body144, formed integrally on the lower portion of the main bearing body142so as to mount on the base100through the open press-fit portion132of the stator130; a ball bearing150for causing the rotational center of the hub120to be rotatably supported on the center of the aerodynamic bearing140; and an annular permanent magnet160, fitted on an inner circumferential surface of the hub120adjacent to the cores134around which the coil136of the stator130is wound, for generating driving force for rotating the hub120by means of a magnetic field established in cooperation with the coil136.

When power is supplied to the spindle motor100for hard disk drives according to the present invention, a magnetic field is established between the cores134wound around by the coil136of the stator130and the permanent magnet160. Then, the hub120rotates about the ball bearing150. Once the hub120rotates, air begins to flow between the hub120and the aerodynamic bearing140, thus forming a layer of air. Most of the load to which this air layer is subjected is thrust load in a non-contact state.

Description will be made in detail below regarding construction of the spindle motor100for hard disk drives according to the present invention. First, as shown inFIGS. 4 to 8, the base110serves as a lower portion of the spindle motor100. The base100is provided with a seating recess112(FIG. 4), which is formed in a concentric concave shape and to a predetermined depth. That is, the concentric seating recess112is formed on an upper portion of the base110to a predetermined depth.

The base100, constructed as mentioned above, is provided with the stator130and the aerodynamic bearing140in a space between the seating recess112and the hub120rotatably fitted above the base110. The stator130and the aerodynamic bearing140will be described below.

The hub120rotates by means of a magnetic field established between the coil136of the stator130and the permanent magnet160. As shown inFIGS. 4 and 8, the hub120is provided with a lower cylindrical section122formed with an open lower portion and positioned in the seating recess112of the base110, and a platter mounting section124integrally formed on the cylindrical section122and mounted with a platter (not shown) called a magnetic disk. Here, the cylindrical section122has a smaller outer diameter than the seating recess112of the base110, while the cylindrical section122has a larger inner diameter than an outer diameter of the main bearing body142of the aerodynamic bearing140.

The hub120, constructed as above, is fitted in such a way that the cylindrical section122is rotatably positioned in the seating recess112of the base110, without generating mechanical contact between an outer circumferential surface of the cylindrical section122and an inner circumferential surface of the seating recess112, between a lower surface of the cylindrical section122and a bottom surface of the seating recess112, or between an inner circumferential surface of the cylindrical section122and an outer circumferential surface of the main bearing body142of the aerodynamic bearing140.

Meanwhile, the hub120is provided with a spindle shaft126, which downwardly extends from the lower surface of the hub120, i.e., a lower surface of a transition between the platter mounting section and the cylindrical section122in a conical form. The spindle shaft126is inserted into an inner race of the ball bearing150. The platter mounting section124belonging to the upper portion of the hub120is provided with a cavity124aopen in an upward direction, so as to reduce the total weight of the hub120as much as possible.

The stator130functions to generate a driving force for rotating the hub120through a magnetic field, which is established in cooperation with the permanent magnet160by a power supply. The stator130is fixedly mounted on the auxiliary bearing body144of the aerodynamic bearing140. Therefore, the stator130is arranged in the space between the seating recess112of the base110and the cylindrical section120of the hub120, together with the aerodynamic bearing140.

The construction of the stator130, as mentioned above, is provided with a vertically open press-fit portion132at the center thereof, and includes a plurality of magnetically inducible cores134integrally formed along an outer circumference of the stator at the same angular distance, and a coil136wound around each core134and establishing a magnetic field in cooperation with the permanent magnet160by supplying power to convert each core134into an electromagnet.

The stator130constructed as mentioned above is not seated in the seating recess112of the base110by itself, but is positioned in the space between the seating recess112of the base110and the cylindrical section122of the hub120after it is firmly fitted on the outer circumferential surface of the auxiliary bearing body144of the aerodynamic bearing140.

The aerodynamic bearing140is arranged in the space between the base110and the hub120, establishing aerodynamic pressure in cooperation with the lower surface of the hub120while the hub120rotates. The aerodynamic bearing140includes a disk-shaped main bearing body142formed with at least one air groove142aon the upper surface and/or the outer circumferential surface thereof, and an auxiliary bearing body144integrally formed on the lower portion of the main bearing body142and fixedly fitted in the seating recess112of the base110through the open press-fit portion132aof the stator130within the space between the base110and the hub120.

The aerodynamic bearing140is fixedly supported in the seating recess112of the base110, as follows: First, the auxiliary bearing body144of the aerodynamic bearing140is press-fitted into the open press-fit portion132of the stator130so as to fix the stator130on the outer circumferential surface of the auxiliary bearing body144, and sequentially a bottom surface of the auxiliary bearing body144is firmly seated on a bottom surface of the seating recess112of the base110, all being concentrically arranged with respect to each other.

The main bearing body142of the aerodynamic bearing140as mentioned above has a smaller outer diameter than an inner diameter of the cylindrical section122of the hub120, so that the main bearing body142can be fitted so as not to allow contact with the inner circumferential surface of the cylindrical section122of the hub120. Further, the main bearing body142of the aerodynamic bearing140is fitted so as not to allow the upper surface of the main bearing body142to come into contact with the lower surface of the hub120.

Meanwhile, the air groove142a, which is formed on the main bearing body142of the aerodynamic bearing140, may be formed on the upper surface of the main bearing body142and/or on the outer circumferential surface of the main bearing body142. It is preferred that the air groove142ais concentrically formed on the upper surface of the main bearing body142and/or that the air groove142ais mono-directionally formed on the outer circumferential surface of the main bearing body142.

The ball bearing150is used to allow the spindle shaft126of the hub120to be rotatably supported at the center of the aerodynamic bearing140. As shown inFIGS. 4 to 8, the ball bearing150is fixedly supported in a central through-hole146, which passes through the rotational center of the aerodynamic bearing140, in particular of the auxiliary bearing body144of the aerodynamic bearing140.

The spindle shaft126projected from the lower surface of the hub120is inserted into an inner race of the ball bearing150. In other words, the spindle shaft126of the hub120is pivoted in both radial and thrust directions by the ball bearing150, which comes into direct contact with a lower center of the hub120, so that during an initial starting (or low-speed rotation) of the spindle motor100, mechanical contact resulting in starting failure or noise accompanying rotation of the hub120is no longer generated between the hub120and the aerodynamic bearing140.

As mentioned above, during an initial starting of the spindle motor100(during a low-speed rotation), the spindle shaft126of the hub120is compensatively supported by the ball bearing150in both radial and thrust directions, so that mechanical contact resulting in starting failure or noise accompanying rotation of the hub120is not generated between the hub120and the aerodynamic bearing140. As a result, the hub120is capable of rotating without deviating from its rotational center.

In contrast, during a high-speed rotation of the spindle motor100, aerodynamic pressure, which is established between the hub120and the aerodynamic bearing140through the air groove142aof the aerodynamic bearing140, allows most of the thrust load of the hub120to be supported on the aerodynamic bearing140, so that the rotational rigidity of the ball bearing150against external disturbance as well as the capability of the hub120to rotate without a slant is improved. Therefore, the spindle motor100is capable of maintaining a high rotational precision.

As a result, it is possible for the spindle motor100of the present invention to rotate at a high speed even though the ball bearing150is employed to the spindle motor. That is, when the hub120rotates at a low speed, the ball bearing150compensatively supports the spindle shaft126of the hub120in both radial and thrust directions so that the ball bearing150is subjected to radial and thrust loads from the hub120. In contrast, when the hub120rotates at a high speed, the aerodynamic bearing140supports most of the radial and thrust loads from the hub120so that the ball bearing150is subjected to a slight level of thrust load from the hub120, which enables the spindle motor100to be rotated at a high speed.

Further, the aforementioned ball bearing150is provided at a lower position than the main bearing body142of the aerodynamic bearing140, in particular in the auxiliary bearing body144, and thus the ball bearing150has a rotational supporting point located under the main bearing body142.

The permanent magnet160generates a driving force for rotating the hub120by means of magnetic field, which is established between the coil134of the stator130and the permanent magnet160by supplying power. The permanent magnet160is fitted on the inner circumferential surface of the hub120adjacent to the cores134, around which the coil136of the stator130is wound. Therefore, the magnetic field is established between the permanent magnet160and the coil136.

The permanent magnet160has an annular ring shape and has a size compatible with the inner diameter of the cylindrical section122of the hub120. So, the permanent magnet160is fixedly fitted on the inner circumferential surface of the cylindrical section122of the hub120, which faces toward the cores134of the stator130.

As mentioned above, since the permanent magnet160is fixedly fitted on the inner circumferential surface of the cylindrical section122of the hub120, the magnetic field is established between the permanent magnet160and the coil134of the stator130by supplying power, thus rotating the hub120in one direction.

In brief, the spindle motor100for hard disk drives according to the present invention is designed so that when the hub120rotates at a low speed, mechanical contacts resulting in starting failure and noise accompanying rotation of the hub120is no longer generated between the hub120and the aerodynamic bearing140, by compensatively supporting the hub120in both radial and thrust directions through the ball bearing150, and when the hub120rotates at a high speed, most of the thrust load of the hub120is supported on the aerodynamic bearing140by establishing aerodynamic pressure between the hub120and the aerodynamic bearing140through the air groove142aof the aerodynamic bearing140. Therefore, the spindle motor100is capable of improving the rotational rigidity of the ball bearing150against external disturbance as well as the capability of the hub120to rotate without a slant, thereby allowing maintenance of a high rotational precision.

Further, the spindle motor100for hard disk drives according to the present invention can be constructed so that the ball bearing150for rotatably supporting the hub120is provided at a lower position than an upper horizontal plane of the main bearing body142of the aerodynamic bearing140, as shown inFIG. 7, so that the ball bearing150has a rotatable supporting point under the upper horizontal plane of the main bearing body142of the aerodynamic bearing140.

Here, in order to rotatably mount the hub120at the center of the aerodynamic bearing140by aid of the ball bearing150, the ball bearing150is fitted in a thrust or vertical direction into the central through-hole146, which is located under the upper horizontal plane of the main bearing body142of the aerodynamic bearing140and which is opened vertically at the center of the aerodynamic bearing140. Further, the spindle shaft126, which extends downwardly from the lower surface of the hub120to take a conical shape, is press-fitted into the inner race of the ball bearing150. Description will be made regarding various constructions in which the ball bearing150for rotatably supporting the hub120can be mounted at different positions.

FIG. 9is a cross-sectional view of a spindle motor for hard disk drives with a pivot structure according to one embodiment of the present invention, andFIG. 10is a cross-sectional view showing a spindle motor for hard disk drives with a pivot structure according to another embodiment of the present invention.

First, as shown inFIG. 9, a spindle motor200for hard disk drives according to the present invention may be designed to mount a ball bearing250for rotatably supporting a hub220at a first position, wherein the ball bearing250is mounted at the rotational center of the hub220flush with an upper horizontal plane of a main bearing body242of an aerodynamic bearing240, and thus the ball bearing250has a rotatable supporting point flush with the upper horizontal plane of the main bearing body242.

As mentioned above, in order to make the rotatable supporting point of the ball bearing250flush with the upper horizontal plane of the main bearing body242, the hub220is provided with a central through-hole226, which is formed to pass through the center of the hub220in a vertical direction. Further, the ball bearing250is fitted in a thrust or vertical direction into the central through-hole226, until the ball bearing250is flush with the upper horizontal plane of the main bearing body242of aerodynamic bearing240. Finally, the aerodynamic bearing240is formed with a upward supporting shaft246at the center of the upper surface thereof, and then the supporting shaft246is press-fitted into an inner race of the ball bearing250.

Of course, the spindle motor200for hard disk drives shown inFIG. 9is similar to the spindle motor100for hard disk drives shown inFIGS. 4 to 8, in that the combination of the ball bearing250with the aerodynamic bearing240is made to enable the hub220to follow the point-contact supporting construction on the basis of the rotational principle of the whirligig. However, the difference between them is dependent on a position where the ball bearing250is mounted.

Meanwhile, as shown inFIG. 10, a spindle motor300for hard disk drives according to the present invention may be designed to mount a ball bearing350for rotatably supporting a hub320at a second position, wherein the ball bearing350is mounted at an upper center of the hub320at a higher position than an upper horizontal plane of a main bearing body342of an aerodynamic bearing340, and thus the ball bearing350has a rotatable supporting point at the higher position than the upper horizontal plane of the main bearing body342of the aerodynamic bearing340.

As mentioned above, in order to provide the rotatable supporting point of the ball bearing350at a higher position than the upper horizontal plane of the main bearing body342of the aerodynamic bearing340, the hub320is provided with a central through-hole326, which is formed to pass through the center of the hub320in a vertical direction. Further, the ball bearing350is fitted in a thrust or vertical direction into the central through-hole326so that the ball bearing350is positioned at a higher position than the upper horizontal plane of the main bearing body342of the aerodynamic bearing340. Finally, the aerodynamic bearing340is formed with a upward long supporting shaft346at the center of the upper surface thereof, and then the supporting shaft346is press-fitted into an inner race of the ball bearing350.

Similarly, the spindle motor300for hard disk drives shown inFIG. 10is similar to the spindle motor100for hard disk drives shown inFIGS. 4 to 8and to the spindle motor200for hard disk drives shown inFIG. 9, in that combination of the ball bearing350with the aerodynamic bearing340is made to enable the hub320to follow the point-contact supporting construction on the basis of the rotational principle of the whirligig. However, the difference among them is dependent on a position where the ball bearing350is mounted.

FIG. 11is a perspective view of a second embodiment for an aerodynamic bearing assembly of a spindle motor with a pivot structure according to the present invention,FIG. 12is a perspective view of a third embodiment for an aerodynamic bearing assembly of a spindle motor with a pivot structure according to the present invention,FIG. 13is a perspective view of a fourth embodiment for an aerodynamic bearing assembly of a spindle motor with a pivot structure according to the present invention,FIG. 14is a perspective view of a fifth embodiment for an aerodynamic bearing assembly of a spindle motor with a pivot structure according to the present invention,FIG. 15is a perspective view of a sixth embodiment for an aerodynamic bearing assembly of a spindle motor with a pivot structure according to the present invention,FIG. 16is a perspective view of a seventh embodiment for an aerodynamic bearing assembly of a spindle motor with a pivot structure according to the present invention, andFIG. 17is a perspective view of a eighth embodiment for an aerodynamic bearing assembly of a spindle motor with a pivot structure according to the present invention.

FIGS. 11 to 17illustrate various embodiments for an aerodynamic bearing assembly. First,FIG. 11shows a construction in that an air groove142bis provided on an outer circumferential surface of a main bearing body142of an aerodynamic bearing140.

The air groove142bas shown inFIG. 11is formed on the outer circumferential surface of the main bearing body142instead of the upper horizontal surface of the main bearing body142of the aerodynamic bearing140as shown inFIG. 8, so that aerodynamic pressure is generated between the outer circumferential surface of the main bearing body142and the inner circumferential surface of a cylindrical section122, which is formed on an lower portion of the hub120, while the hub120rotates. That is, the embodiment inFIG. 11is a construction in which of an upper horizontal surface of the main bearing body142of the aerodynamic bearing140, an outer circumferential surface of the main bearing body142of the aerodynamic bearing140, a lower horizontal surface of the hub120and a lower inner circumferential surface of the hub120, only the outer circumferential surface of the main bearing body142of the aerodynamic bearing140is provided with the air groove142b.

By contrast,FIG. 12shows a construction in which of an upper horizontal surface of the main bearing body142of the aerodynamic bearing140, an outer circumferential surface of the main bearing body142of the aerodynamic bearing140, a lower horizontal surface of the hub120and a lower inner circumferential surface of the hub120, both the upper horizontal surface and the outer circumferential surface of the main bearing body142of the aerodynamic bearing140are provided with air grooves142aand142b, respectively. The air grooves142aand142b, which are formed on the upper horizontal surface and the outer circumferential surface of the main bearing body142of the aerodynamic bearing140, cause aerodynamic pressure to be generated between the upper horizontal surface of the main bearing body142and the lower horizontal surface of the cylindrical section122of the hub120as well as between the outer circumferential surface of the main bearing body142and the inner circumferential surface of the cylindrical section122of the hub120, while the hub120rotates.

Further,FIG. 13shows a construction in which of an upper horizontal surface of the main bearing body142of the aerodynamic bearing140, an outer circumferential surface of the main bearing body142of the aerodynamic bearing140, a lower horizontal surface of the hub120and a lower inner circumferential surface of the hub120, the lower horizontal surface of the hub120or a lower horizontal surface of a transition between the cylindrical section122and a platter mounting section124is provided with an air groove122a. Here, it should be noted that such an air groove is not formed on the aerodynamic bearing140. The air groove122a, which is formed on the lower horizontal surface of the hub120, causes aerodynamic pressure to be generated between the upper horizontal surface of the main bearing body142of the aerodynamic bearing140and the lower horizontal surface of the hub120, while the hub120rotates.

FIG. 14shows a construction in which of an upper horizontal surface of the main bearing body142of the aerodynamic bearing140, an outer circumferential surface of the main bearing body142of the aerodynamic bearing140, a lower horizontal surface of the hub120and a lower inner circumferential surface of the hub120, the lower inner circumferential surface of the hub120is provided with an air groove122b. Here, it should be also noted that such an air groove is not formed on the aerodynamic bearing140. Therefore, the air groove122b, which is formed on the lower inner circumferential surface of the hub120, causes aerodynamic pressure to be generated between the outer circumferential surface of the main bearing body142of the aerodynamic bearing140and the lower inner circumferential surface of the hub120, while the hub120rotates.

FIG. 15shows a construction in which two among an upper horizontal surface of the main bearing body142of the aerodynamic bearing140, an outer circumferential surface of the main bearing body142of the aerodynamic bearing140, a lower horizontal surface of the hub120and a lower inner circumferential surface of the hub120, e.g., both the lower horizontal surface of the hub120and the lower inner circumferential surface of the hub120, are provided with air grooves122aand122b, respectively. Here, it should be also noted that such air grooves are not formed on the aerodynamic bearing140. The air grooves122aand122b, which are formed on the lower horizontal surface and the lower inner circumferential surface of the hub120, cause aerodynamic pressure to be generated between the outer circumferential surface of the main bearing body142of the aerodynamic bearing140and the lower inner circumferential surface of the hub120as well as between the outer circumferential surface of the main bearing body142and the lower inner circumferential surface of the hub120, while the hub120rotates.

FIG. 16shows a construction in which of an upper horizontal surface of the main bearing body142of the aerodynamic bearing140, an outer circumferential surface of the main bearing body142of the aerodynamic bearing140, a lower horizontal surface of the hub120and a lower inner circumferential surface of the hub120, both the upper horizontal surface of the main bearing body142of the aerodynamic bearing140and the lower inner circumferential surface of the hub120are provided with air grooves142aand122b, respectively. Therefore, the air grooves122aand122b, which are formed on the upper horizontal surface of the main bearing body142of the aerodynamic bearing140and the lower inner circumferential surface of the hub120, cause aerodynamic pressure to be generated between the upper horizontal surface of the main bearing body142of the aerodynamic bearing140and the lower horizontal surface of the hub120as well as between the outer circumferential surface of the main bearing body142and the lower inner circumferential surface of the hub120, while the hub120rotates.

FIG. 17shows a construction in which of an upper horizontal surface of the main bearing body142of the aerodynamic bearing140, an outer circumferential surface of the main bearing body142of the aerodynamic bearing140, a lower horizontal surface of the hub120and a lower inner circumferential surface of the hub120, both the outer circumferential surface of the main bearing body142of the aerodynamic bearing140and the lower horizontal surface of the hub120are provided with air grooves142band122a, respectively. Therefore, the air grooves142aand122a, which are formed on the outer circumferential surface of the main bearing body142of the aerodynamic bearing140and the lower horizontal surface of the hub120, cause aerodynamic pressure to be generated between the outer circumferential surface of the main bearing body142of the aerodynamic bearing140and the lower inner circumferential surface of the hub120as well as between the upper horizontal surface of the main bearing body142and the lower horizontal surface of the hub120, while the hub120rotates.

The construction of the air groove(s) for implementing each embodiment shown inFIGS. 1 to 17, as mentioned above, is different from that shown inFIGS. 1 to 8, but its operation shown inFIGS. 1 to 17is the same as that shown inFIGS. 1 to 8.

FIG. 18is a cross-sectional view of a ninth embodiment for an aerodynamic bearing assembly of a spindle motor with a pivot structure according to the present invention,FIG. 19is a cross-sectional view of a tenth embodiment for an aerodynamic bearing assembly of a spindle motor with a pivot structure according to the present invention, andFIG. 20is a cross-sectional view of an eleventh embodiment for an aerodynamic bearing assembly of a spindle motor with a pivot structure according to the present invention.

InFIGS. 18 to 20, there is shown a construction for minimizing friction between a lower horizontal surface of a hub120and an upper horizontal surface of a main bearing body142of the aerodynamic bearing140during an initial starting. First, as shown inFIG. 18, the upper horizontal surface of the main bearing body142of the aerodynamic bearing140is provided with an oilless bearing170, which takes a ring shape.

The oilless bearing170constructed, as mentioned above, is mounted on the upper horizontal surface of the main bearing body142and is spaced apart from the lower horizontal surface of the hub120by a predetermined interval, so that friction between the lower horizontal surface of the hub120and the upper horizontal surface of the main bearing body142is minimized by preventing the hub120from being declined during an initial starting of the spindle motor100. In this way, by prevention of the declination of the hub120and thus minimizing the friction between the lower horizontal surface of the hub120and the upper horizontal surface of the main bearing body142, mechanical contact resulting in noise and starting failure can be eliminated.

Further, the oilless bearing170mounted on the upper horizontal surface of the main bearing body142of the aerodynamic bearing140may be provided with an air groove170-1, for example on the upper surface of the oilless bearing facing to the lower horizontal surface of the hub120.

It goes without saying that the oilless bearing170shown inFIG. 18may be employed in the spindle motor in which the upper horizontal surface of the main bearing body142of the aerodynamic bearing140is provided with the air groove142ashown inFIG. 8, or in the spindle motor100in which the outer circumferential surface of the main bearing body142of the aerodynamic bearing140is provided with the air groove142bshown inFIG. 11, or in the spindle motor100in which both the upper horizontal surface and the outer circumferential surface of the main bearing body142of the aerodynamic bearing140are provided with the air grooves142aand142b, respectively, shown inFIG. 12.

Similarly, it is natural that the oilless bearing170shown inFIG. 18may be employed in the spindle motor100in which the lower horizontal surface of the hub120is provided with the air groove122ashown inFIG. 13, or in the spindle motor100in which the inner circumferential surface of the cylindrical section122of the hub120is provided with the air groove122bshown inFIG. 14, or in the spindle motor100in which both the lower horizontal surface of the hub120and the inner circumferential surface of the cylindrical section122of the hub120are provided with the air grooves122aand122b, respectively, shown inFIG. 15, or in the spindle motor100in which both the upper horizontal surface of the main bearing body142of the aerodynamic bearing140and the inner circumferential surface of the cylindrical section122of the hub120are provided with the air grooves142aand122b, respectively, shown inFIG. 16, or in the spindle motor100in which both the outer circumferential surface of the main bearing body142of the aerodynamic bearing140and the lower horizontal surface of the hub120are provided with the air grooves142band122a, respectively, shown inFIG. 17.

FIG. 19shows a construction in which the lower horizontal surface of the hub120is provided with an oilless bearing170ain a ring shape, unlike the construction ofFIG. 18in which the upper horizontal surface of the main bearing body142of the aerodynamic bearing140is provided with an oilless bearing170in a ring shape. This oilless bearing170a, constructed as mentioned above, is mounted on the lower horizontal surface of the hub120and is spaced apart from the upper horizontal surface of the main bearing body142at a predetermined interval, so that friction between the lower horizontal surface of the hub120and the upper horizontal surface of the main bearing body142is minimized by preventing the hub120from being declined during an initial starting of the spindle motor100. In this way, by prevention of the declination of the hub120and thus minimizing the friction between the lower horizontal surface of the hub120and the upper horizontal surface of the main bearing body142, mechanical contact resulting in noise and starting failure can be eliminated. Here, the oilless bearing170amounted on the lower horizontal surface of the hub120may be provided with an air groove170a-1, for example on the lower surface of the oilless bearing facing to the upper horizontal surface of the main bearing body142of the aerodynamic bearing140.

Meanwhile, the oilless bearing170amounted on the lower horizontal surface of the hub120, as shown inFIG. 19, may be employed in the spindle motor in which the upper horizontal surface of the main bearing body142of the aerodynamic bearing140is provided with the air groove142aas shown inFIG. 8, or in the spindle motor100in which the outer circumferential surface of the main bearing body142of the aerodynamic bearing140is provided with the air groove142bas shown inFIG. 11, or in the spindle motor100in which both the upper horizontal surface and the outer circumferential surface of the main bearing body142of the aerodynamic bearing140are provided with the air grooves142aand142b, respectively, as shown inFIG. 12.

Similarly, it will be apparent to those in the art that the oilless bearing170amounted on the lower horizontal surface of the hub120as shown inFIG. 19may be employed in the spindle motor100in which the lower horizontal surface of the hub120is provided with the air groove122a, as shown inFIG. 13, or in the spindle motor100in which the inner circumferential surface of the cylindrical section122of the hub120is provided with the air groove122b, as shown inFIG. 14, or in the spindle motor100in which both the lower horizontal surface of the hub120and the inner circumferential surface of the cylindrical section122of the hub120are provided with the air grooves122aand122b, respectively, as shown inFIG. 15, or in the spindle motor100in which both the upper horizontal surface of the main bearing body142of the aerodynamic bearing140and the inner circumferential surface of the cylindrical section122of the hub120are provided with the air grooves142aand122b, respectively, as shown inFIG. 16, or in the spindle motor100in which both the outer circumferential surface of the main bearing body142of the aerodynamic bearing140and the lower horizontal surface of the hub120are provided with the air grooves142band122a, respectively, as shown inFIG. 17.

FIG. 20shows a construction in which both the upper horizontal surface of the main bearing body142of the aerodynamic bearing140and the lower horizontal surface of the hub120are provided with oilless bearings170and170aopposite to each other in a ring shape. These oilless bearings170and170aare spaced apart from each other at a predetermined interval, so that friction between the lower horizontal surface of the hub120and the upper horizontal surface of the main bearing body142is minimized by preventing the hub120from being declined during an initial starting of the spindle motor100. Consequently, by prevention of the declination of the hub120and the resulting minimization of the friction between the lower horizontal surface of the hub120and the upper horizontal surface of the main bearing body142, mechanical contact resulting in noise and starting failure can be eliminated.

Here, any one of two oilless bearings170and170amay be provided with an air groove170-1or170a-1. For example, the air groove170-1may be formed on the upper surface of the oilless bearing170, which is mounted on the upper horizontal surface of the main bearing body142of the aerodynamic bearing140, or the air groove170a-1may be formed on the lower surface of the oilless bearing facing170a, which is mounted on the lower horizontal surface of the hub120.

Meanwhile, these oilless bearings170and170aas shown inFIG. 20may be also employed in the spindle motor100in which the upper horizontal surface of the main bearing body142of the aerodynamic bearing140is provided with the air groove142aas shown inFIG. 8, or in the spindle motor100in which the outer circumferential surface of the main bearing body142of the aerodynamic bearing140is provided with the air groove142b, as shown inFIG. 11, or in the spindle motor100in which both the upper horizontal surface and the outer circumferential surface of the main bearing body142of the aerodynamic bearing140are provided with the air grooves142aand142b, respectively, as shown inFIG. 12.

Similarly, it will be easily understood to those in the art that the oilless bearings170and170amay be employed in the spindle motor100in which the lower horizontal surface of the hub120is provided with the air groove122a, as shown inFIG. 13, or in the spindle motor100in which the inner circumferential surface of the cylindrical section122of the hub120is provided with the air groove122b, as shown inFIG. 14, or in the spindle motor100in which both the lower horizontal surface of the hub120and the inner circumferential surface of the cylindrical section122of the hub120are provided with the air grooves122aand122b, respectively, as shown inFIG. 15, or in the spindle motor100in which both the upper horizontal surface of the main bearing body142of the aerodynamic bearing140and the inner circumferential surface of the cylindrical section122of the hub120are provided with the air grooves142aand122b, respectively, as shown inFIG. 16, or in the spindle motor100in which both the outer circumferential surface of the main bearing body142of the aerodynamic bearing140and the lower horizontal surface of the hub120are provided with the air grooves142band122a, respectively, as shown inFIG. 17.

According to the present invention as mentioned above, the hub, a rotatable object, of the spindle motor for hard disk drives is not only pivoted in both radial and thrust directions by the ball bearing, which comes into direct contact with the center of the hub, so as to perform rotation according to the rotational principle of the whirligig, but also is subjected to the thrust load through the aerodynamic bearing assembly with the air groove(s) without being in contact with it, so that mechanical contacts resulting in noise and starting failure of the aerodynamic bearing assembly and/or the hub can be prevented during an initial starting (during a low-speed rotation), and thus the hub can maintain an excellent rotational precision.

While this invention has been described in connection with what are presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiment and the drawings, but, on the contrary, it is intended to cover various modifications and variations within the spirit and scope of the appended claims.

According to the present invention as mentioned above, the rotatable hub of the spindle motor for hard disk drives is designed not only to be pivoted in both radial and thrust directions by the ball bearing, which comes into direct contact with the center of the hub, so as to perform rotation according to the rotational principle of the whirligig, but also to be subjected to the thrust load through the aerodynamic bearing assembly with the air groove(s) without being in contact with it, so that the hub can maintain a rotational center without mechanical contact resulting in noise and starting failure of the aerodynamic bearing assembly during an initial starting (during low-speed rotation).

Further, according to the present invention as mentioned above, the hub, which is designed to have a conical structure like a whirligig and thus to have a rotatable point-contact supporting structure through the ball bearing is combined with the aerodynamic bearing with at least one air groove, which is formed on at least one of the upper horizontal surface of the main bearing body of the aerodynamic bearing, the outer circumferential surface of the main bearing body of the aerodynamic bearing, the lower horizontal surface of the hub and the inner circumferential surface of the cylindrical section of the hub, so that rotational rigidity of the bearing against disturbance as well as its capability of rotating without a slant is improved, and thus an excellent rotational precision can be obtained.

In addition, according to the present invention, the hub is designed to have a conical structure like a whirligig and thus to have a rotatable point-contact supporting structure through the ball bearing, so that even though static electricity is generated by friction between the air caused by a high-speed rotation and the platter, the static electricity can be discharged through the ball bearing. Therefore, structural safety of the spindle motor can be improved.