COOLING FAN

Abstract

A cooling fan for cooling a heat source includes a frame (10), a stator (20) mounted in the frame, a rotor (30) rotatably attached in the frame, a cover (40) fixed on the frame, and a pair of bearings (50, 60) received in the cover and the frame respectively. The rotor includes an impeller and a shaft (36) inserted through the impeller, wherein the shaft has an upper portion being received in one of the pair of bearings in the cover, and a lower portion being received in another one of the pair of bearing in the frame; thus, a vibration of the shaft can be prevented by supports of the pair of bearings, and the rotor is able to maintain a stable rotation, as the cooling fan is in a high speed operation.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cooling fan, and more particularly to a cooling fan having a pair of bearings for providing a stable operation to the cooling fan.

2. Description of Related Art

With continuing development of the electronic technology, electronic components such as CPUs generate more and more heat that is required to be dissipated immediately. A heat sink is often mounted on the electronic component for absorbing heat therefrom, and a fan is also provided to further remove heat from the heat sink with its forced airflow.

Conventionally, the fan includes a frame, a stator attached in the frame, a bearing received in the stator, and a rotor rotatably mounted to the stator. The rotor includes an impeller and a shaft extending downwardly from the impeller, wherein a lower portion of the shaft is enclosed by the bearing. When the fan operates, the impeller is rotated around the shaft with a support provided by the bearing.

However, the shaft only has the lower portion received in the bearing, while an upper portion thereof is not supported by any structure, which leads the impeller fixed on a upper portion of the shaft is prone to perform a vibration when the impeller is in a high speed rotation. This vibration would cause the fan to have an unstable operation that may generate a noise and reduce a lifetime of the fan.

What is needed, therefore, is a heat dissipating device which can overcome the above-mentioned disadvantages.

SUMMARY OF THE INVENTION

A cooling fan for cooling a heat source includes a frame, a stator mounted in the frame, a rotor rotatably attached in the frame, a cover fixed on the frame, and a pair of bearings received in the cover and the frame respectively. The rotor includes a impeller and a shaft inserted through the impeller, wherein the shaft has an upper portion being received in one of the pair of bearings in the cover, and a lower portion being received in another one of the pair of bearing in the frame; thus, a vibration of the shaft can be prevented by supports of the pair of bearings, and the rotor is able to maintain a stable rotation, when the cooling fan is in a high speed operation.

Other advantages and novel features of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present apparatus can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present apparatus. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.

FIG. 1 is a view of a vertical section of a cooling fan in accordance with a preferred embodiment of the present invention;

FIG. 2 is an isometric view of a cover of the cooling fan of FIG. 1; and

FIG. 3 is an isometric view of the cooling fan of FIG. 1 with the cover being removed for clarity.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, a cooling fan in accordance with a preferred embodiment of the present invention for cooling a heat source (not shown), comprises a frame 10, a stator 20 disposed in the frame 10, a rotor 30 rotatably installed on the stator 20, a cover 40 secured on the frame 10 to cover the stator 20 and the rotor 30, and a pair of bearings 50, 60 respectively contained in a bottom of the frame 10 and in the cover 40.

Referring to FIGS. 1 and 3, the frame 10 is used for being fixed on a structure (not shown) for mounting the cooling fan thereon. The frame 10 comprises a square lower plate 12, a square upper plate 14 parallel to the lower plate 12, and an annular sidewall 16 sandwiched between and interconnecting the lower plate 12 and the upper plate 14. Each of the upper plate 14 and the lower plate 12 has four circular holes 120, 140 defined in four corners thereof respectively. Four grooves 142 are defined near the four circular holes 140 of the upper plate 14 respectively, each of which defines a threaded hole 1420 at a bottom face thereof. A circular through hole 18 is defined through the upper plate 14 and the lower plate 12 for forming a cylindrical space to receive the stator 20 and the rotor 30 therein. A collar 122 is formed in a central area of a bottom of the through hole 18 with a plurality of ribs 123 extending outwardly and radially from a circumferential periphery of the collar 122 to connect with the sidewall 16, thereby securing the collar 122 to the sidewall 16. The collar 122 has a hollow tube 124 extending upwardly and perpendicularly from a center area of a top face thereof for accommodating a lower one, in this embodiment, the bearing 50 of the pair of bearings 50, 60 therein. An annular wall 126 is formed outwardly and horizontally around a lower portion of the tube 124. An annulus 128 extends inwardly and vertically from an inner face of the tube 124 and opposite to the annular wall 126.

The pair of bearings 50, 60 can be oil-containing bearings, or ball bearings. The lower bearing 50 of the pair of bearings 50, 60 is received in the tube 124 of the frame 10 in such a manner that a bottom face of the lower bearing 50 of the pair of bearings 50, 60 contacts a top face of the annulus 128 on the tube 124, and an outer face of the lower bearing 50 contacts the inner face of the tube 124. The lower bearing 50 of the pair of bearings 50, 60 defines a cylindrical passage (not labeled) therein, which is located coaxially with the tube 124.

The stator 20 is disposed in the frame 10 and comprises a circular base 22 contacting a top face of the annular wall 126, and a plurality of coils 24 installed on the base 22 for exerting an alternating magnet field when an alternating current is given to the stator 20. The base 22 defines a hole (not labeled) therein to enable the stator 20 to be sleeved onto the tube 124.

The rotor 30 is received in the through hole 18 of the frame 10. The rotor 30 comprises a hub 32, a permanent magnetic sleeve 38 installed into the hub 32, a plurality of blades 34 extending radially and outwardly from a circumference of the hub 32, and a shaft 36 inserted through the hub 32. The hub 32 comprises a disk (not labeled) and an annular flange (not labeled) extending downwardly and perpendicularly from a rim of the disk. A central area of a top face of the disk is concaved to form a cavity 320 in the hub 32. The shaft 36 is inserted through a center of the disk of the hub 32 with an upper portion thereof extending beyond the center of the disk and partly exposed within the cavity 320; and a lower portion inserted into the passage of the lower bearing 50 of the pair of bearings 50, 60 so as to be confined by the lower bearing 50 of the pair of bearings 50, 60, whereby the lower portion of the shaft 36 is supported to be prevented from vibration. The shaft 36 defines a recess (not labeled) near a bottom portion thereof for being snapped by the annulus 128 of the frame 10, thus preventing the rotor 30 from falling off from the frame 10. The magnetic sleeve 38 has an annular configuration contacting an inner circumference of the flange of the hub 32, wherein the magnetic sleeve 38 surrounds the shaft 36 and has a lower portion opposing to the coils 24 of the stator 20.

Also referring to FIG. 2, the cover 40 rests on the frame 10 to sandwich the rotor 30 and the stator 20 with the frame 10. The cover 40 has four straight beams 42 connect with each other to construct a square configuration therefor. A circular plate 44 is formed in a central area of the cover 40 corresponding to the disk of the hub 32 in a manner such that the circular plate 44, the disk, and the collar 122 are in alignment with each other. Four beams 48 connect the circular plate 44 with the four beams 42 respectively, wherein the four beams 48 are distributed evenly around the circular plate 44, so that four identical openings 480 each having a shape similar to a square, are defined between the circular plate 44 and the four beams 42, 48. A hollow, tubular body 46 extends downwardly and perpendicularly from a bottom face of the circular plate 44, thereby to form a cylindrical space 460 together with the circular plate 44. The tubular body 46 has an exterior diameter less than a diameter of the cavity 320 in the hub 32, and a height larger than that of the cavity 320, whereby the tubular body 46 can be partly accommodated in the cavity 320 with its top portion located beyond the hub 32. Four locking feet 420 are formed downwardly and perpendicularly from four corners of the cover 40 respectively corresponding to the four threaded holes 1420 of the frame 10. The cover 40 is fixed on the frame 10 by fitting the four locking feet 420 into the four threaded holes 1420 of the frame 10 respectively, and putting the tubular body 46 into the cavity 320 of the hub 32 with a gap defined between the circular plate 44 and a top face of the shaft 36 for preventing an interference from occurring between the shaft 36 and the cover 40. When the fan is assembled completely, the circular plate 44, the tubular body 46, the pair of bearings 50, 60, the hub 32, the magnetic sleeve 38, the hollow tube 124, and the collar 122 would be coaxial with each other.

The upper bearing 60 of the pair of bearings 50, 60 is installed into the cylindrical space 460 of the cover 40 with its top face contacting the bottom face of the circular plate 44 securely, its outer face contacting an inner face of the tubular body 46 of the cover 40, and its inner face contacting an outer face of the upper portion of the shaft 36, whereby the upper portion of the shaft 36 is confined to be prevented from a vibration when the rotor 30 is in rotation.

In use, when an electric power is given to the cooling fan, the coils 24 of the stator 20 generates the alternating magnet field that interacts with the magnetic sleeve 38 of the rotor 30, thereby driving the rotor 30 to rotate around the shaft 36 in a high speed. Due to the lower portion and the upper portion of the shaft 36 being supported by the lower one 50 and the upper bearing 60 of the pair of bearings 50, 60, respectively, vibrations caused by unsymmetric forces acting on two ends of the shaft 36 can be prevented. Therefore, the cooling fan can operate in a stable condition without noise generated, and the lifetime of the cooling fan is prolonged accordingly.

It is believed that the present invention and its advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the invention.

Claims

1. A cooling fan adapted for cooling a heat source, comprising:

a frame;

a lower bearing received in the frame;

a stator attached in the frame and surrounding the lower bearing;

a rotor installed in the frame, the rotor comprising: a hub enclosing the stator; a plurality of blades extending outwardly and radially from the hub; and a shaft extending through the hub with a lower portion of the shaft being inserted into the lower bearing;

a cover fixed on the frame to cover the rotor; and

an upper bearing received in the cover to accommodate an upper portion of the shaft therein, wherein when the cooling fan is in operation, supports respectively provided by the lower bearing to the lower portion of the shaft, and the upper portion to the upper portion of the shaft cooperatively prevent the shaft from vibration.

2. The cooling fan as claimed in claim 1, wherein the cover comprises a plurality of beams connecting with each other to define an opening, a plate surrounded by the plurality of beams, and a plurality of additional beams interconnecting the plate and the plurality of beams, the plurality of beams being secured on the frame to fix the cover on the frame.

3. The cooling fan as claimed in claim 2, wherein cover comprises four beams and four additional beams, the four additional beams dividing the opening into four identical areas each having a shape similar to a square.

4. The cooling fan as claimed in claim 2, wherein the cover further comprises a tubular body extending downwardly from the plate, the upper bearing being received in the tubular body.

5. The cooling fan as claimed in claim 4, wherein the hub of the rotor comprises a disk having a central area concaved downwardly to form a cavity therein, and an annular flange extending downwardly from a periphery of the disk, the disk of the hub being in alignment with the plate of the cover.

6. The cooling as claimed in claim 5, wherein the tubular body of the cover has an exterior diameter less than a diameter of the cavity of the hub, and a height larger than that of the cavity, the tubular body being partly received in the cavity of the hub.

7. The cooling fan as claimed in claim 5, wherein the upper portion of the shaft is located above the disk and partly exposed within the cavity of the hub, and the lower portion of the shaft is located below the disk.

8. The cooling fan as claimed in claim 5, wherein the frame comprises a lower plate, an upper plate connecting the plurality of beams of the cover thereon, and an annular sidewall interconnecting the lower plate and the upper plate, a through hole being defined through the lower plate and the upper plate for receiving the stator and the rotor therein.

9. The cooling fan as claimed in claim 8, wherein the frame further comprises a collar formed in a center of the through hole with a plurality of ribs connecting the collar to the annular sidewall of the frame, the collar being alignment with the disk of the hub.

10. The cooling fan as claimed in claim 9, wherein a hollow tube extends upwardly from the collar of the frame with the stator disposed therearound, the lower bearing being received in the hollow tube for accommodating the lower portion of the lower bearing therein.

11. A cooling fan adapted for dissipating heat from a heat source, comprising:

a frame;

a stator mounted in the frame, the stator having a plurality of coils for performing a magnet field when given an alternating current;

an impeller disposed in the frame, the impeller having a magnetic sleeve for being repulsed or attracted by the magnet field to rotate;

a cover secured on the frame to sandwich the stator and the impeller between the cover and the frame;

a first bearing being received in the cover;

a second bearing being received in the frame; and

a shaft extending through the impeller, the shaft having an upper portion being inserted into the first bearing, and a lower portion being inserted into the second bearing, thus the shaft can be supported at two ends thereof by the first bearing and the second bearing respectively.

12. The cooling fan as described in claim 11, wherein the impeller has a central area concaved downwardly to form a cavity, the upper portion of the shaft being exposed within the central area of the impeller to be received in the first bearing.

13. The cooling fan as described in claim 12, wherein the cover comprises a rectangular, annular bracket, a circular plate in a center of the cover, a plurality of beams connecting the circular plate with the rectangular, annular bracket to define four openings in the cover, and a tubular body extending downwardly from the circular plate and having a lower portion partly received in the cavity of the impeller.

14. The cooling fan as described in claim 13, wherein the first bearing is received in the tubular body of the cover to support the upper portion of the shaft, which is spaced a distance from the circular plate of the cover for preventing an interference between the shaft and the cover.

15. The cooling fan as described in claim 14, wherein the frame has a hollow tube formed at a lower portion thereof with the second bearing received therein, the hollow tube being surrounded by the stator that is surrounded by the magnetic sleeve of the impeller.

16. The cooling fan as described in claim 15, wherein the first bearing, the second bearing, the circular plate of the cover, the impeller, and the hollow tube of the frame are coaxial with each other.