COOLING FAN HAVING BENT BEARING HOUSING FOR RETAINING LUBRICANT

Abstract

A cooling fan includes a stator, a base supporting the stator, and a rotor positioned to rotate with respect to the stator. The base includes a bearing housing and a central hole defined in the bearing housing. The rotor includes a hub and a shaft extending from the hub. An end of the shaft is fixed in the hub, and another end of the shaft is extending in the central hole defined in the bearing housing. The bearing housing includes a main cylindrical portion and a protruding portion bent radially inward from a top end of the main portion, and the protruding portion thus serves as a lubricant retaining portion of the bearing housing.

Description

BACKGROUND

1. Technical Field

The present disclosure relates to a cooling fan typically employed in an electronic device such as a computer, and more particularly to a cooling fan which has a bearing housing with a bent end in order to retain lubricant in the bearing housing.

2. Description of Related Art

With the continuing development of electronics technology, heat-generating electronic components such as CPUs (central processing units) are generating more and more heat when in operation. In typical devices that employ CPUs, the heat requires immediate dissipation. Cooling fans are commonly used in combination with heat sinks for cooling the CPUs.

A typical cooling fan comprises a fan housing having a bearing housing extending upwardly therefrom, a bearing received in the bearing housing, a stator mounted around the bearing housing, and a rotor rotatable with respect to the stator. The rotor includes a hub and a shaft extending from the hub into the bearing. The bearing housing has an opening defined at a top end thereof. In assembly of the cooling fan, the bearing is inserted into the bearing housing through the opening. Lubricant is injected into the bearing housing to lubricate the bearing and the shaft. Traditionally, a discrete retaining ring is located at the top end of the bearing housing to retain the lubricant in the bearing housing, so as to maintain the lubrication of the bearing and the shaft.

However, rotation of the rotor with respect to the stator during the working lifetime of the cooling fan is liable to cause the discrete retaining ring to loosen and become deformed. As such, there is a high risk of the lubricant leaking out of the bearing housing, resulting in increased friction between the shaft and the bearing. When this happens, the performance of the cooling fan deteriorates, and the lifespan of the cooling fan is shortened.

What is needed, therefore, is an improved cooling fan which can overcome the above-described shortcomings

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an assembled view of a cooling fan according to an exemplary embodiment of the present disclosure.

FIG. 2 is essentially an exploded view of the cooling fan of FIG. 1, showing the parts prior to assembly of the cooling fan, including a bearing housing partly cut away for clarity.

FIG. 3 is an enlarged view of a circled portion III of FIG. 2.

FIG. 4 is an inverted view of FIG. 2.

FIG. 5 is an abbreviated, cross-sectional view of the cooling fan of FIG. 1, taken along a line V-V thereof.

FIG. 6 is an enlarged view of a circled portion VI of FIG. 5.

FIG. 7 is an abbreviated, cross-sectional view of a cooling fan according to another exemplary embodiment of the present disclosure.

FIG. 8 is an enlarged view of a circled portion VIII of FIG. 7.

DETAILED DESCRIPTION

Exemplary embodiments of a cooling fan in accordance with the present disclosure will now be described in detail below and with reference to the drawings.

FIGS. 1 and 2 show a cooling fan 100 in accordance with an exemplary embodiment of the disclosure. The cooling fan 100 includes a fan housing 10, a bearing assembly 20, a stator 30, and a rotor 50. The rotor 50 surrounds the stator 30. The stator 30 and the rotor 50 are received in the fan housing 10.

The fan housing 10 includes a plate 11, a sidewall 13 extending vertically and upwardly from a circumferential edge of the plate 11, and a bearing housing 14 extending vertically and upwardly from a center of the plate 11.

The plate 11 is flat, and an air inlet 111 is defined in a central portion of the plate 11. In particular, the air inlet 111 occupies an annular area, and in this embodiment includes three centrosymmetric openings. Thus the plate 11 includes a base 113 located in a center of the air inlet 111, and three connecting sheets 115 extending from a periphery of the base 113 to connect with portions of the plate 11 surrounding the air inlet 111. In this embodiment, the base 113 and the connecting sheets 115 are integral portions of the plate 11.

The bearing housing 14 is formed on the center of the base 113. In this embodiment, the bearing housing 14 is integrally formed with the base 113. That is, the bearing housing 14 is integrally formed with the plate 11, with the bearing housing 14 and the plate 11 being a single monolithic body of the same material.

The sidewall 13 includes an arc-shaped surrounding wall 131 surrounding a majority of the rotor 50, a first air-guiding wall 133, and a second air guiding wall 135. The first air-guiding wall 133 and the second air-guiding wall 135 extend outwardly from two ends of the surrounding wall 131, respectively. The first air-guiding wall 133 and the second air-guiding wall 135 are spaced from and parallel to each other, whereby an air outlet 134 is defined therebetween.

The bearing housing 14 is a central tube and extends from the center of the base 113. A central hole 140 vertical to the base 113 is defined in the bearing housing 14. The bearing housing 14 has an opening defined at a top end of the central hole 140. The central hole 140 has a uniform inner diameter throughout its axial length.

Referring to FIG. 3, the bearing housing 14 includes a main portion 141, and a protruding portion 145 extending upwardly from a top end of the main portion 141 away from the base 113.

The main portion 141 is cylindrical, and extends vertically and upwardly from the center of the base 113. The protruding portion 145 extends upwardly from the center of the top end of the main portion 141. The central hole 140 extends through the bearing housing 14 from a top end of the protruding portion 145 to a bottom end of the main portion 141 connecting the base 113. Inner cylindrical surfaces of the main portion 141 and the protruding portion 145 are coplanar. The protruding portion 145 is cylindrical (or annular), and an outer diameter thereof is smaller than an outer diameter of the main portion 141.

The bearing assembly 20 includes a bearing 21 and a disk 23. The bearing 21 is a sleeve bearing and made from sintered powder such as copper powder or ceramic powder. A plurality of pores (not shown) is defined in the bearing 21, and the pores communicate with each other. The bearing 21 is received in the central hole 140 of the bearing housing 14 via the opening of the bearing housing 14. The bearing 21 defines an axial hole 211 therein. A plurality of channels 213 is defined in the bearing 21. Each channel 213 extending from a center of a top end of the bearing 21 radially outward to a peripheral side surface of the bearing 21, and then down along a peripheral wall of the bearing 21 along a direction parallel to a axis of the bearing 21 to a bottom of the bearing 21. Thus, each channel 213 is L-shaped, and innermost extremities of the channels 213 at the top end of the bearing 21 communicate with the axial hole 211 of the bearing 21. The channels 213 are radially symmetrically arranged around the axis of the bearing 21. With the above-described configuration, lubricant at the top of the axial hole 211 is guided to a top portion of the bearing 21, and then returns to a bottom portion of the bearing 21 (see below). The disk 23 is made of wear-resistant material, and is located at a bottom end of the central hole 140.

The stator 30 includes an iron core 31, a coil 33, a circuit board 35, and an insulating frame 37. The insulating frame 37 encloses the iron core 31 therein. The coil 33 is twined around the insulating frame 37. The circuit board 35 is located at a bottom end of the insulating frame 37 and electrically connected with the coil 33. The core 31, the insulating frame 37 and the circuit board 35 are arranged along a common axis. As such, a mounting hole 39 is commonly defined through the core 31, the insulating frame 37 and the circuit board 35.

Referring to FIG. 4, the rotor 50 includes a hub 51, a shaft 53, a magnetic ring 55, and a plurality of fan blades 57.

The hub 51 includes a circular base plate 511, and a surrounding sidewall 513 extending vertically and upwardly from a circumferential edge of the base plate 511. A fixing seat 5112 is formed in a center of the base plate 511, and the fixing seat 5112 fixes a top end of the shaft 53 therein. A free end of the shaft 53 extends down away from the fixing seat 5112. Preferably, the shaft 53 defines an annular slot 531 in a circumferential wall thereof, at a position near a top end of the shaft 53 close to the hub 51.

The magnetic ring 55 is attached to the inner surface of the sidewall 513. The fan blades 57 extend radially and outwardly from a periphery of the hub 51. An inner diameter of the magnetic ring 55 and an inner diameter of the hub 51 are both larger than an outer diameter of the iron core 31 and an outer diameter of the insulating frame 37, so that the iron core 31 and the insulating frame 37 can be received in the magnetic ring 55 and the hub 51.

The hub 51 encloses the stator 30 and the magnetic ring 55 therein. The magnetic ring 55 is spaced from the iron core 31 and surrounds the periphery of the iron core 31.

Referring to FIGS. 5 and 6, when assembling the cooling fan 100, the disk 23 is inserted into and located at the bottom of the central hole 140. The bearing 21 is inserted into the central hole 140. The top end of the bearing 21 is lower than the top end of the protruding portion 145, and the bottom end of the bearing 21 abuts against the disk 23. Then, the protruding portion 145 of the bearing housing 14 is bent radially and inwardly to form a lubricant retaining portion 1451. The lubricant retaining portion 1451 is annular, and defines a through hole 1453 in the center thereof. The through hole 1453 communicates with the central hole 140, and is aligned with the axial hole 211. An inner diameter of the through hole 1453 and an inner diameter of the axial hole 211 are both slightly larger than an outer diameter of the shaft 53. The free end of the shaft 53 is extended through the through hole 1453 of the lubricant retaining portion 1451 and the axial hole 211 of the bearing 21 sequentially, to abut against the disk 23. In this embodiment, the lubricant retaining portion 1451 is formed by hot-melting the protruding portion 145 sufficiently to allow it to be bent.

The lubricant retaining portion 1451 is located between the bottom end of the fixing seat 5112 and the slot 531. An upper surface of the lubricant retaining portion 1451 is near and spaced from the bottom end of the fixing seat 5112, to define a gap 1500 therebetween. The gap 1500 helps ensure that the fixing seat 5112 does not interfere with the lubricant retaining portion 1451. The slot 531 is located in the central hole 140, and completely below the lubricant retaining portion 1451.

An annular narrow space 1600 is defined between the inner edges of the lubricant retaining portion 1451 and a periphery of the shaft 53. The space 1600 helps ensure that the shaft 53 rotates within the lubricant retaining portion 1451 without friction. Preferably, as indicated above, the lubricant retaining portion 1451 is located above the slot 531, surrounding the shaft 53. Alternatively, the lubricant retaining portion 1451 can extend into the slot 531 (see FIGS. 7 and 8).

Furthermore, the lubricant retaining portion 1451, the bearing 21 and the shaft 53 cooperatively form a lubricant reservoir 60 above the top portion of the bearing 21. During operation, the rotor 50 is driven to rotate by the interaction between an alternating magnetic field established by the outer cores 31 of the stator 30 and the magnetic ring 55 of the rotor 50. Lubricant creeps up along the rotating shaft 53 under the influence of the centrifugal force generated by the rotation of the shaft 53, and then escapes to the lubricant reservoir 60 through in a very small cylindrical clearance 1700 located between the bearing 21 and the shaft 53. When the lubricant reaches the top end of the bearing 21, the lubricant escapes into the lubricant reservoir 60. As indicated above, the lubricant reservoir 60 is cooperatively defined between the top end of the bearing 21, the lubricant retaining portion 1451 and the shaft 53. The slot 531 of the shaft 53 prevents the lubricant from continuously creeping up along the shaft 53. Since the lubricant reservoir 60 is almost or substantially hermetically sealed by the retaining portion 1451, the retaining portion 1451 can prevent the lubricant from leaking out of the lubricant reservoir 60. In addition, the lubricant in the lubricant reservoir 60 is guided by the channels 213 to return to the bottom portion of the bearing 21, which helps maintain the lubrication of the bearing 21 and the shaft 53.

In summary, the lubricant retaining portion 1451 is formed by bending the protruding portion 145 of the bearing housing 14 which is formed integrally with the base 113. Therefore no discrete retaining ring or locking disk is needed to prevent the lubricant from leaking out of the lubricant reservoir 60, which increases the efficiency of assembling the cooling fan 100 and reduces costs. Furthermore, because the lubricant retaining portion 1451 is located below the fixing seat 5112 with the upper surface of the lubricant retaining portion 1451 being spaced by the gap 1500 from the fixing seat 5112, the bottom end of the fixing seat 5112 does not interfere with the lubricant retaining portion 1451 when the rotor 50 is rotating relative to the bearing 21 at high speed. Moreover, with the narrow space 1600, the shaft 53 does not interfere with the inner edges of the lubricant retaining portion 1451.

It is to be understood, however, that even though numerous characteristics and advantages of the embodiments have been set forth in the foregoing description, together with details of the structures and functions of the embodiments, the disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principles of the disclosure to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.

Claims

1. A cooling fan comprising:

a stator;

a rotor positioned to rotate with respect to the stator, the rotor comprising a hub and a shaft extending from the hub, an end of the shaft being fixed in the hub; and

a base supporting the stator, the base comprising a bearing housing and a central hole defined in the bearing housing, another end of the shaft extending in the central hole of the bearing housing, wherein the bearing housing comprises a main cylindrical portion and a protruding portion bent radially inward from a top end of the main portion, and the protruding portion thus serves as a lubricant retaining portion of the bearing housing.

2. The cooling fan of claim 1, wherein the lubricant retaining portion is annular, and defines a through hole in the center thereof.

3. The cooling fan of claim 1, wherein the shaft defines an annular slot in a circumferential wall thereof, at a position near a top end of the shaft close to the hub.

4. The cooling fan of claim 3, wherein the slot is located in the central hole, and is completely below the lubricant retaining portion.

5. The cooling fan of claim 3, wherein the lubricant retaining portion extends into the slot.

6. The cooling fan of claim 3, wherein an upper surface of the lubricant retaining portion is near and spaced from the hub, to define a gap therebetween.

7. The cooling fan of claim 1, wherein inner cylindrical surfaces of the main portion and the protruding portion are coplanar before the protruding portion is bent radially inward from the top end of the main portion.

8. The cooling fan of claim 7, wherein an outer diameter of the protruding portion is smaller than an outer diameter of the main portion before the protruding portion is bent radially inward from the top end of the main portion.

9. The cooling fan of claim 1, wherein the lubricant retaining portion is a hot-melted portion of the bearing housing.

10. The cooling fan of claim 1, further comprising a bearing received in the bearing housing, wherein the shaft extends through the bearing, a plurality of channels is defined in the bearing, and each channel extends from a center of a top end of the bearing radially outward to a peripheral side surface of the bearing, and then down along a peripheral wall of the bearing along a direction parallel to an axis of the bearing to a bottom of the bearing.

11. The cooling fan of claim 10, wherein the bearing defines an axial hole therein, the shaft extends through the axial hole, each channel is L-shaped, innermost extremities of the channels at the top end of the bearing communicate with the axial hole, and the channels are radially symmetrically arranged around the axis of the bearing.

12. The cooling fan of claim 1, further comprising a bearing received in the bearing housing, wherein the shaft extends through the bearing, and the lubricant retaining portion, the bearing and the shaft cooperatively form a lubricant reservoir above a top portion of the bearing.

13. A cooling fan comprising:

a base;

a bearing housing extending upwardly from the base, the bearing housing defining a central hole therein; and

a rotor positioned to rotate with respect to the base and bearing housing, the rotor comprising a shaft, the shaft extending in the central hole of the bearing housing, wherein the shaft defines an annular slot in a circumferential wall thereof, a top end of the bearing housing is bent radially inward and extends into the annular slot, and the top end of the bearing housing serves as a lubricant retaining portion substantially sealing a top end of the central hole of the bearing housing.

14. The cooling fan of claim 13, wherein the bearing housing includes a main cylindrical portion and the top end extending from the main portion and the top end is bent radially inward from the main portion to serve as the lubricant retaining portion.

15. The cooling fan of claim 13, wherein the lubricant retaining portion is a hot-melted portion of the bearing housing.

16. The cooling fan of claim 13, wherein a disk is located at a bottom end of the central hole, and the disk is made of wear-resistant material.