Coil housing for a brushless fan

Abstract

A coil housing for a stator in a brushless fan is adapted to reduce the effect of permanent magnets in the fan when power is secured to the fan. The coil housing with an upper and lower case. Each case has multiple radial L-shapes protrusions that hold the coil in position. Each protrusion has a foot perpendicular to the cases. Adjacent feet are separated by an actual distance and a virtual distance. Each foot has edges configured to minimize the virtual distance between adjacent feet so individual magnets in the ring of magnets in the fan do not act on a single foot.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a coil housing for a brushless fan, and more particularly to a coil housing that is not held as securely in one position by the permanent magnets when power has been secured to the brushless fan.

[0003] 2. Description of Related Art

[0004] With reference to FIGS. 7 and 8, a conventional brushless fan comprises a blade assembly (20), a stator (40), a circuit board (60) and a fan housing (80). The circuit board (60) is securely mounted on the fan housing (80). The stator (40) comprises a coil housing (not numbered) and an annular coil (45). An upper case (41) and a complementary lower case (43) form the coil housing. The annular coil (45) is mounted between the upper case (41) and the lower case (43). The stator (40) is securely attached to the circuit board (60). When the stator (40) is powered up, electricity applied to the stator (60) induces an electromagnet in the coil (45) in the stator (40), magnetizes the upper case (41) and the lower case (43) with opposite polarity and causes the blade assembly (20) to rotate. The blade assembly (20) comprises multiple blades (not numbered), a hub (not numbered), a central shaft (10) and a cylindrical permanent magnet (21). The central shaft (10) extending from the hub rotatably extends through the stator (40). The cylindrical permanent magnet (21) has multiple magnetic elements (not numbered).The permanent magnet (21) are formed in a ring that is mounted in the hub of the blade assembly (20). A conventional brushless fan stator (40) has multiple L-shaped protrusions (411, 431) extending from the upper case (41) and the lower case (43). Each protrusion (411, 431) has a foot (not numbered) that is perpendicular to the upper and lower cases (41, 43) and parallel to the magnet elements. When the external power to the fan is interrupted or secured, the magnet elements attract the feet of the protrusions (411, 431) and slow and stop the rotating blade assembly (20). When the blade assembly (20) stops rotating, the magnet elements attract a corresponding foot and hold the blade assembly (20) in place. To start the electric fan, more electrical current must be applied to the blade assembly (20) to overcome the magnetic attraction between magnet elements in the blade assembly (20) and the feet of the protrusions (411, 431) in the stator (40). The increased electrical current when starting the brushless fan reduces the life of the brushless fan and ultimately may represent an electrical hazard.

[0005] To overcome the shortcomings, the present invention provides a coil housing with protrusions on the upper and lower cases to mitigate the aforementioned problem.

SUMMARY OF THE INVENTION

[0006] The main objective of the invention is to reduce the ability of permanent magnets in the blade assembly to hold the protrusions on the upper and lower cases of the coil housing of a brushless fan in one place. When the brushless fan is operating, an attractive force exists between feet on protrusions around the edge of the stator and the permanent magnets of blade assembly. The shape of the protrusions and feet mitigate the ability of the attractive force to resist the rotation of the blade assembly. Therefore, the magnetic attraction between the feet and the permanent magnets has less tendency to slow, stop or hold the blade assembly when power is interrupted.

[0007] Other objectives, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is an exploded perspective view of a brushless fan with a stator and a first embodiment of a coil housing in accordance with the present invention;

[0009] FIG. 2 is perspective view of the stator in FIG. 1;

[0010] FIG. 3 is a top plan view of the stator in FIG. 1 mounted in a hub of the blade assembly;

[0011] FIG. 4 is a perspective view of a stator for a brushless fan with a second embodiment of a coil housing in accordance with the present invention;

[0012] FIG. 5 is a perspective view of a stator for a brushless fan with a third embodiment of a coil housing in accordance with the present invention;

[0013] FIG. 6 is a perspective view of a stator for a brushless fan with a fourth embodiment of a coil housing in accordance with the present invention;

[0014] FIG. 7 is an exploded perspective view of a conventional brushless fan; and

[0015] FIG. 8 is a cross sectional side plan view of the conventional brushless fan in FIG. 7.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

[0016] With reference to FIGS. 1 through 3, a brushless fan comprises a fan housing (90), a circuit board (70), a stator (50A) and a blade assembly (30).

[0017] The blade assembly (30) consists of multiple fan blades (not shown), a cylindrical permanent magnet (31), a hub (32) and a central shaft (10). The cylindrical permanent magnet (31) has multiple magnetic elements (not numbered) and is mounted in the hub (32) of the blade assembly (30).

[0018] The stator (50A) comprises a coil housing (not numbered), an annular coil (55) and a bearing device (57). The coil housing has an upper case (51) and a lower case (53). The coil (55) is mounted inside the coil housing between the upper and the lower cases (51,53), and the annular coil (55) have an exterior radius. The upper case (51) and the lower case (53) are circular with a center (not numbered) and a through hole (not numbered) formed at the center through which the bearing device (57) is mounted. Multiply protrusions (511A, 531A) with a distal end and a proximal end extend radially from the upper and lower cases (51A, 53A). The protrusions (511A, 531A) respectively correspond to alternate electromagnetic poles generated by the coil (55) when electrical power is applied to the brushless fan.

[0019] A foot is formed on the distal end of each protrusion (511A, 531A) by bending the distal end at a right angle to the protrusion (511A, 531A). Each foot has an arced surface corresponding to the exterior radius of the annular coil (55), a distal edge (not numbered), a proximal edge (not numbered) and a lead and following edge. Adjacent feet have an actual separation and a virtual or radial separation. A relatively large actual separation between adjacent feet allows the feet to act as identifiable electromagnetic poles of the stator (50A). A relatively small virtual or radial separation between adjacent feet ensures that no permanent magnet element is ever over a gap between adjacent feet.

[0020] With reference to FIGS. 2 and 3, each protrusion (511A, 531A) has two radial edges extending from the center of the corresponding case (51A, 53A). At least one of the leading or following edges of each foot is an inclined edge (66) to increase the actual separation between adjacent feet while minimizing the virtual or radial separation between adjacent feet.

[0021] With reference to FIG. 4 or 5, each protrusion (511B, 511C, 531B, 531C) has two radial edges extending from the center of the corresponding case (51B, 51C, 53B, 53C). If the inclined edge (66) of a foot on the upper protrusion (511B, 511C) is the leading or following edge, the inclined edge (66) of a foot on the lower protrusion (531B, 531C) is the following or leading edge depending on the rotational direction. At least one of the leading and following edges of each foot is an inclined edge (66) to increase the actual separation between adjacent feet while minimizing the virtual or radial separation between adjacent feet.

[0022] With reference to FIG. 6, each protrusion (511D, 531D) has two radial edges extending from the center of the corresponding case (51D, 53D). Both the leading and following edges of each foot are inclined edges to increase the actual separation between adjacent feet while minimizing the virtual or radial separation between adjacent feet.

[0023] In all other aspects, the brushless fan is conventional, and further description of the convention features is not included.

[0024] The circuit board (70) is securely attached to the stator (50A), and the stator (50A) is securely mounted in the fan housing (90).

[0025] The central shaft (10) rotatably extends through the bearing device (57) in the stator (50A), and the bearing device (57) allows the central shaft (10) rotate freely.

[0026] With reference to FIGS. 2 through 6, the stator (50A-D) has four embodiments comprising multiply protrusions (511A-D, 531A-D), and the multiply protrusions (511A-D, 531A-D) have feet with various inclined edges (66) in each embodiment. As the brushless fan is powered up, the protrusions (511, 531) on the upper and lower case (51, 53) form alternative magnetic poles to attract or to repel the annular permanent magnet (31) in the blade assembly (30). Therefore, the blade assembly (30) rotates when power is applied. When power is interrupted during the operation of the brushless fan, the blade assembly (30) stops but is not held in a fixed position because the permanent magnet elements do not uniquely align with the individual feet. The inclined edge(s) (66) of the feet on the multiple protrusion's (511A-D, 531A-D) lower the effect of the magnetic attractive force on the individual feet since the permanent magnet elements easily overlap adjacent feet. Because the permanent magnet elements overlap adjacent feet on the multiple protrusions (511A-D, 531A-D), the blade assembly (30) easily rotates when power applied.

Claims

1. A coil housing for a brushless fan that includes a fan housing, a circuit board, a stator and a blade assembly; where the blade assembly includes a central shaft that rotatably extends through the stator; and the stator includes a bearing device through which the central shaft of the blade assembly rotatably extends; the coil housing comprises;

an upper case, which is circular with a center, adapted to be securely mounted on the bearing device and having multiple radial protrusions extending from the center of the upper case;

multiple upper feet respectively extending from the multiple protrusions of the upper case; each upper foot has at least one inclined edge;

a lower case, which is circular with a center, connected to the upper case and adapted to be securely mounted on the bearing device, and having multiple radial protrusions extending from the center of the lower case; and

multiple lower feet respectively extending from the multiple protrusions of the lower case; each lower foot has at least one inclined edge to increase an actual separation between adjacent upper feet on the upper case while minimizing a virtual or radial separation between adjacent feet.

2. The coil housing as claimed in claim 1, wherein each upper foot has a leading edge and a following edge opposite to the leading edge;

each upper foot has one inclined edge formed on the leading edge of the upper case;

each lower foot has a leading edge facing the following edge of an adjacent upper foot and a following edge opposite to the leading edge of the lower foot and facing the leading edge of an adjacent upper foot; and

each lower foot has one inclined edge formed on the leading edge of the lower case.

3. The coil housing as claimed in claim 1, wherein each upper foot has a leading edge and a following edge opposite to the leading edge;

each upper foot has one inclined edge formed on the leading edge of the upper case;

each lower foot has a leading edge facing the following edge of an adjacent upper foot and a following edge opposite to the leading edge of the lower foot and facing the leading edge of an adjacent upper foot; and

each lower foot has one inclined edge formed on the following edge of the lower case.

4. The coil housing as claimed in claim 1, wherein each upper foot has a leading edge and a following edge opposite to the leading edge;

each upper foot has one inclined edge formed on the following edge of the upper case;

each lower foot has a leading edge facing the following edge of an adjacent upper foot and a following edge opposite to the leading edge of the lower foot and facing the leading edge of an adjacent upper foot; and

each lower foot has one inclined edge formed on the leading edge of the lower case.

5. The coil housing as claimed in claim 1, wherein each upper foot has a leading edge and a following edge opposite to the leading edge;

each upper foot has one inclined edge formed on the following edge of the upper case;

each lower foot has a leading edge facing the following edge of an adjacent upper foot and a following edge opposite to the leading edge of the lower foot and facing the leading edge of an adjacent upper foot; and

each lower foot has one inclined edge formed on the leading edge of the lower case.

6. The coil house as claimed in claim 1, wherein each upper foot has two inclined edges respectively formed on two edges of the upper foot; and

each lower foot has two inclined edges respectively formed on two edges of the lower foot.