Micro-fan

Abstract

Disclosed herewith is a micro-fan. The micro-fan includes a hub attached to a rotating shaft and a plurality of blades extended from the side surface of the hub. In the micro-fan, if a leading edge is defined as the foremost edge of each of the blades consisting of a straight line portion and one or more arc portions, a trailing edge is defined as the rearmost edge of each of the blades, a chord line is defined as a line connecting two opposite points respectively situated in the leading and trailing edges and a blade angle is defined as an angle formed by the chord line and the horizontal line passing through the same point of the leading edge as that through which the chord line passes and lying in the same vertical plane as that in which the leading edge lies, the straight line portions of the leading and trailing edges are perpendicular to the hub and form a predetermined inside angle.

Description

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates generally to a micro-fan in which the leading and trailing edges of each blade are each formed by a straight line and one or more arcs, thereby reducing the noise of rotation as well as generating an optimal volume of air and optimal wind pressure.

[0003] 2. Description of the Prior Art

[0004] A micro-fan is generally used to cool a microprocessor that is operated in a small-sized space such as a notebook computer or personal computer. A small-sized axial flow fan is generally employed as such a micro-fan.

[0005] Currently, the micro-fan is secured to a microprocessor, or independently mounted on a notebook computer. The personal computer is miniaturized, whereas a central processing unit is large-capacity and high-speed, thereby considerably increasing load capacity and generating high temperature heat.

[0006] Such heat generated in the central processing unit causes an apparatus to break down or causes principal parts to be damaged.

[0007] Accordingly, the cooling of the central processing unit becomes an important technical task, however, cooling fans for central processing units that are currently employed are not sufficient to cope with such a task.

[0008] The cooling performance of a cooling fan is generally improved by increasing the volume of air circulated by the fan. This air volume of the fan is dependent upon various factors, such as the size and shape of its blades and the number of rotations per unit time during operation. Meanwhile, problems, such as limitation in space, power consumption and the occurrence of noise should be taken into consideration, together with the above-described factors.

[0009] Accordingly, in the design of a fan, it is necessary to satisfy high performance conditions, such as the prevention of energy loss by the separation of air flow, a reduction in noise, the minimization of energy loss between the inlet side and outlet side of each blade, a static pressure rise, and the like.

[0010] In particular, it is proven by various experiments that the majority of fan noise is a function of the number of rotations per unit time, the tip clearance of each blade, the number of blades, chord length, chamber, the sweep of each blade, and the like.

[0011] FIG. 1 is a plan view showing the structure of a general micro-fan currently used. Reference numeral 1 designates a hub rotated while being attached to the shaft of a motor, reference numeral 2 designates blades integrated with the side surface of the hub, and reference numeral 3 designates a duct surrounding the hub 1 and the blades 2 and guiding air through a guide hole formed between the blades 2 and itself.

[0012] The hub 1 is the rotating member of a fan motor, which is provided with a magnet in its interior, and is rotated by electromagnetic force caused by the interaction of itself with a stator coil while being powered on.

[0013] The blades 2 are radially outwardly extended from the side surface of the hub 1, and function to suck cold air from the outside and supply the air to a microprocessor while being rotated together with the hub 1.

[0014] The duct 3 is provided outside of the blades 2 to surround the blades 2, and function as a guide for guiding air sucked by the blades 2 toward a microprocessor.

[0015] FIG. 2 is a front view showing a conventional blade that is formed on the hub 1 in the conventional micro-fan. In the conventional micro-fan, the blade 2 has an upwardly curved sectional shape, and is inclined from its one end attached to the hub 1 to its other end.

[0016] The duct 3, which surrounds and is slightly spaced apart from the outer edges of the blades 2, is integrated with the stationary member of the motor at its lower portion, and is secured to a microprocessor by means of securing means such as screws.

[0017] In particular, a guide hole 3a formed between the outer edges of the blades 2 and the inner edge of the duct 3 allows air sucked by the blades 2 to smoothly flow toward a microprocessor.

[0018] In consequence, as the hub 1 is rotated by the application of power to the motor, a plurality of blades 2 integrated with the hub 1 are rotated, together with the hub. In this case, air is sucked from the outside by pressure difference between the surfaces of each blade, and, finally, is supplied to the microprocessor.

[0019] The inflow of air is based on a principle that pressure on the inner surface of each blade 2 is rapidly reduced in comparison with pressure on the outer surface of the blade 2 owing to the upwardly cured shape of the blade 2, and air is moved to a relatively lower pressure position.

[0020] However, most micro-fans currently used are fabricated for the purpose of simply sucking air from the outside, so the shape of each blade 2 is simply designed without regard for high performance.

[0021] Generally, the volume of air generated by a fan is dependent upon the size and shape of the blades of the fan and the number of rotations per unit time during operation. The blade 2 applied to a micro-fan currently used, as shown in FIG. 2, has a sectional shape in which a lower straight line is connected by an upper arc at its both ends. As for the angles of inclination of each blade with regard to the hub 1, a hub-side angle is designed to be identical to a duct-side angle.

[0022] In the conventional cooling fan, the cooling fan is designed in consideration of noise limitation, so the cooling fan itself does not produce great noise. However, when the cooling fan is used while being assembled with a heat sink or the like, a separation of air flow occurs because of the creation of a vortex at the tip of the blade. The separation of air flow disturbs a surrounding flow field, and can be a cause of a reduction in performance of a fan and an increase in noise.

[0023] High-capacity and high-speed microprocessors currently being developed provide relatively faster processing speeds, so the cooling of the microprocessors cannot be performed properly by the conventional micro-fans having the conventional blades. The development of a micro-fan that copes with the above-described current trend has been eagerly pursued.

SUMMARY OF THE INVENTION

[0024] Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a micro-fan, which is capable of suppressing the occurrence of noises as well as providing sufficient cooling efficiency while being assembled with a heat sink or the like.

[0025] In order to accomplish the above object, the present invention provides a micro-fan, comprising: a hub attached to a rotating shaft; and a plurality of blades extended from the side surface of the hub; wherein, if a leading edge is defined as the foremost edge of each of the blades consisting of a straight line portion and one or more arc portions, a trailing edge is defined as the rearmost edge of each of the blades, a chord line is defined as a line connecting two opposite points respectively situated in the leading and trailing edges and a blade angle is defined as an angle formed by the chord line and the horizontal line passing through the same point of the leading edge as that through which the chord line passes and lying in the same vertical plane as that in which the leading edge lies, the straight line portions of the leading and trailing edges are perpendicular to the hub and form a predetermined inside angle.

[0026] The leading and trailing edges may have straight line portions that form an inside angle ranging from 30 to 60°.

[0027] The leading and trailing edges may have straight line portions that extend over about 50 to 70% of a blade width that ranges from the innermost edge to the outermost edge of the blade.

[0028] The blade may have a length that ranges from the leading edge to the trailing edge and is increased in a radially outward direction.

[0029] The blade angle may be gradually reduced in a radially outward direction.

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The above and other objects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0031] FIG. 1 is a plan view of a conventional micro-fan;

[0032] FIG. 2 is an enlarged side view of a blade of the conventional micro-fan;

[0033] FIG. 3 is a perspective view showing a micro-fan in accordance with the present invention;

[0034] FIG. 4 is a front view of FIG. 3;

[0035] FIG. 5 is a cross section showing a blade of the micro-fan of the present invention;

[0036] FIG. 6 is a plan view showing the micro-fan of the present invention; and

[0037] FIG. 7 is a schematic diagram illustrating the design principle of the micro-fan of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0038] Reference now should be made to the drawings, in which the same reference numerals are used throughout the different drawings to designate the same elements.

[0039] In the design of a micro-fan, principal factors that should be considered to allow the micro-fan to have high performance are the rotational speed of the fan, the angle of its blade, the number of its blades and the shape of its blade. Of such principal variables, the most important factor that should be considered to minimize energy loss between the inlet side and outlet side of the blade and maximize a static pressure rise is the shape of each blade.

[0040] In a general micro-fan, the outer edges of the blades of the micro-fan are constructed to be surrounded by a duct (not shown).

[0041] The outer edges of the blades and the inner edge of the duct are spaced slightly apart from each other to form a guide hole therebetween. This guide hole functions as a guide for smoothly guiding cold air sucked by the blades in a direction.

[0042] In the meantime, while the blades are rotated together with the hub, the inflow of air is based on a principle that pressure on the inner surface of each blade is rapidly reduced in comparison with pressure on the outer surface of the blade owing to the upwardly curved shape of the blade, and air is moved to a relatively lower pressure position.

[0043] General shapes employed in the design of blades belong to the “Circular Arc” system proposed in the United Kingdom or the “National Advisory Committee for Aeronautics” system proposed in U.S. The angle of each blade is determined to prevent energy loss caused by the separation of air.

[0044] The micro-fan of the present invention is characterized in that its leading and trailing edges are each formed by a straight line and one or more arcs and the straight line portions of the leading and trailing edges form a predetermined inner angle.

[0045] FIG. 3 is a perspective view showing a micro-fan in accordance with the present invention. FIG. 4 is a side view of the micro-fan shown in FIG. 3. FIG. 6 is a plan view showing the micro-fan of the present invention.

[0046] In accordance with the present invention, a plurality of blades 200 are radially outwardly extended from the circumferential surface of a hub 100. In this case, an airfoil that is applied to the design of an aircraft wing is employed as the shape of each blade. The surfaces of each blade 200 are twisted at a predetermined angle.

[0047] FIG. 5 is a sectional view showing the blade 200 employed in the micro-fan of the present invention. The micro-fan of the present invention is characterized in that leading and trailing edges are each formed by a single straight line and one or more arcs.

[0048] In more detail, if a leading edge 210 is defined as the foremost edge of each blade 200 of the micro-fan, a trailing edge is defined as the rearmost edge of each blade 200 and a chord line 230 is defined as a line connecting two opposite points respectively situated in the leading and trailing edges 210 and 220, the leading and trailing edges are each formed by a single straight line and one or more arcs.

[0049] As depicted in FIG. 7, the straight line portion of the leading edge 210 is formed to be perpendicular to the hub 100, and the straight line portion of the trailing edge 220 is formed to be perpendicular to the hub 100.

[0050] The straight line portions of the leading and trailing edges 210 and 220 form an inside angle ranging from 30 to 60°.

[0051] In the meantime, the length of the blade 200, that is, the distance ranging from the leading edge 210 to the trailing edge 220 is increased in a radially outward direction.

[0052] In the blade 200, the straight line portions of the leading and trailing edges preferably extend over about 50 to 70% of a blade width that ranges from the innermost edge to the outermost edge of the blade 200.

[0053] A blade angle, that is, an inclined angle formed by a chord line 230 and the horizontal line passing through the same point of the leading edge 210 as that through which the chord line 230 passes and lying in the same vertical plane as that in which the leading edge 210 lies is gradually reduced in a radially outward direction.

[0054] As described above, in the micro-fan of the present invention, the leading and trailing edges of the blade 200 are each formed by a straight line and one or more curves, so an increase in the volume of air circulated, a static pressure rise and a reduction in the influence of drag and friction are caused, thereby promoting effective air flow.

[0055] The following table shows comparisons between the noises of various unassembled micro-fans and the noises of various micro-fans assembled with heat sinks or the like. 1 Size 50 × 50 × 15 60 × 60 × 15 60 × 60 × 10 RPM 4000 4500 4000 Db 25 32 28 (unassembled fan) Db (fan assembled 25 32 28 with a component)

[0056] As apparent from the above table, there is no difference in noise that is generated by an unassembled micro-fan and a micro-fan assembled with a heat sink or the like. That is, when the micro-fan of the present invention is assembled with another component, the noise of the micro-fan is not increased.

[0057] By way of an example, a micro-fan of 60×60×15 mm size is described.

[0058] First of all, {0, 0} is assigned to central coordinates, and 42° is chosen as a sweep angle shown in FIG. 7.

[0059] The curved line portion of the leading edge is made to coincide with an arc portion of a circle that has a center at coordinates {7.25, 22.14} and has a radius of 11.6. The circle comes into contact with the straight line portion of the leading edge at the center of the blade width.

[0060] The blade width is constant and the blade angle has been determined, so the trailing edge is determined depending on the leading edge.

[0061] As described above, the noises generated by the blade are mostly caused by a tip clearance. In the micro-fan of the present invention, static pressure is concentrated on the leading edge of a blade and is small on the trailing edge of the blade, so the assembly of the micro-fan to a heat sink or the like does not increase the noises of the micro-fan.

[0062] Accordingly, in a state where the micro-fan is assembled with a heat sink or the like, a separation of air flow by the occurrence of a vortex is reduced, so the performance of the micro-fan is improved and the noise of the micro-fan is reduced.

[0063] As a result, the reliability of a product employing the micro-fan of the present invention can be considerably improved.

[0064] Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

1. A micro-fan, comprising:

a hub attached to a rotating shaft; and

a plurality of blades extended from the side surface of said hub;

wherein, if a leading edge is defined as the foremost edge of each of said blades, a trailing edge is defined as the rearmost edge of each of said blades consisting of a straight line portion and one or more arc portions, a chord line is defined as a line connecting two opposite points respectively situated in the leading and trailing edges and a blade angle is defined as an angle formed by said chord line and the horizontal line passing through the same point of the leading edge as that through which the chord line passes and lying in the same vertical plane as that in which the leading edge lies, the straight line portions of said leading and trailing edges are perpendicular to said hub and form a predetermined inside angle.

2. The micro-fan according to claim 1, wherein said leading and trailing edges have straight line portions that form an inside angle ranging from 30 to 60°.

3. The micro-fan according to claim 1, wherein said leading and trailing edges have straight line portions that extend over about 50 to 70% of a blade width that ranges from the innermost edge to the outermost edge of said blade.

4. The micro-fan according to claim 1, wherein said blade has a length ranging from said leading edge to said trailing edge, said length being increased in a radially outward direction.

5. The micro-fan according to claim 1, wherein said blade angle is gradually reduced in a radially outward direction.