[0001] The disclosure relates to a cooling fan, and particularly to a centrifugal fan.
[0002] The centrifugal fan is one of the commonly used heat dissipating devices, the characteristics
of the air entering the fan casing from an axial inlet opening near the shaft of the
impeller and being displaced from a radial outlet opening at one side of the casing
are particularly advantageous for the heat dissipation of miniaturized electronic
products. However, the periodic changes in air pressure will occur in operation of
the centrifugal fan and lead to a source of noise. These periodic changes in pressure
are directly related to the number of fan blades, the shape of fan blades, the distribution
of fan blades, and even the rotation speed of the impeller. In particular, when the
shape of the respective blades is the same and the distribution of blade pitch is
uniform, the noise from resonance of the fan blades causing troubles in use.
[0003] Referring to Figure 1, an impeller of a conventional centrifugal fan 9 is shown to
include a hub 90, a ring member 91 surrounding the hub 90, and a plurality of blades
92 radially extending from the ring member 91. The arc distances (D) between each
two adjacent blades 92, with the same imaginary circular line as a reference, are
designed to exhibit continuous variations according to the requirement of reducing
noise. In the clockwise direction (R) as depicted in Figure 1, the arc distances (D)
between each two adjacent blades 92 gradually decrease from the 12 o'clock position
and then gradually increase from the 6 o'clock position. That is, any two adjacent
arc distances (D) of these blades 92 in the same imaginary circular line are different,
such that the blades 92 to be rendered by unequal spacing arrangement, thereby reducing
the resonance of blades 92 and the noise generated during rotation of the centrifugal
fan 9.
[0004] However, in this way of design, if the running test result of the centrifugal fan
is not as expected, it must be re-adjusted the appropriate spacing variation or spacing
ratio variation one by one for each blade 92, so that not only the time and cost of
the design are huge, but also relatively precise processes are required for actual
manufacturing in considering accurately matching the design data, therefore, the costs
of design and manufacturing are bound to be high.
[0005] Therefore, the object of the disclosure is to provide a centrifugal fan capable of
reducing noise with reduced design and manufacturing costs.
[0006] According to the disclosure, a centrifugal fan includes a casing and an impeller
module. The casing defines an accommodating space having an air inlet and an air outlet.
The impeller module is mounted in the accommodating space and is rotatable about an
axis for allowing air flow to enter from the air inlet and exit from the air outlet.
The impeller module includes a body and a plurality of blade units connected to and
annularly distributed along a circumference of the body. Each of the blade units has
a plurality of blades that are equi-angularly arranged along the circumference of
the body. A blade spacing which is defined between each adjacent pair of the blades
of one of the blade units is different from a blade spacing which is defined between
each adjacent pair of the blades of another one of the blade units.
[0007] Further, the present disclosure is to provide a variation of the centrifugal fan
capable of reducing noise with reduced design and manufacturing costs.
[0008] Accordingly, this variation of the disclosed centrifugal fan includes a casing and
an impeller module. The casing defines an accommodation space having an air inlet
and an air outlet. The impeller module is mounted in the accommodating space and is
rotatable about an axis for allowing air flow to enter from the air inlet and exit
from the outlet. The impeller module includes a body and a plurality of blade units
connected to and angularly distributed in a rotational direction along a circumference
of the body. Each of the blade units has a plurality of blades with a blade spacing
being defined between each adjacent pair of the blades. For each of the blade units,
the blade spacings among the blades are different, and the blades are arranged in
a manner that the blade spacings increases in the rotational direction.
[0009] Other features and advantages of the disclosure will become apparent in the following
detailed description of the embodiments with reference to the accompanying drawings,
of which:
Figure 1 is a top view illustrating an impeller of a conventional centrifugal fan;
Figure 2 is a partly cross-sectional view illustrating a first embodiment of a centrifugal
fan according to the present disclosure,
Figure 3 is a top view of an impeller module of the first embodiment;
Figure 4 is a top view of an impeller module of a second embodiment of the centrifugal
fan according to the present disclosure; and
Figure 5 is a top view of an impeller module of a third embodiment of the centrifugal
fan according to the present disclosure.
[0010] Before the present disclosure is described in greater detail, it should be noted
that where considered appropriate, reference numerals or terminal portions of reference
numerals have been repeated among the figures to indicate corresponding or analogous
elements, which may optionally have similar characteristics.
[0011] As shown in Figures 2 and 3, the first embodiment of a centrifugal fan according
to the present disclosure includes a casing 1 which defines an accommodating space
100 having an air inlet 101 and an outlet 102, and an impeller module 2 which is mounted
in the accommodating space 100 and which is rotatable about an axis for allowing air
flow to enter from the air inlet 101 and then exit from the outlet 102.
[0012] In this embodiment, the impeller module 2 includes a body 20, and three blade units
21 connected to the body 20 and annularly distributed along a circumference of the
body 20. Each of the blade units 21 has a plurality of blades 211 extending from the
body 20 away from the axis, and are equi-angularly arranged along the circumference
of the body 20. In this embodiment, each adjacent pair of the blades 211 of one of
the blade units 21 defines a blade spacing (X1) therebetween, each adjacent pair of
the blades 211 of another one of the blade units 21 defines a blade spacing (X2) therebetween,
and each adjacent pair of the blades 211 of the last one of the blade units 21 defines
a blade spacing (X3) therebetween. The blade spacings (X1, X2, X3) among the blade
units 21 are of different sizes, and the three blade units 21 are arranged in the
order of size of the predetermined blade spacings (X1, X2, X3). With the full circle
around the body 20 as a reference, a blade unit 21 is formed every 120 degrees, with
the blade spacings of the three blade units 21 varied from (X1) to (X2) and then to
(X3), thereby providing asymmetrically distributed blades 211 as a whole for the impeller
module 2 of the first embodiment.
[0013] Since the blades 211 of the impeller module 2 in the first embodiment are asymmetrically
distributed, the noise from resonance during rotation of the impeller module 2 can
be reduced. Further, in the design of the first embodiment, it is only needed to provide
three blade units 21 with different blade spacings (X1, X2, X3), thus obviating the
necessity of adjusting the continuous spacing variation between each adjacent blades
92 as illustrated in Figure 1. Therefore, it can effectively reduce the costs of design
and testing. In addition, because the design is relatively simple, high-precision
processes are not required, thereby reducing the cost incurred in manufacturing.
[0014] It should be particularly noted that the first embodiment is described by taking
the form of three blade unit 21 as an example. In actual implementation, for the consideration
of other requirements, four to six blade units 21 may be designed for an impeller
module 2 without excessive difficulty. This can also provide an impeller module 2
with asymmetrically distributed blades 211 in terms of the blade spacing, and achieve
the effect of reducing the costs of design and manufacturing.
[0015] As shown in Figure 4, the second embodiment of a centrifugal fan of the present disclosure
has a structure similar to that of the first embodiment. The main difference between
this embodiment and the first embodiment resides in the following. The impeller module
2 in this embodiment includes four blade units 21. The four blade units 21 includes
two first blade units 2101 with one blade spacing (X4), and two second blade units
2102 with a different blade spacing (X5). The first and second blade units 2101, 2102
are arranged in alternate. In the second embodiment, since only two different spacings
(X4, X5) are used in the four blade units 21, the resonance of blades 211 can be prevented
in a simpler design to achieve the purpose of reducing noise during operation.
[0016] As shown in Figure 5, the third embodiment has a structure similar to that of the
first embodiment. The main difference between this embodiment and the first embodiment
resides in the following. The blade unit 21 in this embodiment are annularly distributed
in a rotational direction (R1) along the circumference of the body 20. Each of the
blade units 21 has four blades 211 with the blade spacings among the blades 211 being
different. Specifically, each of the blade units 21 has three blade spacings (Y1,
Y2, Y3), and the four blades 211 are arranged in a manner that the blade spacings
(Y1, Y2, Y3) increases in the rotational direction (R1). Given that each blade unit
21 has four blades 211 with three different spacings (Y1, Y2, Y3), in the design of
the third embodiment, it is only needed to configure the three blade spacings (Y1,
Y2, Y3) rather than to adjust the continuous spacing variation between each adjacent
blades 92 as illustrated in Figure 1, so that the cost of design and testing can be
effectively reduced as in the first embodiment, which in turn reducing the cost incurred
in manufacturing.
[0017] To be particularly noted that the third embodiment is described with respect to the
blade units 21 with four blades 211 as an example, this embodeiment may be implemented
depending on the actual requirements with appropriate adjustments. For example, each
blade unit 21 has only three blades 211, or has five blades 211, the intended effect
of this disclosure can still be achieved without unduly raising the design difficulty.
[0018] In summary, the impeller module 2 of the centrifugal fan 2 of the present disclosure
is designed in a relatively simple manner to prevent the resonance of blades, thereby
reducing the noise during operation, and effectively reducing the costs of design,
testing, and manufacturing.
[0019] In the description above, for the purposes of explanation, numerous specific details
have been set forth in order to provide a thorough understanding of the embodiments.
It will be apparent, however, to one skilled in the art, that one or more other embodiments
may be practiced without some of these specific details. It should also be appreciated
that reference throughout this specification to "one embodiment," "an embodiment,"
an embodiment with an indication of an ordinal number and so forth means that a particular
feature, structure, or characteristic may be included in the practice of the disclosure.
It should be further appreciated that in the description, various features are sometimes
grouped together in a single embodiment, figure, or description thereof for the purpose
of streamlining the disclosure and aiding in the understanding of various inventive
aspects, and that one or more features or specific details from one embodiment may
be practiced together with one or more features or specific details from another embodiment,
where appropriate, in the practice of the disclosure.
1. A centrifugal fan including:
a casing (1) defining an accommodatng space (100) having an air inlet (101) and an
air outlet (102); and
an impeller module (2) mounted in said accommodating space (100) and rotatable about
an axis for allowing air flow to enter from said air inlet (101) and exit from said
air outlet (102), said impeller module (2) including a body (20) and a plurality of
blade units (21) connected to and annularly distributed along a circumference of said
body (20), characterized in that:
each of said blade units (21) has a plurality of blades (211) that are equi-angularly
arranged along said circumference of said body (20), a blade spacing which is defined
between each adjacent pair of said blades (211) of one of said blade units (21) being
different from a blade spacing which is defined between each adjacent pair of said
blades (211) of another one of said blade units (21).
2. The centrifugal fan as claimed in claim 1,
characterized in that:
said plurality of blade units (21) includes at least three blade units (21);
the blade spacings among said blade units (21) are different; and
said blade units (21) are arranged in the order of size of the blade spacings.
3. The centrifugal fan as claimed in any one of claims 1 and 2, characterized in that said impeller module (2) includes exactly three blade units (21).
4. The centrifugal fan as claimed in claim 1, characterized in that said impeller module (2) includes exactly four blade units (21).
5. The centrifugal fan as claimed in claim 4, characterized in that said four blade units (21) includes two first blade units with one blade spacing
and two second blade units with a different blade spacing, said first and second blade
units being arranged in alternate.
6. A centrifugal fan including:
a casing (1) defining an accommodation space (100) having an air inlet (101) and an
air outlet (102); and
an impeller module (2) mounted in said accommodating space (100) and rotatable about
an axis for allowing air flow to enter from said air inlet (101) and exit from said
air outlet (102), said impeller module (2) including a body (20) and a plurality of
blade units (21) connected to and annularly distributed in a rotational direction
along a circumference of said body (20), each of said blade units (21) having a plurality
of blades (211) with a blade spacing being defined between each adjacent pair of said
blades (211);
characterized in that, for each of said blade units (21), the blade spacings among said blades (211) being
different, and said blades (211) being arranged in a manner that the blade spacings
increases in the rotational direction.
7. The centrifugal fan as claimed in claim 6, characterized in that each blade unit (21) has four blades (211).