Fluid reaction surfaces (i.e. – impellers) – Specific blade structure – Cantilever blade
Reexamination Certificate
2001-12-21
2004-01-06
Look, Edward K. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
Specific blade structure
Cantilever blade
C416S22300B, C416SDIG002
Reexamination Certificate
active
06672840
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a refrigerator, and more particularly, to an axial flow fan for condenser for reducing flow noise in a refrigerator.
2. Description of the Related Art
In general, a refrigerator in use for freezing or cooling foods includes a housing for defining receiver spaces therein divided into freezer and refrigerator compartments, upper and lower doors installed in one side of the housing for opening/shutting the freezer and refrigerator compartments and instruments which include a compressor, a condenser and an evaporator for carrying out a cooling cycle for cooling the freezer and refrigerator compartments.
In such a refrigerator, a gaseous refrigerant in low temperature and pressure is compressed to have a high temperature and pressure by a compressor. The compressed hot and high-pressure gaseous refrigerant is cold compressed to a high-pressure liquid while passing through a condenser. The high-pressure refrigerant is lowered in temperature and pressure while passing through capillaries, and consequently absorbs heat from the surrounding to cool the neighboring air in the evaporator while being converted to a gas having a low temperature and pressure. The cold air cooled via the evaporator is circulated into the freezer and refrigerator compartments through the operation of a blower fan so that the freezer and refrigerator compartments are lowered in temperature.
In a refrigerator as shown in
FIG. 1
, a condenser
10
and a compressor
12
are installed in a so-called machine room in the outer bottom of a housing, and a blower fan assembly is arranged in one side thereof for absorbing the outer air into the machine room and flowing the same toward the condenser
10
to effectively cool a refrigerant introduced into the condenser
10
.
The blower fan assembly is comprised of an axial flow fan
20
and a motor
22
for driving the axial flow fan
20
, in which the axial flow fan
20
, as shown in
FIG. 2
, is constituted by a hub
201
connected to the rotation axis of the motor
22
and a number of blades
202
arranged in the outer periphery of the hub
201
.
According to the blower fan assembly, the axial flow fan
20
is rotated through operation of the motor
22
to cause the pressure difference between the front and rear surfaces of the blades
202
. This pressure difference causes the outer air to be flown into the machine room and then toward the condenser
10
.
Examples of characteristic factors for determining the blowing characteristics of such an axial flow fan
20
include a sweep angle, the maximum camber amount, the number of the blades
202
and the like. The sweep angle, as shown in
FIG. 2
, means an angle &agr; defined by the Y axis and a line passing the center of the inner side of the blade
202
and the center of the hub
201
, in which the Y axis is a line that connects between the center of the inner side of the blade
202
or the center of a portion of the blade contacting with the hub
201
and the center of the outer side or tip of the blade.
Also, as shown in
FIG. 2B
, the maximum camber amount p means the straight length between a chord connecting the leading edge L. E. and a trailing edge T. E. of the blade
202
and the maximum camber position P.
In this case, the sweep angle &agr; is a factor for determining flow noise of the axial flow fan
20
, a large value of the sweep angle &agr; increases the phase difference of airflow between the hub
201
and the tip of the blade
202
whereas a small amount of sweep angle &agr; decreases the phase difference of the airflow.
For example, comparing two axial flow fans with the same blade number and blowing amount, a blade with a sweep angle of 30°, as shown in
FIG. 3A
, allows an airflow to pass through the blade during rotation thereof for about 23° whereas a blade with a sweep angle of 60°, as shown in
FIG. 3B
, allows an airflow to pass through the blade during rotation thereof for about 49°.
In other words, according to the sweep angle &agr;, the airflow passing the outer end or tip of the blade has the phase difference of 23° and the airflow passing the inner end of the blade has the phase difference of 49°.
Therefore, such a phase difference of the airflow causes a phase difference between noises from the outer end of the blade
202
and from the inner end thereof, in which the frequency passing through the blade decreases as the phase difference is larger.
The maximum camber amount p is a factor for determining the pressure difference between the upper and lower surfaces of the blade
202
, in which increment of the maximum camber amount p increases the pressure difference between the upper and lower surfaces thereby increasing the blade-passing frequency also.
Meanwhile, according to the structure of the machine room with a simple passage and a small value of passage resistance, it is efficient that the axial flow fan
20
is configured to have a low level of noise even if a blowing pressure is more or less low rather than the blowing pressure is high. However, the axial flow fan
20
applied to a conventional blower fan assembly has a configuration in which a space between the blades
202
is narrow and the sweep angle &agr; is small whereas the camber amount is large and the number of the blades
202
is three.
Since the narrow space between the blades
202
resultantly causes the blades
202
to be large sized, the airflow generated on the surface of the blades
202
may have a large peeling range and a large pressure-fluctuating range, which are reasons for increasing flow noise. Further, the sweep angle &agr; is small and the maximum camber amount p is large so that flow noise is increased due to the foregoing characteristics of the sweep angle and the maximum camber amount.
Therefore, the axial fan for condenser in the refrigerator of the related art has loud flow noise thereby degrading the performance of the refrigerator as a problem.
SUMMARY OF THE INVENTION
Accordingly, the present invention has been devised to solve the foregoing problems of the related art and therefore it is an object of the invention to provide an axial flow fan for condenser in a refrigerator, the axial flow fan comprising three blades, wherein the diameter of a hub is 23.3±5% of the outside diameter of the axial flow fan and the width of each of the blades is 36.6±3% of the outside diameter of the axial flow fan.
Also, in order to obtain the foregoing object of the invention, it is provided an axial flow fan for condenser in a refrigerator, the axial flow fan comprising three blades, wherein the ratio of the inside diameter to the outside diameter is 23.0±5%, the maximum camber position is 0.65 uniformly distributed from the hub to the tip, and the maximum camber has curved distributions of 4.0 to 5.0% from the hub to the maximum camber position and of 5.0 to 6.0% from the maximum camber position to the tip.
REFERENCES:
patent: 6394754 (2002-05-01), Choi
Baek Seung-jo
Jung Young-gyu
Kim Chang-joon
Birch & Stewart Kolasch & Birch, LLP
LG Electronics Inc.
Look Edward K.
McCoy Kimya N
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