JP5727833B2 - Centrifugal fan - Google Patents

Description

  The present invention relates to a centrifugal fan, and more particularly to a centrifugal fan provided with an impeller stored between an upper casing and a lower casing.

  A centrifugal fan (centrifugal blower) is a fan that blows air in a centrifugal direction by rotating an impeller having a plurality of blades (also referred to as blades or impellers). A centrifugal multiblade fan, which is a fan of this type, has a configuration in which an impeller having a large number of blades arranged around the rotation axis of a motor is stored in a casing having a suction port and a discharge port. The centrifugal multiblade fan causes air sucked from a suction port to flow between the blades from the center of the impeller, and is ejected toward the outside of the impeller by a centrifugal action accompanying the rotation of the impeller. The air ejected from the outer periphery of the impeller passes through the inside of the casing, becomes high-pressure air, and is ejected from the discharge port.

  Centrifugal multiblade fans are widely used in home appliances, OA equipment, industrial equipment cooling, ventilation, air conditioning, and vehicle blowers. The blowing performance and noise of the centrifugal multiblade fan are greatly affected by the blade shape and casing shape of the impeller.

  FIG. 9 is a perspective view of a conventional centrifugal fan, and FIG. 10 is a view showing a blade shape of the centrifugal fan of FIG. 9 as seen through the upper casing 5 side.

  In the centrifugal fan 1, the central impeller 3 rotates to blow air. The impeller 3 has seven blades 2 and is rotated around a rotation axis by a fan motor built in the centrifugal fan 1. The direction of rotation is clockwise in FIG.

  The impeller 3 is accommodated in the casing 4. The casing 4 is composed of a plate-like upper casing 5 and a lower casing 6, and supports 7 a to 7 d are provided at four corners of the casing 4 in order to hold them at equal intervals. An air inlet 8 is provided at the top of the centrifugal fan 1. The air outlet 9 is provided between the columns of the casing 4. That is, the four sides 4 directions of the casing 4 are the air outlets 9 (open casing type). In addition, the casing 4 is good also as providing the blower outlet which collects the air blown from the impeller 3 to one direction (scroll casing type | mold).

  As shown in FIG. 10, each blade 2 has an arc shape, and has a surface (pressure surface) on the side that pushes out air by movement and a surface (negative pressure surface) on the opposite side. Yes.

  The struts 7 a to 7 d have a function of connecting the upper casing 5 and the lower casing 6, and three or more (four in this case) are formed around the impeller 3. The interval between two adjacent columns is equal. That is, the plurality of angles θ1 to θ4 formed by the plurality of straight lines connecting the rotation shaft of the impeller 3 and each of the columns 7a to 7d are all equal.

  The following prior art exists as a device for the casing (housing) shape in the fan of the prior art.

  Patent Document 1 listed below describes a centrifugal fan that forms a barricade that extends outward on one side of an air inlet and prevents foreign matter from entering the air inlet.

  Patent Document 2 listed below discloses a centrifugal fan that includes a circuit board that protrudes radially outward from a housing, and at least one of the electronic components is disposed radially outward from the inner peripheral surface of the side wall portion of the housing. Has been.

  Patent Document 3 below discloses a centrifugal fan in which a side wall portion of a housing is formed by a main body side wall portion of a housing body and a cover side wall portion of a housing cover.

  Patent Document 4 below describes a centrifugal fan in which an exhaust port is provided on a side surface of a housing, and a flow path toward the exhaust port is formed between a side wall portion and an outer periphery of an impeller portion. An air inlet is formed at the bottom of the housing.

JP 2006-336642 A JP 2010-275958 A JP 2007-239712 A JP 2007-218234 A

  As devices become smaller, thinner, denser and more energy efficient, the market strongly demands higher static pressure and higher efficiency for the fan motors mounted on them.

  Even in the centrifugal fan shown in FIGS. 9 and 10, improvements are desired with respect to the air flow rate, static pressure, and noise level.

  In particular, the centrifugal fan shown in FIGS. 9 and 10 has a problem that the level of both discrete frequency noise (narrow band noise) and broadband noise is high, and the noise level when mounted on a device is high.

  Here, “discrete frequency noise” is noise that depends on the blade passing frequency, and is also called NZ noise. Discrete frequency noise is noise having a characteristic peak at a specific frequency in a narrow frequency band. The frequency is represented by the equation fnz = [rotational frequency: n] × [number of blades: z]. Since the discrete frequency noise is generated in the second order, the third order,... In addition to the first order component, it becomes a serious problem in actual listening. That is, there is a risk that noise is generated as clear sound when a centrifugal fan is mounted on a device. The cause of broadband noise is dominated by turbulent flow, and it is also required to reduce broadband noise in order to determine the total noise level.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide a centrifugal fan capable of reducing noise without adversely affecting the air flow characteristics.

According to one aspect of the present invention for achieving the above object, a centrifugal fan connects an upper casing, a lower casing, an impeller stored between the upper casing and the lower casing, and an upper casing and a lower casing. Three or more struts formed around the impeller, and among the three or more struts, an interval between adjacent struts is different from an interval between other adjacent struts, and the impeller The plurality of angles formed by the plurality of straight lines connecting the rotation axis and each of the three or more support columns have different angles .

  Preferably, the upper casing and the lower casing have a quadrangular outer shape in plan view, the number of support columns is 4, and the support columns are provided at corner portions of the upper casing and the lower casing.

  Preferably the struts are streamlined.

  Preferably, in the centrifugal fan, a space surrounded by the upper casing, the lower casing and the support column functions as an air outlet.

  According to the present invention, it is possible to provide a centrifugal fan capable of reducing noise without adversely affecting airflow characteristics.

It is a perspective view of the centrifugal fan in one of the embodiments of the invention. It is a center longitudinal cross-sectional view of the centrifugal fan of FIG. It is a figure which shows the blade | wing shape and the position of a support | pillar of the centrifugal fan of FIG. 1 in the state seen from the upper casing 5 side. It is a figure for demonstrating the structure of the impeller 3 of FIG. It is a figure which shows the blade | wing shape of the centrifugal fan in a modification, and the position of a support | pillar in the state seen permeate | transmitted from the upper casing 5 side. It is the figure which showed the static pressure-air volume characteristic of the centrifugal fan demonstrated in FIGS. 1-4 and the conventional centrifugal fan demonstrated in FIG.9 and FIG.10. It is the figure which showed the noise level which the conventional centrifugal fan demonstrated in FIG. 9 and FIG. 10 generate | occur | produces. It is the figure which showed the noise level which the centrifugal fan in this Embodiment demonstrated in FIGS. 1-4 demonstrated. It is a perspective view of the conventional centrifugal fan. It is a figure which shows the blade | wing shape of the centrifugal fan of FIG. 9 in the state seen permeate | transmitted from the upper casing 5 side.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a perspective view of a centrifugal fan according to one embodiment of the present invention, and FIG. 2 is a central longitudinal sectional view of the centrifugal fan of FIG. FIG. 3 is a view showing the blade shape of the centrifugal fan of FIG. 1 and the position of the support post viewed from the upper casing 5 side.

  With reference to FIGS. 1-3, in the centrifugal fan 1, ventilation is performed when the center impeller 3 rotates. The impeller 3 has seven blades 2 that are arranged at equal intervals, and is rotated around a rotating shaft 11 by a fan motor 13 built in the centrifugal fan 1. The direction of rotation is clockwise in FIG.

  The impeller 3 is stored (stored) in the casing 4. The casing 4 is composed of a plate-like upper casing 5 and a lower casing 6 each having a quadrangular outer shape in plan view, and the columns 7 a to 7 d are provided on the four casings 4 in order to hold them at equal intervals. It is provided at the corner. An air inlet 8 is provided at the top of the centrifugal fan 1. The air outlet 9 is provided between the columns of the casing 4. That is, the four sides 4 directions of the casing 4 are the air outlets 9 (open casing type). In addition, the casing 4 is good also as providing the blower outlet which collects the air blown from the impeller 3 to one direction (scroll casing type | mold).

  As shown in FIG. 2, the impeller 3 includes a disk-shaped main plate 21, an annular shroud 23, and a plurality of blades 2 arranged on the circumference provided between the main plate 21 and the shroud 23. It is possible to rotate around the rotating shaft 11.

  As seen in FIG. 3, a plurality of angles θ1 to θ4 formed by a plurality of straight lines connecting the rotation axis (rotation center) of the impeller 3 and each of the support columns 7a to 7d have different angles. That is, the space | interval between a certain adjacent support | pillar among the support | pillars 7a-7d differs from the space | interval between the other adjacent support | pillars. Here, “adjacent struts” refers to any of a set of struts 7a and 7b, struts 7b and 7c, struts 7c and 7d, and struts 7d and 7a.

  Each of the columns 7a to 7d desirably has a streamlined shape that minimizes the resistance of the air blown out from the impeller 3 as seen in a plan view in FIG.

  FIG. 4 is a view for explaining the structure of the impeller 3 of FIG.

  As shown in the figure, each of the plurality of blades 2 rotates around the center O in the direction of arrow “A” (clockwise direction). Each blade 2 has a pressure surface 2a facing the front side in the rotation direction and a negative pressure surface 2b facing the opposite side. The pressure surface 2a is a surface on the side that pushes air during rotation.

  One end of each blade 2 is formed on the inner diameter portion (inner periphery) having a radius of D1 from the center O, and the other end of each blade 2 is formed on the outer diameter portion (outer periphery) having a radius of D2 from the center O. The part is located.

  In FIG. 4, the shape when the blade | wing 2 is seen from the direction where the rotating shaft of the impeller 3 extends is shown. For this reason, in FIG. 4, all of the pressure surface 2a, the negative pressure surface 2b, the outer peripheral edge, and the inner peripheral edge are represented by curves. The inlet angle α of the blade 2 is 45 ° and the outlet angle β is 30 °.

  Here, the entrance angle α is an angle at which the tangent of the inner peripheral edge at the point where the curve indicating the pressure surface 2a shown in FIG. 4 and the inner peripheral edge are in contact with the tangent of the curve indicating the pressure surface 2a at that point. Yes, it shows the corner on the side of 90 ° or less. The outlet angle β is an angle at which the tangent of the outer peripheral edge at the point where the curve indicating the pressure surface 2a shown in FIG. 4 and the outer peripheral edge are in contact with the tangent of the curve indicating the pressure surface 2a at that point. The angle on the side that is 90 ° or less is shown.

  The shape of the curve indicating the pressure surface 2a shown in FIG. 4 can be expressed by a shape connecting at least three kinds of arcs, or a shape combining a plurality of higher-order functions passing through three points.

  In addition, the diameter of the inner periphery in FIG. 4 is 70 mm, and the diameter of an outer periphery is 120 mm.

  FIG. 5 is a view showing the blade shape of the centrifugal fan and the position of the column in the modified example as seen from the upper casing 5 side.

  Also in this modification, a plurality of angles θ1 to θ4 formed by a plurality of straight lines connecting the rotation shaft (rotation center) of the impeller and each of the columns 7a to 7d have different angles. Further, in the columns 7a to 7d, the intervals between adjacent columns are unequal (the intervals between adjacent columns among the columns 7a to 7d are different from the intervals between other columns).

  Here, it is designed such that θ1 = 85 °, θ2 = 99 °, θ3 = 89 °, and θ4 = 87 °.

  The fan can be applied to all centrifugal fans such as a turbo type, a multi-blade type, and a radial type. As a device equipped with a fan, it can be applied mainly to products that require suction cooling (such as home appliances, PCs, OA devices, and in-vehicle devices).

  FIG. 6 is a diagram showing static pressure-air volume characteristics of the centrifugal fan described in FIGS. 1 to 4 and the conventional centrifugal fan described in FIGS. 9 and 10.

  In the graph, the horizontal axis indicates the air volume, and the vertical axis indicates the static pressure. The characteristic of the conventional centrifugal fan is described with a dotted line in the graph, and the characteristic of the centrifugal fan described with reference to FIGS.

  As shown in the figure, compared with the prior art, the fan of the present embodiment can obtain a higher static pressure at any air volume.

  FIG. 7 is a diagram showing a noise level generated by the conventional centrifugal fan described in FIGS. 9 and 10, and FIG. 8 is generated by the centrifugal fan in the present embodiment described in FIGS. It is the figure which showed the noise level.

  The horizontal axis in each graph indicates the frequency, and the vertical axis indicates the noise level (unit: dB (A)) at that frequency.

  In the noise frequency analysis result of FIG. 7, there is a prominent peak (discrete frequency noise) protruding from the broadband noise in the frequency range of 1 to 4 kHz which is the most problematic in real hearing (sound as a clear sound). On the other hand, in the noise frequency analysis result of FIG. 8, these peaks are almost eliminated. Thus, by arranging the columns at unequal intervals as in the present embodiment, the generation of discrete frequency noise is suppressed without deteriorating the air flow characteristics, leading to a reduction in noise of -3 dB (A). .

  Furthermore, the suppression of discrete frequency noise reduces the primary peak level of the NZ noise, and the second and third harmonics disappear. That is, by shifting the synchronization of the blade passing frequency noise, it is possible to suppress and eliminate the NZ noise first, second, and third harmonics.

  In addition, according to FIG. 8, the noise level in the high frequency band (portion surrounded by an ellipse in the figure) is slightly increased as compared with FIG. The human audible frequency range is 20 Hz to 20 kHz, but even in a portion where the noise level is slightly increased, the level itself is low and is far from the frequency range of 1 to 4 kHz that is easy to hear. Further, such a high frequency region is sound-insulated when mounted on a set device, and it is extremely rare that it becomes a problem in practice.

  In addition, the number of support | pillars is not restricted to 4, If this is 3 or more, this invention can be implemented.

  In addition, regarding the interval between adjacent support columns, if any one interval is different from any other one interval, the effect of the present invention is achieved. The interval includes a distance interval and an angular interval.

  The numerical values shown in the above embodiment are ideal numerical values, and the fan can be manufactured at a level that can achieve the object of the invention even if an error of about ± 10% is included. For example, the angle θ1 in FIG. 5 may be in the range of 76.5 ° to 93.5 ° including an error of about ± 10% at 85 °. Similarly, the numerical values such as the angle and the diameter are allowed to include an error of about ± 10%.

  The numerical values shown in the above embodiment are ideal numerical values, and are not limited thereto. The centrifugal fan includes three or more struts formed around the impeller, and among these three or more struts, an interval between adjacent struts may be different from an interval between other adjacent struts. That's fine. Note that each of a plurality of angles θ1, θ2,... Θn (n is the number of columns and n ≧ 3) formed by a plurality of straight lines connecting the rotation shaft of the impeller and three or more columns is 180 It is desirable to make it below °. By setting it as 180 degrees or less, an upper casing and a lower casing can be fixed more firmly, and it can prevent that the rotating shaft of a motor shakes collectively. For example, when there are three columns and the casing has a square shape, the columns are provided at three corners so that θ1 = 180 °, θ2 = 90 °, θ3 = 90 °, and all angles are 0 °. The angle is 180 ° or less. In addition, when there are four columns and the casing has a square shape, columns are provided at two corners facing each other, and two columns are provided only in one of two regions separated by a straight line connecting the columns. Thus, θ1 = 180 °, θ2 <90 °, θ3 <90 °, θ4 <90 °, and all angles are 0 ° or more and 180 ° or less.

  The above-described embodiment is to be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Centrifugal fan 2 Blade | blade 2a Pressure surface 2b Negative pressure surface 3 Impeller 4 Casing 5 Upper casing 6 Lower casing 7a-7d Support | pillar 8 Inlet 9 Outlet 11 Rotating shaft 13 Fan motor 21 Main plate 23 Shroud α Inlet angle β Outlet angle

Claims (4)

An upper casing,
A lower casing,
An impeller stored between the upper casing and the lower casing;
Three or more struts formed around the impeller for connecting the upper casing and the lower casing;
Of the three or more struts, an interval between adjacent struts is different from an interval between other adjacent struts ,
A centrifugal fan in which a plurality of angles formed by a plurality of straight lines connecting the rotation shaft of the impeller and each of the three or more struts have different angles . The upper casing and the lower casing have a quadrangular outer shape in plan view,
The number of struts is 4,
The centrifugal fan according to claim 1, wherein the struts are provided at corner portions of the upper casing and the lower casing. The centrifugal fan according to claim 1, wherein the support column has a streamlined shape. The centrifugal fan according to any one of claims 1 to 3 , wherein a space surrounded by the upper casing, the lower casing, and the support column functions as an air outlet.