JP2012189047A - Impeller, and centrifugal fan provided therewith - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an impeller having a blade form suited to air flow, and a centrifugal fan provided therewith.SOLUTION: The centrifugal fan has the impeller including a main plate, a shroud and a plurality of blades provided between the main plate and the shroud and arranged on a circumference. The impeller can rotate around a rotary shaft. The plurality of blades have a pressure face 2a and a negative pressure face 2b, and have a shape, when viewing the pressure face 2a from the extending direction of the rotary shaft, of connecting at least three kinds of arcs (R1, R2, R3), or a shape shown by combining a plurality of high-order functions passing through three points (A, B, C).

Description

  The present invention relates to an impeller and a centrifugal fan equipped with the impeller, and more particularly to an impeller designed to reduce noise and improve air flow characteristics, and a centrifugal fan equipped with the impeller.

  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. 14 is a perspective view of a conventional centrifugal fan, and FIG. 15 is a plan view showing a state where a casing lower plate of the centrifugal fan of FIG. 14 is removed.

  In the centrifugal fan 1, air is blown by the rotation of the central impeller 3 ′. The impeller 3 ′ has 21 blades 2 ′, and is rotated around a rotation axis by a fan motor built in the centrifugal fan 1. The rotation direction is counterclockwise 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 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 column 7 and the column 7 of the casing 4. That is, the four sides 4 directions of the casing 4 are the air outlets 9 (open casing type). Note that the casing 4 may be provided with a blowout port that collects the air blown from the impeller 3 ′ in one direction (scroll casing type).

  As shown in FIGS. 14 and 15, one blade 2 ′ has an arc shape, and a surface (pressure surface) on the side that pushes out air by movement, and a surface on the opposite side (negative pressure surface) In general, each has the same arc shape. As shown in FIG. 15, the thickness of the blade 2 ′ is constant from the inner peripheral side to the outer peripheral side of the impeller 3 ′.

  The following prior art exists as a device for the shape of the blades in the conventional fan.

  In Patent Document 1 below, there is a multiblade blower fan in which the cross-sectional shape of at least a part of the suction surface of the blade (blade) first half from the radially inner end to the radially intermediate portion in the air flow direction is formed by a polygonal straight line. It is disclosed.

  Patent Document 2 below discloses a centrifugal multiblade fan in which the leading edge of a blade is formed into a steep square shape with a curvature radius of 0.2 mm or less.

  Patent Document 3 below discloses a multiblade centrifugal blower configured by forward-facing blades that are curved so that the blade outlet of the impeller is inclined in the rotation direction. The blade has an airfoil shape in which the blade thickness is gradually reduced from the front of the blade to the rear of the blade. The inflow angle of the blade is set in consideration of the angle of air flowing in along the cone portion, that is, the inclination angle of the cone portion. The outflow angle is set in consideration of the slip rate.

  Patent Document 4 below discloses a multiblade fan including an impeller made up of a plurality of blades arranged in parallel in a circumferential direction at a predetermined pitch in a fan housing having a predetermined shape. The warp line radius of the impeller outer peripheral side of each blade is larger than the warp line radius of the impeller inner peripheral side.

  Patent Document 5 listed below discloses an impeller of a sirocco fan formed by arranging and providing a plurality of blades on the circumference. The outline of the cross section of the tip of the slat and the outline of the cross section of the base end are formed by a two-dimensional curve in a specific range, and the attachment angle of the slat is set in a specific range.

JP 2005-155579 A JP 2007-278268 A JP 2001-329994 A JP 2001-280288 A Japanese Patent Laid-Open No. 11-148495

  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.

  However, as shown in FIG. 15, the shape of the pressure surface of the blade 2 'formed of one arc has a problem that it is not suitable for the flow of wind. That is, the pressure surface and the suction surface of the blade 2 ′ in FIG. 15 both match the shape of a single arc having a certain diameter. With such a blade shape, the air flow rate and static pressure are reduced. There is also a problem that the noise level is deteriorated.

  In particular, the centrifugal fan shown in FIGS. 14 and 15 has a problem that both the level of 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 an impeller having a blade shape suitable for a wind flow, and a centrifugal fan including the impeller.

  According to one aspect of the present invention, an impeller is an impeller comprising a main plate, a shroud, and a plurality of blades arranged on a circumference provided between the main plate and the shroud, The plurality of blades have a pressure surface and a suction surface, and when the pressure surface is viewed from the direction in which the rotation shaft extends, the shape is at least three types of arcs. It has a connected shape or a shape shown by combining a plurality of higher order functions passing through three points.

  There are preferably three types of arcs, and each arc has a different coordinate center and a different diameter.

  Preferably, the shape of the pressure surface when viewed from the direction in which the rotation axis extends is a shape in which three arcs are connected, and the arcs located at both ends of the three arcs have substantially the same radius. The center arc of the two arcs has a radius of about 35-40% of the radius of the arc located at both ends of the three arcs.

  Preferably, each of the plurality of blades has a shape that decreases in thickness as it moves away from the rotation axis.

  Preferably, the thickness of each of the plurality of blades is maintained within a predetermined range when the blade is moved away from the rotation axis by a predetermined distance.

  A centrifugal fan according to another aspect of the present invention includes the impeller according to any one of the above and a casing for storing the impeller, and the air sucked from the suction port is caused by centrifugal force accompanying the rotation of the impeller. Blow out toward the outside of the impeller diameter.

  ADVANTAGE OF THE INVENTION According to this invention, the impeller which has a blade | wing shape suitable for the flow of a wind, and the centrifugal fan provided with the same can be provided.

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 of the centrifugal fan of FIG. 1 in the state seen permeate | transmitted from the upper casing 5 side. It is a figure for demonstrating the structure of the impeller 3 of FIG. It is a 1st figure for demonstrating the blade | wing shape of the impeller 3. FIG. It is a 2nd figure for demonstrating the blade | wing shape of the impeller 3. FIG. It is a 3rd figure for demonstrating the blade | wing shape of the impeller 3. FIG. It is a 4th figure for demonstrating the blade | wing shape of the impeller 3. FIG. It is a 5th figure for demonstrating the blade | wing shape of the impeller 3. FIG. It is a figure for demonstrating the modification of the blade | wing shape of the impeller. It is the figure which showed the static pressure-air volume characteristic of the centrifugal fan demonstrated in FIGS. 1-9, and the conventional centrifugal fan. It is the figure which showed the simulation result of the air volume in the centrifugal fan demonstrated in FIGS. It is the figure which showed the simulation result of the air volume in the conventional centrifugal fan. 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. 14 in the state seen from the lower casing 6 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 as seen through 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 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 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 column 7 and the column 7 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.

  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.

  5-8 is a figure for demonstrating the blade | wing shape of the impeller 3. FIG.

  The cross-sectional shape of the pressure surface 2a described above is determined as follows. As shown in FIG. 5, the outer peripheral edge is a circle having a diameter of 120 mm, the inner peripheral edge is a circle having a diameter of 70 mm, and the two are described as concentric circles C1 and C4. The inner peripheral edge and the outer peripheral edge are determined by design specifications and the size of the motor, and are not limited to these sizes.

  Next, a circle C2 having a size 3/4 (diameter 90 mm) with respect to the circle C1 indicating the outer periphery is drawn as a concentric circle of the circles indicating the outer periphery and the inner periphery. In addition, a circle C3 (diameter 80 mm) is drawn as a concentric circle of the circle indicating the outer periphery and the inner periphery between the circle C4 indicating the inner periphery and the circle C2 having a size of 3/4 with respect to the outer periphery.

  As shown in FIG. 6, the entrance angle α (45 °), the exit angle (30 °), and the warp angle (55 °) are determined. The entrance angle affects the noise level. By setting it to 45 °, the NZ sound is greatly reduced. The exit angle affects the static pressure and depends on the design goal. The angle of warp also affects the static pressure and depends on the design goal. A position where the entrance angle α is measured is indicated by a point D, and a position where the exit angle β is measured is indicated by a point A. A straight line passing through the points A and O is referred to as a line segment L1, and a straight line passing through the points D and O is referred to as a line segment L2. The warp angle is an angle defined by two straight lines L1 and L2 passing through the center O of the circle. Point A is the intersection of one straight line L1 that passes through the center O of the circle and defines the warp angle, and the outer peripheral edge C1. Point D is the intersection of another straight line L2 that passes through the center O of the circle and defines the curvature angle, and the inner peripheral edge C4.

  As shown in FIG. 7, between the straight lines L1 and L2 defining the warp angle, a straight line that passes through the center O of the circle and forms an angle (16.5 °) that is 3/10 of the warp angle is drawn. A point B is defined as an intersection of the straight line and the circle C2. Further, a straight line passing through the center O of the circle between the straight lines L1 and L2 defining the warp angle and forming an angle (8.25 °) of the straight line L2 and 3/20 of the warp angle is drawn. The point of intersection with is point C.

  As shown in FIG. 8, three arcs R3, R2, and R1 connecting points A, B, C, and D are drawn. At this time, the arcs of the arcs R3 and R2 and the arcs of the arcs R2 and R1 are drawn in a tangent relationship. Here, the tangent relationship refers to a relationship in which tangents of two arcs overlap at a connection point of two arcs.

  FIG. 9 is a view for explaining the blade shape of the impeller 3, and is a view showing the characteristics of the arcs R1 to R3.

Considering a coordinate system in which the point D, which is the position where the entrance angle α is measured, is the origin, the right direction in the X (horizontal) direction is positive, and the upward direction in the Y (vertical) direction is positive.
R1 has a base point (coordinate of the center) of (X, Y) = (− 34.2 mm, 35.8 mm), a radius of 50 mm, and an arc whose ends are points C and D;
R2 has a base point (coordinates at the center) of (X, Y) = (− 10.1 mm, 15.7 mm), a radius of 18 mm, and an arc whose ends are points B and C;
R3 has a base point (coordinates at the center) of (X, Y) = (− 42.8 mm, 20.8 mm), a radius of 51 mm, and an arc whose ends are points A and B.

  When the radius of the arc is shown, the radius of R3 and the radius of R1 are almost equal (the difference is within 3%), and the radius of the arc R2 between them is about 35-40% of the radius of each of the arcs R1, R3. It is. The position of the base point of the three arcs is an example, and the present invention is not limited to this.

  With respect to the suction surface, the outer shape of the blade-shaped blade is reduced by making the blade thickness thinner toward the point A through the point D and along the shape of the pressure surface. Obtainable. For example, by defining the radius of curvature of the suction surface at point A and obtaining a curve in which the radius of curvature decreases toward the point D, a shape as shown in FIG. 9 can be obtained.

  The fan in the present embodiment configured as described above has the following characteristics. That is, the shape of the pressure surface of the blade is constituted by three arcs (R1, R2, R3). Further, the shape of the pressure surface of the blade can be expressed by a combination of the following high-order functions (the high-order function is a higher-order function of a quadratic function or higher). .

y = 0.108x ³ -0.375x ² + 0.767x
y = −2.56x ³ + 30.0x ² -119.3x + 174.9
(The tip of the blade is the origin. The predetermined numerical range of each of the above formulas is the shape of the pressure surface of the blade. The equation is an example and is not limited to this.)
By determining the shape of the blades in this way, it becomes possible to produce an efficient fan along the air flow, and there is an effect that high flow rate, high static pressure, and low noise can be achieved. .

  Further, the fan in the present embodiment 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. 10 is a view for explaining a modification of the blade shape of the impeller 3.

  The shape of the blade can be determined by the combination of arcs and mathematical formulas as described above. Further, as shown in FIG. 10, the thickness of the blade tip can be freely adjusted. For example, as shown in FIG. 10, the rigidity of the blade can be increased by preventing the tip portion of the blade from being less than a predetermined thickness (increasing the thickness of the blade at the outer edge than in FIG. 9). That is, the blade rigidity can be increased by keeping the thickness within a predetermined range (not lower than the predetermined thickness) for the portion of the blade that is separated from the rotation shaft by a predetermined distance or more.

  FIG. 11 is a diagram showing static pressure-air flow characteristics of the centrifugal fan described in FIGS. 1 to 9 and a conventional centrifugal fan.

  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. 12 is a diagram showing the simulation results of the air volume in the centrifugal fan described in FIGS. 1 to 9, and FIG. 13 is a diagram showing the simulation results of the air volume in the conventional centrifugal fan.

  In the figure, the flow of air around the blades 2, 2 'is indicated by arrows, and the speed of the air is indicated by the shading of the lines. Dark arrows mean a faster flow than light arrows. As shown in FIGS. 12 and 13, according to the shape of the blade in the present embodiment, the wind speed can be generally increased, and thereby a high flow rate can be achieved. Moreover, according to this Embodiment, there exists an effect that air can be accelerated by the blade | wing shape from the root part of a blade | wing to the front-end | tip part of a blade | wing.

  Moreover, according to the centrifugal fan demonstrated in FIGS. 1-9, there exists an effect that generation | occurrence | production of discrete frequency noise is suppressed. Specifically, there is a reduction effect of 1.5 dB (A) compared to a conventional fan. Further, the NZ noise primary peak level can be reduced, and the occurrence of the NZ noise secondary peak can be significantly suppressed. In the frequency range of 1 to 4 kHz, which is the most problematic in actual listening (sound as a clear sound), there is no significant peak protruding from broadband noise, and there is an effect that a fan with a large industrial value can be provided.

  The shape of the pressure surface of the fan is not limited to three arcs, and may be a shape in which three or more arcs are combined. The numerical values shown in the above embodiment are ideal numerical values, and a 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 radius of the arc R1 in FIG. 9 may be in a range of 45 mm to 55 mm including an error of about ± 10% in 50 mm. Similarly, the numerical values such as the coordinate values, angles, and diameters described above are allowed to include an error of about ± 10%.

[Effects of the embodiment]
As described above, by making the fan blade shape into a combination of three or more arcs or a high-order curve, it is possible to create an efficient blade shape along the air flow. This has the effect of reducing pressure and noise. Further, by setting the blade shape to three arcs or a smooth curve (second-order or third-order higher-order function), the blade tip thickness can be freely adjusted, and the blade rigidity can be increased. Furthermore, the aerodynamic noise is reduced, leading to an effect of reducing noise.

  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 7 Support | pillar 8 Suction port 9 Outlet 11 Rotating shaft 13 Fan motor 21 Main plate 23 Shroud α Inlet angle β Outlet angle

Claims (6)

A main plate,
Shroud,
An impeller provided with a plurality of blades arranged on a circumference provided between the main plate and the shroud,
It is possible to rotate around the rotation axis,
The plurality of blades have a pressure surface and a suction surface,
When the pressure surface is viewed from the direction in which the rotating shaft extends, the shape of the impeller has a shape formed by connecting at least three kinds of arcs or a combination of a plurality of higher-order functions passing through three points. .   2. The impeller according to claim 1, wherein the arc has three types, and each arc has a different diameter centered at a different coordinate position.   The shape of the pressure surface when viewed from the direction in which the rotating shaft extends is a shape in which three arcs are connected, and arcs located at both ends of the three arcs have substantially the same radius, The impeller according to claim 1 or 2, wherein a central arc of the three arcs has a radius of about 35 to 40% of a radius of an arc located at both ends of the three arcs.   4. The impeller according to claim 1, wherein each of the plurality of blades has a shape that decreases in thickness as it moves away from the rotation shaft. 5.   5. The impeller according to claim 4, wherein the thickness of each of the plurality of blades is maintained within a predetermined range as the distance from the rotation shaft increases by a predetermined distance. An impeller according to any one of claims 1 to 5,
A casing for storing the impeller,
A centrifugal fan that blows out the air sucked from the suction port toward the outside of the diameter of the impeller by the centrifugal force accompanying the rotation of the impeller.