AIR BLOWER

Abstract

An air blower is provided with a drive motor and an air blowing fan which has a hub mounted to the drive motor and blades which are provided to the hub. The air blower is characterized in that serrations comprising triangle-shaped protrusions are provided to the front edge of each of the blades so as to be arranged along the front edge and in that the pitch, the height, or the direction of the serrations is changed according to the flow of air at a radial position on the air blowing fan.

Description

TECHNICAL FIELD

The present invention relates to an axial flow blower, centrifugal blower, diagonal flow blower, etc., more particularly relates to a structure of a fan blade which can suppress disturbances in the air flow and reduce noise.

BACKGROUND ART

Better blower performance and lower noise are being sought from axial flow blowers etc. PLT 1 discloses providing a plurality of triangular shape projections in a sawtooth manner (hereinafter referred to as “serrations”) in a chord line direction with an all leading edge part of each blade to reduce the noise of rotation due to the blower fan.

In general, the flow of air near a blade surface of a blower greatly differs depending on the part. The further to the outer circumference side in the radial direction of the blower fan the blower fan is, the higher the flow rate is. Further, the direction of the air flow at the outer circumference side of the blower fan, with respect to the direction of rotation, greatly changes depending on the design of the blade (forward curved blade or backward curved blade). That is, in a forward curved blade (forward swept wing), the flow becomes an axial flow which concentrates at the blade center, while in a backward curved blade (sweptback wing), the flows becomes a slanted flow which heads toward the blade outer circumferential direction. Furthermore, at the blade end part, a back flow also occurs from a positive pressure surface to a negative pressure surface side. In such a prior art as PLT 1, serrations which were provided with a blade could not sufficiently suitably deal with changes in the flow of air depending on the portion of the blade and a sufficient noise reduction effect sometimes could not be obtained. Further, a drop in the air flow was sometimes caused or the drive torque increased and a drop in efficiency was caused.

CITATIONS LIST

Patent Literature

PLT 1: Japanese Unexamined Patent Publication No. 2000-087898

SUMMARY OF INVENTION

Technical Problem

The present invention, in consideration of the problem, provides a blower which prevents a drop in the air flow while effectively reducing the fan noise.

Solution to Problem

To solve the problem, an aspect of the invention of claim 1 provides a blower comprising a drive motor and a blower fan having a hub which is attached to the drive motor, and a plurality of blades which are provided at the hub, wherein the blades are provided at their blade leading edge parts with serrations comprised of pluralities of triangular shape projecting parts along the blade leading edge parts and the serrations are changed in pitch, height, or direction according to the flows of air at radial direction positions of the blower fan.

To solve the problem, an aspect of the invention of claim 10 provides a blower fan having a hub which adapts to be attached to a drive unit, and a plurality of blades which are provided at said hub, wherein

each said blade has a first portion of a blade leading edge part of said blade which has a first distance in the radial direction from the center of rotation of said blade, and a second portion of a blade leading edge part of said blade which has a second distance in the radial direction from the center of rotation of said blade, said blade leading edge part is provided with a plurality of serrations which stick out to an upstream side of flow of air, wherein said serrations have first slanted sides which are slanted with respect to a direction of flow of air, and second slanted sides which are slanted in a different direction from said first slanted sides with respect to a direction of flow of air, and at least one of a pitch, height, and direction of said projections at said first portion differs from at least one of a pitch, height, and direction of said projections at said second portion.
Note that the parenthesized reference notations show the correspondence with specific examples which are described in the later mentioned embodiments.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front schematic view of a first embodiment of the present invention.

FIG. 2 is a schematic view of a blade of a first embodiment of the present invention.

FIG. 3 is a view of one example of the results of simulation analyzing the structure of the flow around leading edge serrations by CFD (computational fluid dynamics).

FIG. 4 is an explanatory view of the results of simulation of FIG. 3.

FIG. 5 is a cross-sectional view of a blade of the simulation of FIG. 3.

FIG. 6A is an explanatory view for explaining a general axial flow blower.

FIG. 6B is a cross-sectional view developed along the line A-A of FIG. 6A.

FIG. 6C is an explanatory view for explaining a positive pressure surface and a negative pressure surface of a blade of FIG. 6B.

FIG. 7 is a schematic view of a blade of a second embodiment of the present invention.

FIG. 8 is a schematic view of a blade of a third embodiment of the present invention.

FIG. 9 is a schematic view of a blade of a fourth embodiment of the present invention.

FIG. 10 is a schematic view of a blade of a fifth embodiment of the present invention.

FIG. 11 is a schematic view of a blade of a sixth embodiment of the present invention.

FIG. 12 is a schematic view of a blade of a seventh embodiment of the present invention.

FIG. 13 is a schematic view of a blade of an eighth embodiment of the present invention.

FIG. 14 is a schematic view of a blade of a ninth embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

Below, referring to the figures, embodiments of the present invention will be explained. In the embodiments, parts configured the same will be assigned the same reference notations and explanations will be omitted.

First Embodiment

Referring to FIG. 1, a blower 10 is a so-called electric blower comprising a blower fan 1 which is placed in a shroud 200 and which is driven to rotate by a drive motor (electric motor) 300. The blower 10 is fastened to an engine side of an automobile radiator by mounts 250 which are provided near the four corners of the shroud 200 and blows air for cooling use to the core part of the radiator. The outside shape of the shroud 200 forms a rectangular shape corresponding to the core part of the radiator. At the approximate center, a ring-shaped shroud ring part 210 is formed so as to encircle the blower fan 1 by its outer circumference. This shroud ring part 210 is provided at the shroud 200 so as to be positioned at the outside of the ring 2 of the blower fan 1 in the radial direction. There may also be no ring 2 of the blower fan 1 in the present embodiment. The blower 10 and the later explained blades 3 of the present invention are not limited to use for an automobile radiator. They are may be used for general industrial use. The explanation will mainly be given for an axial flow blower, but similar effects can be obtained even for a centrifugal blower, diagonal flow blower, and cross-flow blower. The drive motor 300 is not necessarily limited to an electric motor.

Between the shroud ring part 210 and the rectangular shape outer circumference part of the shroud 200, an air conduit 220 is formed which expands toward the upstream side of air of the blower fan 1. At the center of the shroud ring part 210, a circular motor holding part 230 is formed. This motor holding part 230 is supported by a plurality of motor stays 240 which extend radiately to the outside in the radial direction and are connected to the shroud ring part 210. At the motor holding part 230, an electric motor 300 is fastened. The shaft of the electric motor 300 and the hub 4 of the blower fan 1 (see FIG. 2) are fastened. The blower 10 comprises this blower fan 1, electric motor 300, etc. The hub 4 of the blower fan 1 is cylindrical in shape and is provided with a plurality of blades 3 in the radial direction.

Parameters of the blades 3 such as the chord line C, positive pressure surface, negative pressure surface, angle of attack a, lift, etc. are the same as the general definitions such as shown in FIGS. 6A to 6C. Further, a blade shape where the blade end part at the outer circumference side is curved backward in the direction of rotation of the blower fan 1 will be called a “backward curved blade”, while a blade shape where the blade end part at the outer circumference side is curved forward in the direction of rotation of the blower fan 1 will be called a “forward curved blade”. At the blade leading edge part of the blade 3, a plurality of serrations (triangular shape projecting parts) are formed. The serrations have first slanted sides 3a which are slanted with respect to the direction of flow of air and second slanted sides 3b which are slanted in a different direction from the first slanted sides 3a with respect to the direction of flow of air (see FIG. 7). In the triangular shape projecting parts which form the serrations, here, the bottom side of the triangular shape projecting part will be called the “pitch p” of the serrations (triangular shape projecting parts), the line segment bisecting the vertex a of the triangular shape projecting part will be called the “direction” of the serrations (triangular shape projecting parts), and the distance of the bisecting line segment of the vertex to the bottom side will be called the “height h” of the serrations (triangular shape projecting parts). The larger “size” of the serrations (triangular shape projecting parts) indicates the larger of the pitch or height of the serrations. The vertexes a of the triangular shape projecting parts are called vertexes a of the serrations. In the case where the sides of the triangular shapes are curved, the shapes are generally based on these.

First, to start, the effects of the serrations which form the basis of the present invention will be explained. The simulation of FIG. 3 is the case where the triangular shape projecting parts of the serrations are the same shapes in the direction of the blade leading edge. FIG. 3 is a view of a blade leading edge as seen from an upper position. The arrow marks which are shown in FIG. 3 show projections of the tangential velocity of the flows around the serrations on the projection plane of the X-Z plane (S plane of FIG. 4). A flow from the valley parts at the two sides to the top surface of a peak part can be seen as occurring. At the serrations, first, at the tip parts of the peaks, small vortexes occur. These grow to large vortexes further toward the valleys. Further, backward the peaks, it is believed that downward flows occurred by the vortexes, press down the flow separation, which particularly easily occurs at the negative pressure surface with the large flow rate, and therefore reduce the flow separation. Due to this, the disturbances near the blade surface are eased and the fluctuation of pressure at the blade surface is suppressed, so it becomes possible to obtain an effect leading to lower noise.

The first embodiment of the present invention is an embodiment changing the pitch, height, or direction of the serrations according to the flow of air at the radial direction position of the blower fan 1, in order to utilize the above basic effect of the serrations. That is, the first embodiment differs in at least one of the pitch, height, and direction of serrations in the first portion and second portion which are different in distance in the radial direction of the blower fan from the center Q of rotation of the blade 3. As one example of the first portion and second portion of the blade 3, parts differing in the flow rate of air (flow rates of FIGS. 7 and 8) and directions of flow etc. may be mentioned. However the invention is not limited to these portions, but portions of any two locations along the blade 3. The flow of air near the blade surfaces of the blower greatly differ depending on the portion. The nearer to the outer circumference side in the radial direction of the blower fan the portion of the blade is, the higher the flow rate is. Further, at a forward curved blade, the flow becomes an axial flow which concentrates at the blade center, while at a backward curved blade, the flow becomes a diagonal flow which heads toward the outer circumferential direction of the blade. Furthermore, at the blade outer end part, a back flow arises from the positive pressure surface to the negative pressure surface. Changing the pitch, height, or direction of serrations in accordance with the flow of air at radial direction positions of the blower fan 1 (at least two locations) is extremely important in reducing the flow separation. Due to this, the basic effect of the serrations is exhibited, disturbances near the blade surfaces are eased, and pressure fluctuations at the blade surfaces are suppressed, so it becomes possible to obtain an effect leading to lower noise.

The first embodiment is a fan which is characterized by providing flow control shapes which minimize the noise which is produced due to disturbance of the air at different positions of the blades. Due to the flow control shapes, the effect is obtained of both noise reduction and prevention of a drop in the air flow and increase of the drive torque. The blades have serration shape (sawtooth teeth) portions. The serration shapes are changed according to the flow of air. According to this, it is possible to suitably set the serration shapes at the individual portions which differ in direction of air flow and flow rate, so it is possible to realize the effect of both noise reduction and the prevention of both a drop of the air flow and increase of the drive torque.

Second and Third Embodiments

The second and third embodiments are embodiments corresponding to the case where the air near a blade surface of the blower flows in the circumferential direction of the blower fan. The second embodiment, as shown in FIG. 7, is characterized in that the further to the blade outside diameter side the blade is, the larger the sizes of the serrations are made. The serrations are directed toward the circumferential direction of the blower fan. According to this, the size of the serrations is increased at the portion with a large flow rate at the blade outer circumference side, and the whirled air flow which is formed at the serrations, becomes weaker at a portion further toward the blade inside circumference side and becomes stronger at a portion further toward the blade outer circumference side. Due to this, at the flow with a high flow rate where flow separation would easily occur, it is possible to form a downward flow toward the blade surface and reduce the flow separation to obtain the effect of both noise reduction and the prevention of a drop in the air flow and increase of the drive torque at the blade as a whole.

The third embodiment, as seen in FIG. 8, is characterized in that the further to the blade outside diameter side the blade is, the more acute the vertices a of the serrations is. According to this, the serration angle is made acute at the portion of the large flow rate at the blade outer circumference side, and the whirled air flow which is formed at the serrations becomes weaker at a portion further to the blade inside circumference side and becomes stronger at a portion further to the blade outer circumference side. Due to this, at the flow with a high flow rate where flow separation would easily occur, it is possible to strengthen the downward flow at the blade surfaces formed at the serration valley parts in order to achieve both noise reduction, and prevention of both a drop in air flow and increase in drive torque in the blade as a whole. The invention is not limited to the case of making the pitch p of the serrations constant and increasing the height h of the serrations to make the angle acute. It is also possible to make the serration angle acute, regardless of the length of the bottom sides of the triangular shaped projections, at the portions with a large flow rate at the blade outer circumference side.

Fourth Embodiment

The fourth embodiment, as seen in FIG. 9, is characterized in that the blade trailing edge 7 is also provided with serrations and in that the blade leading edge 6 and blade trailing edge 7 are changed in serration shapes. When the blade trailing edge 7 is provided with serrations, since the flow at the high pressure blade positive pressure surface and the flow at the low pressure blade negative pressure surface are mixed near the blade trailing edge, the flows of the two surfaces gradually cross due to the serrations, so it is possible to suppress the disturbances in the flow of air of the blade trailing edge. The blade leading edge 6 and the blade trailing edge 7 may be suitably set with serration shapes. If the blade trailing edge 7 is made smaller in size of serrations compared with the blade leading edge 6, the serrations at the blade leading edge side, which are provided for suppressing flow separation, can be made larger so as to form a radiated flow. On the other hand, the serrations at the blade trailing edge side, which are provided for suppressing disturbances of the air flow, can be made smaller so as to make the flows at the positive and negative pressure surfaces gradually cross. Therefore, the effect is obtained of both noise reduction, and the prevention of both a drop in the air flow and increase of the drive torque. It is also possible to change the range of provision of serrations between the blade trailing edge and the blade leading edge, and possible to provide serrations at only suitable positions of the blade leading edge 6 and blade trailing edge 7.

In the following fifth and sixth embodiments, embodiments are explained which correspond to the case where the flow of air near the blade surfaces of the blower is a diagonal flow slanted with respect to the circumferential direction of the blower fan.

Fifth and Sixth Embodiments

The fifth embodiment, as shown in FIG. 10, is an embodiment corresponding to the case where the flow of air near the blade surfaces of the blower is a diagonal flow. The fifth embodiment matches the direction of the serrations of the blade leading edge with the direction of diagonal flow. The sixth embodiment, as shown in FIG. 11, is characterized by changing the range of provision of serrations between the blade trailing edge 7 and the blade leading edge 6. For example, when the air flow becomes a diagonal flow such as with a backward curved blade, the air flows on the blade surface in the direction to the outer circumference, from the blade leading edge 6 toward the blade trailing edge 7. At this time, at the blade leading edge side where there is interference with the air flow at all positions of the blade, serrations are provided over a wide range, while at the blade trailing edge side, serrations are provided at only the parts with remarkable diagonal flow, so noise reduction and prevention of a drop of air flow and increase of drive torque can both be realized.

The following seventh and eighth embodiments are embodiments corresponding to the case where the flow of air near the blade surface of the blower is a back flow from the positive pressure surface of the blade end part to the negative pressure surface side.

Seventh and Eighth Embodiments

The seventh embodiment, as shown in FIG. 12, is characterized by making the serration shapes of the blade end part smaller. According to this, the serration shapes are made smaller at the blade end part where the disturbance of the air flow due to the back flow is large, so the swirl of the air flow formed at the serrations is subdivided. Due to this, the disturbance of the air flow at the blade end part can be reduced, so the effect is obtained of noise reduction, and prevention of both a drop in air flow and increase of drive torque. The eighth embodiment, as shown in FIG. 13, is characterized by making the serration shapes of the blade end part at the blade trailing edge 7 smaller. Operational effects similar to the seventh embodiment are obtained.

Ninth Embodiment

The ninth embodiment, as shown in FIG. 14, is an embodiment which makes the direction of the serrations of the blade leading edge 6 match the direction of diagonal flow and makes the serration shapes of the blade end part match the air flow due to the back flow, so as to deal with the flow of air near the blade surface of the blower. The ninth embodiment is included in the first embodiment. According to this, it is possible to set the direction of the serrations to match the direction of flow, so the effect is obtained of noise reduction, and prevention of both a drop in air flow and increase in drive torque. Of course, combinations of the fifth and sixth embodiments for the diagonal flow and the seventh and eighth embodiments for the back flow is included in the ninth embodiment. The present invention was described with reference to specific embodiments selected in accordance with the purpose of illustration, but it is clear that a person skilled in the art could conceive of numerous modifications without departing from the basic concept of the present invention and scope of disclosure of the same.

REFERENCE SIGNS LIST

• • 1 blower fan
  • 3 blade
  • 4 hub
  • 300 drive motor

Claims

1. A blower comprising

a drive motor and

a blower fan having a hub which is attached to said drive motor, and a plurality of blades which are provided at said hub, wherein

said blades are provided at their blade leading edge parts with serrations comprised of pluralities of triangular shape projecting parts along the blade leading edge parts and said serrations are changed in pitch, height, or direction according to the flows of air at radial direction positions of said blower fan.

2. The blower according to claim 1, wherein said serrations have a pitch or height which becomes larger as the serrations are further to the blade outside diameter side.

3. The blower according to claim 1, wherein said serrations have an angle of vertices which becomes smaller as the serrations are further to the blade outside diameter side.

4. The blower according to claim 1, wherein said serrations have a direction in the circumferential direction of the blower fan.

5. The blower according to claim 1, wherein said serrations have a direction in the direction of flow of air other than the circumferential direction of the blower fan.

6. The blower according to claim 1, wherein said serrations have a pitch, height, or direction made a magnitude or a direction corresponding to a back flow at the blade end part.

7. The blower according to claim 1, wherein said blades have a blade trailing edge part with serrations comprised of a plurality of triangular shape projecting parts along the blade trailing edge part.

8. The blower according to claim 7, wherein said serrations of said blade trailing edge part have a pitch or height smaller than said serrations of said blade leading edge part.

9. The blower according to claim 7, wherein said serrations of said blade leading edge part and said serrations of said blade trailing edge part are different in set position in radial direction position of the blower fan.

10. A blower fan having a hub which adapts to be attached to a drive unit, and a plurality of blades which are provided at said hub, wherein

each said blade has a first portion of a blade leading edge part of said blade which has a first distance in the radial direction from the center of rotation of said blade, and a second portion of a blade leading edge part of said blade which has a second distance in the radial direction from the center of rotation of said blade,

said blade leading edge part is provided with a plurality of serrations which stick out to an upstream side of flow of air, wherein said serrations have first slanted sides which are slanted with respect to a direction of flow of air, and second slanted sides which are slanted in a different direction from said first slanted sides with respect to a direction of flow of air, and

at least one of a pitch, height, and direction of said projections at said first portion differs from at least one of a pitch, height, and direction of said projections at said second portion.