JP2008303760A - Axial blower - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an axial blower capable of suppressing blowing noise small without deteriorating blowing performance. <P>SOLUTION: The axial blower is equipped with: an impeller including a boss 3 rotated around an axis, a plurality of blades 4 disposed on the outer peripheral face of the boss 3 and each having a shape surrounded by a base edge part 4a, an outer peripheral edge part 4b, a front edge part 4c, and a rear edge part 4d; a bell-mouth 6 disposed coaxially with the boss 3, and having a rotational direction front end side of the blade 4 projecting from an opening on one side and surrounding a rotational direction rear end side of the blade 4; and a rib 5 projecting from a negative pressure face 4e of the blade 4. In the rib 5, a rib front end 5a is connected to a portion of the front edge part 4c separated from a front end in the rotational direction of the outer peripheral edge part 4b or near thereto, and a rib rear end 5b is connected to a portion of the outer peripheral edge part 4b separated from a front end in the rotational direction of the outer peripheral edge part 4b. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an axial blower used for an air conditioner, a ventilator or the like.

  A conventional blower is surrounded by an impeller composed of a motor, a hub attached to the motor, and a plurality of blades provided around the hub, an orifice surrounding the outer periphery of the discharge side of the blade, and the orifice. And plate-like ribs that are attached to the suction surface side of the outer peripheral end of the non-blade so as to increase in height from the suction side to the discharge side of the vane. In the conventional blower, the air flow is blown out to the outer periphery of the impeller that is not surrounded by the orifice, or sucked from the center between the blades of the impeller, which is suppressed by the rib, and the deterioration of the blowing performance and the increase of the blowing noise (For example, refer to Patent Document 1).

Japanese Patent No. 3205009

  However, in the conventional blower, since the rib is attached to the outer peripheral end of the blade farthest from the rotating shaft, the relative speed of the airflow flowing into the blade from the front end of the rib is increased, and the blowing noise generated by the rib is large. There is a problem of becoming. The end of the rib on the discharge side of the blade has a stepped height from the suction surface of the blade, and the airflow is discontinuous at this portion and a separation flow is generated, so that the blowing noise increases. There is a problem. Furthermore, since the rib extends from the suction side to the discharge side in a region not surrounded by the orifice, the flow of airflow sucked into the blades from above the orifice toward the motor shaft is obstructed. Thereby, there exists a problem that the flow of airflow becomes unstable and ventilation noise increases.

  This invention was made in order to solve said problem, and it aims at obtaining the axial flow fan which can suppress ventilation noise small, without reducing ventilation performance.

  A boss that is rotated around the axis, and a base edge that is disposed on the outer peripheral surface of the boss and serves as a joint portion with the outer peripheral surface of the boss, along a circle with a predetermined radius centered on the boss axis. After connecting the outer peripheral edge having a predetermined length, the base edge and the front edge of the outer peripheral edge in the rotational direction, and connecting the rear edge of the root edge and the outer peripheral edge in the rotational direction An impeller having a plurality of blades formed in a shape surrounded by an edge portion, and arranged coaxially with the boss, protruding from the opening on one side to the front end side in the rotation direction of the blade, and the rear end in the rotation direction of the blade A bell mouth surrounding the side, and a rib projecting from a suction surface portion of the wing projecting from an opening on one side of the bell mouth, wherein the rib has a front end of the rib from a front end in the rotation direction of the outer peripheral edge. Connected to the vicinity of the front edge part separated by a predetermined distance or the vicinity thereof, the rear end of the rib is the outer peripheral edge part It is connected to a part of the outer peripheral edge that is separated from the front end in the rotation direction by a predetermined distance, and the rib rear end side of the protruding end surface of the rib is gradually lowered from the suction surface to coincide with the suction surface at the rib rear end. It is characterized by being formed into a smooth continuous curved surface.

According to this invention, the blowing noise of the axial-flow fan can be suppressed to a low level without reducing the blowing performance.

The best mode for carrying out the present invention will be described below with reference to the drawings.
1 is a perspective view of an axial blower according to the present invention, FIG. 2 is a front view of the axial blower according to the present invention, FIG. 3 is a sectional view taken along the line III-III in FIG. 2, and FIG. The axis of the boss has a radius that is the same as the distance from the axial center of the boss of the axial flow fan to the outer peripheral edge of the blade, and is arranged coaxially with the axial center of the boss so as to surround the blade and the rib. FIG. 5 is a side view in which a cylindrical surface is developed on a plane after projecting blades, ribs, and bellmouths in the radial direction centered on the center, and FIG. 5 is a conceptual view of the flow of blade tip vortices generated in the axial blower according to the present invention. FIG. FIG. 6 is a diagram showing the relationship between Ib / If and specific noise difference ΔKs in the axial fan according to the present invention, and FIG. 7 shows the relationship between t / la and specific noise difference ΔKs in the axial fan according to the present invention. 8 is a diagram showing the relationship between Rw / (Rw + Rr) and the specific noise difference ΔKs in the axial fan according to the present invention, FIG. 9 is a perspective view of the axial fan of the comparative example, and FIG. 10 is the axial flow of the comparative example. It is a figure which shows notionally the flow of the blade tip vortex which generate | occur | produces in an air blower.

1 to 4, the axial blower 1 includes an impeller 2, a bell mouth 6, and a rib 5.
The impeller 2 includes a boss 3 and three blades 4 provided on the outer peripheral surface of the boss 3 in the circumferential direction. A rotating shaft of a motor (not shown) is disposed coaxially with the boss 3, and the blade 4 rotates around the axis of the boss 3 in conjunction with the driving of the motor.

  As shown in FIG. 2, the wing 4 has a predetermined length along a circle having a predetermined radius centered on the base of the base 4 a and the boss 3, which is a joint portion with the outer peripheral surface of the boss 3. After connecting the front edge part 4c which connects the rotation direction front ends of the outer peripheral edge part 4b, the base edge part 4a, and the outer peripheral edge part 4b, and the rotation direction rear ends of the base edge part 4a and the outer peripheral edge part 4b. It is formed in a shape surrounded by the edge 4d. In addition, the axial height of the boss 3 on the main surface of each blade 4 increases in the axial direction of the boss 3 toward the rear in the rotational direction of the blade 4 and toward the center in the radial direction. The main surface of the wing 4 is inclined so as to face the other side.

  The bell mouth 6 has a cylindrical shape and is arranged coaxially with the boss 3 so as to surround the impeller 2. At this time, in FIG. 2, there is a predetermined gap in the radial direction of the bell mouth 6 between the outer peripheral edge 4 b of the wing 4 and the inner peripheral surface of the bell mouth 6. 1, 3, and 4, the front end side in the rotational direction of the wing 4 protrudes from an opening on one side of the bell mouth 6, and the rear end side in the rotational direction of the wing 4 surrounds the bell mouth 6. Has been. As a result, when the blade 4 is rotated, the surface on one side of the main surface of the blade 4 in the axial direction of the boss 3 (the rotational axis direction of the blade 4) becomes the negative pressure surface 4e. The other surface is the positive pressure surface 4f. That is, when the wing 4 is rotated, air is blown from the opening on the other side of the bell mouth 6 as shown by the white arrow in FIG.

  The rib 5 is a plate-like member, and is attached to the negative pressure surface 4e so as to protrude upward with respect to the negative pressure surface 4e of the blade 4 and to protrude substantially vertically. At this time, the rib front end 5a is disposed at a portion of the front edge 4c that is separated from the outer peripheral front edge 4g (the front end in the rotation direction of the outer peripheral edge 4b) by a predetermined distance, and the rib rear end 5b is the outer front edge 4g. Is disposed at a portion of the outer peripheral edge portion 4b that is separated by a predetermined distance. That is, the rib 5 is connected to the negative pressure surface 4e in a state where the rib front end 5a is aligned with a predetermined portion of the front edge portion 4c on the inner peripheral side from the outer peripheral edge portion 4b, and the rib rear end 5b is It is attached so as to be connected to the suction surface 4e in a state where it is smoothly aligned with a portion of the outer peripheral edge portion 4b spaced from the front edge 4g by a predetermined distance from the rear edge in the rotational direction.

  Further, the end surface on the protruding side of the rib 5 protruding from the negative pressure surface 4e (hereinafter referred to as a protruding end surface 5d) gradually increases the height from the negative pressure surface 4e from the rib front end 5a coinciding with the negative pressure surface 4e. The height from the negative pressure surface 4e is highest at the intermediate portion 5c, and the height from the negative pressure surface 4e is gradually decreased toward the rib rear end 5b from the intermediate portion 5c to coincide with the negative pressure surface 4e at the rib rear end 5b. It is formed into a smooth continuous curved surface.

  Further, the height position of the boss 3 in the axial direction of the boss 3 (that is, the axial direction of the bell mouth 6) at the rib rear end 5 b is from the opening on one side of the bell mouth 6 toward one side in the axial direction of the boss 3. It is in a place separated by a predetermined distance.

Next, the blade tip vortex will be described in detail with reference to FIG.
In the axial blower 1 configured as described above, when the blade 4 is rotated, a spiral air flow called a blade tip vortex 7 is generated between the suction surface 4e side of the blade 4 and the above-described pressure surface 4f side. Due to the pressure difference, it first occurs on the outer peripheral edge 4b side of the front edge 4c of the negative pressure surface 4e. The generated blade tip vortex 7 gradually develops while moving along the outer peripheral edge 4b from the front edge 4c toward the rear edge 4d on the suction surface 4e. However, the blade tip vortex 7 moves in the circumferential direction on the suction surface 4e to reach the rib 5, and further changes the moving direction so as to go radially outward along the wall surface of the rib 5, and finally Detach from the outer peripheral edge 4b outward in the radial direction. That is, the blade tip vortex 7 is detached from the suction surface 4e before it greatly develops.

  Although not shown in the figure, the blade tip vortex is also generated at the portion of the negative pressure surface 4e on the rear edge 4d side and the outer peripheral edge 4b side from the position where the rib 5 is disposed and is directed into the bell mouth 6, but the rib 5 is disposed. Since the distance from the position to the trailing edge 4d is shortened, the blade tip vortex does not develop greatly, and the airflow flowing into and out of the bell mouth 6 is not greatly disturbed.

  According to the axial blower 1 of the present invention, the position of the rib front end 5a is disposed in a portion of the front edge portion 4c that is separated from the outer peripheral front edge end 4g by a predetermined distance. Therefore, the distance from the rotating shaft of the blade 4 to the rib front end 5a is shorter than the distance from the rotating shaft of the blade 4 to the outer peripheral edge 4b. Therefore, the relative velocity of the airflow flowing into the blade 4 from the rib front end 5a of the axial blower 1 with respect to the rib 5 is reduced from the front end of the rib of the conventional axial blower attached along the outer peripheral end (edge). It becomes slower than the relative velocity of the airflow flowing into the (wing) with respect to the rib. That is, the blowing noise generated at the rib 5 of the axial blower 1 can be reduced.

  Further, as described above, in the conventional axial blower, the height of the end portion of the rib on the side opposite to the rotation direction of the blade (the rear end of the rib) is increased stepwise from the suction surface of the blade. In this case, at the rear end of the rib, the rib wall that has been raised stepwise suddenly disappears, causing a discontinuity in the air flow and violent vortices, which increases the blowing noise.

  On the other hand, in the axial blower 1, the protruding end surface 5d of the rib 5 gradually increases in height from the rib front end 5a coinciding with the negative pressure surface 4e, and the height from the negative pressure surface 4e becomes the highest at the intermediate portion 5c, The height from the suction surface 4e is gradually lowered from the intermediate portion 5c toward the rib rear end 5b, and the rib rear end 5b is formed into a smooth continuous curved surface that matches the suction surface 4e. Therefore, since the height of the rib 5 with respect to the suction surface 4e does not change in a step shape, the airflow is suppressed from being discontinuous as much as possible when flowing along the wall surface of the rib 5, and vortex shedding occurs. Can be avoided. That is, the blowing noise of the axial blower 1 can be suppressed to a low level without reducing the blowing performance.

  Further, the blade tip vortex 7 generated on the outer peripheral edge 4b side of the front edge portion 4c of the negative pressure surface 4e is separated from the negative pressure surface 4e at the arrangement portion of the rib rear end 5b of the outer peripheral edge portion 4b before it greatly develops. Therefore, the turbulence of the airflow due to the blade tip vortex 7 can be suppressed. That is, the blowing noise of the axial blower 1 can be suppressed to a low level without reducing the blowing performance. Furthermore, the rib 5 projects from the suction surface 4 e of the wing 4 projecting from the bell mouth 6, and the height position of the rib rear end 5 b in the axial direction of the boss 3 is predetermined from one end surface of the bell mouth 6. It is in a place separated by a distance. Accordingly, since the lateral suction flow of the air current is ensured without being obstructed by the arrangement of the rib 5, the air current is not disturbed, and the air blowing noise of the axial blower 1 is reduced without reducing the air blowing performance. It can be kept small.

Next, since the effect of the present invention characterized by attaching the rib 5 was confirmed by a test, the contents thereof will be specifically described below. The test was performed by preparing an axial blower of a comparative example, measuring specific noise (described later) of the axial blower 1 and specific noise of the axial blower 11 of the comparative example under various conditions, and comparing the results. .
As shown in FIG. 9, the axial blower 11 of the comparative example is configured in the same manner as the axial blower 1 except that the rib 5 is omitted.

  First, FIG. 4 shows the blade front-and-rear end distance If, the blade inner portion distance Ib, the rib maximum height t, the blade front-and-rear end length la, the rib front-and-rear end length Rw, and the rib-bell mouth length Rr in the axial blower 1. This will be described with reference to FIG.

  The blade front and rear end distance If is the distance between the outer peripheral front edge 4g and the outer peripheral rear edge 4h (the rear end in the rotational direction of the outer peripheral edge 4b) of the blade 4 in the rotational axis direction of the blade 4, The partial distance Ib is a distance between the outer peripheral trailing edge 4 h of the wing 4 and one end face of the bell mouth 6 in the axial direction of the boss 3. The rib maximum height t is the maximum height of the rib 5 from the suction surface 4e of the blade 4 in the normal direction of the suction surface 4e of the blade 4, and the blade front and rear end length la is the axis of the boss 3. The center of the axis of the boss 3 is centered on a cylindrical surface having the same radius as the distance from the outer peripheral edge 4b of the wing 4 and arranged coaxially with the axis of the boss 3 so as to surround the wing 4 and the rib 5. The length of the straight line connecting the outer peripheral leading edge 4g and the outer trailing edge 4h of the blade 4 in a side view in which the cylindrical surface is developed on a plane after projecting the blade 4, the rib 5 and the bell mouth 6 in the radial direction That's it. Also, as shown in FIG. 2, the rib front and rear end length Rw is the length on the suction surface 4e of the blade 4 from the rib front end 5a to the rib rear end 5b, and is the rib-bell mouth length. Rr is an outer region from the outer peripheral edge portion 4b of the wing 4 where the rib rear end 5b is located to the outer peripheral edge portion 4b where the axial position of the boss 3 is the same as the one end surface of the bell mouth 6. It is the length (in the circumferential direction) along the peripheral edge 4b. The blade front and rear end distance If and the blade inner blade portion distance Ib are similarly defined in the axial flow fan 11 of the comparative example. Hereinafter, the blade front / rear end distance If, the blade inner portion distance Ib, the rib maximum height t, the blade front / rear end length la, the rib front / rear end length Rw, and the rib-bell mouth length Rr will be described by describing only the reference numerals.

And the following evaluation was performed with respect to the axial-flow fan 1 and the axial-flow fan 11 of a comparative example.
First, the specific noise Ks of the axial fan 1 and the specific noise Ks of the axial fan 11 of the comparative example were measured using Ib / If as a parameter. The specific noise Ks represents the magnitude of the blowing noise when the airflow blown from the axial blower is unit pressure and unit pressure. The larger the specific noise Ks, the larger the blowing noise of the axial blower. Means that. The specific noise Ks is expressed by the following equation (1).
Ks = SPL-10 log (Ps ^2.5 Q) (1)
Here, SPL represents the noise level, Ps represents the static pressure, and Q represents the air volume.
The measurement of the noise level SPL conforms to JIS8346.

The relationship between the specific noise difference ΔKs of the axial fan 1 obtained from the measurement result of the specific noise Ks and Ib / If is shown by a solid line in FIG.
Here, the specific noise difference ΔKs is expressed as a difference between the specific noise Ks observed in the axial blower 1 and the specific noise Ks at the value of Ib / If at which the axial blower 11 of the comparative example has the lowest noise. Is.
In FIG. 6, the dotted line shows the difference between the specific noise Ks observed in the axial flow fan 11 of the comparative example and the specific noise Ks at the Ib / If value at which the axial flow fan 11 of the comparative example produces the lowest noise. It is shown as a specific noise difference ΔKs. That is, the specific noise difference ΔKs of the axial flow fan 11 of the comparative example is normalized by setting the specific noise Ks at the value of Ib / If at which the axial flow fan 11 of the comparative example has the lowest noise as 0 [dBA]. Are the same.

  As shown in FIG. 6, the specific noise difference ΔKs has a characteristic of continuously changing in a downwardly convex shape when Ib / If is continuously changed from near 0.15 to 0.5. When Ib / If is approximately 0.3, the minimum value is obtained. And if it was the same value of Ib / If, the specific noise difference (DELTA) Ks of the axial flow fan 1 became a value smaller than the specific noise difference (DELTA) Ks of the axial flow fan 11 of a comparative example. In addition, when Ib / If is in the range of 0.23 <Ib / If <0.42, the specific noise difference ΔKs of the axial blower 1 is smaller than 0 [dBA].

The above results are then considered.
As described above, since the blade tip vortex 7 generated on the outer peripheral edge 4b side of the leading edge 4c of the suction surface 4e is separated from the suction surface 4e before it develops greatly, the turbulence of the air flow due to the blade tip vortex 7 Is suppressed, and the specific noise Ks of the axial blower 1 is reduced.

On the other hand, in the axial blower 11 of the comparative example, as shown in FIG. 10, since the rib 5 is not provided, the blade tip vortex 12 generated on the outer peripheral edge 4b side of the front edge 4c on the negative pressure surface 4e is The blade 4 gradually develops while moving on the suction surface 4e in the circumferential direction from the front edge 4c toward the rear edge 4d without being separated from the outer peripheral edge 4b of the blade 4. That is, since the developed blade tip vortex 12 disturbs the airflow flowing into and out of the bell mouth 6, the specific noise Ks of the axial blower 11 of the comparative example is increased.
Therefore, if the Ib / If values are the same, the specific noise difference ΔKs of the axial flow fan 1 is smaller than the specific noise difference ΔKs of the axial flow fan 11 of the comparative example.

  Further, when Ib / Ib is gradually reduced from the value of Ib / If at which the blowing noise of the axial flow fan 1 becomes the smallest, in other words, the ratio of the region of the blade 4 surrounded by the bell mouth 6 is gradually increased. If it is made smaller, a sufficient increase in static pressure cannot be obtained, the blowing performance is lowered, and the specific noise difference ΔKs increases.

  In addition, that the ventilation performance of the axial-flow fan 1 is reduced is that the specific noise Ks observed in the axial-flow fan 1 is minimized. As can be seen from the fact that the specific noise difference ΔKs of the axial flow fan 1 is smaller than the specific noise difference ΔKs of the axial flow fan 11 of the comparative example, the blowing performance of the axial flow fan 1 is equal to Ib / If. The air blowing performance of the axial blower 11 of the comparative example is improved.

  When Ib / If = 0.23, the specific noise Ks of the axial flow fan 1 is the same as the specific noise Ks at the value of Ib / If at which the axial flow fan 11 of the comparative example has the lowest noise. Thus, when Ib / If is made smaller than 0.23, the specific noise Ks of the axial fan 1 becomes larger than the minimum value of the specific noise Ks of the axial fan 11 of the comparative example, so that the specific noise difference ΔKs is 0 [dBA]. Become bigger.

  Further, when the value of Ib / If is increased from the value of Ib / If where the blowing noise of the axial blower 1 is minimized, in other words, the ratio of the region of the wing surrounded by the bell mouth 6 is increased. Then, the air blowing performance of the axial blower 1 gradually decreases due to an increase in pressure loss due to the flow of air flowing to the negative pressure surface 4e from the positive pressure surface 4f being hindered by the ribs 5. . That is, the specific noise Ks increases. When Ib / If = 0.42, the specific noise Ks of the axial blower 1 is the same as the specific noise Ks under the condition that the lowest noise is obtained in the axial blower 11 of the comparative example, and Ib / If Is made larger than 0.42, the specific noise Ks of the axial fan 1 becomes larger than the minimum value of the specific noise Ks of the axial fan 11 of the comparative example, and the specific noise difference ΔKs becomes larger than 0 [dBA].

  If the blade 4 is formed so as to satisfy 0.23 <Ib / If <0.42, the static pressure rise is not excessively reduced, and the rib 5 excessively reduces the pressure surface 4f to the suction surface. It does not hinder the flow of airflow that is going to wind up to 4e. Therefore, if 0.23 <Ib / If <0.42, the effect of suppressing the development of the blade tip vortex 7 is great against the deterioration of the blowing performance of the axial blower 1, so that the specific noise difference ΔKs is 0 [ dBA].

Next, the specific noise Ks of the axial fan 1 was measured using t / la as a parameter. FIG. 7 shows the relationship between t / la obtained from the measurement result and the specific noise difference ΔKs.
In FIG. 7, the specific noise difference ΔKs of the axial flow fan 1 is shown by a solid line, and in the axial flow fan 11 of the comparative example, the specific noise difference ΔKs (ie, ΔKs = 0 [dBA]) under the lowest noise condition. Are shown with dotted lines.
As shown in FIG. 7, the specific noise difference ΔKs has a characteristic of continuously changing in a downwardly convex shape when t / la is continuously increased from 0, and t The minimum value is obtained when / la is approximately 0.16. Further, when 0 <t / la <0.025, the specific noise difference ΔKs becomes smaller than 0 [dBA], and the blowing noise can be effectively reduced.

The above results are then considered.
When the rib 5 is disposed on the blade 4 so as to satisfy 0 <t / la <0.025, t is an appropriate height with respect to la, and is generated by attaching the rib 5. Pressure loss due to wall friction or the like is reduced. Therefore, since the effect of suppressing the development of the blade tip vortex 7 is great against the deterioration of the blowing performance of the axial blower 1, the specific noise difference ΔKs becomes smaller than 0 [dBA].
On the other hand, at t / la ≧ 0.025, the rib height becomes too high with respect to la, and the pressure loss increases, so the blowing performance decreases, and the specific noise difference ΔKs becomes 0 [dBA] or more. Become.

Next, the specific noise Ks of the axial blower 1 was measured using Rw / (Rw + Rr) as a parameter. FIG. 8 shows the relationship between Rw / (Rw + Rr) obtained from the measurement results and the specific noise difference ΔKs.
In FIG. 8, the specific noise difference ΔKs of the axial flow fan 1 is shown by a solid line, and only the specific noise difference ΔKs (that is, ΔKs = 0 [dBA]) under the lowest noise condition in the axial flow fan of the comparative example. Are shown with dotted lines.

  As shown in FIG. 8, the specific noise difference ΔKs has a characteristic of continuously changing in a downwardly convex shape when Rw / (Rw + Rr) is continuously changed from 0 to 1, and Rw The minimum value is obtained when / (Rw + Rr) is approximately 0.5. When Rw / (Rw + Rr) <0.88, the specific noise difference ΔKs becomes smaller than 0 [dBA], and the blowing noise can be effectively reduced.

Next, the above results will be considered.
When Rw / (Rw + Rr) <0.88, the blade tip vortex 7 is separated from the outer peripheral edge 4 b of the blade 4 at a position away from the bell mouth 6. Therefore, the blade tip vortex 7 is separated from the outer peripheral edge 4b without disturbing the airflow flowing into and out of the bell mouth 6, so that the specific noise difference ΔKs is 0 [Rw / (Rw + Rr) <0.88. dBA].

On the other hand, when the rib 5 is disposed on the wing 4 so as to satisfy Rw / (Rw + Rr)> 0.88, the distance between the rib rear end 5b and one end of the bell mouth 6 is shortened. In this case, since the portion of the outer peripheral edge 4 b of the blade 4 from which the blade tip vortex 7 is separated approaches the bell mouth 6, the airflow flowing into and out of the bell mouth 6 is disturbed by the blade tip vortex 7. For this reason, when Rw / (Rw + Rr) ≧ 0.88, the specific noise difference becomes 0 [dBA] or more.
As described above, as described based on the measurement results shown in FIG. 6 to FIG. 8, by providing the rib 5, the blowing noise of the axial blower 1 reduces the blowing performance of the axial blower 1. It was confirmed that it can be kept small.

  In the above-described embodiment, the rib 5 has a protruding end surface 5d that gradually increases in height from the rib front end 5a that coincides with the negative pressure surface 4e, and the intermediate portion 5c has the highest height from the negative pressure surface 4e. The height from the suction surface 4e is gradually lowered from the intermediate portion 5c toward the rib rear end 5b, and the rib rear end 5b is described as being formed into a smooth continuous curved surface that matches the suction surface 4e. The shape of the rib 5 is not limited to this.

  The rib 5 is connected to the negative pressure surface 4e in a state where the rib front end 5a is aligned with a predetermined portion of the front edge portion 4c on the inner peripheral side from the outer peripheral edge portion 4b, and the rib rear end 5b is the outer peripheral front edge. The rib front end 5a side and the rib rear end can be connected to the negative pressure surface 4e in a state of being smoothly aligned with the portion of the outer peripheral edge 4b spaced from the end 4g by a predetermined distance from the rotation direction rear end. The shape of the protruding end surface 5d on the 5b side does not necessarily have to be a smooth curved surface. That is, the rib front end 5a is connected to the suction surface 4e in a state where the rib front end 5a is aligned with a predetermined portion of the front edge portion 4c on the inner peripheral side from the outer peripheral edge portion 4b, and the rib rear end 5b is connected to the outer peripheral front edge end 4g. Air flow from the rib front end 5a to the blade 4 as long as it is attached to the suction surface 4e in a state of being smoothly aligned with the portion of the outer peripheral edge 4b that is separated from the rear end in the rotation direction by a predetermined distance. The relative velocity with respect to the rib 5 can be reduced, and the tip vortex 7 is separated before it is greatly developed. That is, the blowing noise of the axial blower 1 can be reduced. At this time, when the rib front end 5a side and the rib rear end 5b side of the projecting end surface 5d are not formed into smooth curved surfaces, the airflow is disturbed and the effect of reducing the blowing noise is diminished, but the rib front end 5a is the outer peripheral edge. The rib rear end 5b is connected from the outer peripheral front edge 4g to the rear end in the rotational direction by a predetermined distance so as to be connected to the suction surface 4e in a state of being aligned with a predetermined portion of the front edge 4c on the inner peripheral side from the portion 4b. It does not counteract all the effects of reducing the blowing noise caused by being attached so as to be connected to the suction surface 4e in a state of being smoothly aligned with the part of the outer peripheral edge 4b that is spaced apart.

  The rib 5 has a rib front end 5a aligned with a predetermined portion of the front edge 4c on the inner peripheral side from the outer peripheral edge 4b, and the rib rear end 5b has an outer peripheral edge excluding the outer peripheral front edge 4g. Although described as being connected to the suction surface 4e in a state of being matched with the portion 4b, the arrangement position of the rib front end 5a is not limited to the above. Even when the rib front end 5a is connected to the negative pressure surface 4e near the predetermined portion of the front edge portion 4c on the inner peripheral side from the outer peripheral edge portion 4b, the effect of reducing the blowing noise due to the arrangement of the rib 5 can be obtained.

  Since the blade tip vortex 7 generated near the blade tip has a small force, it is not always necessary to move the blade tip vortex 7 radially outward by the rib 5 in this region. However, if the blade tip vortex 7 is moderately developed, it is difficult to move the blade tip vortex 7 radially outward even if it has a rib. Therefore, the rib front end 5a is located in front of the outer peripheral edge 4b on the inner peripheral side. It is necessary to be connected on the negative pressure surface 4e in the vicinity of a predetermined portion of the edge 4c.

It is a perspective view of the axial blower concerning this invention. 1 is a front view of an axial blower according to the present invention. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. 2. A cylindrical surface having the same radius as the distance from the boss axis of the axial fan according to the present invention to the outer peripheral edge of the wing, and arranged coaxially with the boss axis so as to surround the wing and the rib, It is the side view which developed the cylindrical surface on the plane after projecting a wing, a rib, and a bell mouth in the diameter direction centering on the axis of a boss. It is a figure which shows notionally the flow of the blade tip vortex which generate | occur | produces in the axial-flow fan which concerns on this invention. It is a figure which shows the relationship between Ib / If and specific noise difference (DELTA) Ks in the axial blower which concerns on this invention. It is a figure which shows the relationship between t / la and the specific noise difference (DELTA) Ks in the axial-flow fan which concerns on this invention. It is a figure which shows the relationship between Rw / (Rw + Rr) and specific noise difference (DELTA) Ks in the axial-flow fan of this invention. It is a front view of the axial-flow fan of a comparative example. It is a figure which shows notionally the flow of the blade tip vortex which generate | occur | produces in the axial-flow fan of a comparative example.

Explanation of symbols

  2 impeller, 3 boss, 4 blades, 4a root edge portion, 4b outer peripheral edge portion, 4c front edge portion, 4d rear edge portion, 4e negative pressure surface, 4f positive pressure surface, 5 rib, 5a rib front end, 5b rib rear end, 5c middle part, 5d protruding end face, 6 bell mouth.

Claims (5)

A boss rotated around an axis, and a base edge portion disposed on an outer peripheral surface of the boss, each serving as a joint portion with the outer peripheral surface of the boss, and having a predetermined radius centered on the axis of the boss An outer peripheral edge having a predetermined length along the circle, a front edge connecting the root edges and the front edges in the rotation direction of the outer peripheral edges, and a rotation direction of the root edges and the outer peripheral edges. An impeller having a plurality of blades formed in a shape surrounded by a rear edge portion connecting the rear ends;
A bell mouth that is arranged coaxially with the boss, protrudes from the opening on one side of the wing in the rotation direction front end side, and surrounds the wing rotation direction rear end side;
A rib projecting from a portion of the suction surface of the wing projecting from an opening on one side of the bell mouth,
The rib is connected to a portion of the front edge portion where the rib front end is separated from the front end in the rotation direction of the outer peripheral edge portion by a predetermined distance or in the vicinity thereof, and the rib rear end is connected to the front end in the rotation direction of the outer peripheral edge portion. An axial blower characterized in that it is smoothly connected to a portion of the outer peripheral edge separated by a predetermined distance.   The protruding end surface of the rib has an intermediate portion between the rib front end and the rib rear end that has the largest height from the suction surface, and from the rib front end that coincides with the suction surface to the rib 2. The axial flow fan according to claim 1, wherein the blower is formed in a smooth continuous curved surface up to the rear end.   The distance (If) between the front end and the rear end in the rotational direction of the outer peripheral edge in the axial direction of the boss, the rear end in the rotational direction of the outer peripheral edge in the axial direction of the boss, and the bell mouth 3. The shaft according to claim 1, wherein the distance (Ib) between the opening surface on one side is configured to satisfy 0.23 <Ib / If <0.42. Current blower.   From the front end of the rib to the rear end of the rib, the length (Rw) on the suction surface of the blade, and from the portion of the outer peripheral edge of the blade where the rear end of the rib is disposed, the axis of the boss The length (Rr) along the outer peripheral edge to the outer peripheral edge where the height in the heart direction is the same as the opening on the one side of the bell mouth is Rw / (Rw + Rr) <0. The axial flow blower according to any one of claims 1 to 3, wherein the axial flow blower is configured to satisfy.   The boss has a radius that is the same as the distance from the axial center of the boss to the outer peripheral edge of the wing, and is disposed on a cylindrical surface that is coaxial with the boss axial center so as to surround the wing and the rib. In the side view in which the cylindrical surface is developed on a plane after projecting the blade and the rib in the radial direction centered on the axial center of the axis, the maximum of the rib from the suction surface in the normal direction of the suction surface And the distance (la) of the straight line connecting the front end in the rotational direction of the outer peripheral edge and the rear end in the rotational direction of the outer peripheral edge satisfies 0 <t / la <0.025. It is comprised so that it may be satisfied, The axial-flow fan of any one of Claim 1 thru | or 4 characterized by the above-mentioned.

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