JPH06280799A - Blast device - Google Patents

Abstract

PURPOSE:To suppress the generation of fan noise to a low value in terms of a hearing feeling by a method wherein the frequency of a fundamental peak of interference noise between a stay and a blade is shifted to a high frequency. CONSTITUTION:The number (x) of stays 6 to support an electric motor 5 and the number (y) of blades 3 arranged to an axial flow fan 4 driven with the aid of the electric motor 5 are set to x= 12 and y=11 being an original relation. The axial flow fan 4 is rotationally driven at 2000 rpm with the aid of the electric motor 5. The fundamental peak frequency of interference noise between the stay 6 and the blade 3 is determined by a product of the lowest common multiple of the number (x) of the stays 6 and the number (y) of the blades 3 and the number of revolutions per one second of the axial flow fan 4, whereby the fundamental peak frequency (f) of a blast device 1 is f=12X11X2000/60=4400, and the generation of fan noise is reduced in terms of functions and a hearing feeling.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air blower in which a motor for rotationally driving an axial fan is supported by a plurality of stays arranged to face the axial fan.

[0002]

2. Description of the Related Art FIG. 4 shows an example of an air blower in which a motor is supported by a plurality of stays arranged to face an axial fan. The blower 100 includes an axial fan 102 having five blades 101, and the axial fan 1
The motor 104 is supported by the five stays 103 on the air suction side of 02. The five blades 101 are provided at equal intervals, and the five stays 103 are also provided at equal intervals.

In the blower 100, when the motor 104 operates, the axial fan 102 sucks air from the stay 103 side. At this time, turbulence of air occurs downstream of the stay 103 due to the air flow passing through the stay 103.
When this turbulence reaches the rotating wing 101, the stay 10
An interference sound is generated due to the air turbulence caused by No. 3. As shown in FIG. 5, when the stay 103 and the blades 101 interfere with each other, the rotation speed of the axial fan 102 used is 2000 rpm.
, The basic peak frequency is about 167 Hz, and a peak appears in its multiple (C in the figure). For the purpose of avoiding a match between the pitch of the stay 103 and the pitch of the wing 101, FIG.
As shown in, the number of stays 103 is 5 and the number of wings 101 is 3
When the number of sheets is one, as shown in FIG. 7, when the rotational speed of the axial fan 102 is 2000 rpm, the interference sound has a basic peak frequency of about 500 Hz, and a peak appears in its multiples (D in the drawing). . Note that the peak E shown in the figure is the peak of the wind noise caused by the blade 101.

[0004]

Problems to be Solved by the Invention Wing 101 and stay 10
The interference noise peak of 3 significantly increases the rotational noise.
Therefore, in order to eliminate the peak of this interference sound, a method of making the mounting pitch of the fans unevenly spaced has been attempted, but the air flow between the blades 101 becomes non-uniform, and the noise level of the entire frequency is reduced. While rising, interference peaks also appeared due to the mounting pitch of the stays 103 provided at equal intervals, and as a result, rotation noise could not be reduced.
Therefore, various researches were conducted to make the fan noise comfortable to hear. As a result of this research, we felt that discomfort was felt when the peak of the interference sound was in the low frequency range, and by setting the peak of the interference sound in the high frequency range, it was possible to feel pleasant to the ear even if the interference sound occurred. I found it. Further, it has been found that at a high frequency of 2 KHz or higher, the audible noise level is lowered in hearing, so that the fan noise can be heard relatively comfortably and the noise due to the peak of the interference noise can be reduced and heard.

In order to simply shift the peak of the interference sound to a high frequency, the rotational speed of the axial fan 102 may be increased, but the wind noise of the fan rapidly increases, so the blade 10
The peak of the interference sound must be raised to a high frequency depending on the number of 1 and the number of stays 103. Therefore, as shown in FIG. 8, the number of blades 101 is three, and the stay 10
When the number of 3 is increased to 12, the blower 10 of FIG.
Although the number of stays 103 is more than doubled as compared with 0, the interference sound has a basic peak frequency of about 400 Hz when the rotational speed of the axial fan 102 used is 2000 rpm, as shown in FIG. F) in the figure, the basic peak frequency is lower than 500 Hz of the blower 100 of FIG. Even if the number of stays 103 and the number of blades 101 and 12 are increased, the basic peak frequency is about 40.
0Hz, even if the number of stays and the number of blades are increased,
The basic peak frequency does not increase.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to set the fundamental peak frequency of an interference sound to 2K.
Set it to Hz or higher to make the fan noise comfortable and
The purpose of the present invention is to provide an air blower capable of suppressing fan noise to the ear.

[0007]

The blower of the present invention employs the following technical means. The blower includes an axial fan having a plurality of blades that are rotationally driven to generate an air flow, a motor that rotationally drives the axial fan, and a plurality of fans that are arranged to face the axial fan and support the motor. And a stay. The blower has the number of stays x, the number of blades y, and the number of revolutions of the axial fan per minute of Nf. The stays and the blades are provided at equal intervals, and The number of stays x and the number of blades y have a prime relationship with each other and satisfy 2000 <x · y · Nf / 60.

[0008]

The basic peak frequency of the interference sound between the stay and the blade is obtained by the product of the least common multiple of the number of stays x and the number of blades y and the rotation speed of the axial fan for 1 second. In the air blower of the present invention, the number of stays x and the number of blades y are relatively prime. That is, the least common multiple of the number of stays x and the number of wings y is x
・ It becomes y. Therefore, the basic peak frequency f increases as it is by increasing the number of stays x and the number of wings y. Then, the number of stays x and the number of blades y are set so as to satisfy xy · Nf / 60> 2000 based on the number of rotations per minute Nf of the axial fan used. As a result, the basic peak frequency of the interference sound between the wing and the stay becomes 2 KHz or higher.

[0009]

According to the blower of the present invention, since the basic peak frequency of the interference sound between the blade and the stay is 2 KHz or more,
The fan noise is audibly comfortable, and the fan noise can be suppressed audibly low.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an air blower of the present invention will be explained based on an embodiment shown in the drawings. [Configuration of Embodiment] FIGS. 1 to 3 show an embodiment of the present invention. FIG. 1 is a front view of a blower, and FIG. 2 is a side view of the blower. The blower device 1 of the present embodiment is a push-type blower device for forcibly sending air from a traveling direction side of a vehicle to a heat exchanger 2 such as a refrigerant condenser or a radiator, and is an axial fan having y blades 3. 4 and the axial fan 4 is energized for N minutes
The electric motor 5 that rotates f times and x stays 6 that support the electric motor 5 on the air intake side of the axial fan 4.
And a fan shroud 8 integrally provided with a shroud portion 7 that covers the periphery of the axial fan 4.

The number of stays x and the number of wings 3 y.
Is provided in a relatively prime relationship, and the electric motor 5 of the present embodiment rotationally drives the axial fan 4 at 2000 times per minute. Further, in this embodiment, the number x of the stays 6 is 12 so that the basic peak frequency of the interference sound between the blades 3 and the stays 6 is 4 KHz or more and xy · Nf / 60> 4000 is satisfied. And the number y of wings 3 is 1
I have one.

The axial fan 4 is composed of a boss portion 9 which is rotationally driven by an electric motor 5 and eleven blades 3 which are radially provided on the boss portion 9.
Has a fan shape that extends from the boss portion 9 in the radial direction. The angles of the adjacent blades 3 are all set equal.

The fan shroud 8 has a substantially cylindrical shroud portion 7 that covers the periphery of the axial fan 4, and 12 stays 6 that support the electric motor 5 on the air intake side of the shroud portion 7. It is integrally molded by.
Each stay 6 has a leg portion 6a extending from the shroud portion 7 on the air intake side and parallel to the axial direction of the axial fan 4, and a radial rib 6b extending from the leg portion 6a toward the electric motor 5 on the inner periphery. It consists of and. The angles of the adjacent stays 6 are all set equal.

[Operation of Embodiment] Next, the operation of the above embodiment will be briefly described. When the electric motor 5 is energized, the electric motor 5 rotationally drives the axial fan 4 2000 times per minute, and the axial fan 4 also rotates 2000 times per minute. Then, the 11 blades 3 of the axial fan 4 suck air from between the stays 6 into the shroud portion 7, and blow the sucked air toward the heat exchanger 2. At this time, the stays 6 are moved by the air flow passing between the stays 6.
Turbulence occurs downstream of. This turbulent rotating wing 3
When it reaches, the interference sound due to the air turbulence due to the stay 6 is generated. The blower 1 of the present embodiment has 12 stays x and 11 blades y of 11, and they are in a prime relationship, and the least common multiple thereof is as large as 12 × 11. Since the rotational speed Nf of the axial fan 4 per minute is 2000 times, the basic peak frequency f obtained by f = x · y · Nf / 60 is f = 12 × 11 × 2000/60 = 4400 The basic peak frequency of the interference sound between the wing 3 and the stay 6 becomes 4.4 KHz as shown in the noise characteristic of FIG. 3 (A in the figure). The small peak B in FIG. 3 is the peak of the wind noise generated by the blade 3.

[Effects of the Embodiment] The blower 1 of this embodiment
As shown in FIG. 3, when the basic peak frequency of the interference sound between the wing 3 and the stay 6 becomes 4.4 KHz, the timbre is sensually improved and there is less discomfort. Also, 2
Frequencies above KHz are hard for the human ear to hear. That is,
The basic peak frequency of the interference sound of this embodiment is 4.4 KHz, which is at the lower limit of the roundness, and the peak of the interference sound is reduced to the same level as that of other fan noises in terms of hearing. In this way, the timbre of the fan noise is sensually improved, discomfort is reduced, and the peak of the interference sound is wiped out by another fan noise, so that the fan noise can be reduced in terms of hearing.

[Modification] In the above embodiment, the motor and stay are provided on the air intake side of the axial fan, but they may be provided on the blowout side. In this case, it is possible to set the peak of the interference sound due to the pressure fluctuation due to each blade generated immediately after the axial fan in the high frequency range. Although an electric motor is shown as an example of the motor, a hydraulic motor may be used. It may be provided so that the rotation speed of the motor changes. In this case, it may be provided so as to satisfy the present invention at least during high-speed rotation. A protective net may be combined with the stay supporting the motor.

[Brief description of drawings]

FIG. 1 is a front view of an air blower (embodiment).

FIG. 2 is a side view of an air blower (embodiment).

FIG. 3 is a characteristic diagram of fan noise showing a relationship between noise level and frequency (Example).

FIG. 4 is a front view of a blower (prior art).

FIG. 5 is a fan noise characteristic diagram showing the relationship between noise level and frequency (prior art).

FIG. 6 is a front view of a blower (prior art).

FIG. 7 is a characteristic diagram of fan noise showing the relationship between noise level and frequency (prior art).

FIG. 8 is a front view of a blower (prior art).

FIG. 9 is a characteristic diagram of fan noise showing the relationship between noise level and frequency (prior art).

[Explanation of symbols]

 1 Blower 3 Blade 4 Axial fan 5 Electric motor 6 Stay

Claims (1)

[Claims] 1. An axial fan having a plurality of blades that are rotationally driven to generate an air flow, a motor that rotationally drives the axial fan, and a motor that is disposed opposite to the axial fan to support the motor. An air blower comprising a plurality of stays, wherein the number of stays is x, the number of blades is y, the rotational speed of the axial fan per minute is Nf, and both the stays and the blades are equal. An air blower that is provided at intervals, and the number of stays x and the number of blades y are relatively prime and satisfy 2000 <x · y · Nf / 60.