JPH01142348A - Outdoor unit of air conditioner having a plurality of multiblade fan - Google Patents

Abstract

PURPOSE:To prevent noise such as resonance and droning of a fan blowing sound from being generated by a method wherein the number of vanes of a multiblade fan provided to an outdoor unit of an air conditioner are set to have a relatively prime relation having no common diviser to each other. CONSTITUTION:An outdoor unit 1 is provided with adjoining multiblade fans 2 and 3. For example, if the number of vanes of a propeller fan 2 is seven and the number of blades of a propeller fan 3 is four, they have a relatively prime relation having no common divisor. Due to this fact, a droning sound is intermittently hard to hear. A rotary sound of the vanes also includes a high harmonic component of two times and three times in addition to its basic frequency. However, the number of blades of each of a plurality of propeller fans is made relatively prime, thereby such a droning sound may be prevented.

Description

Detailed Description of the Invention [Objective of the Invention] (Industrial Field of Application) The present invention relates to an outdoor unit of an air conditioner having a plurality of multi-blade fans, and particularly to a resonance pump which occurs when these multi-blade fans are operated simultaneously. This invention relates to an i-structure that prevents abnormal noises such as humming.

(Prior Art) Conventionally, in an outdoor unit of an air conditioner having a plurality of multi-blade fans, joint propeller fans having the same number of blades Z are usually used. Therefore, the rotation speed Nl (rpm) of one fan and the rotation speed N2 of the other fan
(rpm) are equal, the rotation sound frequency (NI XZ) of the fans.

N2XZ) coincide, and a resonance phenomenon occurs. Furthermore, even if the rotational speeds Nl and N2 of the fans are not equal, if the rotational speeds of both fans are close to each other, the rotational speed of the two fans is (Nl - N2)XZ
A whirring sound occurs. Therefore, as one of these prevention techniques, the number of revolutions of a plurality of propeller fans is made to be significantly different.

(Problem to be solved by the invention) However, even if the rotation speeds of the fans are made to differ significantly, the fan rotation speed is determined by the air blowing load, so depending on the load condition, the fan rotation speeds may approach each other, causing abnormal Resonance/beating noise occurs.

The present invention has been made in consideration of the above-mentioned circumstances, and an object of the present invention is to prevent the resonance/beating noise peculiar to an outdoor unit of an air conditioner having a plurality of multi-blade fans.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention sets the number of blades of a plurality of multi-blade fans arranged in an outdoor unit of an air conditioner to a common common divisor. It is an elementary relationship.

(Function) Since the number of blades of multiple multi-blade fans has a prime relationship with each other with no common divisor, abnormal noise such as resonance or humming will not occur even if these multiple multi-blade fans are operated at the same time. .

(Example) FIG. 1 is a typical example of an outdoor unit of an air conditioner having a plurality of multi-blade fans. In this outdoor unit 1, two propeller fans 2.3 as multi-blade fans are arranged adjacent to each other, and each is rotationally driven by a fan motor 4.5. 6 is a heat exchanger, and 7 is a compressor.

Two propeller fans? , 3, one propeller fan 2 has 7 blades as shown in Fig. 2, and the other propeller fan 3 has 4 blades as shown in Fig. 3. The relationship between the number of sheets, 7 and 4, is a prime relationship with no common divisor.

FIG. 4 shows a time axis waveform of the rotation sound of one propeller fan 2. Now, the rotation speed of this propeller fan 2 is NA
(rps), and the number of blades is ZA, then 1/ (N
A rotating sound with a period of AZA) is generated.

FIG. 5 is a time axis waveform of the rotation sound of the other propeller fan 3. Now, set the rotation speed of this propeller fan 2 to NB (
rps) and the number of blades is ZB, then 1/(N
A rotating sound with a period of B ZB') is generated.

FIG. 6 shows the whirring phenomenon between the two propeller fans 2.3 when they are operated simultaneously.

The beat period is 1/INA ZA -NB ZB I
In general, the larger the beat period, the greater the intermittentness of the beat sound, so the denominator INAZA-NB Z
Increasing B l is effective as a means to remove the beat sound from the audible range.

Comparing the cases of this embodiment in which the number of blades of the propeller fan 2.3 is 7 and 4, these rotational speeds are NA =
100Orpm, NB = 100Orpm, N
Since A ZA = 106Hz and NB ZB = 64Hz, l NA ZA -NB ZB 1 = 42Hz
As a result, the humming noise becomes intermittently difficult to hear.

In addition to the fundamental frequency NZ, the rotation sound of the blades also includes harmonic components such as double harmonic 2NZ and triple harmonic 3NZ. By making the number of blades relatively prime, it is possible to prevent such high-frequency humming noise.

In the above embodiment, the number of blades of the plurality of multi-quality fans is 7,
Although the case where there are four blades is taken as an example, the number of blades only needs to be in a relatively prime relationship with no common divisor, and therefore the relationship between an odd number of blades or between an odd number and an even number may be used.

[Effects of the Invention] As described above, the present invention prevents the generation of noise such as resonance and buzzing of the fan air blowing sound by a simple means of changing the number of blades in an outdoor unit of an air conditioner having a plurality of multi-blade fans. It can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a diagram showing an example of the structure of an outdoor unit of an air conditioner having two multi-blade fans, Fig. 2 is a diagram showing one of the multi-blade fans, and Fig. 3 is a diagram showing the other multi-blade fan. , 4th
The figure shows the time axis waveform of the rotation sound of the multi-blade fan in Fig. 2, Figure 5 shows the time axis waveform of the rotation sound of the multi-blade fan in Fig. 3, and Figure 6 shows the time axis waveform of the rotation sound of the multi-blade fan in Fig. 2. 4 is a diagram showing a time-axis waveform of a humming sound when the multi-blade fan of FIG. 3 is operated simultaneously. FIG. In the figure, l is an outdoor unit, 2.3 is a propeller fan, and 4
．． 5 indicates a fan motor.

Claims (1)

[Claims] An outdoor unit of an air conditioner having a plurality of multi-blade fans, characterized in that the number of blades of the plurality of multi-blade fans arranged in the outdoor unit of the air conditioner are in a prime relationship with no common divisor.