JP2006211770A - Rotating machine and operation method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rotating machine and operation method capable of suppressing noises without impairing ventilation characteristics with simple configuration. <P>SOLUTION: This machine, including a cooling fan 11 mounted on an shaft end of a rotating machine body 1 and a fan cover 12 covering the cooling fan 11, sucking air from a suction opening 16 of the fan cover 12 and discharging air from a discharge opening 17 to an outer periphery section of the machine body 1, is structured so that a frequency f<SB>z</SB>of vane rotating noise and a frequency of an integral multiple of f<SB>z</SB>may not meet or approximate a Helmholtz resonance frequency of a space in the fan cover 12. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a rotating machine such as an induction motor provided with a cooling fan outside a main body and a method for operating the same.

  A conventional rotating machine such as an induction motor provided with a cooling fan outside the main unit will be described with reference to FIG. The rotating machine body 1 includes a cylindrical stator frame 2 and a disk-shaped bearing bracket 3. A stator core 4 is fixed to the inner peripheral surface of the stator frame 2, and the stator core 4 is attached to the stator core 4. A stator winding 5 is wound. Inside the stator core 4, a rotor 6 is disposed with a predetermined interval, and a rotating shaft 7 of the rotor 6 is supported by the bearing bracket 3 via a bearing 8. Both ends of the rotating shaft 7 are configured to protrude outward from the rotating machine body 1. A plurality of cooling fins 9 are formed on the outer peripheral surface of the stator frame 2 in the direction along the rotation shaft 7, and a ventilation path is formed between the cooling fins 9.

  A cooling fan 11 having, for example, eight blades is attached to the left end portion of the rotating shaft 7 opposite to the load side end portion, and is configured to rotate integrally with the rotating shaft 7. Yes. A fan cover 12 is attached to the left bearing bracket 3 so as to cover the cooling fan 11, for example, by screwing. An intake port 16 is formed on the left end surface of the fan cover 12 facing the cooling fan 11.

  In the rotating machine configured as described above, when the rotor 6 is driven to rotate and the cooling fan 11 rotates, air is sucked from the intake port 16 as indicated by an arrow B by the air blowing action. The sucked air is blown from the discharge ports 17 to the cooling fins 9 by the cooling fan 11, thereby cooling the rotating machine body 1.

The noise during the operation of the rotating machine having such a configuration (for example, the rotation frequency F is 4200 rpm (rotation / min) = 70 Hz) was investigated. FIG. 12 shows the result of frequency analysis of the noise waveform obtained by the sound level meter using FFT. From this result, it can be seen that if the rotation frequency is F and the number of blades is Z, noise with a dominant frequency f _Z (= F · Z = 70 × 8 = 560 Hz) is generated greatly. The f _Z component is called generally blade rotation noise.

  Furthermore, a fine jagged spectrum can be seen in the entire frequency range. This is noise generated by vortex, separation, or flow disturbance generated by blade rotation, and is generally referred to as random noise.

  FIG. 13 is a system diagram summarizing the causes of the cooling fan noise. The cooling fan noise can be roughly classified into two types, one is noise from a noise generation source, and the other is noise from a noise propagation path. Regarding the former, 1. 1. noise generated by rotating blades; 2. Noise caused by vortices and separation generated by blades; There is noise due to turbulence. For the latter, there is resonant noise in the space inside the fan cover. Therefore, there are two methods for reducing noise leaking from the fan cover: a method for suppressing the noise source itself and a method for suppressing noise in the noise propagation path.

  In the prior art, as a method of suppressing the noise source itself, 1. Make the blade spacing uneven. It is disclosed that the blade shape is streamlined. In the prior art, as a method of suppressing the propagation path of the cooling fan noise, there is a method of reducing noise with a silencer, which is disclosed, for example, in Patent Document 1 below.

  As shown in FIG. 14, a fan cover 12 is arranged so as to cover a cooling fan 11 attached to the left end of a rotating machine body 1, and a porous plastic is disposed on the inner surface of the fan cover 12. A sound absorbing member 14 made of glass wool, felt rock wool or the like is attached. However, in a sound absorbing device with a sound absorbing member attached, the sound absorbing member deteriorates with age, and the sound absorbing member must be replaced each time. There is a specification that the rotary machine is maintenance-free for 10 years, and the sound absorbing member may not be used.

As a silencer that does not rely on a sound absorbing member, a double-structure fan cover disclosed in Patent Document 2 is known. As shown in FIG. 15, a cooling fan 11 is attached to the left end of a rotating machine body 1 having a rotor 6 and a stator core 4 inside, and a fan cover 12a having a double structure is formed so as to surround the cooling fan 11. 12b is arranged. However, such a double-structure fan cover improves the sound insulation performance but may impair the ventilation characteristics. Moreover, since the dimension of the rotating machine in the axial direction becomes large, the space for mounting the rotating machine must be widened. In addition, there are problems such as increased costs.
Japanese Patent Laid-Open No. 62-217833 JP-A-7-298545

  The present invention has been made in view of the above situation, and an object of the present invention is to provide a rotating machine with a simple configuration and reduced noise without impairing ventilation characteristics, and an operation method thereof.

In order to achieve the above object, the invention of claim 1 is provided with a cooling fan attached to a shaft end of a rotating machine body and a fan cover that covers the cooling fan, and sucks air from the intake port of the fan cover and rotates from the discharge port. in the rotating machine which is adapted spit air to the outer peripheral portion of the machine body, so that the Helmholtz resonant frequency of the space inside the fan cover an integral multiple of the frequency of the frequency f _Z and f _Z of the blade rotation noise do not match or approximate The configuration is as follows.

The invention according to claim 7 is provided with a cooling fan attached to the shaft end of the rotating machine body and a fan cover covering the cooling fan, and sucks air from the air inlet of the fan cover and discharges air from the discharge port to the outer periphery of the rotating machine body. method of operating a rotary machine so as to spit, and how to prevent the match or approximate the Helmholtz resonance frequency f of the space between the integral multiple of the frequency of the frequency f _Z and f _Z the fan inside the cover of the blade rotation noise To do.

  According to the present invention, it is possible to provide a rotating machine with a simple configuration and reduced noise without impairing ventilation characteristics and an operation method thereof.

Hereinafter, rotating machines according to first to sixth embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
As shown in FIG. 1, the rotating machine of the present embodiment includes a cooling fan 11 attached to the shaft end of the rotating machine body 1 and a fan cover 12 that covers the cooling fan 11. in the rotating machine which is adapted spit air to the outer peripheral portion of the rotating machine main body 1 from the suction discharge port 17, the Helmholtz resonance frequency of the frequency f _Z and f _Z an integral multiple of the frequency and spatial fan cover 12 of the blade rotation noise And are not matched or approximated.

ここで、ｃは音速、Ｌはファンカバーの板厚さ、ｄはファンカバーの入口直径、Ｓはファンカバーの入口断面積であり、

である。 Here, when the number of fan blades is Z and the rotation frequency of the rotating machine is F, f _Z = F × Z. The Helmholtz resonance frequency f is calculated by the following equation (1).

Here, c is the speed of sound, L is the thickness of the fan cover, d is the diameter of the fan cover inlet, and S is the inlet cross-sectional area of the fan cover.

It is.

  FIG. 2 shows the resonance characteristics of the fan cover 12 having an inlet diameter d = 0.49 m. The resonance frequency of the fan cover 12 was measured by generating white noise by placing a speaker inside the fan cover 12. It can be seen from the waveform in FIG. 2 that there is a resonance frequency at 580 Hz.

  That is, 580 Hz is the Helmholtz resonance frequency inside the fan cover 12 shown in FIG. The Helmholtz resonance frequency f calculated by the above equation (1) is also 580 Hz.

The noise when the number of blades Z = 8 and the rotational frequency F = 60 Hz was measured with a sound level meter and subjected to FFT analysis is shown in FIG. Normally, the blade rotation sound frequency f _Z = 480 Hz appears predominantly, but it can be seen from FIG. 3 that the blade rotation sound frequency does not occur predominantly.

Thus rotating machine of the embodiment, and the volume V of the cavity of the fan cover 12, the plate thickness L of the fan cover 12, the cross-sectional area S of the air inlet of the fan cover 12 to the parameter, blade rotation noise f _Z By making the fan cover 12 shape such that the frequency of (rotation frequency F × fan blade count Z, f _Z = F × Z) and the Helmholtz resonance frequency of the space in the fan cover are not approximate, Sound can be reduced, and noise can be effectively reduced.

(Second Embodiment)
A second embodiment of the present invention is shown in FIGS.
In the rotating machine according to the present embodiment, the shape of the intake port 16 is substantially circular (see FIG. 1) suitable for processing the fan cover 12 so that the inlet cross-sectional area S of the fan cover 12 can be easily calculated in the equation (1). 4) Or a substantially square shape (FIG. 5). With this configuration, the Helmholtz resonance frequency can be accurately calculated, and the blade rotation noise can be reduced, so that noise can be effectively reduced.
As another action, the inlet cross-sectional area S of the intake port 16 in the substantially quadrangular shape (FIG. 5) can be larger than that of the substantially circular shape (FIG. 4).

(Third embodiment)
As shown in FIG. 6, the rotating machine according to the third embodiment of the present invention has a plurality of air inlets in the fan cover 12 so that the inlet cross-sectional area S of the fan cover 12 can be easily calculated in the equation (1). 16, 16a are provided. As a result, blade rotation noise can be reduced, so that noise can be effectively reduced.

  As another function, since the flow of air flowing into the fan cover 12 can be dispersed and the flow velocity can be reduced, noise can be effectively reduced. Further, as another action, the inlet cross-sectional area of the intake ports 16 and 16a can be easily changed, so that it is possible to easily cope with the case of changing the rotational speed.

(Fourth embodiment)
As shown in FIG. 7, the rotating machine according to the present embodiment has a blade rotation sound f _Z (rotation frequency F × number of fan blades Z, f _Z = F × Z) and a Helmholtz in the space in the fan cover 12. In order to set the plate thickness of the fan cover 12 and the cross-sectional area of the air inlet 16 of the fan cover 12 so that the resonance frequency is not approximated, an elastic member 18 is attached to the air inlet 16 of the fan cover 12 to generate blade rotation sound. The shape of the intake port 16 is taken into consideration. By doing in this way, since a blade | wing rotation sound can be reduced, a noise can be reduced effectively.

(Fifth embodiment)
As shown in FIGS. 8 to 9, the rotating machine according to the present embodiment reduces the radiated noise by providing a soundproof member 19 on the radially inner side of the intake port 16. FIG. 12 shows the FFT analysis result when the electric motor is operated at a rotational frequency of 4200 rpm (rotation / minute). From this result, it can be seen that a 560 Hz component is generated predominately. Therefore, what kind of sound pressure distribution was generated from where was measured using acoustic holography. From the result of acoustic holography, it was found that noise was radiated from the intake port 16. According to the present embodiment, as shown in FIGS. 8 to 9, the noise radiated can be reduced by providing the soundproofing member 19 on the inner side in the radial direction of the air inlet 16.

(Sixth embodiment)
In the present embodiment, as shown in FIG. 10, a sound absorbing member 20 is attached to the inner surface of the soundproof member 19 of the fan cover 12. Thereby, since a blade | wing rotation sound can be reduced, a noise can be reduced effectively.

  The first to sixth embodiments described above relate to a rotating electrical machine, but have a fan, for example, an electric motor, a blower, a compressor, a ventilation fan, an air conditioner, a jet fan, a board incorporating a fan, The present invention can also be applied to a housing incorporating a fan. Needless to say, the cooling fan 11 can have any shape such as a radial fan or a mixed flow fan.

1 is an axial sectional view showing a configuration of a rotating machine according to a first embodiment of the present invention. The graph which shows the resonance frequency waveform in the fan cover with an inlet diameter of 0.49 m, and demonstrates the effect | action of the rotary machine of the 1st Embodiment of this invention. The graph which shows the frequency analysis result which shows that the blade | wing rotation sound has disappeared, and demonstrates the effect of the rotary machine of the 1st Embodiment of this invention. The 1st structure of the rotary machine of the 2nd Embodiment of this invention is shown, (a) is an axial sectional view, (b) is the left view of (a). The 2nd structure of the rotary machine of the 2nd Embodiment of this invention is shown, (a) is axial direction sectional drawing, (b) is a left view of (a). The structure of the rotary machine of the 3rd Embodiment of this invention is shown, (a) is an axial sectional view, (b) is the left view of (a). The structure of the rotary machine of the 4th Embodiment of this invention is shown, (a) is an axial sectional view, (b) is the left view of (a). The 1st structure of the rotary machine of the 5th Embodiment of this invention is shown, (a) is an axial sectional view, (b) is the left view of (a). The 2nd structure of the rotary machine of the 5th Embodiment of this invention is shown, (a) is an axial sectional view, (b) is a left view of (a). The structure of the rotary machine of the 6th Embodiment of this invention is shown, (a) is axial sectional drawing, (b) is the left view of (a). The structure of the conventional rotary machine is shown, (a) is an axial sectional view, (b) is a left side view of (a). The graph which shows the frequency analysis result in the conventional rotary machine. The system diagram which shows the classification | category of a cooling fan noise. The axial sectional view of the conventional rotary machine which attached the sound-absorbing material to the inner periphery of the fan cover. An axial sectional view of a conventional rotating machine having a double fan cover structure.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Rotating machine main body, 2 ... Stator frame, 3 ... Bearing bracket, 4 ... Stator iron core, 5 ... Stator winding, 6 ... Rotor, 7 ... Rotating shaft, 8 ... Bearing, 9 ... Cooling fin, 11 DESCRIPTION OF SYMBOLS Cooling fan, 12, 12a, 12b ... Fan cover, 14 ... Sound absorption member, 16, 16a ... Intake port, 17 ... Discharge port, 18 ... Elastic member, 19 ... Sound insulation member, 20 ... Sound absorption member.

Claims (7)

A rotating machine having a cooling fan attached to a shaft end of a rotating machine body and a fan cover that covers the cooling fan, and sucking air from an intake port of the fan cover and discharging air from the discharge port to an outer peripheral part of the rotating machine body in the rotating machine being characterized in that so as not to match or approximate the Helmholtz resonance frequency of the spatial frequency f _Z and f the integral multiple of the frequency fan in the cover of the _Z of the blade rotation noise.   The rotating machine according to claim 1, wherein the shape of the air inlet of the fan cover is substantially round or square.   The rotating machine according to claim 1, wherein at least one air inlet of the fan cover is provided.   The rotating machine according to claim 1, wherein an elastic member is provided at an air inlet of the fan cover.   The rotating machine according to claim 1, further comprising a soundproofing member provided radially inward of the air inlet of the fan cover.   The rotating machine according to claim 5, further comprising a sound absorbing member inside the fan cover of the sound insulating member. A rotating machine having a cooling fan attached to a shaft end of a rotating machine body and a fan cover that covers the cooling fan, and sucking air from an intake port of the fan cover and discharging air from the discharge port to an outer peripheral part of the rotating machine body 5. the method of operation of the rotating machine, characterized in that to avoid the match or approximate the Helmholtz resonance frequency of the spatial frequency f _Z and f the integral multiple of the frequency fan in the cover of the _Z of the blade rotation noise operation .

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