JPS59600A - Low-noise fluid shifter - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a low-noise system comprising a case having an acoustic chamber connected to the interior of the case by at least one sound propagating opening and a nine-turn impeller fitted therein. The present invention relates to a fluid moving device.

The substantial source part for a rotary sound source in the case of a radial fluid displacement device without guide wheels lies in the case protrusion, where the circumferential wall of the case is transformed into a duct by means of a bend. In this respect, the helical case has the smallest diameter.

In the case of an axial displacement device, radial guide vanes supporting the circumferential earring of the impeller and mounted across the flow groove form the substantial sound source.

In the case of fluid displacement devices, it is known to provide a perforated wall in the case protrusion or in the bent part of the guide vane in order to arrange the resonator behind it (European Patent Application No. 003).
No. 9459). This resonator has an actual interference sound frequency of λ/
It is of type 4. The standing wave contains vibrations in phase opposite to the vibrations of the rotating sound, thereby canceling out the rotating sound portion. The interfering rotational noise of the fluid moving device is substantially attenuated.

A drawback of conventional sound compensation is that a λ/4 type resonator must be tuned to each parasitic frequency, and this frequency is substantially dependent on the velocity of the fluid moving device. If the speed is variable, a constant adjustment of the length of the λ/4 resonator is required according to the respective speed.

It is an object of the invention to provide a low-noise fluid movement device of the above type, in which the sound compensation is automatically adjusted in response to changes in the speed of the device.

To solve this problem, the present invention provides an acoustic chamber with an inverse sound source excited by a frequency that varies according to the speed of the impeller.

A reverse sound source is an active sound source or loudspeaker. The sound source described above operates with a frequency that varies depending on the speed of the impeller. In this way, the frequency of the inverse sound source is automatically adjusted depending on the respective speed of the impeller. The counter-sound source should, if possible, have an opposite phase depending on the amount of frequency interference of the rotating sound, thereby ensuring that said amount of rotating sound and the transmitted sound are at least partially extinguished. produce sound. As a result, the noise level is lower.

Contrary to the prior art, a fluid moving device according to the present invention comprises:
In other words, it does not have a resonator with a fixed or variable resonant frequency, but a compensating back source that is effective in the actual source region of the rotating sound. -ing

Preferably, the inverse sound source is operated by an adjustable phase shifting circuit such that the phase position of the transmitted sound is displaced by 180° relative to the phase position of the rotating sound. Such a phase shift is easily accomplished and manually controllable. The reason for this is that the phase of the excitation signal of the inverse sound source must be shifted as far as possible to achieve the lowest rotational sound level relative to human hearing ability. It is possible to automatically adjust the phase shift circuit to set the most effective corresponding phase position. For this purpose, a blue transducer and a corresponding controller are required to produce the rotational sound.

The frequency at which the inverse sound source is activated can be obtained by a sensor responsive to an element rotating with the impeller drive shaft. In this regard, it is possible to mount the coding disc against the axis of the impeller in such a way that the marks pass by a contactless sensor that generates the pulses.Due to the respective distribution of the marks in the coding disc, the frequency of generation can be adjusted depending on the speed. Corresponds to a specific harmonic of the rotational tone shown. Typically, the main interference frequencies of noise in fluid moving devices are considered to be the vane frequency (speed x number of impeller blades) and its multiples. By subtracting the excitation frequency for the counter-sound source by the impeller speed from the velocity measurements, it is established that the frequency of the counter-sound source is always exactly equal to the frequency of the pressure change in fundamental aerodynamics.

According to another variant of the invention, the inverse sound source is activated by at least one pressure sensor that converts the noise into electrical vibrations. This pressure sensor may be a microphone located in the area of the source of the interference noise. The counter-sound source is controlled by a control circuit in such a way that the pressure fluctuations formed at the point of the pressure sensor have only a minimum amplitude.

According to a further advantageous embodiment of the invention, several inverse sound sources operating with different frequencies can be provided. This reverse sound source can be commonly controlled by one sensor, or can be controlled by different sensors. The sensors located in different parts of the case each have different frequency sensitivities.

In the fluid moving device of the present invention, the intended shape and geometrical dimensions of the case do not need to be changed depending on the amount of sound source.

Therefore, the features and effectiveness of the fluid transfer machine remain unchanged.

Hereinafter, the present invention will be described in detail with reference to embodiments shown in the accompanying drawings.

FIG. 1 shows an axial displacement device comprising a casing 10 having a spiral-shaped peripheral wall 11 connected to the outer wall of a tangential duct 12.

In the casing 10, an impeller 13 with blades 14
is pivoted. The drive shaft on which the impeller 13 is mounted is not shown in FIG. 1 for better visibility. - the point at which the pivot wall 11 of one casing has the shortest diameter with respect to the axis of the impeller 13 is closed by a casing projection with a bending section such that the casing 11 changes the upper wall 16 of the duct 12;

In fact, the casing protrusion 15 is a substantial source of rotational noise.

The housing projection 15 is a wall with a large number of holes leading into the closed sound source chamber 17 behind it. All of the walls of the sound source chamber 17 are covered, except for the opening of the casing protrusion 15 and the part where the loudspeaker 18 is mounted.
It's closed. The latter operation will be described later, but this loudspeaker transmits sound into the acoustic chamber 17 to the hole in the casing protrusion 15; It forms a sub-sound source that creates acoustic vibrations.

According to FIG. 2, a sensor placed next to a signal board 20 attached to the drive shaft 19 of the impeller 13 produces an electrical pulse in response to each passing mark. This pulse is applied to a phase shifting circuit 22 which allows the phase position of the pulse to be manually changed instantaneously. In its simplest configuration, phase shift circuit 22 consists of a delay circuit or RC element.

The output of phase shift circuit 22 is for the amplifier of loudspeaker 18. The frequency at which the amplifier operates is equal to the number of revolutions of the drive shaft 10 multiplied by the number of marks on the coding disk 20. If the loudspeaker operates at a lower frequency, a frequency divider circuit can be connected after the sensor +j-21 to create a pulse rather than to destroy the frequencies one after the other.

According to the principles of the invention, the sub-sound source with the loudspeaker 18 is
Produces a sound having a frequency equal to the frequency of the interfering element of the rotating sound. If the phase shift circuit 22 and amplifier are set optimally,
The corresponding rotary sound component and the sound transmission produced by the loudspeaker 18 at least partially cancel each other out in the area of the housing projection 15 .

In the embodiment of FIG. 3, a microphone 24 is provided in the casing 1 for receiving the rotational sound produced by the casing protrusion 15 and for supplying an electrical signal corresponding to the amplifier 25.
0 covers it. By means of the phase shift circuit 22, the output signal of the amplifier is directed into the acoustic chamber 17 and reaches the loudspeaker 18, as shown in FIG. The phase shift circuit 22 is adjusted so that the amplitude of the rotational sound that can be heard is the minimum value. Furthermore, the level of the reverse sound source may be changed by the loudspeaker 25.

According to another embodiment, the counter-source control microphone is positioned at a suitable point inside or outside the fluid displacement device. Here, a reduction in noise level is particularly desirable. That is, it is desirable to attach it to a chamber connected to a fluid moving device.

The shape of the hole in the casing protrusion 15 may be arbitrary.

It is also possible to provide the perforated wall with an opening that is closed by a diaphragm.

The counter-sound source can be a diaphragm arranged in a casing projection, or it can also be activated directly by a vibration generator (non-uniform propagation noise generator).

The present invention applies to all fluid moving devices, i.e. fans.
, blower, ventilator 1
Alternatively, it can be used in a multi-stage compressor, compressor, compressor, and pump.

[Brief explanation of drawings]

FIG. 1 is a schematic perspective view of the trickle moving device, FIG. 2 is a schematic diagram showing the operating state of the reverse sound source, and FIG. 3 is a schematic diagram of the second embodiment showing the operating state of the sound source. be. 10... Gauging, 13... Impeller, 17...
Sound source room, 18... Loudspeaker, 2o... Signal board, 22.
...Phase shift circuit, 24...Microphone.

Claims (1)

Claims: (1) In an apparatus comprising a case having an acoustic chamber coupled to an interior chamber of the case by at least one acoustic propagation opening and a rotary impeller fitted therein, the acoustic chamber (17 )
A low-noise fluid movement device, characterized in that the counter-sound source (18) located at is activated by a frequency that varies depending on the speed of the impeller (13). (2) The inverse sound source (18) is connected to the adjustable external phase conversion circuit (2).
2) A fluid moving device according to claim 1, characterized in that it operates according to 2). (3) A sensor (21) that acts on an element that rotates together with the rotation shaft (19) of the rotary impeller (13) detects a reverse sound source (
18) A fluid displacement device according to claim 1 or 2, characterized in that it generates a signal for the periodic actuation of: <4) at least one pressure sensor (24) comprising: A fluid displacement device according to claim 1, characterized in that it converts fiber sound into electrical vibrations and that its output signal - amplification and phase shifting being selective - activates a counter-sound source. (5) The fluid moving device according to claim 1, wherein the plurality of inverse sound sources are operated at different frequencies. (6) A fluid displacement device according to claim 1, characterized in that the acoustic chamber (17) is closed to the interior of the case by a perforated wall. (7) A fluid displacement device according to claim 1, characterized in that the acoustic chamber (17) is closed to the interior of the case by a diaphragm.