JPS6220713A - Noise reducing device of air conditioning device - Google Patents

Abstract

PURPOSE:To enable reduction of the generation of noise, by a method wherein noise is detected to fetch it as an electric signal, which produces a signal in a reverse phase, and further, through regulation of a level depending upon an air conditioning mode, sound wave in a reverse phase and having the same level as that of noise is radiated from a sound generating means. CONSTITUTION:An output from a microphone 1 for detection of noise is inputted as a signal of a given frequency range to an inverter 5 after a very low frequency range is cut through a pre-amplifier 3 and a filter circuit 4. Phase inversion is made on the signal by the inverter 5 to output it to a power amplifier 6. Meanwhile, signals 10-12 from an air conditioning mode detecting circuit 9 are inputted to a power amplifier 6 through a power amplifier control circuit 7, and the degree of amplification of the power of the power amplifier 6 is decided by an air conditioning mode 9. A signal 5 in a reverse phase is regulated by the air conditioning mode to radiate it through a speaker 8. This causes erasing of noise, resulting in reduction of the generation of noise.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a noise reduction device for an air conditioner, particularly an automatic sound air conditioner.

[Prior art and problems to be solved by the invention]

In recent years, as the quality of vehicles has improved, the demand for low noise inside the vehicle interior has increased significantly.In particular, the noise generated by automotive air conditioners is especially loud, so there is a need to develop low noise air conditioners. I'm in a situation where I can't.

However, the noise of air conditioners varies depending on the air conditioning mode (ventilation,
The sound pressure level varies depending on the location (heating, etc.).
A satisfactory device capable of reducing noise having such different sound pressure levels has not yet been obtained.

In view of the above circumstances, an object of the present invention is to provide one form of a device that can reduce the noise generated by an air conditioner even under conditions where the sound pressure level of the noise differs. .

[Means for solving problems]

According to the present invention, a sound generating means provided on a noise propagation path of an air conditioner, a sound generating means provided upstream of the sound generating means on the noise propagation path detects the noise, and converts the noise into an electrical signal. a noise detection and conversion means that converts the signal into a signal and outputs it; an air conditioning mode detection means that detects the air conditioning mode of the air conditioner; noise control means for adjusting the level of the signal of the opposite phase generated according to the air conditioning mode detected by the air conditioning mode detection means, and supplying the level-adjusted signal to the sound generation means; Thereby, there is provided a noise reduction device for an air conditioner, characterized in that a sound wave having substantially the same sound pressure level as the noise of the air conditioner and having an opposite phase is generated from the sound generating means. be done.

[For production]

Noise generated by the air conditioner is detected by the noise detection and conversion means, converted into an electrical signal, and inputted to the noise control means. On the other hand, the air conditioning mode of the air conditioner is detected by the air conditioning mode detection means and input to the noise control means. The noise control means inverts the phase of the electrical signal from the noise detection degree conversion means, adjusts the level of the phase-inverted signal according to the air conditioning mode detected by the air conditioning mode detection means,
Supplied to sound generating means. Thereby, the sound waves from the sound generating means are generated at approximately the same sound pressure level as the noise of the air conditioner.

That is, even if the sound pressure level of the noise varies depending on the air conditioning mode, the noise generated by the air conditioner can be reduced by the sound wave interference effect of the sound waves radiated from the sound generating means.

〔Example〕

A noise reduction device as an embodiment of the present invention is shown schematically in FIG. 1 together with an air conditioner for an automobile, and in more detail in FIG. 2.

First, the configuration of this device including the air conditioner will be explained. The fan 21 receives driving force from the motor 23 and rotates.
Air (indicated by arrow a) is sucked in from the suction port 25 (intake port having an internal air port, external air port, switching damper 24a, etc.) of the internal/external air switching box 24. This air is rectified in one direction by the scroll casing 22, and then discharged. It is discharged from the outlet 26 (
The discharged air is conditioned by the cooling heat exchanger 27 and the heating heat exchanger 28, and is operated in various modes (ventilation (VENT), heater (IIεAT)
), the defrost l-(DuF)) is discharged into the passenger compartment through a duct that connects the outlet and the passenger compartment (indicated by arrow C).

The microphone 1 for detecting the noise of the fan 21 is installed near the discharge port 26 of the scroll casing 22 at a position that does not impede the airflow. This microphone 1 detects the noise generated by the fan 21, converts it into an electrical signal, and outputs it to the noise control circuit 2.

FIG. 3 shows the apparatus shown in FIGS. 1 and 2 in block form. This will be explained below with reference to FIG.

In the noise control circuit 2, the preamplifier 3 is the microphone 1.
The noise signal output from the filter circuit 4 is amplified and transmitted to the filter circuit 4. This filter circuit 4 filters noise signals inputted from the microphone 1 via the preamplifier 3 in an extremely low frequency range (50H or less) and a high frequency range (200H or less).
0H and above) and outputs a signal in a predetermined frequency range to the inverter 5.

The inverter 5 inverts the phase of the signal in this predetermined frequency range and outputs it to the power amplifier 6.

On the other hand, the power amplifier control circuit 7 has a function of selecting one of the power amplification degrees for the power amplifier 6 which has power amplification degrees set in a plurality of stages (four stages in the example shown in FIG. 4). have. This selection of the power amplification degree is performed according to the air conditioning mode detected by an air conditioning mode detection circuit 9, which will be described later.

An acoustic speaker 8 is connected to the rear stage of the power amplifier 6, and the speaker 8 is provided on the wall of the duct between the discharge port 26 and the cooling heat exchanger 27, as shown in FIG. There is. The location where the speaker 8 is provided is preferably on the downstream side of the location where the microphone 1 is installed on the noise propagation path.

On the other hand, the air conditioning mode detection circuit 9 is connected to the fan speed detection circuit 10. Inside air/outside air mode detection circuit 11 and VENT
- IIEAT (DEF) Consists of mode detection circuit 12.

The fan speed detection circuit 10 includes a relay circuit 30 (relay 3
0a (L mode), 30b (M mode) and 30c (H mode)) and outputs them to the power amplifier control circuit 7.

The inside air/outside air mode detection circuit 11 detects inside air or outside air mode using a limit switch 31 that is turned on and off depending on the position of the switching damper 24a, and outputs the detected mode to the power amplifier control circuit 7.

VENT-F! EAT(DEF)-11-- The mode detection circuit 12 is turned on and off depending on the position of the damper 32, or is turned on or off by the mint switch 33.
) -E-)' is detected and output to the power amplifier control circuit 7.

The four levels of power amplification of the power amplifier 6 controlled by the power amplifier control circuit 7 are set to approximately the same level as the fan noise, depending on the combination of various modes detected by the air conditioning mode detection circuit 9. It has been adjusted. However, since fan noise is hardly a problem when the fan speed is in L mode or off mode, power amplification is not performed.

Preferably, the time required for the noise detected by the microphone 1 to reach the speaker 8 via the noise control circuit 2, and the propagation of this same noise in the duct from the location where the microphone 1 is installed to the location where the speaker 8 is installed, are also preferably determined. The time required to do this is set equal. In order to perform this adjustment, it is necessary to make the filter circuit 4 in the noise control circuit 2 wait for the delay characteristics, and examples of the circuit configuration are shown in FIGS. 6, 7, and 8.

Now, let's say that the input and output characteristics of microphone 1 are G.

If the input/output characteristic of the speaker 8 is Gs, and the spatial transfer characteristic between the microphone and the speaker is aSS, then the filter circuit 4 has a delay characteristic (see Fig. 5) calculated by G = Gxs/(GW x Gs). Must be.

In FIG. 5, when the frequency bands r and -r, that is, the gain is almost constant and the phase is only delayed,
For example, as shown in FIG. 6, the filter section can be constructed using a solid state delay element (bucket brigade device (BBD)).

Furthermore, as shown in FIG. 7, a certain degree of delay adjustment is also possible using an equalizer of several bands.

Furthermore, in the case where the microphone and speaker are installed at a particularly large distance, calculation time for configuring the digital filter can be secured, so that implementation is also possible (see FIG. 8). In this case, assuming that it constitutes an FIR filter, a desired signal can be obtained by convolving the impulse response obtained by inverse Fourier transform of the phase/gain characteristics shown in FIG. 5 and the input signal.

Next, the operation of the apparatus shown in FIGS. 1 and 2 will be explained with reference to FIGS. 3 and 4.

First, noise is generated as the fan 21 rotates. At this time, fan speed, inside air or outside air mode, VEN
T or I (EAT(DEF) Mo 1' Niyo JI),
++7) Noise levels vary. Assume now that the detected fan speed is M mode, and that the inside air mode and VENT mode are detected.

In this case, the power amplification degree of the power amplifier 6 to be set becomes a level "1" as shown in FIG. 4.

On the other hand, noise from the fan 21 is detected by the microphone 1, converted into an electrical signal, and transmitted to the noise control circuit 2.

In the noise control circuit 2, this electrical signal of noise is amplified through a preamplifier 3, and filtered by a filter circuit 4 with a predetermined delay time into frequency components of a predetermined bandwidth (bands f and ft in FIG. 5). corresponding) are filtered out. Furthermore, this signal in the predetermined frequency range is phase-inverted by the inverter 5, power-amplified by the power amplifier 6 to the above-mentioned 1'' level, and then transmitted to the acoustic speaker 8.

In this way, the acoustic speaker 8 emits sound waves that have almost the same sound pressure level as the noise generated by the fan 21 and have an opposite phase. noise is reduced.

Although the apparatus shown in FIG. 2 uses the acoustic speaker 8 as the sound generating means, it is also possible to use other types of means. For example, FIG. 9 shows a sound generating means consisting of a ceramic vibrator 8a and a vibration transmission plate 8b.

In FIG. 9, the vibration transmission plate 8b is attached to the case 3 of the heat exchanger 27 in order to prevent disturbance of the air flow (indicated by the arrow) and to amplify the vibration of the vibrator 8a. This part is molded so that a part of it protrudes,
It is provided with an L-shaped configuration. A ceramic vibrator 8a is fixed to the vibration transmission plate 8b, and preferably a notch 8c is provided in the vibration transmission plate 8b so that the case 34 does not vibrate.

Although the frequency characteristics of fan noise are not taken into account in the above embodiments, if it is taken into account that not only the sound pressure level but also the frequency characteristics of fan noise differ depending on various modes and fan speeds, it is possible to A circuit can be added to control the power amplification degree of the power amplifier to suit the frequency characteristics of the noise. - Also, in the apparatus shown in FIGS. 2 and 9,
Although the power amplification degree of the power amplifier 6 is set to four stages, it is not limited thereto and can be set to any number of stages other than four stages.

Furthermore, it is also possible to arrange the microphone l on the suction side of the fan 21, that is, on the inside/outside air switching box 24. In this case, the acoustic speaker 8. Alternatively, the vibrator 8a and the vibration transmission plate 8b are also arranged in the inside/outside air switching box 24.

〔Effect of the invention〕

According to the present invention, even if the sound pressure level of the noise differs depending on the air conditioning mode of the air conditioner, it is possible to radiate a sound wave with an opposite phase to the noise corresponding to each sound pressure level of the noise, thereby eliminating sound wave interference. As a result, the noise of the air conditioner can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a block diagram schematically showing a noise reduction device as an embodiment of the present invention together with an air conditioner. FIG. 2 is a detailed configuration diagram of the apparatus shown in FIG. 1. FIG. 3 is a block diagram of the noise reduction device shown in FIGS. 1 and 2. FIG. 4 is a diagram showing an example of the configuration of the power amplifier control circuit in FIG. 3. FIG. 5 is a phase/gain characteristic diagram of the filter circuit in FIG. 3. FIGS. 6 to 8 are diagrams showing configuration examples of filter circuits. FIG. 9 is a diagram showing a modification of the sound generating means. It is. 1...Microphone, 2...Noise control circuit. 3...Preamplifier. 4, 4a, 4b, 4cm filter circuit. 5... Inverter, 6... Power amplifier. 7...Power amplifier control circuit. 8...Speaker for acoustics. 8a... vibrator, 8b... vibration transmission plate. 9...Air conditioning mode detection circuit. 10...Fan speed detection circuit. 11...Inside air/outside air mode detection circuit. 12 ・VENT ・IIEAT (DEF)
'Detection circuit. 21...Fan, 30a-30c...Relay. 31, 33...Limit switch.

Claims (4)

[Claims] 1. A sound generating means provided on a noise propagation path of an air conditioner, a sound generating means provided upstream of the sound generating means on the noise propagation path, detects the noise, converts the noise into an electrical signal, and outputs it. a noise detection conversion means; an air conditioning mode detection means for detecting an air conditioning mode of the air conditioner; noise control means for adjusting the level of the signal according to the air conditioning mode detected by the air conditioning mode detecting means and supplying the level-adjusted signal to the sound generating means, thereby reducing the noise of the air conditioner. 1. A noise reduction device for an air conditioner, characterized in that a sound wave having substantially the same sound pressure level as the sound pressure level and having an opposite phase is generated from the sound generating means. 2. 2. The apparatus according to claim 1, wherein said sound generating means is an acoustic speaker. 3. The sound generating means includes a vibrator that vibrates in response to a signal supplied from the noise control means, and a vibration transmission plate to which the vibrator is fixed and which amplifies the vibration of the vibrator and radiates the signal. An apparatus as claimed in claim 1 comprising: 4. The noise control means includes a power amplifier that amplifies the signal supplied to the sound generation means, and a power amplifier that controls the power amplification degree of the power amplifier according to the air conditioning mode detected by the air conditioning mode detection means. 2. The apparatus of claim 1, including a control circuit.