EP2518414A1

EP2518414A1 - Air conditioner

Info

Publication number: EP2518414A1
Application number: EP10838843A
Authority: EP
Inventors: Satoshi Michihata; Masayuki Tsuji; Noboru Yashima
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2009-12-25
Filing date: 2010-05-20
Publication date: 2012-10-31
Also published as: JP2011137560A; CN102686951A; WO2011077602A1

Abstract

To provide an air-conditioning apparatus capable of performing highly accurate active noise reduction.

An air-conditioning apparatus 1 includes a housing in which an air inlet 3 and an air outlet 5 are formed, a blower fan 2 having an impeller 25, a heat exchanger 4, a noise detection microphone 6 that detects noise generated from the blower fan 2, a control speaker 8 that outputs a control sound which reduces the noise, a noise reduction effect detection microphone 9 that detects a noise reduction effect, and a signal processing device 10 that generates the control sound based on detection results of the noise detection microphone 6 and the noise reduction effect detection microphone 9. The noise detection microphone 6 is arranged in a cylindrical region A defined by an inscribed circle tangential to inner peripheral portions of blades of the impeller 25 in which the inscribed circle is extended in a direction of a rotation axis of the impeller 25, and is disposed on a stator blade attachment member 7 of the blower fan 2.

Description

Technical Field

The present invention relates to an air-conditioning apparatus to which noise reduction means that reduces noise of a blower fan and the like is attached.

Background Art

In order to reduce noise such as a driving sound of a blower fan or the like, passive noise reduction methods have been used such as sound absorption and sound insulation. However, it is known that these methods are effective for reduction of noise in a relatively high frequency band, but are less effective for noise in a low frequency band such as a rotating sound of a fan.
As an improved method of reducing noise, an active noise reduction method has been used that reduces noise by outputting from a speaker or the like a control sound which has the same amplitude as and a phase opposite to the noise and thereby interfering with the noise. Such an active noise reduction method typically includes a sound receiver (sensing microphone or the like), a signal processing device including a digital filter and an adaptation algorithm, a sound output device (control speaker or the like), and an error signal detection sensor (evaluation microphone or the like). Then, the sound receiver is disposed on a downstream side of the sound source so as to detect sound generated from the sound source, and a control signal having the same amplitude as and a phase opposite to the noise is produced based on the detected sound. The control signal produced by the signal processing device is input to the sound output unit, and is output as a control sound. Further, a control result of the active noise reduction is evaluated by the error signal detection sensor disposed at a control point at which noise is to be reduced, and a filter coefficient of the digital filter of the signal processing device is updated such that the error signal detected by the error signal detection sensor is minimized.
However, it is known that the above-described active noise reduction method cannot reduce noise unless spatial coherence of sound is obtained. In particular, in the case of a sound source such as a blower fan that produces an air current, if the sound receiver is located close to the sound source, coherence with the error signal detection sensor cannot be obtained due to a turbulent flow at an air outlet of the blower fan. Therefore, it has been necessary to increase the distance between the sound receiver and the sound source so as to reduce the effect of the turbulent flow.
In order to solve such a problem with the above-described active noise reduction method, for example, a noise reduction device has been proposed in which "a mesh type flow rectifying member 10 is arranged between a sound source (fan) 6 arranged in a flow passage in a duct 5 and a sound receiver 1 (sensing microphone). With this configuration, sound generated from the sound source 6, that is, a flow of fluid (air) that transmits the sound is rectified into a substantially uniform flow so as to obtain coherence. Therefore, it is possible to effectively perform active noise control even when the sound receiver 1 is disposed close to the sound source 6" (see Patent Literature 1, for example).
Further, for example, another noise reduction device has been proposed in which "a microphone 21 that detects noise generated by fan blades 23 of an air-sending device 20 and that supplies the detected noise as a reference signal x to a controller is provided inside a rotation shaft 31 of an electric motor 30 that rotates and drives the fan blades 23" (see Patent Literature 2, for example).

Citation List

Patent Literature

Patent Literature 1: Japanese Unexamined Patent Application Publication No. 5-188976 (Abstract, Fig. 1)
Patent Literature 2: Japanese Unexamined Patent Application Publication No. 5-289677 (Abstract, Fig. 2)

Summary of Invention

Technical Problem

However, in the noise reduction device disclosed in Patent Literature 1, since the flow rectifying member needs to be disposed between the blower fan and the sound receiver, the sound receiver cannot be arranged immediately under the fan. Therefore, the noise reduction device of Patent Literature 1 has a problem in that the size of the system cannot be reduced. Moreover, the noise reduction device of Patent Literature 1 has another problem in that the manufacturing cost is increased due to the increased number of components.
Meanwhile, in the noise reduction device disclosed in Patent Literature 2, the sound receiver may come into contact with the rotation shaft rotating at high speed. If the sound receiver comes into contact with the rotation shaft rotating at high speed, the sound receiver will detect abnormal sound generated by the contact. Further, this may result in malfunction of the sound receiver. Therefore, the noise reduction device of Patent Literature 2 has a problem in that the sound receiver needs to be installed so as not to be in contact with the rotation shaft, which allows little installation freedom. Moreover, the noise reduction device of Patent Literature 2 has another problem in that a precise installation is necessary, which makes the mechanism of the blower fan complex, and increases the cost of the blower fan.
The invention has been made to overcome the above-described problems and an object thereof is to provide an air-conditioning apparatus capable of performing highly accurate active noise reduction without increasing the number of components of a noise reduction device, and without changing a mechanism of a blower fan.

Solution to Problem

An air-conditioning apparatus according to the invention includes a housing in which an air inlet and an air outlet are formed; a blower fan having an impeller; a heat exchanger; a noise detection device detecting noise generated from the blower fan; a control sound output device outputting a control sound which reduces the noise; a noise reduction effect detection device detecting a noise reduction effect of the control sound; and a control sound generation device generating the control sound on the basis of detection results of the noise detection device and the noise reduction effect detection device, in which the noise detection device is arranged in a cylindrical region that is an inscribed circle, which is tangential to inner peripheral portions of blades of the impeller, extended in a direction of a rotation axis of the impeller and is disposed on an immobile member of the blower fan or a downstream side of the blower fan.

Advantageous Effects of Invention

In the air-conditioning apparatus according to the invention, the noise detection device is disposed in the cylindrical region defined by the inscribed circle tangential to the inner peripheral portions of the blades of the impeller in which the inscribed circle is extended in the direction of the rotation axis of the impeller, and is disposed on the immobile member of the blower fan or the downstream side of the blower fan. Accordingly, it is possible to provide an air-conditioning apparatus capable of performing highly accurate active noise reduction without increasing the number of components and without changing the mechanism of the blower fan.

Brief Description of Drawings

[Fig. 1] Fig. 1 is a cross-sectional view illustrating a configuration of an air-conditioning apparatus according to Embodiment 1 of the invention.
[Fig. 2] Fig. 2 is a front view of an air-conditioning apparatus according to Embodiment 1 through Embodiment 3 of the invention.
[Fig. 3] Fig. 3 is a bottom view of a blower fan according to Embodiment 1 of the invention.
[Fig. 4] Fig. 4 is a cross-sectional view of the blower fan shown in Fig. 3.
[Fig. 5] Fig. 5 is a diagram illustrating a signal processing device that generates a control sound according to Embodiment 1 of the invention.
[Fig. 6] Fig. 6 is a diagram illustrating the result of an experiment in which an air current blown from the blower fan of Embodiment 1 of the invention was visualized.
[Fig. 7] Fig. 7 is a circuit diagram of weighting means according to Embodiment 1 of the invention.
[Fig. 8] Fig. 8 is a chart illustrating coherence properties between a detected sound of a noise detection microphone 6 and a detected sound of a noise reduction effect detection microphone 9 when the blower fan 2 was operated in a case where the noise detection microphone 6 was disposed outside a cylindrical region A.
[Fig. 9] Fig. 9 is a chart illustrating coherence properties between a detected sound of the noise detection microphone 6 and a detected sound of the noise reduction effect detection microphone 9 when the blower fan 2 was operated in a case where the noise detection microphone 6 was disposed inside the cylindrical region A.
[Fig. 10] Fig. 10 is a cross-sectional view illustrating another configuration of the air-conditioning apparatus according to Embodiment 1 of the invention.
[Fig. 11] Fig. 11 is a cross-sectional view illustrating still another configuration of the air-conditioning apparatus according to Embodiment 1 of the invention.
[Fig. 12] Fig. 12 is a cross-sectional view illustrating another method of attaching the noise detection microphone according to Embodiment 1 of the invention.
[Fig. 13] Fig. 13 is a cross-sectional view illustrating a configuration of an air-conditioning apparatus according to Embodiment 2 of the invention.
[Fig. 14] Fig. 14 is a diagram illustrating a signal processing device that generates a control sound according to Embodiment 2 of the invention.
[Fig. 15] Fig. 15 is a diagram of waveforms for illustrating a method of calculating noise to be reduced from a sound after interference.
[Fig. 16] Fig. 16 is a block diagram for illustrating a method of estimating a control sound according to Embodiment 2 of the invention.
[Fig. 17] Fig. 17 is a cross-sectional view illustrating another configuration of the air-conditioning apparatus according to Embodiment 2 of the invention.
[Fig. 18] Fig. 18 is a cross-sectional view illustrating still another configuration of the air-conditioning apparatus according to Embodiment 2 of the invention.
[Fig. 19] Fig. 19 is a cross-sectional view illustrating another method of attaching a noise/noise reduction effect detection microphone according to Embodiment 2 of the invention.
[Fig. 20] Fig. 20 is a cross-sectional view illustrating a configuration of an air-conditioning apparatus according to Embodiment 3 of the invention.
[Fig. 21] Fig. 21 is a diagram illustrating a signal processing device that generates a control sound according to Embodiment 3 of the invention.

Description of Embodiments

<A. Embodiment 1>

In the following, an air-conditioning apparatus of the invention is described in detail with reference to the drawings.

<A-1. Configuration>

Fig. 1 is a cross-sectional view illustrating a configuration of an air-conditioning apparatus 1 according to Embodiment 1, taken along a cross-sectional plane X shown in a front view of the air-conditioning apparatus 1 of Fig. 2.
The air-conditioning apparatus 1 shown in Fig. 1 constitutes an indoor unit. An air inlet 3 and an air outlet 5 are open at an upper portion and a lower end, respectively, of the air-conditioning apparatus 1 (to be more specific, a housing of the air-conditioning apparatus 1).
In the air-conditioning apparatus 1, an air flow passage in communication with the air inlet 3 and the air outlet 5 is formed, and a blower fan 2 including an axial fan, which has a substantially vertical rotation axis, is disposed at a lower side of the air inlet 3 of the air flow passage. Further, a heat exchanger 4 that cools or heats air by exchanging heat is arranged under the blower fan 2. The heat exchanger 4 is fixed inside the housing by a heat exchanger fitting 30. As shown by the hollow arrows of Fig. 1, when the blower fan 2 is activated, the blower fan 2 sucks the air from a room through the air inlet 3 into the air flow passage inside the air-conditioning apparatus 1, cools or heats the sucked air with the heat exchanger 4 disposed under the blower fan 2, and blows the air from the air outlet 5 into the room.
Fig. 3 is a bottom view of the blower fan (as viewed from a lower side of Fig. 1) according to Embodiment 1 of the invention. Fig. 4 is a cross-sectional view of the blower fan 2 taken along a cross-sectional plane A shown in Fig. 3. The blower fan 2 includes an impeller 25 which may be referred to as rotor blades, stator blades 26, a stator blade attachment member 7 having an outer peripheral portion to which the stator blades 26 are attached, a motor (not shown), and a rotation shaft (not shown) that transmits power from the motor to the impeller 25. The hatched area shown in Fig. 3 indicates a portion that corresponds to inner peripheries of the blades of the blower fan 2 (i.e., an inscribed circle tangential to inner peripheral portions of the blades of the impeller 25).
The motor serving as the power source of the impeller 25 is disposed inside the stator blade attachment member 7. The motor and a boss portion 27 of the impeller 25 are connected to each other by a rotation shaft 28. Thus, rotation of the motor is transmitted through the rotation shaft 28 to the impeller 25, so that the impeller 25 rotates. The rotation of the impeller 25 causes the air to flow (to be sent) in the direction indicated by the hollow arrows of Fig. 4. It should be noted that the area with diagonal lines in Fig. 4 indicates portions that rotate when the blower fan 2 is in operation. On the other hand, the areas without diagonal lines indicate portions that do not rotate even when the blower fan 2 is in operation (i.e., immobile members). Further, the portion corresponding to the inner peripheries of the blades of the blower fan 2 (i.e., the inscribed circle tangential to the inner peripheral portions of the blades of the impeller 25) corresponds to an outer peripheral portion of the boss portion 27. It should be noted that, in Embodiment 1, the stator blade attachment member 7 is formed to have substantially the same diameter as the diameter of the boss portion 27.
Referring again to Fig. 1, a noise detection microphone 6 serving as a noise detection device that detects an operating sound (noise) of the air-conditioning apparatus 1, including a blowing sound of the blower fan 2, is attached to the stator blade attachment member 7 at positions corresponding to the inner peripheries of the blades of the blower fan 2. That is, the noise detection microphone 6 is arranged in a cylindrical region (hereinafter referred to as a cylindrical region A) defined by extending the inscribed circle tangential to the inner peripheral portions of the blades of the impeller 25 to the direction of the rotation axis of the impeller 25. It should be noted that the stator blade attachment member 7 is independent from the rotatable impeller 25 as shown in Fig. 4, and is configured not to rotate when the blower fan 2 is in operation. Accordingly, the noise detection microphone 6 does not rotate either, when the blower fan 2 is in operation. Further, a control speaker 8 serving as a control sound output device that outputs a control sound with respect to the noise is arranged at a lower side of the noise detection microphone 6 so as to face the center of the air flow passage from a wall of the housing.
Further, on a wall at a lower end of the air-conditioning apparatus, a noise reduction effect detection microphone 9 serving as a noise reduction effect detection device that detects noise coming out from the air outlet 5 and detects a noise reduction effect is attached to, for example, an upper portion of the air outlet 5. This noise reduction effect detection microphone 9 is attached to face a direction away from the flow passage. It should be noted that the installation position of the noise reduction effect detection microphone 9 is not limited to the upper portion of the air outlet 5, and may be in the opening portion of the air outlet 5. For example, the noise reduction effect detection microphone 9 may be attached to a lower portion or a lateral portion of the air outlet 5. Further, the noise reduction effect detection microphone 9 does not need to be disposed so as to accurately face the direction away from the flow passage as long as the noise reduction effect detection microphone 9 is disposed to face away from the air-conditioning apparatus 1 (the housing). That is, the noise reduction effect detection microphone 9 may be installed at any position where noise emitted into the room can be detected.
Further, output signals of the noise detection microphone 6 and the noise reduction effect detection microphone 9 are input to a signal processing device 10 serving as a control sound generation device that generates a signal (a control sound) which controls the control speaker 8.
A noise reduction mechanism of the air-conditioning apparatus 1 includes the noise detection microphone 6, the control speaker 8, the noise reduction effect detection microphone 9, and the signal processing device 10.
Fig. 5 is a block diagram of the signal processing device 10. An electric signal that has been input from the noise detection microphone 6 is amplified by a microphone amplifier 11, and is converted from an analog signal into a digital signal by an A/D converter 12. An electric signal input from the noise reduction effect detection microphone 9 is amplified by a microphone amplifier 11, is converted from an analog signal into a digital signal by an A/D converter 12, and is averaged by being multiplied by a weighting coefficient by weighting means 13. Each of the converted digital signals described above is input to a FIR filter 18 and an LMS algorithm 19. The FIR filter 18 generates a control signal that is corrected so as to have the same amplitude as and a phase opposite to the noise that has been detected by the noise detection microphone 6 and that has reached a location where the noise reduction effect detection microphone 9 is disposed. This control signal is converted from a digital signal to an analog signal by a D/A converter 14, is amplified by an amplifier 15, and is emitted as a control sound from the control speaker 8.

<A-2. Operations>

Next, a description is given on operations of the air-conditioning apparatus 1. When the air-conditioning apparatus 1 is operated, the impeller 25 of the blower fan 2 rotates. Then, the air in the room is sucked from the upper side of the blower fan 2 and is sent to the lower side of the blower fan 2, thereby generating an air current. Accordingly, an operating sound (noise) is generated in the vicinity of the air outlet of the blower fan 2, and the sound propagates to a downstream side.
In the vicinity of the air outlet 5 of the blower fan 2, a turbulent flow is generated by the rotation of the impeller 25. Further, since the air blown from the blower fan 2 is blown from the air outlet of the blower fan 2 toward the outside, the air impinges against a side wall of the housing of the air-conditioning apparatus 1, and a further turbulence of air flow is generated. Therefore, a pressure fluctuation due to the turbulent flow is increased on the side wall of the air-conditioning apparatus 1. In contrast, in the region inside the inner peripheries of the blades of the blower fan 2 (cylindrical region A), the turbulent flow is smaller, and the pressure fluctuation due to the air current is smaller.
In order to support this, the result of an experiment in which an air current blown from the blower fan 2 has been visualized is shown in Fig. 6. Fig. 6 is a photograph taken when the blower fan 2 is operated after attaching the blower fan 2 to a right end of a duct-shaped tube and accumulating white smoke inside the duct. Focusing on the vicinity of the air outlet of the blower fan 2, in the region excluding the vicinity of the stator blade attachment member 7 and the cylindrical region A, the accumulated white smoke has turned thin, which indicates that the white smoke is carried by the air current. On the other hand, in the vicinity of the stator blade attachment member 7 of the blower fan 2 and in the cylindrical region A, the white smoke remains accumulated, and the effect of the air current is small. That is, it is found that the vicinity of the stator blade attachment member 7 of the blower fan 2 and the cylindrical region A is less affected by the air current, and a pressure fluctuation due to a turbulent flow is small.
The air sent from the blower fan 2 passes through the air flow passage and is sent to the heat exchanger 4. For example, during a cooling operation, a refrigerant is supplied to the heat exchanger 4 from a pipe connected to an outdoor unit (not shown). The air that has been sent to the heat exchanger 4 is cooled by the refrigerant flowing through the heat exchanger 4 so as to become cold air, and is directly released from the air outlet 5 into the room.
Next, a description is given on a method of reducing the level of the operating sound of the air-conditioning apparatus 1. The operating sound (noise) of the air-conditioning apparatus 1 including the blowing sound of the blower fan 2 is detected by the noise detection microphone 6 attached to the stator blade attachment member 7 of the blower fan 2. The noise detected by the noise detection microphone 6 is transmitted through the microphone amplifier 11 and the A/D converter 12 so as to be converted into a digital signal, and is input to the FIR filter 18 and the LMS algorithm 19.
A tap coefficient of the FIR filter 18 is successively updated by the LMS algorithm 19. In the LMS algorithm 19, the optimum tap coefficient is updated such that an error signal "e" approaches zero in accordance with Equation 1 (h(n+1)=h(n)+2•µ•e(n)•x(n)).
Where, h: tap coefficient of the filter, e: error signal, x: filter input signal, and µ: step size parameter. Further, the step size parameter µ controls a filter coefficient update amount for each sampling event.
In this way, the digital signal that has passed through the FIR filter 18, the tap coefficient of which has been updated by the LMS algorithm 19, is converted into an analog signal by the D/A converter 14, is amplified by the amplifier 15, and is emitted as a control sound from the control speaker 8 into the air flow passage inside the air-conditioning apparatus 1.
On the other hand, the noise reduction effect detection microphone 9 which is attached to the upper portion of the air outlet 5 of the air-conditioning apparatus 1 to face a direction away from the flow passage detects a resultant sound after interference of the noise, which has propagated through the air flow passage from the blower fan 2 and has been emitted from the air outlet 5 into the room, and the control sound emitted from the control speaker 8. As mentioned above, a signal detected by the noise reduction effect detection microphone 9 is converted into a digital signal, and is averaged by the weighting means 13.
Fig. 7 is a circuit diagram of the weighting means according to Embodiment 1 of the invention.
The weighting means 13 is an integrator including a multiplier 21 that multiplies the input signal by the weighting coefficient, an adder 32, a one-sample delay element 33, and a multiplier 34.
In Embodiment 1, the weighting coefficient of the multiplier 21 can be set from the outside in accordance with the installation environment.
For example, in an environment where disturbance is large and operations are unstable, the weighting coefficient of the multiplier 21 may be reduced. Conversely, in an environment with little disturbance, the weighting coefficient of the multiplier 21 may be increased. In this way, the sensitivity to environmental changes can be altered. In this case, the averaging operation by the weighting means 13 may not be performed until the LMS algorithm 19 becomes stable. This is because the noise is not sufficiently reduced while the LMS algorithm 19 is not stable, and runaway of the output value of the weighting means 13 may occur. Further, the output value of the weighting means 13 may be reset if the output value of the weighting means 13 exceeds a certain value.
The signal averaged in this way is treated as the above-mentioned error signal "e" of the LMS algorithm 19. Then, feedback control is performed such that the error signal "e" approaches zero, and the tap coefficient of the FIR filter 18 is updated as appropriate. As a result, the noise in the vicinity of the air outlet 5 can be reduced by the control sound that has passed through the FIR filter 18.
Since the noise of the air-conditioning apparatus 1 that is perceived by a person is one that has been emitted from the air outlet 5 into the room, the noise emitting into the room can be detected by arranging the noise reduction effect detection microphone 9 to face the inside of the room in a direction away from the flow passage. That is, a sound having high coherence with the noise that has been emitted into the room can be detected by attaching the noise reduction effect detection microphone 9 at the upper portion of the air outlet 5 to face a direction away from the flow passage. Further, since the noise reduction effect detection microphone 9 is not directly hit by the air current, the noise reduction effect detection microphone 9 does not detect wind noise caused by the air current. On the other hand, if the noise reduction effect detection microphone 9 is arranged toward the flow passage, noise inside the flow passage will be detected. Therefore, the noise reduction effect detection microphone 9 cannot detect the changing property of the sound emitted at the air outlet. Accordingly, the property change of the sound detected by the noise reduction effect detection microphone 9 is different from those of the noise in the room. Hence, the coherence between the sound detected by the noise reduction effect detection microphone 9 and the sound emitted into the room is reduced. Moreover, since the noise reduction effect detection microphone 9 is directly hit by the air current, the noise reduction effect detection microphone 9 detects wind noise, which leads to further reduction in coherence.
Further, a large number of sounds other than the noise generated from the blower fan 2 are present in the room, and these sounds other than the noise undermine the stability of the feedback control. To solve this problem, the sounds other than the noise are averaged by providing the weighting means 13 to the preceding step of the feedback control. This allows components of the uncorrelated sounds other than the noise to be canceled, and allows the feedback control to be operated stably. That is, this makes it possible to increase the coherence between the noise detection microphone 6 and the noise reduction effect detection microphone 9.
Further, in Embodiment 1, since the noise detection microphone 6 is attached to the stator blade attachment member 7 of the blower fan 2, the air current does not directly hit the noise detection microphone 6. Therefore, detection of pressure fluctuation components generated due to the turbulent flow detected by the noise detection microphone 6 can be reduced. Accordingly, the noise detection microphone 6 can detect a sound having high coherence with the noise, that is, the operating sound of the blower fan 2. Further, since the noise reduction effect detection microphone 9 is attached to the upper portion of the air outlet 5 to face a direction away from the flow passage, the noise reduction effect detection microphone 9 is not directly hit by the air current, and the noise reduction effect detection microphone 9 is not affected by the air current. Further, since the noise reduction effect detection microphone 9 is allowed to detect only the noise emitted into the room, noise having high coherence with the actual noise heard by a person who is in the room can be detected by the noise reduction effect detection microphone 9. Further, since the sound detected by the noise reduction effect detection microphone 9 is averaged by the weighting means 13 and feedback control is performed, components other than the noise from the air-conditioning apparatus 1 included in the sounds detected by the noise reduction effect detection microphone 9 can be canceled. Therefore, it is possible to obtain high coherence between the detected sounds of the noise detection microphone 6 and the noise reduction effect detection microphone 9. Accordingly, it is possible to obtain high coherence among the noise generated from the blower fan 2, the detected sound of the noise detection microphone 6, the detected sound of the noise reduction effect detection microphone 9, and noise in the room into which noise is emitted from the air-conditioning apparatus 1, and thus a high noise reduction effect is obtained.
A description is given on the result of an experiment in which coherence between the noise detection microphone 6 and the noise reduction effect detection microphone 9 was measured in a case where the noise detection microphone 6 was actually attached inside the inner peripheries of the blades of the blower fan 2 (the cylindrical region A).
Fig. 8 is a chart illustrating coherence properties between a detected sound of the noise detection microphone 6 and a detected sound of the noise reduction effect detection microphone 9 when the blower fan 2 was operated in a case where the noise detection microphone 6 was disposed outside the cylindrical region A. Next, Fig. 9 is a chart illustrating coherence properties between a detected sound of the noise detection microphone 6 and a detected sound of the noise reduction effect detection microphone 9 when the blower fan 2 was operated in a case where the noise detection microphone 6 was disposed inside the cylindrical region A.
By comparing Fig. 8 with Fig. 9, it can be seen that the coherence is obviously high in the case where the noise detection microphone 6 was disposed inside the cylindrical region A.
Further, since the noise detection microphone 6 is attached to the stator blade attachment member 7 of the blower fan 2, the noise detection microphone 6 can easily be attached without increasing the number of components, and the need for a precise attachment mechanism is eliminated. Further, since the noise detection microphone 6 is attached to the stator blade attachment member 7 of the blower fan 2, the distance between the blower fan 2 and the noise detection microphone 6 can be reduced, which allows the height of the air-conditioning apparatus 1 to be reduced.
It should be noted that, in Embodiment 1, the noise detection microphone 6 is disposed on the stator blade attachment member 7. Accordingly, unique machine vibration associated with rotation of the blower fan 2 may be transmitted to the stator blade attachment member 7, and the noise detection microphone 6 may detect the vibration. In this case, the coherence between the noise detection microphone 6 and the noise reduction effect detection microphone 9 may be reduced locally. In such a case, the noise detection microphone 6 may be disposed in an area other than the stator blade attachment member 7 inside the cylindrical region A. For example, as shown in Fig. 10, the noise detection microphone 6 may be disposed on the heat exchanger 4 in the area inside the cylindrical region A. Further, for example, as shown in Fig. 11, the noise detection microphone 6 may be disposed on the heat exchanger fitting 30 in the area inside the cylindrical region A. In the case where the noise detection microphone 6 is disposed as described above, the coherence between the noise detection microphone 6 and the noise reduction effect detection microphone 9 can be further increased compared with the case in which the noise detection microphone 6 is disposed on the stator blade attachment member 7, and a higher noise reduction effect can be obtained.
Further, as shown in Fig. 12, the noise detection microphone 6 may be covered with a wall member 31. Since the wall member can block the air current, the noise detection microphone 6 is less affected by the air current, and a higher noise reduction effect can be obtained. In Fig. 12, the wall member 31 is formed in a substantially cylindrical shape. However, the wall member 31 may be formed in any shape.
Similarly, the noise detection microphone 6 may be covered with the wall member 31 in a case where the noise detection microphone 6 is attached to the heat exchanger 4 or the heat exchanger fitting 30. The noise detection microphone 6 is less affected by the air current, and a higher noise reduction effect can be obtained.
Further, the noise reduction effect detection microphone 9 attached to the upper portion of the air outlet 5 to face a direction away from the flow passage may be covered with a wall member. Since the wall member can block the air current, the noise reduction effect detection microphone 9 is also less affected by the air current, and a higher noise reduction effect can be obtained.
Further, in Embodiment 1, an axial fan is described as an example of the blower fan 2. However, the blower fan 2 may be any fan that blows air by rotation of an impeller.
Further, in Embodiment 1, the FIR filter 18 and the LMS algorithm 19 are used in the signal processing device 10. However, the signal processing device 10 may be any adaptive signal processing circuit that makes the sound detected by the noise reduction effect detection microphone 9 approach zero, and may be one using a filtered-x algorithm that is commonly employed by active noise reduction methods.
Further, the weighting means 13 does not need to be an integrator, and may be any means that can perform an averaging operation.
Further, the signal processing device 10 does not need to be configured to perform adaptive signal processing, and may be configured to generate a control sound using a fixed tap coefficient.
Furthermore, the signal processing device 10 does not need to be a digital signal processing circuit, and may be an analog signal processing circuit.

<A-3. Advantageous Effects>

As described above, in the air-conditioning apparatus 1 according to Embodiment 1, the noise detection microphone 6 serving as a noise detection device is disposed inside the cylindrical region A and on an immobile member of the blower fan 2. Therefore, it is possible to reduce the effect of the air current from the air outlet of the blower fan 2, and thus to detect a sound having high coherence with the noise. Accordingly, active noise reduction can be performed with high accuracy. Further, since the noise detection microphone 6 can be installed without changing the mechanism of the blower fan 2 and without increasing the number of components of the air-conditioning apparatus 1, the air-conditioning apparatus 1 can provide a high degree of installation freedom.
It should be noted that the immobile member of the blower fan 2 is not limited to the stator blade attachment member 7. If, among the components of the blower fan 2, there is an immobile member in which at least a portion thereof is arranged inside the cylindrical region A, the noise detection microphone 6 may be disposed in the area of the immobile member inside the cylindrical region A.
Further, in the air-conditioning apparatus 1 according to Embodiment 1, the noise detection microphone 6 serving as a noise detection device is disposed inside the cylindrical region A and on the downstream side of the blower fan 2. Therefore, it is possible to reduce the effect of the air current from the air outlet of the blower fan 2, and thus to detect a sound having high coherence with the noise. Accordingly, active noise reduction can be performed with high accuracy. Further, since the noise detection microphone 6 can be installed without changing the mechanism of the blower fan 2 and without increasing the number of components of the air-conditioning apparatus 1, the air-conditioning apparatus 1 can provide a high degree of installation freedom. Further, since the unique machine vibration associated with rotation of the blower fan 2 is not detected by the noise detection microphone 6, active noise reduction can be performed with accuracy higher than that in the case in which the noise detection microphone 6 is disposed on an immobile member of the blower fan 2.
It should be noted that, in the case where the noise detection microphone 6 is disposed on the downstream side of the blower fan 2, components on which the noise detection microphone 6 are disposed are not limited to the heat exchanger 4 and the heat exchanger fitting 30. If there is a component in which at least a portion thereof is arranged inside the cylindrical region A and the component is disposed on the downstream side of the blower fan 2, the noise detection microphone 6 may be disposed in the area of the component inside the cylindrical region A.
Further, in the air-conditioning apparatus 1 according to Embodiment 1, the noise reduction effect detection microphone 9 serving as a noise reduction effect detection device is disposed in the opening portion of the air outlet 5, and is arranged so as to face away from the air-conditioning apparatus 1. Therefore, the noise reduction effect detection microphone 9 can detect the noise emitted into the room without being affected by the air current. Accordingly, it is possible to obtain high coherence between the noise emitted into the room from the air-conditioning apparatus 1 and the detected sound of the noise reduction effect detection microphone 9. Therefore, active noise reduction can be performed with high accuracy on the noise emitted into the room from the air-conditioning apparatus 1:
Further, in the air-conditioning apparatus 1 according to Embodiment 1, the signal processing device 10 serving as a control sound generation device is provided with a circuit that applies weight to a detection result detected by the noise reduction effect detection microphone 9 serving as a noise reduction effect detection device, and performs feedback control. Therefore, sounds other than the noise of the air-conditioning apparatus 1 detected by the noise reduction effect detection microphone 9 can be canceled by averaging the sounds. Accordingly, sounds having high coherence with each other can be detected by the noise detection microphone 6 and the noise reduction effect detection microphone 9, so that active noise reduction can be performed with higher accuracy.
Further, in the air-conditioning apparatus 1 according to Embodiment 1, the noise detection microphone 6 is disposed in an area inside the cylindrical region A on the stator blade attachment member 7 of the blower fan 2. Therefore, it is possible to reduce the effect of the air current from the air outlet of the blower fan 2, and thus to detect a sound having high coherence with the noise. Accordingly, active noise reduction can be performed with high accuracy. Further, since the noise detection microphone 6 can be installed without changing the mechanism of the blower fan 2 and without increasing the number of components of the air-conditioning apparatus, the air-conditioning apparatus 1 can provide a high degree of installation freedom.
Further, in the air-conditioning apparatus 1 according to Embodiment 1, the noise detection microphone 6 may be disposed in an area inside the cylindrical region A on the heat exchanger 4. Therefore, it is possible to reduce the effect of the air current from the air outlet of the blower fan 2, and thus to detect a sound having high coherence with the noise. Accordingly, active noise reduction can be performed with high accuracy. Further, since the noise detection microphone 6 can be installed without changing the mechanism of the blower fan 2 and without increasing the number of components of the air-conditioning apparatus, the air-conditioning apparatus 1 can provide a high degree of installation freedom. Further, since the unique machine vibration associated with rotation of the blower fan 2 is not detected by the noise detection microphone 6, active noise reduction can be performed with accuracy higher than that in the case in which the noise detection microphone 6 is disposed on an immobile member of the blower fan 2.
Further, in the air-conditioning apparatus 1 according to Embodiment 1, the noise detection microphone 6 may be disposed in an area inside the cylindrical region A on the heat exchanger fitting 30. Therefore, it is possible to reduce the effect of the air current from the air outlet of the blower fan 2, and thus to detect a sound having high coherence with the noise. Accordingly, active noise reduction can be performed with high accuracy. Further, since the noise detection microphone 6 can be installed without changing the mechanism of the blower fan 2 and without increasing the number of components of the air-conditioning apparatus, the air-conditioning apparatus 1 can provide a high degree of installation freedom. Further, since the unique machine vibration associated with rotation of the blower fan 2 is not detected by the noise detection microphone 6, active noise reduction can be performed with accuracy higher than that in the case in which the noise detection microphone 6 is disposed on an immobile member of the blower fan 2.
Further, in the air-conditioning apparatus 1 according to Embodiment 1, the noise detection microphone 6 may be covered with the wall member 31. Since the wall member 31 blocks the air current, the noise detection microphone 6 is less affected by the air current, and a higher noise reduction effect can be obtained.
Further, in the air-conditioning apparatus 1 according to Embodiment 1, the noise reduction effect detection microphone 9 may be covered with a wall member. Since the wall member blocks the air current, the noise reduction effect detection microphone 9 is less affected by the air current and a higher noise reduction effect can be obtained.

<B. Embodiment 2>

<B-1. Configuration>

In Embodiment 2, a description is given on the air-conditioning apparatus 1 in which the noise/noise reduction effect detection microphone 16 is provided as a noise/noise reduction effect detection device into which the noise detection microphone 6 and the noise reduction effect detection microphone 9 of Embodiment 1 are integrated. It should be noted that, in Embodiment 2, items not specifically described are the same as those of Embodiment 1, and like functions and configurations are denoted by like reference signs.
Fig. 13 is a cross-sectional view illustrating a configuration of an air-conditioning apparatus 1 according to Embodiment 2, taken along a cross-sectional plane X shown in a front view of the air-conditioning apparatus 1 of Fig. 2.
The air-conditioning apparatus 1 shown in Fig. 13 constitutes the indoor unit. The air inlet 3 and the air outlet 5 are open at the upper portion and the lower end, respectively, of the air-conditioning apparatus 1 (to be more specific, the housing of the air-conditioning apparatus 1).
In the air-conditioning apparatus 1, the air flow passage in communication with the air inlet 3 and the air outlet 5 is formed, and the blower fan 2 including the axial fan, which has a substantially vertical rotation axis, is disposed at the lower side of the air inlet 3 of the air flow passage. Further, the heat exchanger 4 that cools or heats air by exchanging heat is arranged under the blower fan 2. The heat exchanger 4 is fixed inside the housing by the heat exchanger fitting 30. As shown by the hollow arrows of Fig. 13, when the blower fan 2 is activated, the blower fan 2 sucks the air from a room through the air inlet 3 into the air flow passage inside the air-conditioning apparatus 1, cools or heats the sucked air with the heat exchanger 4 disposed under the blower fan 2, and blows the air from the air outlet 5 into the room.
In the air-conditioning apparatus 1 of Embodiment 1, generation of a control sound is performed in the signal processing device 17 using two microphones, that is, the noise detection microphone 6 and the noise reduction effect detection microphone 9, for performing active noise reduction. The air-conditioning apparatus 1 of Embodiment 2 differs from the air-conditioning apparatus 1 described in Embodiment 1 in that these microphones are replaced with one microphone, that is, a noise/noise reduction effect detection microphone 16. Further, due to this, the signal processing method differs from that of Embodiment 1, and therefore the components of the signal processing device 17 differ from those of the signal processing device 10 of Embodiment 1.
A control speaker 8 serving as a control sound output device that outputs a control sound with respect to noise is arranged on a side wall of the housing of the air-conditioning apparatus 1 to face the center of the air flow passage. Further, in an area inside the cylindrical region A on the stator blade attachment member 7, the noise/noise reduction effect detection microphone 16 is disposed that detects a resultant sound after interference of the operating sound (noise) of the air-conditioning apparatus 1 including the blowing sound of the blower fan 2 and the control sound emitted from the control speaker 8. It should be noted that the stator blade attachment member 7 is independent from the impeller, and is configured not to rotate when the blower fan 2 is in operation. Accordingly, the noise/noise reduction effect detection microphone 16 does not rotate either, when the blower fan 2 is in operation.
An output signal of the noise/noise reduction effect detection microphone 16 is input to a signal processing device 17 serving as a control sound generation device that generates a signal (a control sound) which controls the control speaker 8.
A noise reduction mechanism of the air-conditioning apparatus 1 includes the noise/noise reduction effect detection microphone 16, the control speaker 8, and the signal processing device 17.
Fig. 14 is a block diagram of the signal processing device 17. An electric signal that has been converted from a sound signal by the noise/noise reduction effect detection microphone 16 is amplified by the microphone amplifier 11, and is converted from an analog signal into a digital signal by the A/D converter 12. The converted digital signal is input to the LMS algorithm 19. Further, a differential signal that is a signal obtained by convolving the output signal of the FIR filter 18 with a FIR filter 20 is input to the FIR filter 18 and the LMS algorithm 19. Next, a convolution operation is performed on the differential signal by the FIR filter 18 using the tap coefficient calculated by LMS algorithm 19. After that, the differential signal is converted from a digital signal into an analog signal by the D/A converter 14, is amplified by the amplifier 15, and is output as a control sound from the control speaker 8.

<B-2. Operations>

Next, a description is given on operations of the air-conditioning apparatus 1. When the air-conditioning apparatus 1 is operated, the impeller 25 of the blower fan 2 rotates. Then, the air in the room is sucked from the upper side of the blower fan 2 and is sent to the lower side of the blower fan 2, thereby generating an air current. Accordingly, an operating sound (noise) is generated in the vicinity of the air outlet of the blower fan 2, and the sound propagates to a downstream side.
As in the case of Embodiment 1, a turbulent flow is generated by rotation of the impeller 25 in the vicinity of the air outlet of the blower fan 2. Further, since the air blown from the blower fan 2 blows from the air outlet of the blower fan 2 toward the outside, the air impinges against the side wall of the housing of the air-conditioning apparatus 1, and a further turbulence of air flow is generated. Therefore, a pressure fluctuation due to the turbulent flow is increased on the side wall of the air-conditioning apparatus 1. In contrast, in the region inside the inner peripheries of the blades of the blower fan 2 (cylindrical region A), the turbulent flow is smaller, and the pressure fluctuation due to the air current is smaller.
The air sent from the blower fan 2 passes through the air flow passage and is sent to the heat exchanger 4. For example, during a cooling operation, a refrigerant is supplied to the heat exchanger 4 from a pipe connected to an outdoor unit (not shown). The air that has been sent to the heat exchanger 4 is cooled by the refrigerant flowing through the heat exchanger 4 so as to become cold air, and is directly released from the air outlet 5 into the room.
Next, a description is given on a method of reducing the level of the operating sound of the air-conditioning apparatus 1. A resultant sound after interference of the operating sound (noise) of the blower fan 2 including the blowing sound of the blower fan 2 and the control sound output from the control speaker 8 is detected by the noise/noise reduction effect detection microphone 16 attached to the stator blade attachment member 7 of the blower fan 2. The noise detected by the noise/noise reduction effect detection microphone 16 is transmitted through the microphone amplifier 11 and the A/D converter 12 so as to be converted into a digital signal.
In order to perform a reduction method equivalent to the operating sound reduction method described in Embodiment 1, it is necessary to input the noise to be reduced to the FIR filter 18. Further, as shown in Equation 1, it is necessary to input to the LMS algorithm 19 the noise to be reduced as an input signal, and the resultant sound after interference with the control sound as an error signal. However, since the noise/noise reduction effect detection microphone 16 can only detect the resultant sound after the interference of the control sound, it is necessary to create noise to be reduced from the sound detected by the noise/noise reduction effect detection microphone 16.
Fig. 15 shows a waveform of the resultant sound after interference of the noise and the control sound ("a" in Fig. 15), a waveform of the control sound ("b" in Fig. 15), and a waveform of the noise ("c" in Fig. 15). In accordance with the superposition principle of sound, b+c=a, in order to obtain "c" from "a", the difference between the "a" and "b" is used. That is, the noise to be reduced can be created from the difference between the sound after interference detected by the noise/noise reduction effect detection microphone 16 and the control sound.
Fig. 16 is a diagram showing a route in which the output control signal from the FIR filter 18, after being output from the control speaker 8 as a control sound and is detected by the noise/noise reduction effect detection microphone 16, is input to the signal processing device 17. This route passes through the D/A converter 14, the amplifier 15, a route from the control speaker 8 to the noise/noise reduction effect detection microphone 16, the noise/noise reduction effect detection microphone 16, the microphone amplifier 11, and the A/D converter 12.
Supposing that this route has a transmission characteristic H, the FIR filter 20 shown in Fig. 14 is one in which this transmission characteristic H is estimated. By convolving the output signal of the FIR filter 18 with the FIR filter 20, the control sound can be estimated as a signal "b" detected by the noise/noise reduction effect detection microphone 16. Then, by using the difference of the sound "a" after interference detected by the noise/noise reduction effect detection microphone 16, the noise "c" to be reduced is generated.
The noise "c" to be reduced, which is generated as described above, is supplied as an input signal to the LMS algorithm 19 and the FIR filter 18. The digital signal that has passed through the FIR filter 18, the tap coefficient of which has been updated by the LMS algorithm 19, is converted into an analog signal by the D/A converter 14, is amplified by the amplifier 15, and is emitted as a control sound from the control speaker 8 into the air flow passage inside the air-conditioning apparatus 1.
On the other hand, the noise/noise reduction effect detection microphone 16 attached to the stator blade attachment member 7 of the blower fan 2 detects the resultant sound after interference of the noise generated from the blower fan 2 and the control sound output from the control speaker 8. Since the sound detected by the noise/noise reduction effect detection microphone 16 has been input as the error signal of the above-described LMS algorithm 19, the tap coefficient of the FIR filter 18 is updated such that this sound after interference approaches zero. As a result, the noise generated from the blower fan 2 can be reduced by the control sound that has passed through the FIR filter 18.
As described above, in Embodiment 2, since the noise/noise reduction effect detection microphone 16 is attached in the area inside the cylindrical region A on the stator blade attachment member 7 in the air-conditioning apparatus 1 in which an active noise reduction method is employed, the air current does not directly hit the noise/noise reduction effect detection microphone 16. This makes it possible to reduce detection of pressure fluctuation components generated due to the turbulent flow. Therefore, it is possible to detect a sound having high coherence with the noise, that is, the operating sound of the blower fan 2, and thus to achieve a high noise reduction effect.
Further, since the noise/noise reduction effect detection microphone 16 is attached to the stator blade attachment member 7 of the blower fan 2, the noise/noise reduction effect detection microphone 16 can easily be attached without increasing the number of components, and the need for a precise attachment mechanism is eliminated. Further, since the noise/noise reduction effect detection microphone 16 is attached to the stator blade attachment member 7 of the blower fan 2, the distance between the blower fan 2 and the noise/noise reduction effect detection microphone 16 may be reduced, which allows the height of the air-conditioning apparatus 1 to be reduced.
It should be noted that, in Embodiment 2, the noise/noise reduction effect detection microphone 16 is disposed on the stator blade attachment member 7. Therefore, unique machine vibration associated with rotation of the blower fan 2 may be transmitted to the noise/noise reduction effect detection microphone 16, and the noise detection microphone 6 may detect the vibration. This may reduce the noise reduction effect. In such a case, the noise/noise reduction effect detection microphone 16 may be disposed in an area other than on the stator blade attachment member 7 inside the cylindrical region A. For example, as shown in Fig. 17, the noise detection microphone 6 may be disposed on the heat exchanger 4 in the area inside the cylindrical region A. Further, for example, as shown in Fig. 18, the noise/noise reduction effect detection microphone 16 may be disposed on the heat exchanger fitting 30 in the area inside the cylindrical region A. In the case where the noise/noise reduction effect detection microphone 16 is disposed as described above, a higher noise reduction effect can be obtained compared with the case in which the noise/noise reduction effect detection microphone 16 is disposed on the stator blade attachment member 7.
Further, as shown in Fig. 19, the noise/noise reduction effect detection microphone 16 may be covered with a wall member 31. Since the wall member can block the air current, the noise/noise reduction effect detection microphone 16 is less affected by the air current, and a higher noise reduction effect can be obtained. In Fig. 19, the wall member 31 is formed in a substantially cylindrical shape. However, the wall member 31 may be formed in any shape.
Similarly, the noise/noise reduction effect detection microphone 16 may be covered with the wall member 31 in a case where the noise/noise reduction effect detection microphone 16 is attached to the heat exchanger 4 or the heat exchanger fitting 30. The noise/noise reduction effect detection microphone 16 is less affected by the air current, and a higher noise reduction effect can be obtained.
Further, in Embodiment 2, an axial fan is described as an example of the blower fan 2. However, the blower fan 2 may be any fan that blows air by rotation of an impeller.
Further, in Embodiment 2, the FIR filter 18 and the LMS algorithm 19 are used as an adaptive signal processing circuit. However, any adaptive signal processing circuit may be used that makes the sound detected by the noise/noise reduction effect detection microphone 16 approach zero.
Further, the signal processing device 17 does not need to be configured to perform adaptive signal processing, and may be configured to generate a control sound using a fixed tap coefficient.
Furthermore, the signal processing device 17 does not need to be a digital signal processing circuit, and may be an analog signal processing circuit.

<B-3. Advantageous Effects>

As described above, in the air-conditioning apparatus 1 according to Embodiment 2, the noise/noise reduction effect detection microphone 16 serving as a noise/noise reduction effect detection device is disposed inside the cylindrical region A and on an immobile member of the blower fan 2. Therefore, it is possible to reduce the effect of the air current from the air outlet of the blower fan 2, and thus to detect a sound having high coherence with the noise. Accordingly, active noise reduction can be performed with high accuracy. Further, since the noise/noise reduction effect detection microphone 16 can be installed without increasing the number of components of the air-conditioning apparatus 1, the air-conditioning apparatus 1 can provide a high degree of installation freedom.
Further, in the air-conditioning apparatus 1 according to Embodiment 2, the noise/noise reduction effect detection microphone 16 serving as a noise/noise reduction effect detection device is disposed inside the cylindrical region A and on the downstream side of the blower fan 2. Therefore, it is possible to reduce the effect of the air current from the air outlet of the blower fan 2, and thus to detect a sound having high coherence with the noise. Accordingly, active noise reduction can be performed with high accuracy. Further, since the noise/noise reduction effect detection microphone 16 can be installed without changing the mechanism of the blower fan 2 and without increasing the number of components of the air-conditioning apparatus 1, the air-conditioning apparatus 1 can provide a high degree of installation freedom. Further, since the unique machine vibration associated with rotation of the blower fan 2 is not detected by the noise/noise reduction effect detection microphone 16, active noise reduction can be performed with an accuracy higher than that in the case in which the noise/noise reduction effect detection microphone 16 is disposed on an immobile member of the blower fan 2.
Further, in the air-conditioning apparatus 1 according to Embodiment 2, the noise/noise reduction effect detection microphone 16 is disposed in an area inside the cylindrical region A on the stator blade attachment member 7 of the blower fan 2. Therefore, it is possible to reduce the effect of the air current from the air outlet of the blower fan 2, and thus to detect a sound having high coherence with the noise. Accordingly, active noise reduction can be performed with high accuracy. Further, since the noise/noise reduction effect detection microphone 16 can be installed without changing the mechanism of the blower fan 2 and without increasing the number of components of the air-conditioning apparatus, the air-conditioning apparatus 1 can provide a high degree of installation freedom.
Further, in the air-conditioning apparatus 1 according to Embodiment 2, the noise/noise reduction effect detection microphone 16 may be disposed in an area inside the cylindrical region A on the heat exchanger 4. Therefore, it is possible to reduce the effect of the air current from the air outlet of the blower fan 2, and thus to detect a sound having high coherence with the noise. Accordingly, active noise reduction can be performed with high accuracy. Further, since the noise/noise reduction effect detection microphone 16 can be installed without changing the mechanism of the blower fan 2 and without increasing the number of components of the air-conditioning apparatus, the air-conditioning apparatus 1 can provide a high degree of installation freedom. Further, since the unique machine vibration associated with rotation of the blower fan 2 is not detected by the noise/noise reduction effect detection microphone 16, active noise reduction can be performed with an accuracy higher than that in the case in which the noise/noise reduction effect detection microphone 16 is disposed on an immobile member of the blower fan 2.
Further, in the air-conditioning apparatus 1 according to Embodiment 2, the noise/noise reduction effect detection microphone 16 may be disposed in an area inside the cylindrical region A on the heat exchanger fitting 30. Therefore, it is possible to reduce the effect of the air current from the air outlet of the blower fan 2, and thus to detect a sound having high coherence with the noise. Accordingly, active noise reduction can be performed with high accuracy. Further, since the noise/noise reduction effect detection microphone 16 can be installed without changing the mechanism of the blower fan 2 and without increasing the number of components of the air-conditioning apparatus, the air-conditioning apparatus 1 can provide a high degree of installation freedom. Further, since the unique machine vibration associated with rotation of the blower fan 2 is not detected by the noise/noise reduction effect detection microphone 16, active noise reduction can be performed with an accuracy higher than that in the case in which the noise/noise reduction effect detection microphone 16 is disposed on an immobile member of the blower fan 2.
Further, in the air-conditioning apparatus 1 according to Embodiment 2, the noise/noise reduction effect detection microphone 16 may be covered with the wall member 31. Since the wall member blocks the air current, the noise/noise reduction effect detection microphone 16 is less affected by the air current and a higher noise reduction effect can be obtained.

<C. Embodiment 3>

<C-1. Configuration>

In Embodiment 3, a description is given on an air-conditioning apparatus in which the noise/noise reduction effect detection microphone 16 is disposed at the upper portion of the air outlet 5 to face a direction away from the flow passage. It should be noted that, in Embodiment 3, items not specifically described are the same as those of Embodiment 1 or Embodiment 2, like functions and configurations are denoted by like reference signs.
Fig. 20 is a cross-sectional view illustrating a configuration of the air-conditioning apparatus 1 according to Embodiment 3, taken along a cross-sectional plane X shown in a front view of the air-conditioning apparatus 1 of Fig. 2.
The air-conditioning apparatus 1 shown in Fig. 20 constitutes the indoor unit. The air inlet 3 and the air outlet 5 are open at the upper portion and the lower end, respectively, of the air-conditioning apparatus 1 (to be more specific, the housing of the air-conditioning apparatus 1).
In the air-conditioning apparatus 1, the air flow passage in communication with the air inlet 3 and the air outlet 5 is formed, and the blower fan 2 including the axial fan, which has a substantially vertical rotation axis, is disposed at the lower side of the air inlet 3 of the air flow passage. Further, the heat exchanger 4 that cools or heats air by exchanging heat is arranged under the blower fan 2. The heat exchanger 4 is fixed inside the housing by the heat exchanger fitting 30. As shown by the hollow arrows of Fig. 20, when the blower fan 2 is activated, the blower fan 2 sucks the air from a room through the air inlet 3 into the air flow passage inside the air-conditioning apparatus 1, cools or heats the sucked air with the heat exchanger 4 disposed under the blower fan 2, and blows the air from the air outlet 5 into the room.
The difference from the air-conditioning apparatus 1 described in Embodiment 2 is that the noise/noise reduction effect detection microphone is disposed at the upper portion of the air outlet 5 to face a direction away from the flow passage. Accordingly, the configuration of a signal processing device 22 also differs from that of the signal processing device 17 of Embodiment 2.
As in the case of Embodiment 2, in the case where the noise/noise reduction effect detection microphone 16 is disposed at the upper portion of the air outlet 5 to face a direction away from the flow passage, the noise/noise reduction effect detection microphone 16 can easily be attached without increasing the number of components, and the need for a precise attachment mechanism is eliminated.
The control speaker 8 serving as a control sound output device that outputs a control sound with respect to noise is arranged on a side wall of the housing of the air-conditioning apparatus 1 to face the center of the air flow passage. Further, the noise/noise reduction effect detection microphone 16 that detects a resultant sound after interference of the operating sound (noise) of the air-conditioning apparatus 1 including the blowing sound of the blower fan 2 and the control sound emitted from the control speaker 8 is disposed at the upper part of the air outlet 5 to face a direction away from the flow passage.
An output signal of the noise/noise reduction effect detection microphone 16 is input to the signal processing device 22 serving as a control sound generation device that generates a signal (a control sound) which controls the control speaker 8.
Fig. 21 is a block diagram of the signal processing device 22. The difference from the signal processing device 17 shown in Fig. 14 is that the weighting means 13 is disposed between the output of the A/D converter 12 and the input of the LMS algorithm 19. The configurations other than that are the same as those of the signal processing device 17 of Embodiment 2.

<C-2. Operations>

Next, a description is given on operations of the air-conditioning apparatus 1. When the air-conditioning apparatus 1 is operated, the impeller 25 of the blower fan 2 rotates. Then, the air in the room is sucked from the upper side of the blower fan 2 and is sent to the lower side of the blower fan 2, thereby generating an air current. Accordingly, an operating sound (noise) is generated in the vicinity of the air outlet of the blower fan 2, and the sound propagates to a downstream side.
As in the case of Embodiment 1, a turbulent flow is generated by rotation of the impeller 25 in the vicinity of the air outlet of the blower fan 2. Further, since the air blown from the blower fan 2 blows from the air outlet of the blower fan 2 toward the outside, the air impinges against the side wall of the housing of the air-conditioning apparatus 1, and a further turbulence of air flow is generated. Therefore, a pressure fluctuation due to the turbulent flow is increased on the side wall of the air-conditioning apparatus 1.
However, in Embodiment 3, the noise/noise reduction effect detection microphone 16 is disposed at the upper portion of the air outlet 5 to face a direction away from the flow passage. Compared with the vicinity of the blower fan 2, the vicinity of the air outlet 5 is separated by a sufficiently large distance from the air outlet of the blower fan 2 where a large turbulent flow is present. Further, in the vicinity of the air outlet 5, the turbulent flow is rectified to some extent by the heat exchanger 4. Therefore, the turbulent flow is smaller in the vicinity of the noise/noise reduction effect detection microphone 16. Furthermore, since the air current does not directly hit the area where the noise/noise reduction effect detection microphone 16 is disposed, the noise/noise reduction effect detection microphone 16 is hardly affected by the turbulent flow. Further, since the noise of the air-conditioning apparatus 1 that is perceived by a person is one that has been emitted from the air outlet 5 into the room, the noise emitting into the room can be detected by arranging the noise/noise reduction effect detection microphone 16 to face the inside of the room in a direction away from the flow passage.
That is, a sound having high coherence with the noise that has been emitted into the room can be detected by attaching the noise/noise reduction effect detection microphone 16 at the upper portion of the air outlet 5 to face a direction away from the flow passage.
Next, a description is given on a method of reducing the operating sound of the air-conditioning apparatus 1. The control sound generating method of Embodiment 3 is similar to the method described in Embodiment 2. The control sound generating method of Embodiment 3 differs from the method described in Embodiment 2 in that the signal input as an error signal to the LMS algorithm 19 is averaged by the weighting means 13.
In the case where the noise/noise reduction effect detection microphone 16 is disposed at the upper portion of the air outlet 5 to face a direction away from the flow passage, the noise detected by the noise/noise reduction effect detection microphone 16 contains a large number of sounds other than the noise generated from the blower fan 2. Thus, these sounds other than the noise undermine the stability of the feedback control. To solve this problem, in Embodiment 3, the sounds other than the noise are averaged by providing the weighting means 13 to the preceding step of the feedback control. This allows components of the uncorrelated sounds other than the noise to be canceled, and allows the feedback control to be operated stably. That is, this makes it possible to increase the coherence between the noise output from the air outlet 5 into the room and the noise/noise reduction effect detection microphone 16.
It should be noted that, as in the case of Embodiment 1, the averaging operation by the weighting means 13 may not be performed until the LMS algorithm 19 becomes stable. This is because the noise is not sufficiently reduced while the LMS algorithm 19 is not stable, and runaway of the output value of the weighting means 13 may occur. Further, the output value of the weighting means 13 may be reset if the output value of the weighting means 13 exceeds a certain value.
Further, in order to further reduce the effect of the air current, the noise/noise reduction effect detection microphone 16 may be covered with a wall member 31. Since the wall member can block the air current, the noise/noise reduction effect detection microphone 16 is less affected by the air current, and a higher noise reduction effect can be obtained.
Further, in Embodiment 3, an axial fan is described as an example of the blower fan 2. However, the blower fan 2 may be any fan that blows air by rotation of an impeller.
Furthermore, the installation position of the noise/noise reduction effect detection microphone 16 is not limited to the upper portion of the air outlet 5, and may be in the opening portion of the air outlet 5. For example, the noise/noise reduction effect detection microphone 16 may be attached to a lower portion or a lateral portion of the air outlet 5. Further, the noise/noise reduction effect detection microphone 16 does not need to be disposed so as to accurately face the direction away from the flow passage as long as the noise/noise reduction effect detection microphone 16 is disposed to face away from the air-conditioning apparatus 1 (the housing). That is, the noise/noise reduction effect detection microphone 16 may be installed at any position where noise emitted into the room can be detected.
Further, in Embodiment 1, the FIR filter 18 and the LMS algorithm 19 are used in the signal processing device 22. However, the signal processing device 22 may be any adaptive signal processing circuit that makes the sound detected by the noise/noise reduction effect detection microphone 16 approach zero, and may be one using a filtered-x algorithm that is commonly employed by active noise reduction methods.
Further, the weighting means 13 does not need to be an integrator, and may be any means that can perform an averaging operation.
Further, the signal processing device 22 does not need to be configured to perform adaptive signal processing, and may be configured to generate a control sound using a fixed tap coefficient.
Furthermore, the signal processing device 22 does not need to be a digital signal processing circuit, and may be an analog signal processing circuit.

<C-3. Advantageous Effects>

As described above, in the air-conditioning apparatus 1 according to Embodiment 3, the noise/noise reduction effect detection microphone 16 serving as a noise/noise reduction effect detection device is disposed in the opening portion of the air outlet 5, and is arranged to face away from the air-conditioning apparatus 1. Therefore, the noise/noise reduction effect detection microphone 16 can detect the noise emitted into the room without being affected by the air current. Accordingly, it is possible to obtain high coherence between the noise emitted into the room from the air-conditioning apparatus 1 and the detected sound of the noise/noise reduction effect detection microphone 16. Therefore, active noise reduction can be performed with high accuracy on the noise emitted into the room from the air-conditioning apparatus 1.
Further, in the air-conditioning apparatus 1 according to Embodiment 3, the signal processing device 22 serving as a control sound generation device is provided with a circuit that applies weight to a detection result detected by the noise/noise reduction effect detection microphone 16 serving as a noise reduction effect detection device, and performs feedback control. Therefore, sounds other than the noise of the air-conditioning apparatus 1 detected by the noise/noise reduction effect detection microphone 16 can be canceled by averaging the sounds. Accordingly, active noise reduction can be performed with higher accuracy.
Further, in the air-conditioning apparatus 1 according to Embodiment 3, the noise/noise reduction effect detection microphone 16 may be covered with the wall member 31. Since the wall member blocks the air current, the noise/noise reduction effect detection microphone 16 is less affected by the air current and a higher noise reduction effect can be obtained.

Reference Signs List

1 air-conditioning apparatus; 2 blower fan; 3 air inlet; 4 heat exchanger; 5 air outlet; 6 noise detection microphone; 7 stator blade attachment member; 8 control speaker; 9 noise reduction effect detection microphone; 10, 17, 22 signal processing device; 11 microphone amplifier; 12 A/D converter; 13 weighting means; 14 D/A converter; 15 amplifier; 16 noise/noise reduction effect detection microphone; 18, 20 FIR filter; 19 LMS algorithm; 21 multiplier; 25 impeller; 26 stator blade; 27 boss portion; 28 rotation shaft; 30 heat exchanger fitting; 31 wall member; 32 adder; 33 delay element; and 34 multiplier.

Claims

An air-conditioning apparatus, comprising:
a housing in which an air inlet and an air outlet are formed;

a blower fan having an impeller;

a heat exchanger;

a noise detection device detecting noise generated from the blower fan;

a control sound output device outputting a control sound that reduces the noise;

a noise reduction effect detection device detecting a noise reduction effect of the control sound; and

a control sound generation device generating the control sound on the basis of detection results of the noise detection device and the noise reduction effect detection device, wherein

the noise detection device is arranged in a cylindrical region that is an inscribed circle, which is tangential to inner peripheral portions of blades of the impeller, extended in a direction of a rotation axis of the impeller and is disposed on an immobile member of the blower fan or a downstream side of the blower fan.
The air-conditioning apparatus of claim 1, wherein
the noise reduction effect detection device is disposed in an opening portion of the air outlet and is arranged to face away from the housing.
The air-conditioning apparatus of claim 1 or 2, wherein
the control sound generation device includes a circuit that applies weight to the detection results detected by the noise reduction effect detection device and that performs feedback control.
The air-conditioning apparatus of any one of claims 1 to 3, wherein
the blower fan includes stator blades on a downstream side of the impeller,
the stator blades are disposed on a stator blade attachment member having at least a portion of the member arranged in the cylindrical region, and
the noise detection device is disposed on the stator blade attachment member in an area in the cylindrical region.
The air-conditioning apparatus of any one of claims 1 to 3, wherein
the heat exchanger is disposed on the downstream side of the blower fan such that at least a portion of the heat exchanger is arranged in the cylindrical region, and
the noise detection device is disposed on the heat exchanger in an area in the cylindrical region.
The air-conditioning apparatus of any one of claims 1 to 3, wherein
the heat exchanger is disposed on the downstream side of the blower fan,
the heat exchanger is fixed to the housing by a fitting having at least a portion of the fitting arranged in the cylindrical region, and
the noise detection device is disposed on the fitting in an area in the cylindrical region.
The air-conditioning apparatus of any one of claims 1 to 6, wherein the noise detection device is covered with a wall member.
The air-conditioning apparatus of any one of claims 1 to 7, wherein the noise reduction effect detection device is covered with a wall member.
An air-conditioning apparatus, comprising:
a housing in which an air inlet and an air outlet are formed;

a blower fan having an impeller;

a heat exchanger;

a control sound output device outputting a control sound that reduces the noise generated from the blower fan;

a noise/noise reduction effect detection device detecting the noise, the noise/noise reduction effect detection device detecting a noise reduction effect of the control sound; and

a control sound generation device generating the control sound based on a detection result of the noise/noise reduction effect detection device, wherein

the noise/noise reduction effect detection device is arranged in a cylindrical region that is an inscribed circle, which is tangential to inner peripheral portions of blades of the impeller, extended in a direction of a rotation axis of the impeller and is disposed on an immobile member of the blower fan or a downstream side of the blower fan.
The air-conditioning apparatus of claim 9, wherein
the blower fan includes stator blades on a downstream side of the impeller,
the stator blades are disposed on a stator blade attachment member having at least a portion of the member arranged in the cylindrical region, and
the noise/noise reduction effect detection device is disposed on the stator blade attachment member in an area in the cylindrical region.
The air-conditioning apparatus of claim 9, wherein
the heat exchanger is disposed on the downstream side of the blower fan such that at least a portion of the heat exchanger is arranged in the cylindrical region, and
the noise/noise reduction effect detection device is disposed on the heat exchanger in an area in the cylindrical region.
The air-conditioning apparatus of claim 9, wherein
the heat exchanger is disposed on the downstream side of the blower fan,
the heat exchanger is fixed to the housing by a fitting having at least a portion of the fitting arranged in the cylindrical region, and
the noise/noise reduction effect detection device is disposed on the fitting in an area in the cylindrical region.
An air-conditioning apparatus, comprising:
a housing in which an air inlet and an air outlet are formed;

a blower fan having an impeller;

a heat exchanger;

a control sound output device outputting a control sound that reduces the noise generated from the blower fan;

a noise/noise reduction effect detection device detecting the noise, the noise/noise reduction effect detection device detecting a noise reduction effect of the control sound; and

a control sound generation device generating the control sound based on a detection result of the noise/noise reduction effect detection device, wherein

the noise/noise reduction effect detection device is disposed in an opening portion of the air outlet and is arranged to face away from the housing.
The air-conditioning apparatus of claim 13, wherein
the control sound generation device includes a circuit that applies weight to the detection result detected by the noise/noise reduction effect detection device and that performs feedback control.
The air-conditioning apparatus of any one of claims 9 to 14, wherein the noise/noise reduction effect detection device is covered with a wall member.