JP2015001693A - Silencer and electronic device provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cooling fan device that allows a silencer that silences noise of a cooling fan to efficiently perform silencing, and to provide the silencer and an electronic device provided with the silencer.SOLUTION: The silencer comprises: a cooling fan of which the number of blades is a multiple of a wavenumber of an FG signal per one rotation; a signal detection part 9 that detects a rotation frequency of the cooling fan and the FG signal indicative of a timing when one period of a rotation of a plurality of blades starts; a reverse phase sound adjustment part 10 that adjusts a frequency of a reverse phase sound and amplitude of a sound pressure level waveform on the basis of a sound pressure level waveform of periodic noise to be generated by the rotation of the plurality of blades and a relation of the reverse phase sound having the sound pressure level waveform of a reverse phase, the FG signal and the rotation frequency of the plurality of blades with the amplitude of the noise sound pressure level waveform; a timing adjustment part 11 that matches the timing when one period of the FG signal and the reverse phase sound starts; and a speaker 12 that outputs the adjusted reverse phase sound.

Description

The present invention relates to a silencer for muting noise generated from a cooling fan or the like installed in, for example, a notebook personal computer, and an electronic apparatus using the same.

In recent years, in electronic devices such as notebook personal computers, the CPU clock frequency has been increased. As the clock frequency increases, the amount of heat generated by the CPU increases, so that it is required to improve the cooling capacity of the cooling fan mounted inside the housing. On the other hand, notebook computers are becoming smaller and the space given to the cooling module is limited. Therefore, although the rotation speed of the cooling fan is increased to increase the air volume, there arises a problem that the sound generated by the rotation of the cooling fan becomes noise. In order to solve this problem, it is known to use an active noise canceling method (hereinafter referred to as an ANC method) that eliminates noise by hitting a sound having an opposite phase and the same amplitude to the noise (for example, ANC method) (for example, , See Patent Document 1).
Further, even in the ANC method, a technique has been developed that predicts the noise to be erased in advance to efficiently widen the range to be erased (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 2002-244677 JP 2010-174771 A

However, the conventional ANC method has the following problems. First, in the routine where the noise signal (analog) collected by the microphone is converted into a digital signal and processed, and the digital signal is converted back to analog and sound is output from the speaker, a time delay occurs in each arithmetic processing. When an out-of-phase sound is emitted, the phase is greatly delayed from the original sound. Therefore, in order to adjust the phase lag, it is necessary to increase the distance between the cooling fan and the speaker so that the processed sound is ahead of the sound speed. However, since a distance of several tens of centimeters is generally required, it is not suitable for small electronic devices such as notebook computers. In addition, as the distance between the cooling fan and the speaker increases, the range in which the noise generated from the cooling fan and the antiphase sound output from the speaker cancel each other out becomes narrower. That is, in other places, the noise of the cooling fan and the antiphase sound are intensified, and the position of the operator is limited. In addition, the structure is large, which increases the cost.

Therefore, a method for predicting the noise to be erased, which is disclosed in Patent Document 2, has been developed in advance, but this method needs to synchronize the FG signal output from the motor with the fan blade noise. This synchronizing operation is necessary every time the motor is stopped and driven, but is complicated and causes a malfunction.

Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a centrifugal fan device, a muffler device, and an electronic apparatus including the same, which can simplify the operation of synchronization and have no malfunction.

Accordingly, the present invention has been made to solve the above-described problem, and includes a cooling fan in which the number of blades is a multiple of the wave number of the FG signal per rotation, the rotation frequency of the cooling fan, and the rotation of the plurality of blades. A signal detector for detecting an FG signal indicating a timing at which one cycle starts, an antiphase sound having a sound pressure level waveform opposite to the sound pressure level waveform of periodic noise generated by rotation of the plurality of blades, and A storage unit that stores the relationship between the rotation frequency of the plurality of blades and the amplitude of the noise sound pressure level waveform, and the relationship between the rotation frequency of the FG signal and the plurality of blades and the amplitude of the noise sound pressure level waveform. An anti-phase sound adjusting unit that adjusts the frequency of the anti-phase sound and the amplitude of the sound pressure level waveform based on the timing, and a timing at which one cycle of the FG signal and the anti-phase sound starts A timing adjustment unit to match, characterized by comprising a speaker for outputting the opposite phase sound is adjusted in the opposite phase sound adjustment portion and said timing adjustment unit.

With the above configuration, the present invention has the following effects. That is, since a reverse phase sound is stored in advance, a microphone is not required, and further complicated calculation processing is not required, so that a phase delay of the reverse phase sound can be prevented. Accordingly, the speaker can be provided in the vicinity of the cooling fan, and the anti-phase sound output from the speaker can eliminate noise generated from the cooling fan in a wide range. Furthermore, since the antiphase sound of only the cooling fan is stored in advance, it is not affected by noise other than the cooling fan. Further, by making the number of blades a multiple of the wave number of the FG signal per rotation, the work of matching the timing at which one cycle of the FG signal and the antiphase sound starts can be simplified, thus preventing a malfunction. be able to.

The perspective view of the centrifugal fan apparatus in a present Example The perspective view of the centrifugal fan apparatus of the state which removed the fan cover in a present Example Operational diagram showing the silencer in this embodiment Waveform diagram showing noise and antiphase sound Waveform diagram showing noise and anti-phase sound when the rotational speed of the centrifugal fan device is higher than in FIG. Conceptual diagram showing the relationship between the position of the housing and the operator and the noise Waveform diagram showing noise heard by the operator Waveform diagram showing FG signal waveform with wave number 2 and anti-phase sound with 13 and 12 blades Waveform diagram showing FG signal waveform with wave number 3 and antiphase sound with 13 and 12 blades

According to a first aspect of the present invention, there is provided a cooling fan in which the number of blades is a multiple of the wave number of the FG signal per rotation, a rotation frequency of the cooling fan, and one cycle of rotation of the plurality of blades. A signal detection unit for detecting an FG signal indicating a timing at which the sound begins, an antiphase sound having a sound pressure level waveform opposite in phase to a sound pressure level waveform of periodic noise generated by rotation of the plurality of blades, and the plurality A storage unit for storing the relationship between the rotation frequency of the blade and the amplitude of the noise sound pressure level waveform, and the relationship between the FG signal, the rotation frequency of the plurality of blades, and the amplitude of the noise sound pressure level waveform. The phase of the antiphase sound adjusting unit for adjusting the frequency of the antiphase sound and the amplitude of the sound pressure level waveform is matched with the timing at which one cycle of the FG signal and the antiphase sound starts. A timing adjustment unit, a muffler, characterized in that and a speaker for outputting the opposite phase sound is adjusted in the opposite phase sound adjustment portion and said timing adjustment unit.

As a result, since a reverse phase sound is stored in advance, a microphone is not required, and further no arithmetic processing is required, so that a phase delay of the reverse phase sound can be prevented. Accordingly, the speaker can be provided in the vicinity of the cooling fan, and the anti-phase sound output from the speaker can eliminate noise generated from the cooling fan in a wide range. Furthermore, since the antiphase sound of only the cooling fan is stored in advance, it is not affected by noise other than the cooling fan.

According to a second aspect of the present invention, there is provided an electronic apparatus equipped with the silencer according to the first aspect, comprising a camera for recognizing a position of an operator who uses the electronic apparatus, and is recognized by the camera. The timing adjustment unit adjusts the timing at which one cycle of the FG signal and the antiphase sound starts depending on the position of the microphone, and the microphone for storing the antiphase sound in advance Is not required, and further arithmetic processing is not required, so that the phase delay of the antiphase sound can be prevented. Accordingly, the speaker can be provided in the vicinity of the cooling fan, and the anti-phase sound output from the speaker can eliminate noise generated from the cooling fan in a wide range. Furthermore, since the antiphase sound of only the cooling fan is stored in advance, it is not affected by noise other than the cooling fan.

Embodiments of the present invention will be described below with reference to the drawings.

(Embodiment) FIG. 1 is a perspective view of a centrifugal fan device in this embodiment. A box-shaped fan case 2 of the centrifugal fan device 1 includes a fan frame 2a located at the lower part and a fan cover 2b located at the upper part. Here, the fan frame 2a is integrally formed with a bottom surface and a side surface by resin molding or die casting of an aluminum alloy, and an exhaust port 3 for exhausting the intake air is disposed on one side surface thereof. An air inlet (not shown) is disposed on the bottom surface. The fan cover 2b is formed into a plate shape by stamping or resin molding of a metal material such as aluminum or stainless steel, and a substantially circular intake port 4 for sucking air is disposed at the center thereof. Yes.

Centrifugal fan 5 is arranged so as to be sandwiched and accommodated between fan frame 2a and fan cover 2b.

FIG. 2 is a perspective view of the centrifugal fan device with the fan cover removed in the present embodiment. In FIG. 2, the centrifugal fan 5 comprises a hub portion 6 having a cylindrical outer peripheral surface and a plurality of blade portions 7 extending radially from the outer peripheral surface in the centrifugal direction.

Further, the surface shape in the direction of the rotation axis in a predetermined region of the surface in the rotational direction (positive pressure surface) of the blade portion 7 is such that the both end portions in the vertical direction of the blade portion 7 are on the rotational direction side than the central portion of the blade portion 7. It is the shape located in. Further, an upper annular plate 8 is provided at the outer peripheral portion of the blade portion 7 so as to be continuously connected to the upper end portion in the rotation axis direction.

Here, when the centrifugal fan 5 rotates at a high speed in the rotation direction indicated by the arrow R, the suction port disposed at the center of the fan cover 2b and the bottom surface of the fan frame 2a are opposed to the upper surface of the hub portion 6. Air is sucked in from the direction of the rotation axis (not shown) of the centrifugal fan 5 (described later) from the air intake port provided, and the sucked air is moved inside the fan case 2 by the rotational movement of the blade portions 7. Since the wind direction is changed to the centrifugal direction of the blade portion 7, most of the blade portion 7 collides with the inner walls of the frame 2a and the cover 2b, and in the same direction as the rotation direction indicated by the arrow R of the centrifugal fan 5 along the inner walls. These airs are sent and exhausted from the exhaust port 3.

Next, specific means of the silencer of the present invention will be described. FIG. 3 is an operation diagram illustrating the silencer in the present embodiment.

In FIG. 3, 1 is a centrifugal fan device, 9 is an FG signal detection unit that detects an FG signal from the centrifugal fan device 1 and generates an FG signal as a complete rectangular wave, and 10 is an anti-phase sound stored in advance. An anti-phase sound adjustment unit 11 that adjusts the frequency and amplitude based on a complete rectangular wave (FG signal) detected by the FG signal detection unit 9 receives an output signal from the anti-phase sound adjustment unit 10, and an operator The timing adjustment unit 12 adjusts the phase of the output signal by an operation from a computer, and 12 is a speaker.

In this embodiment, a notebook PC will be described as an example. In this case, the centrifugal fan device 1 includes a cooling fan mounted on the notebook PC, an FG signal detection unit 9, an antiphase sound adjustment unit 10, The timing adjustment unit 11 is a CPU of a notebook PC or a CPU dedicated to a cooling fan, and the speaker 12 is a speaker mounted on the notebook PC.

Next, the operation of the silencer will be described. The centrifugal fan device 1 repeatedly outputs noise generated during one rotation of the centrifugal fan device 1 every rotation, and has periodicity. Therefore, it is possible to store in advance the anti-phase sound of the noise generated during one rotation of the cooling fan. First, in S <b> 1, the FG signal detection unit 9 detects an FG signal that is rotation cycle information of the centrifugal fan device 1. At this time, as described above, the FG signal is detected as a complete rectangular wave. In S <b> 2, the FG signal of the centrifugal fan device 1 is taken into the antiphase sound adjustment unit 10. The anti-phase sound adjustment unit 10 uses the waveform of the anti-phase sound stored in advance in a storage unit (not shown) so that the frequency and amplitude are equal to the noise from the centrifugal fan device 1 based on the detected FG signal. Adjust to.

As for the amplitude, the noise increases and the amplitude increases depending on the rotational speed of the centrifugal fan device 1. However, by storing in advance the relationship between the FG signal indicating the rotational speed and the amplitude, the amplitude based on the detected FG signal. Is adjusted.

In S <b> 3, the antiphase sound whose amplitude and frequency are adjusted is taken into the timing adjustment unit 11. At the same time, in S4, the FG signal is also sent from the FG signal detection unit 9 to the timing adjustment unit 11 and captured. The timing adjustment unit 11 matches the timing at which one cycle of the antiphase sound starts with the timing at which one cycle of the FG signal corresponding to the actual noise of the centrifugal fan device 1 starts. If there is an input from the operator, the timing at which one cycle of the antiphase sound starts is changed according to the input. In S <b> 5, the antiphase sound adjusted for the start timing of one cycle is output from the speaker 12. Thereby, in S6, the noise from the centrifugal fan apparatus 1 and the antiphase sound output from the speaker are synthesized.

However, the number of blades of a general centrifugal fan is a prime number. This is to prevent the sounds generated by the blades from being combined to produce a loud noise. On the other hand, the wave number of the FG signal of the motor is often two or three wave numbers per rotation. FIG. 8 is a waveform diagram showing FG signal waveforms having a wave number of 2 and anti-phase sounds having 13 and 12 blades. FIG. 8A is a waveform diagram of an FG signal waveform having a wave number of 2 and a fan blade having 13 blades. The timing at which one cycle of centrifugal fan noise starts is the first waveform of the FG signal waveform. Since the positional shift amount differs depending on the waveform, if the first waveform and the second waveform are mistaken, a situation in which the sound cannot be silenced occurs. Moreover, it is difficult to distinguish whether the FG waveform is the first waveform or the second waveform.

Therefore, when the number of blades is set to 12 which is a multiple of two wave numbers as shown in FIG. 8B, all the FG waveforms have the same positional relationship as the noise waveform of the centrifugal fan. Therefore, the antiphase sound of the centrifugal fan noise can be started from any waveform of the FG waveform.

Further, FIG. 9 is a waveform diagram showing an FG signal waveform having a wave number of 3 and anti-phase sounds having 13 and 12 blades. As shown in FIG. 9A, when the wave number is 3, the timing at which one cycle of the centrifugal fan noise starts has a positional relationship between the first waveform, the second waveform, and the third waveform of the FG signal waveform. The amount of misalignment will be different

However, as shown in FIG. 9B, when the number of blades is 12 which is a multiple of the wave number 3, any FG waveform has the same positional relationship as the noise waveform of the centrifugal fan.

In S7, the synthesized centrifugal fan device 1 noise and anti-phase sound reach the operator. At that time, depending on the position of the operator, the noise of the centrifugal fan device 1 may reach the operator without being silenced.

In that case, in S8, the operator himself / herself inputs the timing at which one cycle of the antiphase sound starts to be equal to the timing at which one cycle of the noise of the centrifugal fan device 1 starts. The timing adjusting unit 11 adjusts according to the input of the operator so that the timing at which the centrifugal fan device 1 starts one rotation coincides with the timing at which one cycle of the antiphase sound starts. Then, the adjusted antiphase sound is output from the speaker 12 again, synthesized with the noise of the centrifugal fan device 1, and silenced.

If the number of blades of the centrifugal fan is a prime number, the timing of the FG signal waveform and anti-phase sound needs to be adjusted again when the centrifugal fan is stopped and then restarted. However, if the number of blades is a multiple of the wave number of the FG signal, the amount of timing adjustment deviation can be made the same as the first time, and timing adjustment, which is a complicated operation, can be simplified.

The anti-phase sound stored in advance here differs depending on the shape of the centrifugal fan 5, but has periodicity as described above.

Next, regarding the noise of the centrifugal fan device 1 and its antiphase sound, refer to the waveform indicating the sound pressure level of the noise generated from the centrifugal fan device 1 and the waveform indicating the sound pressure level of the antiphase sound that silences the noise. I will explain. FIG. 4 is a waveform diagram showing noise and anti-phase sound, and FIG. 5 is a waveform diagram showing noise and anti-phase sound when the rotational speed of the centrifugal fan device is higher than that in FIG.

4A is a waveform diagram showing the sound pressure level of noise generated from a normal centrifugal fan device, and FIG. 4B is an antiphase sound that silences the noise of FIG. 4A. It is a waveform which shows the sound pressure level.

By detecting the FG signal shown in FIG. 4A, noise that is actually generated from the centrifugal fan device is specified, and as shown in FIG. 4B, the noise, frequency, and amplitude from the centrifugal fan device are identified. 4 generate a cancel sound having the same reverse phase sound, and the reverse phase sound shown in FIG. 4B is a signal obtained by inverting the positive and negative of the noise from the centrifugal fan device shown in FIG. 4A.

Then, by synthesizing the canceling sound in FIG. 4B and the noise shown in FIG. 4A, the sound pressure level of the combined wave becomes zero, and the noise is muted.

Next, a case where the rotation speed of the motor is increased will be described. Fig.5 (a) is a wave form diagram which shows the sound pressure level of the noise which generate | occur | produces from the centrifugal fan apparatus 1 when rotation speed increases compared with Fig.4 (a), FIG.5 (b) is a figure. It is a wave form diagram which shows the sound pressure level of the antiphase sound which silences the noise of 5 (a). Normally, the centrifugal fan rotates at the speed shown in FIG. 4A. However, when the object to be cooled, such as a CPU, generates heat more than usual, the rotational speed of the centrifugal fan increases. At that time, the noise of the centrifugal fan has a waveform as shown in FIG. At this time, the FG signal detection unit 9 detects a change in the rotational frequency of the centrifugal fan device 1 using the FG signal (FIG. 3, S1), and the antiphase sound adjustment unit 10 adjusts the frequency and amplitude of the antiphase sound (FIG. 3). 3, S2), the waveform of the antiphase sound corresponding to FIG. 4B stored in advance is as shown in FIG. 5B. When the noise generated from the centrifugal fan device shown in FIG. 5 (a) and FIG. 5 (b) are synthesized, the sound pressure level of the synthesized wave becomes zero, and the noise is muted even when the rotational frequency of the centrifugal fan changes. The

In this embodiment, the waveform of the anti-phase sound stored in advance is adjusted based on the detected FG signal, but the anti-phase sound corresponding to the FG signal is stored separately to generate the anti-phase sound. May be.

Next, the phase relationship between the noise of the centrifugal fan device and the antiphase sound will be described with reference to FIGS. FIG. 6 is a conceptual diagram showing the relationship between the position of the housing and the operator and noise, FIG. 7 is a waveform diagram showing noise heard by the operator, and FIG. 6 (a) and FIG. When the operator is located in a range where the noise of the centrifugal fan is not muted and the noise and the antiphase sound are intensified, FIGS. 6 (b) and 7 (b) show that the operator has 1 of the antiphase sound. This is a case where the noise of the centrifugal fan is silenced by adjusting the timing at which the cycle starts. In order to simplify the description, the relationship between noise and antiphase sound will be described using a sine wave. In FIG. 6, + represents a position where the sound pressure level is positive, for example,-represents a position where the sound pressure level is negative, and the frequency of the centrifugal fan noise and the antiphase sound output from the speaker is Suppose they are equal.

In order to mute the noise of the centrifugal fan device, it is necessary to cancel by the antiphase sound as described above. However, depending on the position of the operator who operates the notebook PC, as shown in FIG. In some cases, the sound pressure level of the centrifugal fan noise is-and the sound pressure level of the antiphase sound is-. At this position, as shown in FIG. 7A, the timing at which one cycle of the antiphase sound (cancellation sound) starts is deviated from the timing at which one cycle of centrifugal fan noise (fan noise) begins. As a result of the synthesis, the sounds are strengthened as shown in FIG. The same can be said for the range in which the sound pressure level of the centrifugal fan noise is + and the sound pressure level of the antiphase sound is +.

In such a case, at the operator's position, the sound pressure level of the centrifugal fan noise is + and the sound pressure level of the antiphase sound is-, or the sound pressure level of the centrifugal fan noise is-and the sound of the antiphase sound is The operator adjusts the timing at which one cycle of the antiphase sound starts so that the pressure level becomes +. That is, the timing at which one cycle of the antiphase sound starts is input to the timing adjustment unit so as to be from FIG. 7A to FIG. 7B. As a result, when the centrifugal fan noise and the anti-phase sound are synthesized, the result is as shown in FIG.

In some cases, the timing at which one cycle of the antiphase sound starts cannot be adjusted because the operator is working. In such a case, for example, an electronic device equipped with a centrifugal fan such as a notebook computer is provided with a camera, and the position of the operator is recognized by the camera. The position information of the operator recognized by the camera is sent to the timing adjustment unit. The timing adjustment unit adjusts so that the timing at which one cycle of the antiphase sound starts coincides with the timing at which one rotation of the centrifugal fan starts at the position of the operator. Therefore, wherever the operator is located, the antiphase sound can mute the noise of the centrifugal fan.

Note that the above silencer is not limited as long as it has periodic noise, has a speaker that cancels noise, and has a centrifugal fan device. In addition to the above-described notebook PC, the silencer may also be applied to electronic devices such as desktop PCs and televisions. Available.

The silencer of the present invention can eliminate noise generated from the centrifugal fan over a wide range without delaying the phase of the antiphase sound even when mounted on a miniaturized electronic device. It is useful for electronic devices such as personal computers.

DESCRIPTION OF SYMBOLS 1 Centrifugal fan apparatus 2 Fan case 3 Exhaust port 4 Intake port 5 Centrifugal fan 6 Hub part 7 Blade part 8 Ring plate 9 FG signal detection part 10 Antiphase sound adjustment part 11 Timing adjustment part 12 Speaker

Claims (2)

A cooling fan in which the blade rotates with the number of blades being a multiple of the wave number of the FG signal per rotation;
A signal detection unit for detecting an FG signal indicating a rotation frequency of the cooling fan and a timing at which one cycle of rotation of the plurality of blades starts;
A reverse phase sound having a sound pressure level waveform opposite in phase to a sound pressure level waveform of periodic noise generated by the rotation of the plurality of blades, and a rotation frequency of the plurality of blades and an amplitude of the noise sound pressure level waveform, A storage unit for storing the relationship between
An anti-phase sound adjusting unit that adjusts the frequency of the anti-phase sound and the amplitude of the sound pressure level waveform based on the relationship between the FG signal and the rotation frequency of the plurality of blades and the amplitude of the noise sound pressure level waveform;
A timing adjustment unit for matching a timing at which one cycle of the FG signal and the antiphase sound starts,
A muffler comprising: a speaker that outputs the antiphase sound adjusted by the antiphase sound adjustment unit and the timing adjustment unit. An electronic device comprising the silencer according to claim 1, further comprising a camera that recognizes a position of an operator who uses the electronic device, and the timing adjustment unit is configured to detect the position by the camera. An electronic apparatus characterized by adjusting a timing at which one cycle of an FG signal and the antiphase sound starts.

Images