JP2006258003A - Active muffling device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To eliminate the need of a sensor microphone in an active muffling device and utilizing a fact that a low frequency noise is in proportion to a power generation frequency of a generator to generate a muffling signal from a power generation voltage signal and thereby to muffle the low-frequency noise. <P>SOLUTION: An exhaust duct 7 for muffling communicates with each exhaust part of engines 11, 12, 13, 14 of engine generators 1, 2, 3, 4. A sound wave interference part 7a is disposed to the exhaust duct 7, an error microphone 17 is disposed downstream of the sound wave interference part 7a as a means for detecting the muffling signal. A branch duct 8 communicates with the sound wave interference part 7a, and a speaker 9 is provided as a means for outputting the muffling signal in a phase opposite to the noise in the branch duct 8. The generators 21, 22, 23, 24 are connected with a controller 16 as a control means through a transformer 26 and a frequency converter 25, the power generation frequency of the power generation voltage is converted into a noise signal to be used as a muffling signal and thereby to muffle the low-frequency noise. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an active silencer that reduces noise generated by an internal combustion engine (engine). More specifically, the present invention relates to a technique for reducing low-frequency noise generated from an engine generator by using an active silencer by generating a noise signal from a generated voltage.

Conventionally, in order to reduce noise generated from an internal combustion engine, a technique for arranging a passive silencer or an active silencer in an exhaust duct is known (see, for example, Patent Document 1).
Passive silencers are mainly used to silence high frequencies. This is because, since the wavelength of the high frequency is short, the passive silencer can be configured to be short and can be configured compactly. On the other hand, when trying to mute the low frequency with the passive silencer, the low frequency wavelength is long, so the passive silencer also becomes larger, the weight increases, the space occupied by the passive silencer also increases, It may become impossible to store in the storage room. Therefore, the low frequency is silenced by the active silencer.

  In the active silencer in the prior art disclosed in Patent Document 1, a sound wave interference unit is provided in the middle of an exhaust duct of an engine of an engine generator, and a passive sound silencer is communicated with a noise source side of the sound wave interference unit. A sensor microphone is disposed as a means for detecting noise on the noise source side of the silencer, and an error microphone is disposed as a means for detecting a noise signal after silence on the downstream side (discharge side) of the sound wave interference unit, A branch pipe is communicated with the sound wave interference section, and a speaker is disposed on the branch pipe.

Then, the speaker, the sensor microphone, and the error microphone are connected to a controller serving as a control means, and the controller generates an interference sound having an opposite phase and an equal amplitude to the noise to be erased detected by the sensor microphone and radiates it from the speaker Thus, the two sound waves interfere with each other at the sound wave interference portion to cancel each other and mute. Further, the silencing result is detected by the error microphone, the sound wave that has not been muted is fed back, corrected by the controller, and the corrected interference sound is emitted from the speaker, thereby further enhancing the silencing effect. It was like that.
JP 2001-2221026 A

  By the way, the engine generator can supply power by driving only one engine generator when the supply power is low (when demand is small), but when generating electricity in large facilities such as hospitals and complex buildings. In this configuration, multiple engine generators are installed in parallel and controlled so that the number of operating units can be increased or decreased according to the power demand (load), so that energy can be used effectively and large power can be supplied. Yes.

  If a specific engine generator is controlled so that it always operates among a plurality of engine generators, the engine generator used only when the specific engine generator has the shortest life and other loads are long As a result, the durability of the engine and the generator itself will vary, and the time for parts replacement and maintenance will also vary. Therefore, the start and stop of each engine generator is selected according to the power demand so that the operation times of the plurality of engine generators are approximately the same time, and the engine generators that have been used for a long time are quicker when the load is small. The engine generator that is stopped and has a short total use time is controlled to operate for a long time.

Therefore, when such control is performed, when a plurality of engine generators are operating and stopped, and when the power demand increases or decreases, which engine generator is among those engine generators Is operating in a state where it is difficult to determine which generator will start and which generator will stop next. Therefore, when an active silencer is disposed in the exhaust part of the engine to mute the sound, it is necessary to attach a sensor microphone to the exhaust duct of each engine. Further, since wiring for connecting each sensor microphone is also required, the cost is increased, and a complicated circuit and control are required.
Therefore, the present invention eliminates the sensor microphone in the active silencer and uses the fact that the low frequency noise is proportional to the power generation frequency of the generator to generate a silence signal from the generated voltage signal, It is intended to mute noise.

  The problems to be solved by the present invention are as described above. Next, means for solving the problems will be described.

  That is, in claim 1, a noise-reducing exhaust duct is communicated with an exhaust part of an engine of an engine generator, a sound wave interference part is provided in the sound-reducing exhaust duct, and noise after noise reduction is provided downstream of the sound wave interference part. In an active silencer comprising: a signal detecting means; a branch duct communicating with the sound wave interference unit; a means for outputting a silence signal having a phase opposite to that of the noise arranged in the branch duct; and a control means. It connects with a control means via a transformer and a frequency converter, converts the generated frequency of the generated voltage into a noise signal, and calculates it as a mute signal.

  According to a second aspect of the present invention, the frequency of the noise signal is a predetermined multiple of the rated engine speed.

  According to a third aspect of the present invention, a plurality of the engine generators are arranged so that they can be operated in parallel.

  According to a fourth aspect of the present invention, the silencer exhaust duct is disposed in the vertical direction, and the branch duct is disposed in communication with the lower end of the silencer exhaust duct.

  In claim 5, a silencer exhaust duct is communicated with an exhaust part of an engine of an engine generator, a sound wave interference part is provided in the sound deadening exhaust duct, and a noise signal after noise reduction is provided downstream of the sound wave interference part. In an active silencer, comprising: a detecting means; a branch duct communicating with the sound wave interference unit; a means for outputting a silence signal having a phase opposite to that of the noise disposed in the branch duct; and a control means. A vibration sensor is arranged in the vicinity of the duct for use and connected to the control means, and a signal from the vibration sensor is calculated as a noise signal into a mute signal to mute the sound.

As effects of the present invention, the following effects can be obtained.
According to the first aspect of the present invention, it is possible to omit a sensor microphone serving as a noise detection unit, and to reduce costs. Since a noise signal can be generated from the generated voltage of the engine generator, it can be reliably distinguished from other generated sound waves, and the target frequency to be silenced can be reliably detected and silenced to reduce noise. In addition, it is possible to make the low-frequency noise to be silenced more compact and less expensive than reducing it by a passive silencer.

  According to the second aspect of the present invention, since the rated frequency of the engine is converted into a predetermined multiple to obtain the noise frequency, the conversion can be easily performed and the burden on the control means can be reduced. Also, the circuit configuration can be simplified.

  According to the third aspect of the present invention, a noise signal is generated from the generated voltage even if the second and third units are separately started in a plurality of engine generators. Therefore, a sensor microphone serving as a noise detection means is required for each engine. However, the cost can be reduced.

  According to the fourth aspect of the present invention, the sound wave interference portion can be disposed above the communication portion between the muffler exhaust duct and the branch duct, and the duct communicating between the engine and the sound wave interference portion can be disposed as low as possible. Therefore, duct piping can be easily performed. It becomes difficult for high-temperature exhaust gas to flow through the lower branch duct to the side that emits a muffler signal.

  According to the fifth aspect of the present invention, it is possible to omit the sensor microphone serving as the noise detection means, and to reduce the cost. Since a noise signal can be generated by detecting vibration of the engine itself, it can be reliably distinguished from other generated sound waves, and the target frequency to be silenced can be reliably detected and silenced to reduce noise. In addition, it has become possible to configure a small and inexpensive.

Next, embodiments of the invention will be described.
FIG. 1 is a plan view of an engine generator and a passive silencer part, FIG. 2 is a front view of a passive silencer and an exhaust duct part, FIG. 3 is a side view of an exhaust duct and a branch duct part, and FIG. FIG. 5 is a control block diagram showing another embodiment of the active silencer.

  First, a schematic configuration of the engine generator will be described. In this embodiment, four engine generators 1, 2, 3 and 4 are arranged in parallel, and the engine generators 1, 2, 3 and 4 are operated and stopped according to the load. The number of engine generators that are operated in parallel is not limited, and may be one or two or more.

  As shown in FIGS. 1 and 2, the engine generators 1, 2, 3, and 4 are connected to the output shafts of the engines 11, 12, 13, and 14 with the rotor shafts of the generators 21, 22, 23, and 24. Thus, the generator is operated by the driving force of the engine to generate power. As will be described later, each of the engine generators 1, 2, 3, and 4 is synchronously operated to generate power so as to match the frequency of the commercial power source. Ducts 5a, 5b, 5c, and 5d communicate with exhaust pipes (exhaust manifolds) of the engines 11, 12, 13, and 14, and passive silencers 31 and 32 are connected to the other ends of the ducts 31, 32, 33, and 34, respectively.・ 33 and 34 are connected, and the noise in the high frequency range is muted. Ducts 6a, 6b, 6c, and 6d are further communicated with the downstream side of the passive silencers 31, 32, 33, and 34, and the silencer exhaust duct 7 that forms a flue to the ducts 6a, 6b, 6c, and 6d. Communicated with. The communicating portion between the ducts 6 a, 6 b, 6 c, and 6 d and the silencing exhaust duct 7 is communicated with a sound wave interference portion 7 a provided in the middle part of the proximal end side of the silencing exhaust duct 7.

The silencer exhaust duct 7 is arranged in the vertical direction, the downstream end, that is, the upper end of the silencer exhaust duct 7 is opened, and the base end side, that is, the lower end, branches as shown in FIG. The duct 8 is communicated. The sound wave interference part 7a is arranged in the middle part of the muffler exhaust duct 7, and the ducts 6a, 6b, 6c and 6d are connected in a radial manner so that the vertical height is not increased. Since the silencer exhaust duct 7 and the branch duct 8 are formed of square tubes, the ducts 6a, 6b, 6c, and 6d can be communicated with the four surrounding surfaces.
In the present embodiment, the branch duct 8 communicates in a direction perpendicular to the silencing exhaust duct 7, is configured in an L shape in side view, and extends in the horizontal direction from the lower end of the silencing exhaust duct 7. In this way, the exhaust gas and the like that have entered the muffler exhaust duct 7 from the ducts 6a, 6b, 6c, and 6d rises due to the high temperature, and are difficult to flow downward.

Speakers 9, 9, 9, 9 that emit interference sound having a phase opposite to that of noise are disposed around the end of the branch duct 8 on the side opposite to the exhaust duct, and a cooling fan 10 is disposed at the end of the branch duct 8. Has been. In other words, one end of the branch duct 8 communicates with the base end side of the muffler exhaust duct 7, the cooling fan 10 is disposed at the other end of the branch duct 8, and the branch duct 8 on the downstream side of the cooling fan 10 is connected to the branch duct 8. A speaker 9 is arranged. The number of the speakers 9 is not limited, and the number is determined according to the noise level. In this embodiment, four speakers 9, 9, 9, 9 are arranged and arranged radially on each surface around the square tube.
Thus, by operating the cooling fan 10, the hot air does not flow backward from the duct 6 to the speaker 9 side, and the speaker 9 is not damaged.

Next, the active silencer of the present invention will be described using the control block diagram of FIG.
The speaker 9 is connected to a controller 16 serving as control means and a control panel 18 via an amplifier (amplifier) 15. The amplifier 15 amplifies a mute signal from the controller 16, and the power is supplied from the control panel 18. Yes. The control panel 18 is connected to a commercial power supply so that power can be supplied to the controller 16, the cooling fan 10, the alarm device 29, an amplifier, and the like. Further, the control panel 18 is connected to control units 41, 42, 43, and 44 for rotating the engine 11, 12, 13, and 14 so as to maintain the operation at the start, set rotation, and set phase. In this way, power is supplied from the control panel 18 to each device so that the active silencer is activated when the engine is started and noise is generated.

  Further, a temperature sensor 19 is disposed on the downstream side of the speaker 9 disposed in the branch duct 8, and the temperature sensor 19 is connected to the control panel 18 to detect the temperature in the branch duct 8 and exceed the set temperature. Then, the cooling fan 10 is operated to cool the inside of the branch duct 8, and when a set temperature that adversely affects a higher speaker is reached, an alarm is issued from the alarm device 29 so that a predetermined measure, for example, the engine is stopped. Control.

  Further, an error microphone 17 is disposed as a means for detecting noise after muffing downstream of the sound wave interference portion 7a of the muffler exhaust duct 7, and the error microphone 17 is connected to the controller 16 so that the error microphone 17 Therefore, the noise after mute is detected and fed back.

  The controller 16 is connected to the control panel 18 via a frequency converter 25 and a transformer 26 so that an output voltage is input to the transformer 26. The transformer 26 transforms the AC voltage generated by the generators 21, 22, 23, and 24 to a predetermined voltage, and transforms the voltage to reduce the voltage to be input to the controller 16. The frequency converter 25 is for converting the frequency in order to match the power generation frequency with the noise frequency.

  In such a configuration, any one of the engine generator 1, the engine generator 2, the engine generator 3, or the engine generator 4, or any two, or any three, depending on the load, or Start up everything and generate electricity to supply the necessary power to the facility. At this time, the engine generator 1 (or 2, 3, 4) is operated by the control unit 41 (or 42, 43, 44) and the control panel 18 so that the phase and amplitude coincide with the commercial power frequency.

  On the other hand, among the exhaust noise emitted from the engine generator 1 (or 2, 3 or 4), the high frequency component is silenced by the passive silencer 31 (or 32, 33 or 34), but the low frequency component is the duct. The sound cannot be muted depending on etc. However, this low frequency component is proportional (synchronized) to the rotational speed of the engine 11 (or 12, 13, 14) operated in accordance with the commercial power supply frequency. That is, the low frequency with the power frequency set to a predetermined multiple can be matched with the frequency of the low frequency noise.

  Specifically, it is well known that F = (P × N) / 120, where F is the frequency generated by the engine generator, P is the number of poles, and N is the engine (engine) speed. In the region west of Kansai, the frequency of the commercial power supply is 60 Hz, and the number of poles is specific to the generator. The number of poles is 10 in the generator of this embodiment, and these are substituted for calculation. Then, the rotation speed (synchronous speed) of the engine 11 (or 12, 13, 14) is 720 rpm. That is, the rated speed of the engine 11 (or 12, 13, 14) is operated at 720 rpm. Since the frequency of the commercial power supply is 50 Hz in the regions east of the central region, the rated rotational speed is 600 rpm.

On the other hand, the basic exhaust sound frequency when the engine 11 (or 12, 13, 14) is operated at 720 rpm (720/60 rps) is the rated rotational speed × the number of cylinders / 2, and (720/60) × 6/2 = 36 Hz. That is, a 6-cylinder engine is used as the engine of this embodiment, and the low frequency noise generated from the engine 11 (or 12, 13, 14) is 36 Hz. If a silencer having the same amplitude is generated from the speaker 9, it can be silenced. In the case of a power generation frequency of 50 Hz, the frequency is 30 Hz.
Since the rotation of the engine 11 (or 12, 13, 14), the power generation frequency, and the frequency of the commercial power supply are synchronized, the frequency of the voltage generated by the engine generator 1 (or 2, 3, 4) is converted. Therefore, a reference signal (signal equivalent to noise) can be easily obtained, and the same frequency as the low-frequency noise can be obtained from the generated voltage without the need for a conventional sensor microphone. The mute signal can be easily muffled by generating the mute signal with the controller 16 and amplifying the amplitude with the amplifier 15 and emitting from the speaker 9. In addition, when the exhaust sound of a plurality of frequencies is silenced, the plurality of frequency converters 25 are installed in parallel, and the output signals are added and input to the controller 16 so that the sound can be silenced. The harmonic component of (usually a square wave) can also be silenced.

Based on the above, the silencing action will be described with reference to FIG.
When the engine generator 1 (or 2, 3, 4) is activated, the rotation state of the engine 11 (or 12, 13, 14) is input to the control panel 18. And the control unit 41 (42, 43, 44 not shown) of the engine 11 (or 12, 13, 14) controls the rotation of the engine so as to be in phase with the frequency of the commercial power source, and the generator 21 (22 Generate power from 23 and 24) so that a voltage with the same phase and the same amplitude as the commercial power supply can be obtained.

  This generated voltage is input to the transformer 26 and transformed into a predetermined voltage that can be processed by the frequency converter 25 (for example, transformed from 100 V to 12 V). 12 · 13 · 14) is converted so as to be a predetermined multiple so as to be the same frequency as the low-frequency noise generated from 12.13.14). That is, in this embodiment, conversion is performed from 60 Hz to 36 Hz. A signal obtained by this conversion becomes a reference signal (reference signal) and is input to the controller 16.

  The controller 16 calculates a mute signal having a phase opposite to that of the noise from the reference signal and the noise signal obtained from the error microphone 17 and inputs the mute signal to the amplifier 15 so that the amplifier 15 has the same amplitude as the noise. The mute signal is amplified and a mute sound wave is output from the speaker 9. The sound deadening sound wave is propagated from the branch duct 8 to the sound deadening exhaust duct 7 and is canceled by the sound wave interference part 7a which interferes with the noise generated from the engine 11 (or 12, 13, 14) and propagated to the sound wave interference part 7a. Is muted. Whether or not the sound is muted is detected by the error microphone 17, fed back to the controller 16, the deviation is calculated, and further calculated so that the sound can be muted, and the muting signal is output to the amplifier 15. It is done.

  As described above, even if any engine 11, 12, 13, 14 is activated, the phase of the generated voltage is controlled so as to match the commercial power source. It is possible to generate a mute signal by generating a reference signal from this generated voltage. Therefore, there is no need to provide a sensor microphone in each exhaust pipe of each engine as in the prior art, and it becomes possible to obtain the same frequency as the noise, and it is possible to configure the active silencer at low cost.

  However, a vibration sensor can be used as another means for obtaining the reference signal. That is, the engines 11, 12, 13, and 14 are arranged side by side, and the exhaust pipes of the engines 11, 12, 13, and 14 are also communicated with one silencing exhaust duct 7. Is disposed in the base of the engine 11, 12, 13, 14, in the vicinity thereof, or in the muffler exhaust duct 7, and the vibration sensor 27 is connected to the controller 16 as shown in FIG. 5. However, an amplifier circuit may be interposed between the vibration sensor 27 and the controller 16.

  With this configuration, vibration having the same frequency as the noise generated from the engine 11 (or 12, 13, 14) can be detected by the vibration sensor 27, and the detected noise signal is silenced by the controller 16. Thus, the sound is output to the amplifier 15 and can be silenced by emitting a sound-deadening sound wave from the speaker 9 as described above. In this way, the frequency converter 25 and the transformer 26 shown in FIG. 4 can be omitted, and the cost can be reduced as compared with a structure in which a conventional sensor microphone is provided.

The top view of an engine generator and a passive-type silencer part. The front view of a passive type silencer and an exhaust duct part. The side view of an exhaust duct and a branch duct part. The control block diagram of the active silencer of this invention. The control block diagram which shows the other Example of an active silencer.

Explanation of symbols

1 ・ 2 ・ 3 ・ 4 Engine generator 7 Exhaust duct for silence 7a Sound wave interference part 8 Branch duct 9 Speaker 11 ・ 12 ・ 13 ・ 14 Engine 16 Controller 17 Error microphone 21 ・ 22 ・ 23 ・ 24 Generator 25 Frequency converter 26 Transformer 27 Vibration sensor

Claims (5)

  A silencer exhaust duct communicating with the exhaust part of the engine of the engine generator, a sound wave interference unit provided in the silencer exhaust duct, and a means for detecting a noise signal after muffing downstream of the sound wave interference unit; In an active silencer comprising a branch duct communicating with a sound wave interference unit, a means for outputting a noise cancellation signal having a phase opposite to that of noise arranged in the branch duct, and a control means, etc., the generator is connected via a transformer and a frequency converter. An active silencer, wherein the active silencer is connected to the control means, converts the power generation frequency of the generated voltage into a noise signal, and calculates a noise reduction signal.   2. The active silencer according to claim 1, wherein the frequency of the noise signal is a predetermined multiple of the rated engine speed.   The active silencer according to claim 1, wherein a plurality of the engine generators are arranged so as to be capable of operating in parallel.   2. The active silencer according to claim 1, wherein the silencer exhaust duct is disposed in a vertical direction, and the branch duct is disposed in communication with a lower end of the silencer exhaust duct. A silencer exhaust duct communicating with the exhaust part of the engine of the engine generator, a sound wave interference unit provided in the silencer exhaust duct, and a means for detecting a noise signal after muffing downstream of the sound wave interference unit; In an active silencer comprising a branch duct communicating with a sound wave interference section, a means for outputting a silence signal having a phase opposite to that of noise arranged in the branch duct, a control means, etc., a vibration sensor in the vicinity of the engine generator or the silencer duct Is connected to the control means, and a signal from the vibration sensor is calculated as a noise signal to be a mute signal to mute the sound.

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