JPH0876772A - Active muffler - Google Patents

Abstract

PURPOSE: To improve the volume, tone quality, etc., of a noise canceling sound generated from a speaker for improving a muffler effect in an active muffler constituted so as to generate a sound of a phase opposite to a noise to muffle it from the speaker. CONSTITUTION: A phase setting device PD and a volume setting device VD are provided in a control part ANC of an active muffler, and when the inside of a cabin of a tractor with a cabin is muffled, the fluctuation of the number of revolution of engine and an engine load rate are detected, and an opposite phase sound is formed, and further, in the case of a muffler of band-pass filter passing type, the central frequency of band-pass filter BPF is made settable and in the case of a muffler of the type forming the opposite phase sound by an oscillator, the frequency of the oscillator is made settable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a machine such as a tractor, a combine, a construction machine, a vehicle equipped with a cabin of a vehicle (equipment for isolating at least a crew member or an operator from the outside), or a huller. The present invention relates to a configuration of an active silencer for reducing noise in a room when using the room to perform work.

[0002]

2. Description of the Related Art Conventionally, in order to reduce noise in a room such as a passenger car or a room in which a machine using a large engine is operated, indoor noise is detected by a microphone and the phase of the noise is detected, and vice versa. An active silencer configured to cancel a noise by emitting a sound of a phase from a speaker is known. For example, in Japanese Utility Model Laid-Open No. 5-55198, a configuration in which the active silencer is mounted on a power agricultural machine with a cabin is disclosed.

[0003]

When the active muffler is installed in the interior of a passenger car, the driver's body is large and small, but the driving posture is almost constant, and the ear position does not fluctuate much. Therefore, there is no problem if the volume and phase of the cancellation sound from the speaker are set constant. However, a driver in a cabin such as a tractor or a combine, or an operator who handles a machine indoors should sit down or
When standing up or looking at the state of the working machine in the back of a tractor or the like, the driving (working) posture changes significantly, and the position where the sound is heard changes. Further, the noise source is not always the engine sound as in the case of passenger cars, but there are many sources such as gearboxes and work devices. Includes important sounds that cannot be overlooked in order to learn about the state of the work device, and cannot be uniformly reduced as noise. In order to effectively eliminate noise, it is necessary to set a canceling noise according to individual working conditions, etc., and to cope with the change in noise due to the situation that changes momentarily as described above. However, the conventional active silencer does not meet such a demand.

[0004]

The present invention uses the following means in order to solve the above problems. That is, one or a plurality of noise detection means as an input means, a control section for selectively passing a signal of a specific frequency from the input signal of the detected noise, converting the passed signal into an opposite phase, and amplifying the output, In the active silencer including one or a plurality of speakers as means, the phase conversion rate and the amplification rate in the control unit can be adjusted individually or simultaneously.

Further, in the active silencer having the above structure, the acceleration sensor is used as the noise detecting means.

Further, in the structure for reducing the indoor noise by the active muffler having the above structure, the noise detecting means and the speaker are installed outside the room, and the speaker is opposed to the room.

In addition, in the active muffler having the above structure, the phase conversion rate can be adjusted by the control unit, and the input terminal of the speaker can be switched between positive and negative.

Further, in the active muffler having the above structure, display means for displaying the adjustment result of the phase conversion rate and the amplification rate in the control section is provided.

Further, in the case of reducing the indoor noise of the vehicle with the prime mover by the active silencer having the above-mentioned structure, the amplification factor adjustment in the control section is automatically adjusted based on the detection of the number of revolutions of the prime mover.

Further, in the case of reducing the indoor noise of the vehicle with the prime mover by the active silencer having the above structure, the amplification factor adjustment in the control section is automatically adjusted based on the detection of the prime mover load factor.

In addition, in an active muffler having a structure in which a signal having a waveform similar to noise is oscillated by an oscillator, converted into an opposite phase, amplified, and generated as a noise canceling sound from a speaker, the frequency of the oscillation signal of the oscillator is changed. It can be set freely.

[0012]

First, by making the phase conversion rate changeable in the control section, the phase of the canceling sound from the speaker is exactly the opposite phase to the noise due to the positional relationship of the speaker with respect to the noise detecting means. If there is not, you can correct this shift and generate the opposite phase sound accurately from the speaker to ensure the silencing effect.Also, convert only the noise that should be muted into the opposite phase and output it from the speaker. It is also possible to do. On the other hand, by adjusting the volume output of the speaker, it is possible to balance the volume of the noise and the canceling sound.For example, depending on the position of the listener, the noise and the canceling sound are out of balance, and the canceling sound is When it becomes bigger and becomes annoying, you can adjust the balance to enhance the muffling effect.
Further, when it is desired to hear a certain noise, the volume of the canceling sound can be reduced so that the noise can be heard without being muted.

Further, by using an acceleration sensor in place of a generally used microphone as the noise detecting means, howling can be prevented and the cost is lower than that of a microphone which is expensive for low frequencies.

Also, by disposing the speaker outside the room, the sound is muted before it enters the room, the sound deadening effect is enhanced, and the sound is muted even outside the room. Furthermore, by making the speaker face the room, it is possible to cancel the noise that enters the room by generating a cancellation sound from the speaker.

In addition to adjusting the phase conversion rate, the input terminal of the speaker can be switched between positive and negative, whereby the noise can be phase-converted to 0 ° to 360 °, which is easy and quick. It is possible to effectively form a canceling sound of opposite phase.

Further, since the display means for displaying the adjustment result of the phase conversion rate and the amplification rate is provided, the phase conversion rate and the amplification rate of the cancellation sound from the speaker are optimally adjusted while confirming the display, and the muffling effect is obtained. Can be sure.

Further, in the case of reducing the indoor noise of a vehicle with a prime mover, the amplification factor adjustment in the control section is automatically adjusted based on the detection of the prime mover rotational speed, so that the prime mover changing according to the increase or decrease in the rotational speed. The noise of can be effectively silenced.

Further, in the case of reducing the indoor noise of a vehicle with a prime mover, the amplification factor adjustment in the control section is automatically adjusted based on the detection of the prime mover load factor, so that the prime mover changing according to the increase or decrease of the load factor. In addition, the noise from the transmission case and, in a vehicle such as a tractor, can effectively muff the work sound of the working machine.

In addition, the frequency of the oscillator can be freely set even in the active silencer having a structure in which the sound wave signal having a waveform close to the noise is inversely phase-converted by the oscillator to generate the canceling sound regardless of the noise detection. Thus, it is possible to oscillate a sound wave signal having a frequency most similar to noise.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the structure of the present invention will be described based on the embodiments shown in the accompanying drawings. 1 is a basic block diagram of an active silencer, FIG. 2 is a perspective view of a tractor with a cabin showing a mounting example of a microphone, a speaker and a setting device in the active silencer, and FIG. 3 is a block of an active silencer provided with a bandpass filter. Fig. 4, Fig. 4 is a wiring diagram from a microphone to a bandpass filter, Fig. 5 is a graph showing a frequency attenuation effect in the bandpass filter, Fig. 6 is a block diagram of an active silencer when an acceleration sensor is used as a noise detecting means, FIG. 7 is a block diagram of an active silencer in which the acceleration sensor is noise detection means and the bandpass filter is a lowpass filter only, FIG. 8 is a wiring diagram of the lowpass filter in the case of FIG. 7, and FIG. 9 is a separate active component. Share the speaker with the silencer and audio device. FIG. 10 is a block diagram showing an embodiment, FIG. 10 is a wiring diagram of a speaker input section in FIG. 9, and FIG. 11 is a block diagram showing an embodiment in which an active muffling device and an audio device are housed in one device case and a speaker is shared. FIG. 12 is a block diagram showing an embodiment in which the noise canceling sound is emitted only from the front speaker among the four-channel speakers in the embodiment of FIG. 11, and FIG. 13 is only the bass speaker in the embodiment of FIG. FIG. 14 is a block diagram showing an embodiment configured to generate noise canceling sound from
Is a wiring diagram showing an embodiment in which the phase-converted amplifier circuit is formed by combining an in-phase amplifier circuit and an inverting amplifier circuit. FIG. 15 shows the speaker input section in the embodiment of FIG. FIG. 16 is a block diagram showing an embodiment in which amplification is possible on both the in-phase side and the inversion side, FIG. 16 is a wiring diagram of the speaker input section in FIG. 15, FIG. 17 is a wiring diagram for turning off the active silencer at engine start, Is a block diagram of an active silencer when a plurality of bandpass filters are provided, and FIG. 19 is a block diagram of an active silencer when the break frequencies of the lowpass filter and the highpass filter in the bandpass filter are adjustable. Numeral 20 is an active noise suppressor in which a plurality of bandpass filters are arranged and a phase conversion circuit is arranged directly below each bandpass filter. Block diagram of the location, the graph 21 showing the displacement of the phase transformation angle associated with the set output by the phase setter in the different band-pass filter center frequencies,
FIG. 22 is a block diagram showing a level meter mounting structure which is an indicator when the amplification and phase conversion rate of each of the plurality of bandpass filters can be adjusted, and FIG. 23 is the phase conversion adjustment for each of the plurality of bandpass filters. FIG. 24 is a block diagram when the volume of the speaker can be adjusted by detecting the engine speed in the embodiment of FIG. 23, and FIG. 25 is a band diagram when the engine speed is detected. FIG. 26 is a block diagram when the center frequency of the pass filter is adjustable, FIG. 26 is a block diagram when the phase conversion adjustment is also possible in the embodiment of FIG. 25, and FIG. 27 is automatic volume adjustment by engine load factor detection. FIG. 28 is a block diagram of a case where the engine is started, and FIG. FIG. 29 is a block diagram of an active silencer having a configuration in which a center frequency of a bandpass filter can be automatically set based on detection of an engine speed and an engine load factor. FIG. 30 is a flowchart diagram of the configuration of FIG. 29. 31 is a block diagram of an active silencer having a configuration in which the frequency of a bandpass filter can be set by setting the number of engine explosions (the number of engine cylinders), and FIG. 32 is a flow chart diagram in the configuration of FIG. 31,
FIG. 33 is a flow chart diagram of an active muffling device configured to reduce the volume when the ground work device of the tractor is in the non-working state, FIG. 34 is the same block diagram, and FIG. 35 is the volume decrease due to a decrease in engine speed during headland turning. FIG. 36 is a block diagram of an active muffler, FIG. 36 is a block diagram of an active muffler having a structure in which the volume is reduced when the tractor is running neutral and when the work machine is transmitting neutral. 38 is a block diagram of a silencer, FIG. 38 is a block diagram showing a volume automatic adjusting mechanism based on an operating state of a hydraulic system in a vehicle equipped with a hydraulic system, and FIG. 39 is an automatic volume adjusting based on an operating state of a threshing unit in a combine with a cabin. FIG. 40 is a block diagram showing the mechanism, and FIG. 40 is an active muffling device in a huller. Shows the arrangement, FIG. 41 FIG. 40
42 is a block diagram of an active silencer of a type that generates a noise canceling sound based on an oscillation signal from a sine wave oscillation circuit, and FIG. 43 is an active silencer having a configuration in which the frequency of the oscillation circuit can be set. FIG. 44 is a wiring diagram showing a frequency setting mechanism in a sine wave oscillation circuit, FIG. 45 is a block diagram of an active silencer configured to muffle the sine wave generated by the sine wave oscillation circuit by peak-cutting, and FIG. FIG. 47 is a block diagram showing the peak cutting means in FIG. 45, FIG. 47 is a block diagram of an active silencer configured to oscillate and mute a composite wave of a sine wave and a rectangular wave, and FIG. 48 is an active silencer of sine wave oscillation type. FIG. 49 is a block diagram showing a configuration for automatically adjusting the volume based on engine speed detection, FIG. FIG. 51 is a flowchart of FIG. 50, FIG. 52 is a sine wave diagram, and FIG. 52 is a sine wave active type silencer that automatically sets the frequency of the sine wave by setting the number of engine explosions (the number of engine cylinders). 53 is a block diagram of an active silencer combining a wave oscillation type and a bandpass filter based on noise detection, FIG. 53 shows a bandpass filter based on noise detection unless noise is above a certain frequency in the active silencer of FIG. It is a block diagram of what was constituted so that a passage type active silencer could not be operated.

First, a block diagram showing the basic construction of the active silencer shown in FIG. 1 will be described. In addition,
The following description of the active muffler is assumed to be used for noise reduction in the tractor cabin unless otherwise stated.

The noise is detected by the noise detecting means and converted into an input signal. The noise detecting means mainly uses a microphone (MIC). The input signal of the detected noise is input into the control unit (ACT) of the active noise suppressor, and since the input from the noise detection unit is small, the preamplifier (PRA) is used.
Is amplified in. The preamplifier is provided corresponding to each noise detecting means (microphone), and when a plurality of noise detecting means and preamplifiers are provided, a plurality of inputs are simply added by an adder circuit. When only one noise detecting means is used, the adder circuit is unnecessary. The noise input signal thus input is basically shifted by a half phase (180 °) in the phase conversion circuit (PCC). In this way, the sound wave signal whose phase is shifted for noise cancellation is amplified by the power amplifier (POA) so that the speaker can be driven, and the amplified sound is generated from the speaker (SPK). Although only one is shown in FIG. 1, a plurality of speakers can be connected in parallel to the same power amplifier as shown in FIG.

In this active muffler, the phase conversion circuit (PCC) can input the set value by the phase setting device (PD) and the power amplifier (POA) can input the setting value by the volume setting device (VD). ing. In the phase conversion, there is a case that the phase having the optimum sound deadening effect cannot be obtained by simply shifting the phase by half due to the positional relationship between the noise detecting means and the speaker. Is a variable resistor for compensating for. The volume setting device (VD) is a variable resistor for adjusting the amplification factor of the power amplifier (POA) so that the speaker can generate an appropriate amount of sound to cancel the noise.

The mounting positions of the noise detecting means of the active silencer, the device body in which the control part is installed, and the respective members of the speaker (SPK) will be described. First, if the device body of the control part is inside a cabin or the like. It can be anywhere. However, the setting device (phase setting device (PD) / volume setting device (V
This is the operable range of D)). This phase setting device (P
If the operator's head position or ear position deviates from the original position during operation of D) and the volume setting device (VD), it is possible to confirm the accurate noise reduction effect of the cancellation sound from the speaker. This is because the adjustment work is hindered. Desirably, as shown in FIG. 2, it is an armrest of a seat or its periphery. Further, since a tractor or the like has a working machine mounted on the rear portion, it is often directed rearward, and it is desirable that the position is adjustable even in this posture.

Noise detection means (microphone (MI
Various cases can be considered for the arrangement of C)).
For example, a microphone with a narrow directivity (MIC) may be attached to the front of the cabin to detect the engine sound of a tractor arranged in front of the cabin, or a microphone with a wide directivity (MIC) may be used.
It can be located at the bottom of the cabin and used primarily to detect mission (transmission) noise. In this way, it is also possible to combine and input different types of noises by using microphones (MIC) having different directivities together.

The speaker (SPK) is provided on the ceiling of the room (cabin) to muffle the sound in the room.
(IC) so that it faces. Further, for example, when there are two speakers (SPK), they are arranged on the left and right of the operator's head. Furthermore, if it is installed outside the cabin, the noise reduction effect can be obtained outside the cabin, not only the noise transmitted inside the cabin but also the tractor surrounding the cabin is quiet, and the speaker (SPK) faces the inside of the cabin. By doing so, a canceling sound for the noise transmitted in the cabin is transmitted, so that the silencing effect in the cabin is also enhanced. Further, this direction is made not to coincide with the detection direction of noise detection means such as a microphone (MIC) arranged outdoors (to prevent howling), and is mainly aimed at silencing engine exhaust noise. . The engine exhaust sound is a low frequency sound, easily transmitted to the inside of the cabin,
It is effective to mute the sound outside the cabin.

In the tractor with a cabin shown in FIG. 2, a microphone (MIC) is directed near the engine exhaust port H of the tractor T to detect the engine exhaust sound EN, and back to back so as to prevent howling.
A speaker (SPK) is attached to the side of the bonnet B for the purpose of silencing the exhaust noise outside the cabin, and is directed toward the cabin C to effectively muffle the noise that enters the cabin. Cancel sound SN
Is emitting. In this case, a speaker (SPK) and a microphone (MIC) are used to prevent howling.
It is conceivable to place a sound insulation material between and, and since the microphone (MIC) is close to the exhaust port H,
The heat insulating material may be provided at the tip of the microphone (MIC).

An embodiment of the configuration of the noise detecting means, the control section, and each section of the speaker in the active silencer basically having the above configuration will be described in detail. First, the noise detecting means is generally a microphone (MIC).
The one having a narrow directivity or the one having a narrow band is used for specific noise detection. For example, the engine exhaust sound is mainly detected as described above. On the other hand, the one with a wide directivity or the one with a wide band is used for overall noise detection (for example, the entire cabin). One of these may be used to detect only specific noise, or a plurality of them may be provided with different mounting positions to detect different types of noise.
In the case of FIG. 1, two microphones (MIC) are used, but in some cases, three or more microphones may be used. Further, when one is used, the adder circuit is not required in the control unit (ANC).

The noise detecting means mainly uses a microphone (MIC), but in this case, howling is likely to occur because the sound of the speaker (SPK) is picked up. In addition, a microphone (M
IC) is expensive. On the other hand, an acceleration sensor (AS) such as a piezoelectric element or a capacitance conversion type element can detect the waveform and level of noise at a low price, and can eliminate the harmful effects of howling. So, especially when you want to mute low frequency noise,
As shown in FIG. 6, if the acceleration sensor (AS) is used as the noise detection means and the detection position is the window glass portion in the case of a cabin, noise with a high proportion of low frequency noise can be detected. Parts of the cabin other than the window glass
Although it vibrates with high-frequency noise, the window glass is hard and vibrates for low-frequency sounds, but it is most suitable for detecting low-frequency noise because sounds in the mid-range and above have low levels and do not conduct. This is because it is the part where 6 to 16,
In the combined use example with audio (AUD) equipment, the acceleration sensor (AS) is used as noise detection means, but of course, a microphone (MIC) is also possible. It should be noted that for sounds in the mid-range and above, the level is lower than that of low-frequency noise, and the microphone (MIC) for detecting sounds in the mid-range and above is relatively low cost. MIC) is more effective.

As a means for preventing howling, as described above, the microphone (MIC) and the speaker (S
It is also conceivable to dispose a sound insulating material between it and PK).

Next, a method of using an audio speaker in the embodiment of the speaker will be described. In the case of outputting a cancellation sound in a cabin or the like room, if audio equipment is installed in the cabin, this audio speaker may be used.
9 to 16 show an audio set (AUD), a radio tuner (TU) and a cassette deck (CD).
It discloses that it has a built-in (may be a CD deck). First, when the active silencer (ANC) device case and the audio (AUD) device case are separated as shown in FIG. 9, a harness or connector for connecting the audio speaker (SPK) output terminals is provided as shown in FIG. It suffices to be able to connect a mixing and adding circuit of output signals for producing a canceling sound of the active silencer. Further, as shown in FIG. 11, in one device case including the control unit (ANC) of the active silencer, the mixing and adding circuit is provided in front of the output stage of the speaker (SPK), and the audio (AUD) With the configuration that the noise canceling sound (anti-phase sound) is emitted from the audio speaker (SPK) regardless of whether or not the
Not only the speaker (SPK) but also the power amplifier (PO
The speaker (SPK) driving circuit such as A) and the device case can also be used as those of the audio equipment, and the cost can be reduced.

Also, an audio speaker (SPK)
In the case of a 4-channel type or the like, which is arranged at the front and rear of the room, the speaker (SPK) that emits the antiphase sound can be switched to the front or the rear as shown in FIG. And, for example, when noise enters from the front,
It is effective to emit the antiphase sound to the front from the rear speaker (SPK), and the antiphase sound may be emitted from the front speaker (SPK) to the noise from the rear.
When the audio speakers (SPK) are on the left and right, the volume balance adjuster can adjust the left and right volume balances as shown in FIG. 11 like normal audio output, and there are multiple seats. , It is designed to be able to deal with cases where a person who hears noise is not located in the central part.

Also, an audio speaker (SPK)
Has a speaker (SPK) for each sound with different frequency (for treble and bass), but in this case,
It is costly to apply the output signal of the active silencer to all the speakers (SPK). here,
In the case of silencing low-frequency sounds such as so-called "muffled sound" among noise, as shown in FIG. 13, a speaker for low-frequency output (SP
It is sufficient to apply it only to K). In addition, low-frequency sound has a narrow directivity, so in some cases multiple speakers (SP
In some cases, only one of K) can be used for low frequency sound.

Next, the internal structure of the control unit (ANC) will be described. The present invention, from among the noise mixed with various sounds,
A sound of a certain frequency is selected so that the sound can be silenced. Therefore, in the control unit (ANC), only the sound wave signal to be canceled from the input signal of the detected noise is passed and the phase conversion circuit (PCC) is used. 3), a band pass filter (BPF) is provided to transmit the signal to the above). The bandpass filter (BPF) is composed of a combination of a lowpass filter (LPF) and a highpass filter (HPF). As shown in FIG. 5, the lowpass filter (LPF) has a set frequency (a corner frequency f
_L ) is configured to pass only a sound wave signal having a lower frequency (attenuating the input level of a sound wave signal having a frequency higher than the break frequency f _L ), while the high pass filter (HPF) is configured to It is configured such that only a sound wave signal having a frequency higher than the break frequency f _H ) passes through (the input level of the sound signal having a frequency lower than the break frequency f _H is attenuated). Thus, the band-pass filter (BPF), corner frequency f _H or more, so that passing only acoustic signals of a frequency below corner frequency f _L. Here, the break frequency f _H <f _L is set so that only the sound of a certain specific frequency is passed and the sound is silenced, and sounds of higher and lower frequencies are not muted. (F _H ＞
If it is f _L , the attenuated frequency range is overlapped and no frequency signal is allowed to pass. )

Generally, the frequency of the engine sound is in the relatively low band and the frequency of the transmission (transmission) sound is in the relatively middle band. Therefore, if the band pass filter (BPF) in the control unit (ANC) is set to pass only the sound wave signal of the frequency in the middle band, only the noise generated by the transmission (transmission) can be silenced. In some cases, as shown in FIG. 7 and FIG. 8, the band pass filter (BPF) is composed of only a low pass filter (LPF), and only the sound wave signal of the low band frequency below the break point frequency f _{L is} allowed to pass. For example, only the noise from the engine can be silenced. In the embodiments of FIGS. 9 to 16, the frequency is selected only by the low pass filter (LPF).

In this way, band pass filters (BPFs) of various types having different frequencies of the sound wave signal to be passed can be constructed by setting the corner frequencies f _L and f _H. For example, as shown in FIG. 20, the corner frequency f _L · f _H is set to be low, and the center frequency 60 Hz (6
Band pass filter (BPF) of only passing sound waves around 0 Hz) or band pass filter of center frequency 16 kHz (passing only sound waves around 16 kHz) by setting break point frequencies f _L and f _H to a high level. (BPF)
Can be configured.

These bandpass filters (BPF)
As shown in FIGS. 18 and 20, by arranging a plurality of them in the control unit (ANC), noise can be divided for each frequency to selectively mute or suppress muffling. . In addition, in FIG. 18, although the bandpass filter is collectively divided, the phase conversion is collectively performed by the phase conversion circuit (PCC).
As shown in FIG. 20, each of the band pass filters (BP
Phase conversion (change) circuit (PCC) corresponding to F)
By connecting with, it is possible to effectively muffle noise of various frequencies contained in the noise, and further, it is possible to adjust the phase conversion rate of each phase change circuit (PCC) with the phase setter (PD). By doing so, it is possible to selectively mute only the sound in a specific frequency range. That is, as shown in FIG. 20, if bandpass filters (BPF) with various center frequencies are built in,
It is possible to divide and pass the signal in the frequency range for the built-in band pass filter (BPF) from the detected noise in which various frequency sounds are mixed, and to mute from the divided and passed signals. For what you want to do, the phase setting device (PD) in the phase conversion circuit (PCC) at the latter stage of the band pass filter (BPF) that passes the frequency sound of the sound you want to mute (for example, the center frequency is 60 Hz) is used to perform the reverse phase conversion. By setting so that the phase setter (PD) in the remaining phase conversion circuit (PCC) is set to transmit in the same phase, only the sound in that frequency range (around 60 Hz) can be silenced immediately. .

On the contrary, the provision of a plurality of band pass filters (BPF) as shown in FIG. 20 means that the noise of any frequency can be silenced from the noise mixed with various frequencies. In order not to mute only the sound for confirmation of work, etc., a bandpass filter (BPF) that passes the signal of the sound in the frequency range you want to hear
The phase setter (P) in the subsequent phase conversion circuit (PCC)
D) is set to the same phase, and the other phase conversion circuits (P
The CC) phase setter (PD) may be set to the inverse phase conversion.

Further, for example, when the engine exhaust sound is silenced, the noise includes, in addition to the loudest primary sound, a secondary sound, a tertiary sound, etc., which is an integral multiple of the frequency of the primary sound. In order to effectively mute the secondary and tertiary sounds, a bandpass filter (BPF) set to a center frequency that is an integral multiple of the center frequency of the bandpass filter (BPF) for the primary sound may be used. For example, when the frequency of the primary sound is about 60 Hz, a bandpass filter (BPF) having a center frequency of 60 Hz for silencing the primary sound is provided, and a secondary sound (frequency is 60 × 2 = 120 Hz) and a tertiary sound (60 × 4 = 240HZ) to muffle noise such as
A bandpass filter (BPF) having center frequencies of 120 Hz and 240 Hz may be provided. Note that FIG.
Then, the center frequency of the bandpass filter for secondary sound elimination is 125 Hz, but the effect is that the center frequency is 120 Hz.
It is almost the same as that of Hz.

Further, as shown in FIG. 18, a band-pass filter for independently inputting the input signal of each microphone (MIC) corresponding to a plurality of (two in FIG. 18) noise detecting means (microphones (MIC)). It is also possible to provide (BPF). That is, when a plurality of microphones (MICs) are installed for noise detection of different types (one for engine sound detection and one for mission sound detection), each microphone (MIC) By disposing a bandpass filter (BPF) in which the corner frequencies f _H and f _L are set in correspondence with the input signal, it is possible to select noise with a higher degree of purity and further enhance the silencing effect. When the directivity (band) of the microphone (MIC) is narrow, the microphone (M
Band pass filter (BP) corresponding to the IC
F) may be omitted. The microphone (MIC)
However, since it is installed to detect noise in a certain band to be silenced, the input signal is limited to a frequency in a specific band even without passing through a bandpass filter (BPF). After being amplified, the input signal from the microphone (MIC) is directly input to the phase conversion circuit (PCC) without frequency selection.

A configuration in which the center frequency setting value f of the bandpass filter (BPF) can be adjusted and the sound in the frequency range to be muted can be selected will be described. FIG. 19
Is a low pass filter (LPF) and a high pass filter (HPF) in a band pass filter (BPF).
In order to make it possible to adjust each of the breakpoint frequencies f _L and f _H , a configuration in which a breakpoint frequency setting device (BBD) is provided for each is shown. Make this a dial type, for example,
When the low frequency noise is noisy, the corner frequency setting device (BBD) of the high pass filter (HPF) is turned to the low frequency side to lower the frequency f _{H, so} that the sound wave signal in the lower frequency range becomes higher. When the sound passes through the (HPF) and is muted, and conversely the high frequency noise is noisy, turn the breakpoint frequency setting device (BBD) of the low pass filter (LPF) to the high frequency side and raise the breakpoint frequency f _L. , The sound wave signal in the higher frequency band passes through the low pass filter (LPF) and is silenced. As described above, by making it possible to adjust the pass setting range in the band pass filter (BPF), when the noise in the specific range is felt to be noisy, the noise in the range can be immediately reduced. As described above, a plurality of bandpass filters (BPF) having the center frequency f fixedly set are provided,
Compared to the configuration in which a phase conversion circuit (PCC) is provided after each bandpass filter (BPF), only one bandpass filter (BPF) and phase conversion circuit (PCC) is required, reducing the number of parts and reducing costs. It also leads to realization.

The band pass filter (BP
In addition to using F), there is a method of attaching an oscillation circuit that oscillates a pseudo-waveform (usually a sine wave) similar to the noise waveform. This (sine wave) oscillating circuit (SWC) creates a noise canceling sound in the active muffling device regardless of noise detection, and the active muffling device based on this produces a sound as shown in FIG. And
The configuration of the sine wave oscillator (SWC) is as shown in FIG.
A sine wave having an arbitrary frequency can be oscillated by the frequency setting (changing) device (BD). In a vehicle with an engine, the ratio of low frequency sound formed by engine exhaust sound is large. A noise waveform in a vehicle with an engine is obtained by applying a waveform in the middle frequency range or a high frequency range to this low frequency waveform. The low-frequency engine exhaust sound regularly produces a substantially constant sine wave frequency sound as the engine rotates. Therefore, a sine wave oscillating circuit (SWC) produces a canceling sound regardless of noise detection. Even if it is done, the muffling effect can be obtained.

Further, FIG. 42 shows a sine wave oscillation circuit (SW
It discloses that a muffler using C) is provided with a frequency multiplier circuit (BMC) for multiplying the frequency of an oscillated wave. In this way, when one specific sine wave is divided and passed through each frequency multiplier circuit (BMC), a plurality of sine waves of different frequencies can be output. If a canceling sound is generated by canceling the sound, it is possible to effectively muffle noise in which sounds of different frequencies are mixed.

Strictly speaking, the low-frequency sound in the noise is not a clean sine wave, but a composite wave of a sine wave and a rectangular wave in which the vicinity of the top is crushed. If a wave that is closer to this actual waveform can be oscillated, the silencing effect will be higher. Therefore, in the sine wave oscillator (SWC), as shown in FIG. 45, a peak cut circuit for cutting the peak (top) of the sine wave is provided, or as shown in FIG. 47, a sine wave oscillator circuit (SWC) is provided. A method of oscillating a synthetic wave by combining with a rectangular wave oscillating circuit (NWC) can be considered. Note that in FIG. 45, the peak cut may be corrected by feedback using the method of FIG. 46. That is, the value held by the peak hold circuit is used as the peak cut value (instead of the cut width setting device in FIG. 45).

As shown in FIG. 52, in order to simultaneously muffle low frequency sound of engine exhaust sound and muffle medium or high frequency sound of a transmission or the like, as shown in FIG. It is also conceivable to construct an active silencer that combines with a system. Of these, low-frequency engine exhaust sound is generated by a sine wave oscillator (SWC) to generate a pseudo noise sine wave, and the phase of the noise is inverted. M
Bandpass filter (BP)
F) is passed therethrough, and this is subjected to anti-phase conversion and is added to the anti-phase signal of the preceding sine wave to generate a cancellation sound from the speaker (SPK). In FIG. 53, if no sound of a certain frequency or higher is detected in the noise, the volume in the amplification for the middle and high frequencies is lowered or the OF is reduced.
F, and then use the speaker (S
PK).

Next, the phase setting device (PD) for setting the phase conversion rate in each phase conversion circuit (PCC) will be described. The phase setting device (PD) is a variable resistor,
As shown in FIG. 21, when the resistance value (R) in the phase setting device (PD) is displaced, the conversion phase angle (deg) is displaced. In addition, f in FIG. 21 is a bandpass filter (BP
It is the center frequency of F). If this phase setter (PD) is configured by a dial or the like, and an in-phase amplifier and an inverting amplifier are provided as shown in FIG. 14 and amplification is set to the inverting side and the non-inverting side, the conversion phase angle is 0 °. It is possible to convert up to 360 °.

The phase setting device (PD) can be adjusted only on the normal in-phase side, and as shown in FIGS. 15 and 16, the speaker (SPK) input terminal can be switched between positive and negative.
If a PK) switch is installed, the output signal will be output to the speaker (S
PK) input stage can be inverted, so the conversion phase angle is 0 ° ~
It can be 360 °.

Furthermore, each band pass filter (BPF)
2 is provided at the subsequent stage of the phase change (conversion) circuit (PCC).
3, an amplifier circuit (AMP) is provided, and a volume control circuit (volume setting device (VD)) that adjusts the amplification factor of each amplifier circuit (AMP) (a speaker (SPK ) Determines the volume of the canceling sound produced by).). The reason why the bandpass filters (BPF) are arranged after the bandpass filters is that sounds of various frequencies are mixed in the detected noise, and the sound volumes are different. The signals amplified by the amplification factor set by the volume setting device (VD) are added by the addition circuit, and the amplifier (power amplifier (PK) for outputting the speaker (SPK) is added.
OA)) and output. The phase change circuit (PCC) in each subsequent stage of the plurality of band pass filters (BPF) correctly detects each band pass filter (BP
When the signal that has passed through F) is converted to a phase that cancels it, selective noise cancellation is performed by adjusting the volume setting device (VD) in the amplification circuit (AMP) at the post stage of each bandpass filter (BPF). It can be adjusted. For example, a level setting device (VD) of an amplifier circuit (AMP) at a post-stage of a bandpass filter (BPF) having a center frequency of 60 Hz adjusts the level of the canceling sound to the extent that it cancels the noise of that frequency, and the remaining bandpass filter. (BP
F) If the volume setting device (VD) in the latter stage is set to a weak value or set to zero, only the antiphase sound of about 60 Hz is generated from the speaker (SPK) and only the noise in this range can be silenced. Conversely, if you want to hear only the sound in a specific range, set the volume of the amplification circuit (AMP) at the subsequent stage of the bandpass filter (BPF) whose center frequency is the frequency of the sound to zero, and amplify the other amplification circuit (AMP). The volume of the anti-phase sound is adjusted so that the sound can be muted, and these cancellation sounds are generated from the speaker (SPK).

In the phase setting device (PD) of the phase changing circuit (PCC) and the volume setting device (VD) of the amplifier (power amplifier), the adjustment result can be confirmed and the adjustment work can be performed respectively. A display (level meter) is provided. When a plurality of band pass filters (BPF) are provided as shown in FIG. 22, each phase setter (P P) is provided for each band pass filter (BPF).
D) and a cover of volume setting device (VD) are provided, while a level indicator of the detected noise before passing each bandpass filter (BPF) is also provided, and each bandpass filter (BP)
It is possible to switch between the level display for each F) or the level display at once by the changeover switch.

As described above, the control unit (ANC) of the active noise suppressor includes the frequency selection passage means, the phase conversion means,
And an amplifying means internally provided. next,
The automatic adjustment structure of each of these means will be described.

First, the volume adjustment will be described with reference to FIG. As described above, for example, in an active silencer having a plurality of bandpass filters (BPFs), the volume of the cancellation sound is different for each bandpass filter (BPF) and corresponding to the volume of noise that changes from moment to moment. Adjustment is a very complicated operation, and in the worst case, the adjustment operation is impossible. Therefore, an automatic adjustment mechanism is provided for this volume adjustment. This corresponds to various working conditions and a state that changes moment by moment.
It is for automatically adjusting the output level of PK).
For this purpose, a feedback circuit for detecting a change in noise or silencing effect and transmitting it to the automatic volume setting mechanism is required.
First, there is a microphone (MIC) as the detection means, which is a microphone (MI) of the noise detection means.
C) may be used as it is. As a feedback circuit for automatic volume setting, one bandpass filter (BPF) having the same center frequency as that for noise detection is provided, and a signal passing through each bandpass filter (BPF) is The level of the passing signal is measured by being transmitted to an integrating circuit which is an automatic volume control circuit after the band pass filter (BPF). Based on this level, the volume adjusting circuit (VD ') in the volume setting device (VD) operates and the amplification factor in the amplifying circuit (AMP) is automatically adjusted.

However, the microphone (MIC) as the noise detecting means can be used as the automatic volume setting detecting means in such a case that the mute effect is detected by the microphone (MIC). When the MIC) is outside the room and the speaker (SPK) is inside the room, there is almost no silencing effect in the vicinity of the microphone (MIC) and detection is impossible. Therefore, a microphone (MIC) must be additionally provided and a frequency division means such as a bandpass filter (BPF) must be separately provided, resulting in a great increase in cost and an increase in size of equipment. Therefore, as shown in FIG. 23, the signal to be adjusted passes through each band-pass filter (BPF), and the output signal whose phase has been converted is combined in the adder circuit and then is output to the speaker (SPK) output amplifier. An automatic volume control circuit (AVD) is provided in the amplifier (POA).

On the other hand, as the detection means for feedback, there is a method of utilizing what is already installed depending on the type of noise to be silenced. For example, when the engine sound is muted, the sound volume of the engine sound changes in proportion to the change in the engine speed. Therefore, the sound volume can be adjusted according to this change. As shown in FIG. 24, the accelerator sensor for automatic electronic governor adjustment (A
S) may be used. Alternatively, as shown in FIG. 27, a rack position detection sensor that is a member for detecting the engine load factor attached to the electronic governor may be used. The noise increases in proportion to the amount of accelerator pedal depression and engine speed, and the engine load factor of the electronic governor.Therefore, increase the volume level in proportion to the detected input value to increase the noise level. You can make a cancellation sound that can counter. It can be said that these are configured to detect the change in the cause of noise generation promptly and output a canceling sound of a volume that can oppose it, rather than feedback of the sound deadening effect.

Further, with respect to the phase adjustment, automatic adjustment can be performed. In FIG. 26, the noise that has passed through the bandpass filter (BPF1) and the canceling sound that has passed through the bandpass filter for feedback (BPF2) are added after the volume is automatically adjusted by feedback from the detection result of the engine speed. The figure shows a phase change circuit that performs addition in a circuit and automatically adjusts the added value to be "0".

Further, not only the volume of noise but also the height of the noise change from moment to moment. For example, in the case of engine sound, its frequency is proportional to the engine speed. Therefore,
As with the automatic volume adjustment mechanism, it is impossible to adjust the break frequency for each noise frequency change during work, so a band pass filter (BPF) automatic break frequency adjustment mechanism is provided. Has been. An automatic frequency adjustment mechanism including this feedback circuit will be described.

First, the detection of the noise frequency for setting the frequency of the cancellation sound will be described. First, in a vehicle (tractor) having an engine speed control function by an electronic governor, a rack position detection sensor for detecting the actual engine speed by the electronic governor is provided,
The electronic governor controller calculates the difference (engine load) from the rotational speed set value set by the accelerator sensor. Based on this calculated value, the rack drive solenoid is driven to control the fuel injection amount. , Keep the engine speed at the set value. FIG. 29 shows a configuration in which the signal of the engine load factor calculated in the electronic governor controller having such a structure is input for setting the center frequency of the band pass filter (BPF) of the active silencer.

FIG. 30 shows the control section of the active silencer.
Flow chart for signal input in (ANC)
Where R is the accelerator sensor value, load factor
Target of engine with electronic governor obtained from set values etc.
The engine speed, k is a constant that determines the width of the frequency.
Therefore, the break frequency f in the high pass filter
_HFrom D / A (1),
Point frequency f_LInput the set value from the input terminal D / A (2)
And output to each filter. This filter is noisy
It is also used as an electronic governor controller.
Filter the input signal from the controller and the noise detection signal
To pass the noise, test the noise reduction effect, and determine the center frequency.
Set.

The frequency of the engine sound is proportional to the number of engine explosions. That is, depending on the number of cylinders in the engine,
Different frequencies. 50 and 51 disclose a configuration for determining the fundamental frequency of the canceling sound of the active muffler using the sine oscillation circuit (SWC) by setting the number of cylinders of the engine in addition to the engine speed. There is. Among them, R is the engine speed, E is the voltage value that determines the frequency of the sine wave oscillation circuit, and the wave height setting device is merely for determining the amplification factor. It should be noted that the cylinder setter is compatible with various types of engines, and if the engine of the vehicle to which the active silencer is attached has, for example, two cylinders, the cylinder setter is set as such.

Further, FIGS. 31 and 32 disclose a configuration in which the center frequency of the bandpass filter is set by setting the number of engine cylinders that determines the number of engine explosions. Note that f1 = f _H and f2 = f _L.

As described above, the active silencer automatically adjusts the center frequency in the band pass filter (BPF) in the control unit (ANC), the phase conversion rate in the phase conversion circuit (PCC), and the amplification rate in the power amplifier. It is adjustable, but depending on changes in things that cause noise, it may be necessary to turn on / off the device power,
In addition, it may be difficult to input the feedback circuit (detection of the muffling effect) in the automatic adjustment mechanism, and the volume adjustment or the like may not be well coped with the change of the noise factor. For example, in the above-mentioned volume adjustment, regarding the automatic adjustment of the cancellation sound with respect to the engine sound, the change in the engine exhaust sound was read based on the detection of the engine speed and the engine load factor. There are times when you want to mute noise from work equipment that performs work,
The noise generated by the working device also changes from moment to moment depending on the state of the working device. We could not respond to this change in noise factors, for example, although the noise was reduced,
If the anti-phase noise of the noise is amplified and output from the speaker (SPK) of the active silencer, the speaker (S
The sound from (PK) is too loud and rather annoying. Therefore,
Turns on / off the device power supply in response to changes in various noise factors
It is important to configure so that automatic control such as FF and volume control is performed. Hereinafter, the automatic control structure of the active muffling device that responds to changes in various noise factors will be described.

First, when an active muffling device is provided in a traveling vehicle such as an agricultural moving vehicle such as a tractor, when the engine is stopped, muffling is not necessary and the speaker (SPK) output is wasted. Therefore,
The active silencer is not activated while the engine is stopped, and the active silencer is not activated even if the audio device is turned on when the engine is stopped. The ON / OFF switching of this device may be performed by using a key switch as shown in FIG. 17 (similar to the electrical component in a normal vehicle). If you want to listen to the audio when the engine is stopped, turning on the audio device also activates the circuit for the muffling device, so that the opposite phase sound for muffling contradicts the sound generated from the speaker (SPK) of the audio device. Therefore, ON / OF separate from the audio device
The structure is F. Further, even when the engine is started (idling state), the noise is very small, so the power may be turned off and the engine may be started at the start of traveling or the start of work (detected from the engine speed or the engine load factor). Good.

Further, when the combined use with the audio device is not considered, FIG. 37 discloses a configuration in which the silencer is turned off when the engine is started.

Next, a ground work device (eg, rotary,
When the active muffling device is installed in a tractor that has been pulled up and down (plows, etc.), when the ground work device is raised (non-working state) on a headland, etc.,
Since there is no resistance from the soil, noise is reduced, and the output level of the speaker (SPK) is lowered by a certain amount. For this detection, as shown in FIG. 34, it is preferable to use a lift angle sensor for detecting the lift angle of a lift equipped with a ground work device of a tractor, or a potentiometer in the ground work device. FIG. 33 is a flowchart of this volume automatic control.

Regarding the determination of the reduction range (the level of the cancellation sound) of the output level of the speaker (SPK),
As shown in FIG. 33 (b), the relative positions of the tractor and the working device are made to correspond to each other. Up to a position where the lift is at the lowest position L _MAX , there is a ground work device in the soil, and the frictional force with the soil is reduced in proportion to the lift, and noise is reduced. The output level E is lowered from the output level E _MAX in proportion to the lift rise angle, and the lift is raised to the lift maximum position L _MIN from the rise position where friction with soil disappears.
Until then, _keep it lowered to a constant level E _MIN .

Further, in a tractor equipped with a high-speed tiller, the engine speed is automatically controlled to be reduced by electronic governor control when turning on a headland. This is interlocked with the rise of the ground work device at the time of turning the headland, but FIG. 35 shows a configuration in which this decrease in the engine speed is detected and the volume of the cancellation sound of the silencer is automatically reduced. Is shown.

Next, a method of reducing the output level or turning off the power when the transmission (transmission) of the tractor is in the non-transmission state will be described with reference to FIGS.
7 will be described. The tractor includes a traveling transmission and a PTO shaft transmission that is a transmission mechanism for a work device. When the latter is in the non-transmission state, that is,
When the PTO shaft is not driven, the work device does not drive, noise from the work device does not occur, the engine load factor is low, and the engine noise is low. Further, if the drive transmission is in the non-transmission state, it is in the stopped state, and the engine load due to the drive is not generated, so that the engine noise becomes smaller and smaller. Therefore, the clutch sensor detects whether the clutch is engaged or disengaged in the transmission system from the engine to the traveling transmission, and when the clutch is disengaged, the volume level is lowered or the power source OF is turned off.
F Even if the clutch from the engine to the drive transmission is not disengaged, if the PTO shaft drive clutch in the PTO shaft transmission is disengaged, the volume level is reduced or the power is turned off (when the former clutch is disengaged. Considering that the engine noise, etc. is louder as compared to the amount that the vehicle is being driven. As described above, the volume of the engine sound can be automatically adjusted by detecting the engine speed or the load factor. However, the noise of the transmission (transmission) can be automatically adjusted by this detection method. For this volume adjustment, a bandpass filter (BPF) that allows the transmission of noise frequency signals of the transmission is passed.
You may control about the volume setting device (VD) of the latter part,
It may be performed in the speaker (SPK) output stage after the addition. Further, depending on the case, the power may be turned off. The automatic volume configuration of the muffling device based on the detection of running neutrality by the clutch sensor is also applied to FIG. 39 showing the combine embodiment.

Next, an automatic sound volume adjusting mechanism in the case where an active sound deadening device is provided in a mobile machine for civil engineering construction or a mobile vehicle for agriculture equipped with hydraulic equipment will be described with reference to FIG. In this case, the engine load factor is almost proportional to the pressure change accompanying the driving of the hydraulic equipment. Therefore, the change in the hydraulic pressure of the hydraulic equipment is detected by the pressure detection sensor, and the volume level of the cancellation sound is made proportional to the detected value P (the higher the pressure, the higher the volume level). Also, when the hydraulic pressure exceeds a certain set value, the maximum pressure value P and the minimum pressure setter are set so that the difference between the maximum value and the minimum value of the volume level is suppressed within the allowable range. Set _MAX and minimum pressure value P _MIN .

Next, in the cabin-mounted combine, the volume level of the canceling sound is lowered when the threshing means (coffer drum) or the transmission device to the threshing means is turned off in the configuration as shown in FIG. , Or power off. This is because the maximum engine load source of the combine is the threshing section.

In FIG. 39, two systems are controlled by detecting the rotational speed of the drum cylinder and detecting the running neutral state by the clutch sensor shown in FIG. That is, the body rotation speed sensor and the running neutrality detection sensor (clutch sensor)
Is also used for each control sensor of the combine, and when each sensor detects a decrease in the number of revolutions of the drum and neutrality, it reduces the amplification factor of the amplification circuit to reduce the level of the cancellation sound generated from the speaker. Lower. At this time, the relay solenoid is energized to switch the relay terminal immediately below. The microphone for noise detection on the body should be installed near the body and not affected by rain and dust (inside the cabin). Then, the volume of the canceling sound is increased while the vehicle is running, and is reduced when the vehicle is running neutral. However, the canceling sound is increased when the body is rotating even when the vehicle running is neutral.

Next, as shown in FIG. 40, when an active muffling device is installed to muffle indoor noise when the huller is used indoors, the paddle is supplied to the paddle removing section. When there is no power, or when power is not transmitted to the escapement section, the volume level of the cancellation sound is lowered or the power is turned off. The largest source of noise in a huller is the debarking section, and unless the debarking section is used to drive the debarking, the noise is greatly reduced, so the level of the cancellation noise must be lowered. On the contrary, the cancellation sound becomes loud.

Further, the canceling sound generating speaker (SPK) in this case is made to face at least the operation section side and the brown rice discharging side where the noise leaks from the debarking section,
Make sure that the noise that leaks can be effectively canceled, and the installation location is near the top of the hoistway of the elevator that conveys paddy, brown rice, etc., that is, at the highest point of the huller, and at a place where the cancellation sound can reach far. Install. Fig. 40 shows the speaker installation points when using the huller, * ₁ is the speaker for canceling the noise at the time of removing the paddle, and * ₂ is the part for installing the speaker for canceling the noise of the entire huller. Shows. * ₃ is an alternative to * ₁ , and under the projection surface of the paddy supply hopper,
The speaker is directed to the upper part of the wind selection section and the operation section side. Note that FIG. 41 is an example of a power supply circuit.

[0072]

The present invention has the following effects by being configured as described above. First, in the active silencer, the phase conversion rate in the control unit can be changed as in claim 1, so that the phase of the canceling sound from the speaker with respect to the noise depends on the positional relationship of the speaker with respect to the noise detecting means. If it is not exactly in the opposite phase, this deviation can be corrected and the opposite phase sound can be generated accurately from the speaker to ensure the silencing effect. It is also possible to convert to and output from the speaker. On the other hand, by adjusting the volume output of the speaker, you can balance the volume of the noise and the sound for cancellation,
For example, depending on the listener's position, the balance between the noise and the canceling sound is deviated, the canceling sound becomes louder, and when it becomes rather noisy, balance adjustment can be performed to enhance the silencing effect, Further, when it is desired to hear a certain noise, the volume of the canceling sound can be reduced so that the noise can be heard without being muted. in this way,
It is possible to provide an active muffling device that can freely adjust the muffling effect to the maximum extent.

Further, by using an acceleration sensor instead of a generally used microphone as noise detecting means, howling can be prevented and the cost is lower than that of a microphone that is expensive for low frequencies. .

By disposing the speaker outside the room, the sound is muted before it enters the room, the sound deadening effect is enhanced, and the sound is muted even outside the room. Furthermore, by making the speaker face the room, it is possible to cancel the noise that enters the room by generating a cancellation sound from the speaker.

In addition to the adjustable phase conversion rate as claimed in claim 3, noise can be phase-converted to 0 ° to 360 ° by making the input terminal of the speaker switchable between positive and negative. Therefore, it is possible to easily, quickly, and effectively form an anti-phase canceling sound, and speed up the silencing control.

Further, as in claim 4, by providing the display means for displaying the adjustment result of the phase conversion rate and the amplification rate, the phase conversion rate and the amplification rate of the cancellation sound from the speaker are optimized while confirming the display. Can be adjusted to ensure the sound deadening effect.

Further, in the case of reducing the indoor noise of the motor vehicle, the amplification factor adjustment in the control section is automatically adjusted based on the detection of the prime mover speed to increase or decrease the revolution speed. It is possible to effectively muffle the noise of the prime mover that changes based on.

Further, in the case of reducing the indoor noise of the vehicle with the prime mover, the amplification factor adjustment in the control section is automatically adjusted based on the detection of the prime mover load to increase or decrease the load factor. In addition to the prime mover that changes based on the noise, noise from the transmission case, and in vehicles such as tractors, the sound of the working machine can be effectively silenced.

Further, in the active muffling apparatus having a structure in which the sound wave signal having a waveform similar to the noise is inversely phase-converted by the oscillator to generate the canceling sound regardless of the noise detection, the frequency of the oscillator can be increased. By freely setting, it is possible to oscillate a sound wave signal having a frequency that is most similar to noise, and maximize the sound deadening effect.

[Brief description of drawings]

FIG. 1 is a basic block diagram of an active silencer.

FIG. 2 is a microphone in an active silencer,
It is a perspective view of a tractor with a cabin showing an example of mounting a speaker and a setting device.

FIG. 3 is a block diagram of an active silencer provided with a bandpass filter.

FIG. 4 is a wiring diagram from a microphone to a bandpass filter.

FIG. 5 is a graph showing a frequency attenuation effect in a bandpass filter.

FIG. 6 is a block diagram of an active silencer when an acceleration sensor is used as a noise detecting means.

FIG. 7 is a block diagram of an active silencer in which an acceleration sensor is used as a noise detecting means and a bandpass filter is a lowpass filter only.

8 is a low pass filter wiring diagram in the case of FIG. 7. FIG.

FIG. 9 is a block diagram showing an embodiment in which a speaker is shared by a separate active silencer and audio device.

10 is a wiring diagram of the speaker input section in FIG.

FIG. 11 is a block diagram showing an embodiment in which an active muffler and an audio device are housed in a single device case and share a speaker.

FIG. 12 is a block diagram showing an embodiment in which noise canceling sound is emitted only from a front speaker among four-channel speakers in the embodiment of FIG. 11.

FIG. 13 is a block diagram showing an embodiment in which noise canceling sound is generated only from a bass speaker in the embodiment of FIG. 11.

FIG. 14 is a wiring diagram showing an embodiment in which an amplifier circuit after phase conversion is formed by combining an in-phase amplifier circuit and an inverting amplifier circuit.

FIG. 15 is a block diagram showing an embodiment of the embodiment of FIG. 11 in which the speaker input section can be switched between positive and negative, and amplification can be performed both in phase and on the inverting side.

16 is a wiring diagram of the speaker input unit in FIG.

FIG. 17: The active silencer is turned off when the engine is started.
It is a wiring diagram for F.

FIG. 18 is a block diagram of an active silencer when a plurality of bandpass filters are provided.

FIG. 19 is a block diagram of an active muffling device in the case where the breakpoint frequencies of the low pass filter and the high pass filter in the band pass filter can be adjusted.

FIG. 20 is a block diagram of an active silencer in which a plurality of bandpass filters are arranged and a phase conversion circuit is arranged directly under each bandpass filter.

FIG. 21 is a graph showing the displacement of the phase conversion angle according to the setting output by the phase setting device in the bandpass filters having different center frequencies.

FIG. 22 is a block diagram showing a mounting structure of a level meter, which is a display, when the amplification and phase conversion rate of each of a plurality of bandpass filters can be adjusted.

FIG. 23 is a block diagram when phase conversion adjustment and volume adjustment are enabled for each of a plurality of bandpass filters.

FIG. 24 is a block diagram when the volume of the speaker can be adjusted by detecting the engine speed in the embodiment of FIG. 23.

FIG. 25 is a block diagram when the center frequency of the bandpass filter can be adjusted by detecting the engine speed.

FIG. 26 is a block diagram in the case where phase conversion adjustment is also possible in the embodiment of FIG. 25.

FIG. 27 is a block diagram of a case where automatic volume control is possible by detecting an engine load factor.

FIG. 28: Volume decrease or power supply OF at engine start
It is a block diagram of the active silencer of the composition which carries out F.

FIG. 29 is a block diagram of an active silencer having a configuration capable of automatically setting a center frequency of a bandpass filter based on detection of an engine speed and an engine load factor.

FIG. 30 is a flow chart diagram in the configuration of FIG. 29.

FIG. 31 is a block diagram of an active silencer having a configuration in which the frequency of a bandpass filter can be set by setting the number of engine explosions (the number of engine cylinders).

32 is a flow chart diagram of the configuration of FIG. 31. FIG.

FIG. 33 is a flow chart diagram of an active muffling device configured to reduce the volume when the ground work device of the tractor is brought into a non-working state.

FIG. 34 is a block diagram of the same.

[Fig. 35] Fig. 35 is a block diagram of an active muffling apparatus that reduces the volume due to a reduction in engine speed during headland turning.

[Fig. 36] Fig. 36 is a block diagram of an active silencer configured to reduce the volume when the tractor is running neutral and when the work machine is transmitting neutral.

FIG. 37 is a block diagram of an active silencer having an automatic volume control function based on clutch sensor detection.

FIG. 38 is a block diagram showing a volume automatic adjusting mechanism based on an operating state of a hydraulic system in a vehicle equipped with the hydraulic system.

FIG. 39 is a block diagram showing a sound volume automatic adjustment mechanism based on an operating state of a threshing unit in a combine with a cabin.

FIG. 40 is a view showing the arrangement structure of the active noise canceling device in the huller.

41 is a power supply wiring diagram in FIG. 40. FIG.

FIG. 42 is a block diagram of an active silencer of a type that generates a noise canceling sound based on an oscillation signal from a sine wave oscillation circuit.

[Fig. 43] Fig. 43 is a block diagram of an active silencer having a configuration capable of setting the frequency of an oscillation circuit.

FIG. 44 is a wiring diagram showing a frequency setting mechanism in a sine wave oscillation circuit.

[Fig. 45] Fig. 45 is a block diagram of an active muffling device configured to muffle the sine wave oscillated by a sine wave oscillating circuit by peak cutting.

FIG. 46 is a block diagram showing peak cut means in FIG. 45.

[Fig. 47] Fig. 47 is a block diagram of an active silencer configured to oscillate and mute a composite wave of a sine wave and a rectangular wave.

FIG. 48 is a block diagram showing a configuration for performing automatic sound volume adjustment based on engine speed detection in a sine wave oscillation type active silencer.

FIG. 49 is a block diagram of the same.

FIG. 50 is a block diagram showing a configuration in which the frequency of a sine wave can be automatically set by setting the number of engine explosions (the number of engine cylinders) in the sine wave oscillation type active silencer.

51 is a flowchart of FIG. 50.

FIG. 52 is a block diagram of an active silencer that combines a sine wave oscillation type and a bandpass filter passing type based on noise detection.

53 is a block diagram of the active muffler of FIG. 52 configured so that the band-pass filter passing type active muffler based on noise detection is not activated unless the noise is equal to or higher than a certain frequency.

[Explanation of symbols]

 ANC Active silencer control unit MIC microphone SPK speaker BPF bandpass filter LPF low pass filter HPF high pass filter PCC phase conversion circuit AMP amplification circuit PRA preamplifier POA power amplifier PD phase setting device VD volume setting device SWC sine wave oscillation circuit BD frequency setting device

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location H03H 21/00 8842-5J

Claims (8)

[Claims] 1. One or a plurality of noise detecting means as an input means, and a control section for selectively passing a signal of a specific frequency from an input signal of detected noise, converting the passed signal into an opposite phase, and amplifying the signal. And an active muffler comprising one or a plurality of speakers as output means, wherein the phase conversion rate and the amplification rate in the control unit can be adjusted individually or simultaneously. 2. The active silencer according to claim 1, wherein an acceleration sensor is used as the noise detecting means. 3. The active noise suppressor according to claim 1, wherein the noise detecting means and the speaker are installed outside the room, and the speaker is opposed to the room. Silencer. 4. The active silencer according to claim 1, wherein the control unit can adjust the phase conversion rate, and the input terminal of the speaker can be switched between positive and negative. . 5. The active silencer according to claim 1, further comprising display means for displaying a result of adjusting the phase conversion rate and the amplification rate in the control section. 6. When reducing the indoor noise of a vehicle with a prime mover by the active muffler according to claim 1, the gain adjustment in the control section is automatically adjusted based on detection of the prime mover rotation speed. And active silencer. 7. The active muffler according to claim 1, wherein when the interior noise of a vehicle with a prime mover is reduced, the amplification factor adjustment in the control section is automatically performed based on detection of the prime mover load factor. And active silencer. 8. An active muffler having a configuration in which a signal having a waveform similar to noise is oscillated by an oscillator, converted into an opposite phase, amplified, and generated as a noise canceling sound from a speaker, the frequency of the oscillation signal of the oscillator being changed. An active silencer that can be set freely.