JPH04347312A - Noise prevention device - Google Patents

Abstract

PURPOSE:To form a noise prevention device with a simple structure, and small energy consumption, also capable of reducing intake noise in a wide frequency range. CONSTITUTION:A enclosed chamber 22 is connected to the side wall of an engine intake pipe 1 through a small diameter part 21 so as to form a resonator 2, and a piezoelectric bimorph type vibratory plate 3 is provided on the opening port of a bulkhead 23 in the enclosed chamber 22 of the resonator 2. The vibratory plate 3 is vibrated by a driving signal outputted from a driving control circuit 4. In the driving control circuit 4, original intake pulsation is predicted by an engine rotational speed, a load, and the like, and the driving signal is transmitted to the vibratory plate 3 so as to output control noise. The control noise is synthesized with resonance noise generated in the enclosed chamber 22, and sound pressure of the synthesized noise is in antiphase condition with nearly the same amplitude as that of intake pulsation pressure so as to offset the pulsation pressure effectively, and reduce intake noise.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a noise prevention device that absorbs and reduces noise emitted from an engine intake pipe or the like by using negative phase sound pressure.

0002

2. Description of the Related Art With the recent demand for reducing engine noise, resonators have been provided to prevent intake noise from engine intake pipes. This resonator is shown in Figure 15 (
As shown in 2), a sealed chamber 22 of a predetermined volume is connected to a circulation pipe 1 for pulsating airflow through a small diameter portion 21.
A resonance sound occurs within the body. This resonance sound is in phase with the airflow pulsation and delayed by a certain period of time To, and is equal to the original pulsation pressure P.
When A (Fig. 15 (1), (3)) has a predetermined period τ1 (i.e., a predetermined frequency), the resonant sound pressure PB (Fig. 15 (2)
, (3)) and cancel each other out, and the actual pulsating pressure PA' within the flow pipe 1 approaches zero, thereby reducing noise.

By the way, when the period of the pulsating pressure PA changes to τ2 (FIG. 16), since the delay time To is constant, the antiphase relationship with the resonant sound pressure PB collapses, and as a result, the pulsating pressure PA' increases. The noise is emitted again. In this way, the noise frequency that one resonator can reduce is limited, so it is necessary to install a large number of resonators in the engine room to prevent noise, such as the engine intake pipe of a vehicle, which generates a wide range of intake noise depending on the engine operating condition. It was necessary to install a resonator, which was difficult in the limited space in the engine room.

[0004] Therefore, for example, Japanese Utility Model Application Publication No. 1-174562 proposes a system in which the volume of a resonator resonance chamber is changed according to the engine speed.

[0005]

[Problems to be Solved by the Invention] However, with the above-mentioned proposed device, the control device becomes complicated and a significant increase in cost is unavoidable, and it is hardly effective against high-order components of intake noise that are input at the same time. There was a problem.

SUMMARY OF THE INVENTION The present invention has been made to solve these problems, and it is an object of the present invention to provide a noise prevention device that can effectively reduce airflow noise over a wide range in a small space.

[0007]

[Means for Solving the Problems] To explain the structure of the present invention, a sealed chamber 22 of a predetermined volume is connected to a flow pipe 1 for pulsating airflow connected to an engine E (FIG. 1) by a small diameter portion 21, and a resonator 2 A part of the chamber wall of the resonator 2 is
It is composed of a diaphragm 3 that vibrates with an amplitude and frequency according to an input drive signal and emits a control sound pressure, and detects at least the engine rotation speed and engine load and based on these, detects the resonance sound in the sealed chamber 22. The diaphragm 3 is arranged so that the sound pressure obtained by combining the control sound pressure and the control sound pressure has approximately the same amplitude and opposite phase to the pulsating pressure of the pulsating airflow of the resonator connecting portion 1a.
A drive control means 4 is provided for applying a drive signal to the drive.

In the device configured as described above, when the original pulsating pressure is predicted from the engine speed and load, and the drive signal is determined to output the control sound pressure from the diaphragm, the sound pressure combined with the resonance sound pressure is has substantially the same amplitude and opposite phase as the pulsating pressure, and the pulsating pressure is well canceled and absorbed, thereby effectively reducing the noise emitted from the flow pipe.

The prediction of the pulsating pressure is also made for its high-order components, and by simultaneously generating a drive signal based on this, a control sound pressure component that cancels out the above-mentioned high-order components is generated, thereby suppressing the high-order pulsations. Pressure is also reduced and wide range noise is prevented.

In the present invention, the sound pressure that cancels out the pulsating pressure is generated by combining it with the resonance sound pressure in the resonator, so the level of the control sound pressure can be made relatively small, and the shape of the diaphragm can be changed. It can be made compact and the energy required to drive it can also be reduced.

[0011]

[Embodiment 1] In Fig. 1, an intake pipe 1 extending from an engine E provided with an intake valve E1 has a resonator 2 on a side wall midway.
The resonator 2 includes a small-diameter portion 21 that is directly open-connected to the intake pipe 1 and a rectangular sealed chamber 22 having a predetermined volume. Inside the sealed chamber 22, a partition wall 23 is formed at a position close to the bottom wall, and a diaphragm 3 is formed in the center of the partition wall 23. As the diaphragm 3, a bimorph element or the like in which piezoelectric ceramics are bonded to the front and back sides of a circular metal plate is used, and the outer periphery of the metal plate is fixed to the inner periphery of the opening of the partition wall 23 by gluing or staking.

The diaphragm 3 is caused to vibrate according to the voltage and frequency of a drive signal generated by an external drive control circuit 4. The drive control circuit 4 receives engine speed and engine load signals from known sensors, and also receives an intake pressure signal from a pressure sensor 5 provided on the wall of the intake pipe 1 downstream of the resonator connection portion 1a. There is.

FIG. 2 shows the configuration of the drive control circuit 4. The circuit 4 includes an input circuit 41 for receiving a signal from the pressure sensor 5, a digital filter 42, an output circuit 46 for outputting a signal to the drive plate 3, a CPU 43, a ROM 44, and a RAM 45.

The operation will be explained based on the above configuration. The intake waveform captured by the pressure sensor 5 enters the input circuit 41 of the drive control circuit 4, and is subjected to filtering, amplification, etc. The sound waves generated from the diaphragm 3 are generated using the signal from the pressure sensor 5 as a source, and are then taken into the digital filter 42 to filter out the necessary frequency components, especially the second-order and (n+0.5)-order components of engine rotation. (n is an integer n≧
0), phase control is performed.

In this case, the digital filter 42 is CP
According to the command of U43, filter characteristics are formed for each predetermined rotation speed. Further, as shown in the flowchart of FIG. 3, the CPU 43 takes in the rotation speed and load from the engine in step 100, and detects map information in step 110 based on this rotation speed information. Then, the pre-stored map information is searched, and the secondary and (
n+. Phase data of a frequency corresponding to the 0.5) order component is extracted from the ROM 44. Note that this phase data is created for each intake system path of each internal combustion engine.

A filter characteristic based on the phase data extracted in this way is formed by the digital filter 52,
After passing the intake waveform signal through this, this signal is amplified by the output circuit 46 and output to the diaphragm 3.

In the noise prevention device having such a structure, intake air pulsates within the intake pipe 1 at various frequencies depending on the rotational speed of the engine E, and this is discharged to the outside from the intake port and becomes intake noise. As described above, at frequencies other than the predetermined frequency determined by the volume of the resonator 2, etc., the resonance sound in the resonator sealed chamber 22 and the airflow pulsation are out of phase, so the pulsating pressure is not absorbed and the intake noise is not reduced.

[0018] Here, in the apparatus of the present invention,
From the waveform of the intake pressure, engine speed, and load, the original intake pulsation pressure PA containing higher-order components for each engine speed is determined.
(Fig. 4 (1), (3)) is calculated and predicted, and a drive signal whose phase, frequency, and voltage are determined based on this is output. The drive signal is output to the diaphragm 3, and the diaphragm 3 emits a control sound with a predetermined amplitude and frequency in accordance with the drive signal into the sealed chamber.

In the sealed chamber 22, a resonance sound delayed by the time To is generated as described above in response to the pulsation in the intake pipe 1 (line y in FIG. 4(3)). When the control sound (line z in Fig. 4 (3)) emitted by
The synthesized sound pressure PB has almost the same amplitude as the original intake pulsation pressure PA, but the phase is reversed. Therefore, the original pulsating pressure PA is effectively offset by the synthetic sound pressure PB, and the actual pulsating pressure PA' is sufficiently reduced.

Although the above explanation is about the fundamental wave of the intake pulsation, a drive signal is similarly determined to cancel out the higher-order waves that are occurring at the same time, and this is superimposed on the drive signal for the fundamental wave. When the control sound pressure is applied to the diaphragm 3, the high-order components of the control sound pressure are synthesized with the resonance sound pressure generated in response to the high-order pulsation components, and the high-order pulsation pressure is reduced by this synthesized sound pressure. Ru.

As described above, the device of the present invention can effectively reduce noise in a wide frequency range, including high-order noise, with a simple structure. In addition, the present invention utilizes the resonance sound generated in the sealed chamber of the resonator and synthesizes the control sound emitted from the diaphragm to obtain sound pressure that cancels out and reduces the pulsating sound. Compared to outputting a sound pressure that cancels out pulsation noise, the control sound pressure only needs to be at a low level, and the diaphragm can be made smaller and lighter to save space and save power during driving. .

[0022] The reason why the back of the diaphragm is closed by the bottom wall is to prevent the sound waves from the diaphragm from being emitted directly to the outside, and if this is not a problem, an open structure may be used.

[0023]

[Embodiment 2] In FIG. 5, the sealed chamber 22 of the resonator 2
Inside, partition walls 23A and 23B are formed near the left and right side walls, and each partition wall 23A and 23B has a diaphragm 3A and a diaphragm 3A, respectively.
3B is provided. According to this structure, the substantial vibration area is increased compared to the case of a single diaphragm, and as a result, a powerful control sound can be emitted. In addition, each diaphragm 3A, 3B
The shape of each can be made optimal for the frequency to be muted.

[0024]

Embodiment 3 In FIG. 6, partition walls 23A and 23B are formed vertically at intervals near the bottom wall of a sealed chamber 22, and diaphragms 3A and 3B are provided respectively. In such a structure, the vibration of the diaphragm 3A is energized by the sound wave emitted from the diaphragm 3B, and as a result, a sufficiently large control sound can be obtained from the diaphragm 3A.

[0025]

[Embodiment 4] Fig. 7 shows a configuration in which a large-diameter radiation plate 31 made of foam material is provided in front of a diaphragm 3, and their centers are joined to each other, so that the vibration area is expanded and a powerful control sound is generated. At the same time, the diaphragm 3 is not directly hit by foreign objects, resulting in excellent durability.

[0026]

[Embodiment 5] Since the closed space behind the diaphragm 3 may obstruct its vibration, a communication pipe 231 of an appropriate diameter and length is formed in the partition wall 23 as shown in FIG. By making the pressure behind the diaphragm 3 in phase with the pressure in the closed space 2a and releasing it, the energy of the diaphragm 3 can be used without wastage and power consumption can be reduced.

[0027]

Embodiment 6 It is more effective to provide a plurality of communicating pipes as shown in FIG.

[0028]

[Embodiment 7] In FIG. 10, in addition to the partition wall 23 provided with the diaphragm 3 near the bottom wall of the sealed chamber 22, there is also a communication pipe 241 that divides the inside of the sealed chamber 22 into upper and lower sealed spaces 2a and 2b. By forming the provided partition wall 24, the resonance frequency of the upper sealed space 2a and the resonance frequency of the upper and lower sealed spaces 2a, 2b are combined to reduce intake pulsation as a normal resonator, and furthermore, the control sound of the diaphragm 3 This generates a synthetic sound for pulsation reduction.

[0029]

[Embodiment 8] In FIG. 11, a partition wall 23A is provided with diaphragms 3A and 3B near the left and right side walls of a sealed chamber 22, respectively.
, 23B, and the left and right sealed spaces 2a, 2
A partition wall 24 is provided to partition the closed spaces 2a and 2b, and a control sound is generated in accordance with the resonance sound of each of the closed spaces 2a and 2b.

[0030]

[Embodiment 9] In FIG. 12, resonators 2A and 2B connected to the intake pipe 1 at different positions are connected to a partition wall 2 provided with a diaphragm 3.
It is divided into 3 sections. Each resonator 2A, 2B reduces the intake noise at a predetermined resonance frequency, and when the intake noise deviates from the resonance frequency, the control sound from the diaphragm 3 causes the intake noise to be in reverse phase at each connecting portion 1a, 1b. A synthesized sound is produced.

[0031]

[Embodiment 10] In FIG. 13, the small diameter portion 21 of one resonator 2A is extended beyond the intake pipe 1, and its connecting portion is positioned opposite to the connecting portion 1b of the other resonator 2B. This allows for even more effective noise reduction.

[0032]

[Embodiment 11] In FIG. 14, a partition wall 23 provided with a diaphragm 3 is extended into a single connecting pipe, and each resonator 2A,
The small diameter portion 21 of 2B is sectioned to reduce the installation space.

[0033]

As described above, according to the noise prevention device of the present invention, a diaphragm that emits a control sound is provided in the resonator, and the structure is simple, and the noise prevention device of the present invention can effectively suppress air intake pipes, etc. without requiring a large space or power. airflow noise can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of the device in Example 1.

FIG. 2 is a block configuration diagram of a drive control circuit.

FIG. 3 is an operation flowchart of the drive control circuit.

FIG. 4 is a waveform diagram in Example 1.

FIG. 5 is a cross-sectional view of the device in Example 2.

FIG. 6 is a cross-sectional view of the device in Example 3.

FIG. 7 is a cross-sectional view of the device in Example 4.

FIG. 8 is a cross-sectional view of the device in Example 5.

FIG. 9 is a cross-sectional view of the device in Example 6.

FIG. 10 is a cross-sectional view of the device in Example 7.

FIG. 11 is a cross-sectional view of the device in Example 8.

FIG. 12 is a cross-sectional view of the device in Example 9.

FIG. 13 is a cross-sectional view of the device in Example 10.

FIG. 14 is a cross-sectional view of the device in Example 11.

FIG. 15 is a waveform diagram in a conventional example.

FIG. 16 is a waveform diagram in a conventional example.

[Explanation of symbols]

1 Intake pipe (flow pipe) 1a Resonator connection part 2 Resonator 21 Small diameter part 22 Closed room 3. Vibration plate 4 Drive control circuit (drive control means) E engine

Claims (1)

[Claims] Claim 1: A resonator is formed by connecting a sealed chamber of a predetermined volume to a pulsating airflow distribution pipe connected to an engine through a small diameter section, and a part of the chamber wall of the resonator is controlled to generate amplitude and vibration according to a drive signal. The resonator is composed of a diaphragm that vibrates according to the number of waves and emits a controlled sound pressure, and detects at least the engine rotation speed and engine load. A noise prevention device characterized in that a drive control means is provided for applying a drive signal to the diaphragm so that the pulsating pressure of the pulsating airflow in the connecting portion has approximately the same amplitude and opposite phase.