JPH04113946A - Noise control device for automobile - Google Patents

Abstract

PURPOSE:To reduce noise by providing actuators vibrating vehicle body panels in the vicinity of vibration sensors provided on the body panels, and driving the actuators based on the detected noise on prescribed place in a vehicle room and the detected vibration of the body panels. CONSTITUTION:Microphones 1a-1d as noise sensors are fitted to the head rests 2a-2d of seats, a pair of vibration sensors 6a, 6b are arranged on the dash-panel 3 partitioning an engine room 4 from a vehicle room 5, and small sized electromagnetic actuators 7a, 7b are arranged in the vicinity of them. Vibration sensors 6c, 6d are provided on the center part of a rear parcel 8 and the center part on the back of a trunk lid 10, and electromagnetic actuators 7c, 7d are provided in the vicinity of them. Based on the detected signals of the microphones 1a-1d and the vibration sensors 6a-6d, exciting force to reduce noise level in the vehicle room is calculated by a control means, and the electromagnetic actuators 7a-7d are controlled to be driven following to the calculated results.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) The present invention relates to a noise control device for an automobile that suppresses vehicle interior noise excited by vibrations from the engine, tires, road surface, etc.

(Prior art) As a conventional noise control device of this type, for example,
There is one described in 9-114597. That is, this noise control device includes a noise detection microphone provided inside a sealed structure, an acoustic speaker that generates a canceling sound wave with an amplitude corresponding to the noise detected by the microphone and a phase shift of 180 degrees, and this acoustic speaker. It consists of a control device that controls the When noise occurs inside the sealed structure with such a configuration, a sound wave having the same amplitude and opposite phase as the noise is output from the acoustic speaker.

At this time, the sound waves and the noise cancel each other out, and the noise is reduced.

(Problem to be solved by the invention) By the way, there are two types of noise from automobiles: when the car is stopped and when it is running.
Some are caused by input from the engine or road surface. In other words, from low-frequency noise such as muffled idle noise when idling or muffled sound when driving on relatively rough roads,
There is noise in a wide range of frequencies, from the transmitted sound from the engine when driving to high-frequency noise such as road noise.

Therefore, when the above-mentioned conventional noise control device is used in a car with such noise, the sound waves from the acoustic speaker are output with the same amplitude and opposite phase as the noise in order to reduce the noise. The frequency range that can be achieved is limited by the performance of the acoustic speaker, and the frequency range of the acoustic speaker is mainly affected by the diameter of the acoustic speaker, so this is not the case with small acoustic speakers that can be installed in cars. There is a problem in that it is extremely difficult to generate low frequency sound waves of 100 Hz or less. That is, it is not appropriate to apply a conventional noise control device using a speaker to noise in a low frequency range that causes discomfort to passengers.

The present invention has been made in view of the above points, and an object of the present invention is to provide an automobile noise control device that can deal with noise in a wide frequency range, and to improve the comfort inside the vehicle.

[Structure of the Invention (Means for Solving the Problems)] In order to achieve the above object, the present invention includes a noise sensor that detects noise at a predetermined location in a vehicle interior, a vibration sensor installed on a vehicle body panel, and a vibration sensor installed on a vehicle body panel. An actuator that vibrates a vehicle body panel installed near a vibration sensor, and drives the actuator based on the noise detected by the noise sensor and the vibration detected by the vibration sensor, and vibrates the vehicle body panel in accordance with the detected noise. The structure consists of means for controlling vibration.

(Function) With the above configuration, the actuator can be driven by the control means based on the detected noise at a predetermined location in the vehicle interior and the detected vibration of the vehicle body panel, and the vibration of the vehicle body panel can be controlled in response to the noise situation. can.

(Example) Hereinafter, the present invention will be explained based on the drawings.

FIG. 1 is a block diagram showing an embodiment of an automobile noise control device according to the present invention. In this figure, 1a-1d are
Headrest 2a of the seat near the passenger's ear position
This is a microphone attached to 2d as a noise sensor for detecting vehicle interior noise. 3 is a dash panel that partitions the engine room 4 and the vehicle compartment 5, and a pair of vibration sensors 6a, 6b are arranged on the left and right sides of the dash panel, and small electromagnetic actuators 7a, 7b are arranged as actuators near each vibration sensor 6a, Bb. has been done.

Reference numeral 8 indicates a rear bar cell that serves as a partition between the trunk room 9 and the vehicle interior 5, and 10 indicates a trunk lid as an opening/closing body provided at the upper part of the trunk room. Vibration sensors Be, 6d are provided at the center of the back surface of the device 10, and small electromagnetic actuators 7c, 7d are provided as actuators near them.

Further, FIG. 2 is a block diagram of the control circuit of FIG. 1.

In this figure, a control circuit 11 is provided as a control means for reducing noise in the passenger compartment based on signals detected from the microphones la to 1d and vibration sensors 6a to 6d and a signal of engine rotation speed. ing. This control circuit 11 is a detection circuit 11a.

Arithmetic circuit 11b, drive circuit 11C1 and amplifier circuit 1
1d.

In the above configuration, the noise inside the vehicle is transmitted through the microphone 1a.
1d, vibrations at predetermined locations are detected by the vibration sensors 6a to 6d, and the engine rotational speed is detected, and these are input to the detection circuit 11a. The detection circuit 11a detects these inputs as electrical signals and inputs them to the arithmetic circuit 11b. The arithmetic circuit 11b calculates an excitation force for reducing the noise level in the vehicle interior, that is, at the passenger's ear position. This calculation result is sent to the drive circuit 11c, where the small electromagnetic actuator 7a
~7d is converted into an AC signal for driving. This alternating current signal is amplified by an amplifier circuit lid and input to small electromagnetic actuators 7a to 7d. As a result, vibrations of the vehicle body panels are controlled in response to the noise level inside the vehicle. In other words, by changing the vibration characteristics of each panel 3, 8.10,
Alternatively, each panel 3, 8, 10 can function as a panel speaker.

Next, we will first explain general automobile noise phenomena,
Next, we will specifically explain the influence of small electromagnetic actuators installed on the panel using a mechanical model.

Regarding noise phenomena in automobiles When the noise phenomena in automobiles are classified by frequency in conjunction with vehicle body vibration, they are roughly classified as follows.

1) Below 70 Hz - Below the primary cavity resonance frequency of the vehicle interior In this region, the change in volume of the air inside the vehicle due to the vibration of the large panel of the vehicle body causes noise with a substantially uniform sound pressure inside the vehicle interior.

2) 70 to 120 Hz...In this frequency range where vehicle interior cavity resonance begins to appear, vibration of the vehicle body panel excites vehicle interior cavity resonance, and the sound pressure distribution becomes uneven.

The position of the so-called sound field nodes, where the sound pressure is low, tends to move toward the vibrating panel.

3) 120Hz or higher: In this frequency range, the resonance of each panel of the car body appears at a high density, creating noise, and the phenomenon becomes complicated.

4) Transmitted sound: In addition to the above-mentioned noise from vibrations from the road surface and engine that are transmitted to the vehicle body panels and become sound, there is also external noise such as that from the engine that is transmitted into the interior of the vehicle. There is transmitted sound generated by

In closed structures, this noise transmission is caused by external air vibrations (
Sound) - Structural system vibration - Transmitted as internal air vibration (sound). Therefore, if the structural system does not vibrate, noise will not be transmitted.

Regarding the influence of a small electromagnetic actuator installed on a panel, there are actually countless resonances of the panel, but here, for simplicity, resonance up to the second order is adopted, and the panel is treated as an approximation of a two-degree-of-freedom system. Figure 3 shows a mechanical model of a panel equipped with small electromagnetic actuators. Here, ml,
2+ fI+ f2+ kl+k2 + CI
+ c7 represents each mass, load, spring constant, and damping coefficient when the panel is approximated as a two-degree-of-freedom system, and mol
f O+ kOr CO are the mass, load, spring constant, and damping coefficient of the small electromagnetic actuator. Also,
f, is the excitation force transmitted from the vehicle body to the panel, fl, is the excitation force of the small electromagnetic actuator, XI + X2
+xo represents the displacement of each mass.

Setting up the equation of motion, m, 5<+-f1+F2 (fa +fo + f
+-) m25c2w-f.

mo Xo = f o + f I.

fHwa-, x-c, large, f2- k2 (XI X2) -c2 (large, -large,) fo=ko (XI Xo) +C0 (large, -*,) f,,fi Z x H , Z is the transfer function of the feedback loop from xl to the small electromagnetic actuator.

Figure 4 shows the calculations made by increasing the above-mentioned kinetic force throw formula Z-0, 10, and 20. As can be seen from this figure, by increasing 2, the primary resonance frequency of the panel is pushed to a lower frequency, and the secondary resonance frequency is pushed to a higher frequency. It can also be seen that the vibration of the panel becomes smaller between the primary resonance and the secondary resonance. This indicates that the resonant frequency and vibration amplitude of the panel can be controlled by installing and driving a small electromagnetic actuator on the panel.

Let us consider applying changes in panel resonance due to the installation of such electromagnetic actuators to the above noise phenomenon.

a) Below 70 Hz In this case, by suppressing the vibration amplitude of the panel, the volume change of the air inside the vehicle can be reduced, and the noise can be reduced. In this frequency range, the resonance of the trunk lid as shown in FIG. 5 and the rear resonance of the vehicle body where the rear parcel vibrates around the rear window as shown in FIG. 6 particularly affect the noise inside the vehicle. Therefore, it is desirable to install a small electromagnetic actuator on the rear glass and trunk lid, but installing it in the center of the glass is not practical from the viewpoint of securing rear visibility and appearance, so it is necessary to achieve vibration with the rear glass in this frequency range. It is controlled by installing a small electromagnetic actuator on the rear bar cell.

b) 7C1-120Hz Figure 7 shows the sound pressure distribution of the primary cavity resonance in the vehicle interior. From this resonance mode, it can be seen that the sound pressure is particularly high in the rear seats, causing a noise problem. However, by bringing the resonance frequency of the rear glass close to this primary cavity resonance frequency, this node of the sound pressure distribution can be pushed to the rear, and the noise level in the rear seats can be reduced. Therefore, in this case, a small electromagnetic actuator on the rear bar cell controls the resonance frequency of the rear bar cell and the rear glass, changes the sound pressure distribution of the sound field, and reduces the cabin noise caused by the change in air volume in the trunk lid to the vibration level of the trunk lid. By suppressing the noise, noise can be reduced.

1) 120 Hz or higher Since the phenomenon is complicated in this frequency range, it is better to vibrate the panel with a small electromagnetic actuator and use it as a so-called panel speaker, rather than controlling the vibration characteristics of the panel.

At this time, the appropriate control excitation force to be applied to each panel in order to minimize noise can be determined as follows.

The sound pressure p+ at the noise evaluation point i is the input point j (j-1~
Using the transfer function H1 from n) and the human force load F1, it can be expressed as follows.

Here, if we rewrite the real part of the transfer function and the load with the superscript r1 and the imaginary part with the superscript i, the real part and imaginary part of (1) become ・ ・ ・ (2) ・ ・ ・ ( 3) Now, assuming that j-1 to k (k<n) is the total vibration input to the vehicle body from the engine, tires, road surface, etc., and the vibration input from the small electromagnetic actuator is FA%FB,
(2) , (8) Formula ・ ・ ・ ・ (4) ・ ・ ・ ・ (5) Furthermore, if we set Σ <H',F', -H + F r ) -P'I-, Equations (4) and (5) are -H, P', ) ・ ・ ・ ・ (6) 1 m (pl )−PZe+Σ (H', F'.

-A +H'+mF'+a) ・ ・ ・ ・ (7
) What we want to minimize is the sound pressure p+, so here we can consider minimizing the square of this.

That is, pl' −Re (pl)
2 +1m (pl) 2 =M
In.

,', Re (pl)'-5M1 n.

Im(pl)2-+Min, 2 of (8)
The equation can be solved under constraint conditions determined by the driving capacity of the small electromagnetic actuator.

Here, if equations (6) and (7) are considered according to the configuration of the present invention, the excitation force F'1l of the small electromagnetic actuator is
lIP'm is known because it is determined by the amplitude, frequency, and phase of the drive signal, H', 6, H'+m can be given by vibration experiments or structural analysis studies during vehicle development, and P',. ,pl,. are Re (pl), Im (pl) detected by each microphone and the above F
'm, F'll, HzIR1H'ls, by (
6) It can be easily calculated from equation (7). Once these values are determined and the current vibration state is known, it is possible to feed back the actuator drive signal by substituting these values into equation (8).

■) Transmitted sound The problem here is mainly transmitted sound from the engine. As mentioned earlier, transmitted sound is not a problem unless the intervening structural system vibrates, so here we use a small electromagnetic actuator to suppress the vibration of the dash panel, which serves as the partition between the engine room and the passenger compartment. At this time, the frequency characteristics of engine noise depend on the engine speed, so
As information for controlling the driving force of the small electromagnetic actuator that reduces this transmitted sound, the engine speed is used along with dash panel vibration information. However, if the noise frequency range estimated from this engine speed does not match the high-level frequency range of the noise actually detected by the in-vehicle microphone, it is determined that transmitted sound is not the cause, and the dash panel is also It works as a panel speaker using a small electromagnetic actuator to reduce noise.

[Effects of the Invention] As described above, according to the configuration of the present invention, it is possible to change the vibration characteristics of a panel installed in a vehicle body, or to make the panel function as a panel speaker, so that a wide range of noise inside the vehicle can be suppressed. This makes it possible to control noise in a frequency range, and as a result, the comfort inside the vehicle can be improved.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of an automobile noise control device according to the present invention, Fig. 2 is a block diagram of a control circuit device of the automobile noise control device shown in Fig. 1, and Fig. 3 is an electromagnetic actuator. Figure 4 is a diagram showing the panel vibration characteristics caused by the electromagnetic actuator, Figure 5 is a trunk lid resonance mode diagram, Figure 6 is a vehicle rear resonance mode diagram, and Figure 71! ! J is a side view showing the primary cavity resonance sound pressure distribution in the vehicle interior.・7a-76 1a-1d・68~6d・78~7d・1 microphone (noise sensor) ・Dash panel (body panel) ・Vibration sensor ・Small electromagnetic actuator (actuator) ・Rear parcel (body panel) ・Trunk lid (Vehicle body panel) ・Control circuit (control means) Figure 13

Claims (2)

[Claims] (1) A noise sensor that detects noise at a predetermined location inside the vehicle;
A vibration sensor installed on a vehicle body panel, an actuator installed near the vibration sensor and vibrating the vehicle body panel, and driving the actuator based on noise detected by the noise sensor and vibration detected by the vibration sensor. A noise control device for an automobile, comprising means for controlling vibration of the vehicle body panel in accordance with detected noise. (2) The noise control device for a motor vehicle according to claim 1, wherein the noise sensor is provided at a plurality of locations in a vehicle interior, and the vibration sensor and the actuator are provided respectively on a plurality of predetermined vehicle body panels.