JPS5963251A - Apparatus for reducing noise of vehicle - Google Patents

Abstract

PURPOSE:To reduce noises of an engine, by composing part of an enclosure of a board speaker, and vibrating and controlling said speaker in such a way that the vibrations of the speaker are at the same level as that of the enclosure caused by the noises of the engine and the phase of said speaker is opposite to that of said noises. CONSTITUTION:The enclosure 5 mounted to cover an engine 2 is composes of a board speaker. The vibrations of the enclosure 5 caused by the noises of the engine in the engine room 8 are detected by a vibration detecting sensor 9, and the detected signal is sent to a filter section 12 of a controller 11. This signal is analysed in the filter section 12 with respect to the frequency, and its amplitude and phase are detected by an amplitude detecting section 13 and a phase detecting section 14. The analysed and detected results are sent to an arithmetic section 15. The arithmetic section 15 carries out computation based upon the results, and the enclosure 5 is vibrated and controlled by the computed result in such a way that it is vibrated approximately at the same frequency and level as those of the vibrations of said noises and with an antiphase to that of the vibrations of said noises.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vehicle noise reduction device that efficiently reduces noise outside and inside the vehicle.

The main source of noise outside and inside a vehicle is noise radiated from a vehicle engine. In order to reduce the noise of such engines, in recent years, the space where the engine is mounted (engine room) has been covered with an under cover to create a sound insulating structure, and the inner surface of the plate-shaped member that forms the engine room has been fitted with sound-absorbing and
Various methods have been studied to reduce the noise leaking from the engine room by attaching soundproofing materials, etc., and are being put into practical use.

However, when only the cover and sound absorbing material are used in this way, it is not possible to obtain a sufficient noise reduction effect even if the thickness of the cover is increased or a cover made of vibration damping material such as a composite material is used. However, even if sound absorbing materials, sound insulating materials, etc. were used in combination, there was a limit to the reduction effect.

The present invention has been made in view of the above circumstances, and includes at least a part of the enclosure in the engine room comprised of a board speaker to reduce noise in the engine enclosure caused by noise radiated from the engine into the engine room. By providing a controller that controls the excitation of the board speaker so that it emits vibrations of approximately the same level and approximately opposite phase, the vibration of the enclosure is effectively suppressed by the interference effect of this vibration (sound wave). The purpose is to reduce noise outside and inside the vehicle.

The present invention will be explained in detail below based on an illustrated embodiment.

In this embodiment, the present invention is applied to a cab-over type truck, and an engine 2 is mounted between the left and right frame members 1, 1 that support the body of the truck via a mounting rubber or the like (not shown). The upper part of the cab 3 is supported by the floor panel 4 of the cab 3. An enclosure 5 composed of board speakers is installed on the lower surface of the floor panel 4, and the left and right sides and the bottom of the engine 2 are each composed of board speakers.*These are called side covers and amplifier covers. Enclosure 5,5. It is covered with... By covering the front of the engine 2 with a radiator 6 and the rear cover 7 with a rear cover 7, an engine room 8 is formed with a sound-insulating structure that is sealed to the extent that air permeability is not impaired.

On the other hand, left and right frame members 1. A vibration detection sensor 9.9 that detects the vibration state of the enclosure 5 through the noise state in the engine room 8 is installed, and the enclosure 5 composed of the vibration detection sensor 9 and the board speaker is driven. By connecting the amplifier 10 through the controller 10, the vibration of the enclosure 5 composed of board speakers is controlled in accordance with the vibration state of the enclosure 5 due to the noise radiated from the engine 2 to the engine room 8. There is.

Here, the controller 11 is configured as shown in FIG. 3, for example, and a vibration signal of the enclosure 5 detected via the vibration detection sensor 9 is supplied to the filter section 12. The filter section 12 analyzes the frequency of the vibration signal output from the vibration detection sensor 9, and supplies the analysis results to the amplitude detection section 13 and the phase detection section 14, respectively.

The amplitude detection section 13 detects the amplitude level of each vibration component subjected to frequency analysis, and the phase detection section 14 detects the phase of each vibration component. Information on the amplitude level and phase of each vibration component is then supplied to the calculation unit 15 together with correction information such as the temperature inside the engine room detected via a sensor (not shown). Then, this calculation unit calculates the frequency, amplitude level, and phase of excitation of the board speaker constituting the enclosure 5, and determines whether this vibration and the vibration caused by the noise are approximately the same frequency, approximately the same level, and approximately opposite phase. The enclosure (board speaker) 5 is controlled to vibrate via the amplifier 10 so that
The vibration is controlled.

That is, when noise is radiated from the engine 2 to the engine room 8, the engine room enclosure 5
vibrates and emits noise inside and outside the vehicle.

However, as described above, since the controller 11 controls the excitation of the board speakers constituting the enclosure 5 so as to cause vibrations at approximately the same level and approximately at an opposite phase to that of noise-induced imaging, the enclosure 5 is substantially As a result, the noise radiated outside the vehicle and into the interior of the vehicle is reduced. Note that the phase difference between the noise-induced vibration and the excitation vibration does not have to be completely opposite, and if the phase difference between the two is 180° ± 20°, the noise level radiated from the enclosure 5 can be reduced by about 10 dB. was revealed as a result of the experiment.

Further, since the enclosure 5 is not necessarily required to have a sound insulation function, it is easy to maintain good ventilation in the engine room 80, and the accessibility to the engine 2 can be improved.

In this example, the entire enclosure is made up of board speakers, but the enclosure below the engine, which is easily hit by stones, water, etc. thrown up from the road surface, is made of sheet metal, etc., as in the conventional case. The entire enclosure does not necessarily have to be made up of board speakers, as the durability may be improved, and the outer surface of the enclosure made up of board speakers may be further coated to further improve the sound insulation of the engine room. There isn't.

6-Also, in the embodiment, the vibration state of the enclosure is indirectly detected from the noise state of the engine room, but the vibration of the enclosure may be detected directly.

As explained above, according to the present invention, a part of the engine room enclosure is configured with T-board speakers, and vibrations of the enclosure due to noise radiated from the engine into the enclosure (engine room) are approximately the same. The enclosure (board speaker) is controlled to vibrate so that the vibrations are approximately in opposite phase at the same level, and this vibration control effectively suppresses the vibration of the enclosure to reduce the noise level radiated to the outside and inside of the vehicle. Because I am doing this,
As in the past, using an enclosure made of split plates or composite plates, and a large amount of sound-absorbing and sound-insulating materials can significantly reduce noise outside and inside the vehicle.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an embodiment in which the present invention is applied to a cab-over type truck, FIG. 2 is a sectional view taken at ++-11 in FIG. 1, and FIG. 3 is a block diagram showing an example of a controller. 2... Engine 3... Cab 4... Floor panel 5... Enclosure 6... Radiator 7... Rear cover 8... Engine room 9... Vibration detection sensor 10... Amplifier 11
...Controller patent applicant Hino Motors Co., Ltd.

Claims (1)

[Claims] An engine room enclosure comprising at least a portion of board speakers;
a vibration detection sensor that detects vibrations of the engine room enclosure; and a controller that controls the vibration of the board speaker so as to generate vibrations at approximately the same level and approximately in opposite phase to the vibrations of the enclosure based on the output of the sensor. A noise reduction device for vehicles equipped with