JP2016079849A - Intake noise amplification device for vehicular internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce noise of 100 to 200 Hz becoming discomfort booming noise while amplifying intake noise near 400 Hz as harmonious engine noise.SOLUTION: An intake noise amplification device is constituted by including: an inlet side tubular member connected to an intake system of an internal combustion engine; an outlet side tubular member having an extremity end opened outside; and a bellows-like resonance member positioned at an interface part between both tubular members, and a tube length and the like are tuned to amplify intake noise near 400 Hz. An intermediate part of the outlet side tubular member is provided with an expanded tube part 17, and an end part of the expanded tube part 17 is provided with an acoustic absorber 21 of foamed rubber. The acoustic absorber 21 passes noise near 400 Hz and in turn attenuates a band range of 100 to 200 Hz. With this arrangement, booming noise is reduced.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an improvement in an intake sound amplifying apparatus for a vehicle internal combustion engine using a resonator that vibrates in response to intake air pulsation of the internal combustion engine.

  In order to provide a driver with a lively engine sound in a vehicle such as a so-called sports car, an intake sound amplifying device that amplifies an intake sound in a desired band using vibration of a resonator has been proposed. And are put to practical use (for example, Patent Documents 1 and 2).

  This is because the intake sound inlet side tubular body branched from the intake system of the internal combustion engine, the intake sound outlet side tubular body whose tip is open to the outside (for example, the interior space of the vehicle interior), and these two connected to each other. For example, a bellows-shaped resonator provided so as to seal the tip of the tubular body on the inlet side is provided at the boundary of the tubular body.

  In such an intake sound amplifying device, the resonator vibrates in response to the intake pulsation propagating from the intake system of the internal combustion engine through the inlet side tubular body, and the vibration of the resonator further includes the inlet side tubular body and the outlet. By performing air column resonance inside the side tubular body, the amplified intake sound is emitted from the front end opening of the outlet side tubular body. Here, the tube length of the two tubular bodies and the configuration of the resonator are tuned along a desired band to be amplified.

JP 2008-267220 A JP 2009-270489 A

  When applying the above-described intake sound amplifying device to a vehicle such as a sports car, for example, a comfortable engine sound is provided at the time of acceleration when the driver depresses the accelerator pedal, in an engine rotational speed range slightly higher than the normal rotational speed. Is often tuned so as to amplify an intake noise of about 300 to 400 Hz corresponding to the rotational quaternary component (in the case of an in-line four-cylinder engine).

  However, when the tube length or the like of the tubular body is tuned aiming at about 300 to 400 Hz as described above, a sound of 100 to 200 Hz corresponding to a rotating secondary component is generated at the same time due to air column resonance inside the tubular body. There is. The sound in the band near 100 to 200 Hz is an unpleasant noise called so-called “boom sound” in the passenger compartment, which may be further amplified depending on the configuration of the passenger compartment, and is not preferable.

  In the above-described intake sound amplifying apparatus, if such “boom sound” is silenced, the original intended amplified sound is also reduced. That is, in the conventional intake sound amplifying device, it has been difficult to achieve both the provision of the desired amplified engine sound and the suppression of the “boom sound”.

The present invention relates to an inlet-side tubular body connected to an intake system of an internal combustion engine so as to branch from the intake system, and an outlet-side tubular body connected to the inlet-side tubular body and having a tip opening outward. And a resonance body that is provided at the boundary between these two tubular bodies so as to seal the tip of the inlet-side tubular body and vibrates in response to intake pulsation. In the amplification device,
The inside of the inlet-side tubular body or the outlet-side tubular body is loaded with a sound absorbing material made of foamed rubber that gives a loss to a desired resonance band lower than the frequency band to be amplified. Yes.

  For example, the sound-absorbing material is made of closed-cell or semi-closed-cell foamed rubber, and has a greater loss with respect to a sound in an unfavorable band in a lower frequency band than in a frequency band to be amplified. give. As a result, it is possible to suppress an increase in an unpleasant “boom sound” while securing the originally intended amplified sound. In one example, the sound absorbing material has a characteristic that a loss of 100 to 200 Hz is larger than a loss of 300 to 400 Hz.

  In a preferred embodiment, the sound absorbing material is disposed on the outlet side tubular body.

  In a further preferred aspect, the outlet side tubular body has a pipe expanding part with an enlarged diameter in a part in the longitudinal direction, and the sound absorbing material is arranged in the pipe expanding part. Furthermore, it is possible to arrange the sound absorbing material in a part in the longitudinal direction of the pipe expanding portion.

  In a preferred embodiment, the sound absorbing material is loaded in a compressed state.

  According to the present invention, in an intake sound amplifying apparatus that amplifies intake sound in a preferred band using a resonator, an unpleasant “boom sound” is obtained while ensuring a large amplified sound in a preferred band to be amplified. An increase in sound in a relatively low band can be avoided.

1 is a plan view showing an embodiment of an intake sound amplifying device according to the present invention. The top view shown in the state which has arrange | positioned this intake sound amplifier in the engine room of a vehicle. The figure which showed the exit side tubular body containing a pipe expansion part from the direction different from FIG. Sectional drawing along the AA line of FIG. The perspective view which shows the principal part of a pipe expansion part in the state before welding. Sectional drawing which shows the cross section of a sound pressure generation part. The characteristic view which shows the transfer characteristic of the intake sound amplifier of an Example compared with the comparative example which does not comprise a sound-absorbing material. Explanatory drawing which shows the effect | action of a sound-absorbing material typically. The characteristic view which compares and shows the transfer characteristic of the intake sound amplifier by the position of a sound-absorbing material. Explanatory drawing of arrangement | positioning of the sound absorption material used for experiment of the characteristic view of FIG. The characteristic view which compares and shows the transmission characteristic of the intake sound amplification apparatus by the position where the sound-absorbing material in a pipe expansion part differs. Explanatory drawing of arrangement | positioning of the sound-absorbing material in the pipe expansion part used for experiment of the characteristic view of FIG. The characteristic view which compares and shows the transfer characteristic of the intake sound amplifier when the compression rate of a sound-absorbing material differs. The characteristic view which shows the transmission loss of the sound-absorbing material of open cells and the sound-absorbing material of semi-closed cells. The characteristic view which shows the transmission loss of the sound-absorbing material of closed cells and the sound-absorbing material of semi-closed cells.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a plan view showing an embodiment of an intake sound amplifying apparatus 1 according to the present invention. FIG. 2 shows the intake sound amplifying apparatus 1 disposed in the engine room 3 of the vehicle 2. The intake sound amplifying apparatus 1 includes an inlet side tubular body 4 made of a relatively hard material such as synthetic resin, an outlet side tubular body 5 made of a relatively hard material such as a synthetic resin, and a boundary portion between the two. The sound pressure generating unit 6 is generally composed of three members. The inlet side tubular body 4 is connected to the intake system of the internal combustion engine 7 so as to branch from the intake system. In the illustrated example, the internal combustion engine 7 is an in-line four-cylinder gasoline engine mounted on the vehicle 2 in a so-called vertical configuration, and a throttle body 9 is attached to an intake inlet portion of an intake manifold 8. It is connected to an air cleaner 11 via an intake duct 10. A base end 4 a of the inlet side tubular body 4 is connected to the intake duct 10 at a position immediately upstream of the throttle body 9. Thereby, intake pulsation generated in the intake system of the internal combustion engine 7 is taken into the inlet side tubular body 4.

  The distal end 4b of the inlet side tubular body 4 is connected to one end face of a sound pressure generating portion 6 having a cylindrical shape with an enlarged diameter. The sound pressure generator 6 is fixed to the vehicle 2 via a bracket 13.

  The proximal end 5a of the outlet side tubular body 5 is connected to the other end surface of the sound pressure generating portion 6 having a cylindrical shape. The distal end 5b of the outlet side tubular body 5 opens to the outside as a discharge port for the amplified intake sound. In the example of FIG. 2, the distal end 5 b of the outlet-side tubular body 5 opens toward the inside of the cowl box 12 positioned in front of the driver's seat of the vehicle 2 or toward the dash panel.

  As shown in FIG. 6, the sound pressure generator 6 includes a bellows-like resonator 14 that vibrates in response to intake pulsation. In this resonator 14, a bellows base end 14a is fixed to a disk-like flange 15 in which the tip 4b of the inlet side tubular body 4 opens in the center, and the tip 4b of the inlet side tubular body 4 is sealed. ing. A cup-shaped housing 16 surrounds the bellows-shaped resonator 14 and the free end 14 b, and the base end 5 a of the outlet-side tubular body 5 is connected to the center of the end surface of the housing 16. The base end 5 a of the outlet side tubular body 5 is opened facing the free end 14 b of the bellows-like resonator 14.

  Further, a tube expansion portion 17 whose diameter is partially enlarged to enhance resonance action is provided at an intermediate portion of the outlet side tubular body 5, more specifically at a position closer to the tip 5 b than the center of the outlet side tubular body 5. Is provided.

  In such an intake sound amplifying apparatus 1, the resonator 14 vibrates in response to the intake pulsation taken from the intake system of the internal combustion engine 7, and the vibration of the resonator 14 is further reduced to the inlet side tubular body 4 and the outlet side. By performing air column resonance inside the tubular body 5, the amplified intake sound is emitted from the opening of the tip 5 b of the outlet side tubular body 5. The band of the intake sound amplified in this way varies depending on the configuration of the resonator 14 and the tube lengths of the inlet side tubular body 4 and the outlet side tubular body 5, but in this embodiment, the driver can use the accelerator pedal. Each part is tuned to amplify the intake sound around 400Hz corresponding to the quaternary rotational component in the engine rotational speed range slightly higher than the normal rotational speed so that a comfortable engine sound is provided when accelerating the engine. ing.

  Here, when the tube length or the like is tuned with the aim of around 400 Hz as described above, at the same time, an uncomfortable “buzzing sound” of 100 to 200 Hz corresponding to a rotating secondary component is caused by air column resonance inside the tubular bodies 4 and 5. May be generated. Therefore, in the intake sound amplifying apparatus 1 of the above embodiment, the sound absorbing material 21 made of foamed rubber that gives a loss to the resonance sound of 100 to 200 Hz is provided in the sound path.

  Specifically, as shown in FIG. 3 to FIG. 5, the pipe expansion portion 17 is composed of two cup-shaped members and is welded so as to abut against each other at the center flange 17a. A sound absorbing material 21 made of foamed rubber formed into a disk shape is loaded in a state of being slightly compressed in the diameter direction and the tube axis direction. The sound absorbing material 21 is located at the end of the pipe expanding portion 17 on the sound pressure generating section 6 side, and is held between the tapered end wall 17b of the pipe expanding portion 17 and the four ribs 22 inside. The cylindrical sound-absorbing material 21 is compressed with a compression rate of 7% in the radial direction so that no gap is formed between the cylindrical sound-absorbing material 21 and the inner peripheral wall surface of the pipe expansion portion 17. Further, since the end wall 17b is tapered, the outer peripheral corner portion of the sound absorbing material 21 formed into a columnar shape is positively compressed, and this also prevents the generation of a surrounding gap. In one embodiment, the sound-absorbing material 21 has a thickness of 20 mm (a dimension in the axial direction through which sound is transmitted) in a free state before being loaded into the expanded pipe portion 17.

  As the sound absorbing material 21, for example, an ethylene / propylene / diene rubber (EPDM) type semi-independent semi-open cell foamed rubber available from Nitto Denko Corporation under the trade name “Eptosealer EV1000” is used. Of course, the present invention is not limited to such specific foamed rubber, and various commercially available foamed rubbers can be used, whether they are closed cells or semi-closed cells. Good. Semi-closed bubbles are close to closed cells because communication between the bubbles is blocked in a compressed state.

  FIG. 8 is an explanatory view schematically showing the operation of the sound absorbing material 21. As shown in the figure, the foamed rubber of closed cells or semi-closed cells becomes an aggregate of a large number of thin films that partition the bubbles. When the sound input to the sound absorbing material 21 passes through the sound absorbing material 21, the sound in the band of about 300 to 400 Hz passes through the sound absorbing material 21 without being greatly attenuated. On the other hand, the sound of 100 to 200 Hz, which is a relatively low band, is relatively greatly attenuated when the sound absorbing material 21 passes.

  The graph of FIG. 7 shows the experimental results of measuring the acoustic characteristics of the intake sound amplifying apparatus 1 of the above-described embodiment, and particularly shows the comparison with a comparative example that does not include the sound absorbing material 21. As shown in FIG. 1, in a single unit not attached to the vehicle, a speaker is disposed toward the base end 4a of the inlet-side tubular body 4 serving as an inlet for intake pulsation, and the amplified intake sound is amplified. A microphone is arranged toward the tip 5b of the outlet-side tubular body 5 serving as an outlet, a predetermined sound (so-called white noise) is emitted from the speaker, and the sound collected by the microphone is analyzed. Since the vertical axis in the figure indicates the magnitude of loss as the transfer characteristic (dB), the lower the figure, the louder the sound.

  As shown in the figure, both of the example equipped with the sound absorbing material 21 and the comparative example not equipped with the sound absorbing material 21 have an amplification effect around the target 400 Hz, and the sound near this is operated as a pleasant engine sound. Can be provided.

  However, in the comparative example that does not include the sound absorbing material 21, a sound peak occurs at 100 to 200 Hz at the same time. This is an unpleasant sound for a driver as a so-called “boom sound”. On the other hand, in the embodiment provided with the sound absorbing material 21, the sound peak between 100 and 200 Hz disappears, and only the amplifying action near 400 Hz is obtained. The decrease in sound near 400 Hz compared to the comparative example is very slight.

  Next, the optimal position of the sound absorbing material 21 will be described.

  FIG. 9 and FIG. 10 show the results of examining the optimum position of the sound absorbing material 21 in the whole intake sound amplifying apparatus 1. When the position of the sound absorbing material 21 was changed to six locations indicated by A to F in FIG. 10 and an experiment similar to that described above was performed, results as shown in FIG. 9 were obtained. As shown in the figure, by arranging the sound absorbing material 21 made of foamed rubber at any location of the intake sound amplifying device 1, the peak of 100 to 200 Hz is reduced compared to the comparative example that does not include the sound absorbing material 21. On the other hand, when attention is focused on the target sound around 400 Hz, the embodiment in which the sound absorbing material 21 is disposed in the pipe expansion portion 17 shown as the position F in FIG. Therefore, it can be said that the configuration in which the sound absorbing material 21 is disposed inside the expanded pipe portion 17 is most advantageous. In the configuration in which the sound absorbing material 21 is disposed inside the inlet side tubular body 4 as in the position A in FIG. 10, the sound absorption material repeatedly acts on the sound absorbing material 21 although the attenuation of sound near 400 Hz is small. This is disadvantageous in that the sound-absorbing material 21 is sucked into the intake system when the 21 is deteriorated or dropped. However, if such deterioration and dropout can be prevented, the effect can be obtained even at the position A.

  FIG. 11 and FIG. 12 show the results of studying the optimum position of the sound absorbing material 21 in the expanded pipe portion 17. When the position of the sound absorbing material 21 was changed to five locations indicated by a to e in FIG. 12 and an experiment similar to that described above was performed, results as shown in FIG. 11 were obtained. In FIG. 12, the position c is an end on the sound pressure generating unit 6 side, and the position d is an end on the front end 5 b (see FIG. 1) side that serves as an intake sound discharge port. As shown in the figure, even if the sound absorbing material 21 made of foamed rubber is disposed at any location in the pipe expansion portion 17, the peak of 100 to 200 Hz is reduced as compared with the comparative example that does not include the sound absorbing material 21. However, paying attention to the target sound around 400 Hz, the embodiment in which the sound absorbing material 21 is arranged at the end of the pipe expansion portion 17 on the sound pressure generating portion 6 side shown as the position c in FIG. 12 has the least attenuation. Therefore, it can be said that the configuration in which the sound absorbing material 21 is arranged at the end portion on the sound pressure generating unit 6 side is the most advantageous among the tube expanding portions 17.

  FIG. 13 shows the result of studying the radial compression rate of the sound absorbing material 21 in a state of being loaded in the pipe expansion portion 17. This is an example in which the compression ratio in the radial direction is 2%, 7%, 12%, and 19%, and further, the sound absorbing material 21 is made smaller than the inner diameter of the tube expansion portion 17 so that a gap of 8% is generated. The same experiment as described above was performed for the example. Here, the compression rate is the rate of change of the diameter of the sound absorbing material 21 before and after the tube expansion part 17 is loaded. As shown in the figure, the amplification effect near 400 Hz has little influence on the compression rate. On the other hand, with respect to the peak of 100 to 200 Hz, the example of 2 percent compression and 8 percent gap has the same characteristics as the comparative example not including the sound absorbing material 21, and almost no reduction effect is obtained. This is thought to be due to sound leakage from the surroundings. Therefore, it can be said that it is necessary to have a compression rate of 7% or more. Furthermore, as a preferable compression rate, it is 10 to 25 percent.

  Next, FIG. 14 and FIG. 15 show three types of foamed rubber constituting the sound-absorbing material 21: open cell, closed cell, and semi-closed semi-open cell, when sound is transmitted. The result of having experimented about the characteristic of loss of is shown. This is a foam rubber sample piece fixed to a jig and attached to a speaker for sound measurement, and microphones are installed before and after the jig to measure the loss of sound emitted from the speaker due to the sound absorbing material (sample piece). It is a thing.

  FIG. 14 shows the measurement of four sample pieces with a thickness of 20 mm in the sound transmission direction. Sample piece 1 is a product name “Non-Halo Flame Retardant Foam VO” from Bridgestone Chemicals. It consists of available open cell flexible polyurethane foam. The sample piece 2 is “Eptosealer EV1000” manufactured by Nitto Denko Corporation. The sample piece 3 is “Eptosealer EE1000”, also manufactured by Nitto Denko Corporation, and the sample piece 4 is “Eptosealer No. 685”, also manufactured by Nitto Denko Corporation. These are ethylene-propylene-diene rubber (EPDM) type semi-independent and semi-open cell foamed rubbers similar to the sample piece 2.

  As shown in the figure, these are all effective in reducing the sound of 100 to 200 Hz while transmitting the sound in the vicinity of 400 Hz, but the sample which is a semi-closed cell compared to the sample piece 1 which is an open cell. The pieces 2 to 4 gave better results in terms of reducing sound around 100 Hz.

  FIG. 15 shows the same measurement for four sample pieces with a thickness of 15 mm in the sound transmission direction. In addition to the sample pieces 2 to 4, the sample piece 5 was measured. The sample piece 5 is “Epto Sealer No. 6800” manufactured by Nitto Denko Corporation, which is a closed cell ethylene / propylene / diene rubber (EPDM) foam rubber.

  As shown in the figure, the same result was obtained in reducing the sound of 100 to 200 Hz while transmitting the sound in the vicinity of 400 Hz regardless of whether it is a closed cell or a semi-closed cell.

DESCRIPTION OF SYMBOLS 1 ... Intake sound amplifier 4 ... Inlet side tubular body 5 ... Outlet side tubular body 6 ... Sound pressure generation part 7 ... Internal combustion engine 10 ... Intake duct 14 ... Resonator 21 ... Sound absorbing material

Claims (6)

An inlet-side tubular body connected to the intake system of the internal combustion engine so as to branch from the intake system; an outlet-side tubular body connected to the inlet-side tubular body and having a tip open to the outside; In an intake sound amplifying device for an internal combustion engine for a vehicle, comprising a resonator that is provided at a boundary portion between two tubular bodies so as to seal a tip of an inlet-side tubular body and vibrates in response to intake pulsation,
The inside of the inlet-side tubular body or the outlet-side tubular body is loaded with a sound absorbing material made of foamed rubber that gives a loss to a resonance sound in a desired band lower than the frequency band to be amplified. An intake sound amplifying device for a vehicle internal combustion engine.   2. The intake sound amplifying device for an internal combustion engine for a vehicle according to claim 1, wherein the sound absorbing material is disposed in the outlet side tubular body.   The vehicular internal combustion engine according to claim 2, wherein a part of the outlet side tubular body in the longitudinal direction has a pipe expanding part having an enlarged diameter, and the sound absorbing material is disposed in the pipe expanding part. Inspiratory sound amplifying device.   The intake sound amplifying device for an internal combustion engine for a vehicle according to claim 3, wherein the sound absorbing material is disposed in a part of a longitudinal direction of the pipe expanding portion.   The intake sound amplifying device for an internal combustion engine for a vehicle according to any one of claims 1 to 4, wherein the sound absorbing material is loaded in a compressed state.   The intake sound amplifying device for an internal combustion engine for a vehicle according to any one of claims 1 to 5, wherein the sound absorbing material has a characteristic that a loss of 100 to 200 Hz is larger than a loss of 300 to 400 Hz.

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