JPS643435B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vehicle acoustic device that uses a panel member such as a vehicle interior member as an acoustic diaphragm.

Examples of conventional vehicle audio equipment include those shown in Figure 1~
There is something like the one shown in Figure 3.
No. 135114). First of all, Figure 1 shows driver D for excitation.
It shows the front and rear of the cylindrical frame 1 (the first
A case body is constructed by fixing an excitation plate 2 and a cover plate 3 to both end faces, respectively (top and bottom of the figure), and a ring-shaped magnet 4 is installed in the center of this case body.
A yoke 5 is provided. The yoke 5 consists of a pole piece 5a and a yoke plate 5b, which together with the magnet 4 form a magnetic circuit having a gap, and are elastically supported by the frame 1 via a damper 6 at the yoke plate 5b. There is. Further, a coil 7 wound around a bobbin is arranged in the gap, and the bobbin is fixed to the vibration plate 2. As shown in FIGS. 2 and 3, the driver D configured in this manner is attached to the back side of a panel member 8 forming the rear parcel of an automobile by screws or the like at the frame 1. . In this way, in the panel speaker, the driver D is directly attached to the panel member 8 for the interior of the vehicle interior, and the entire panel member 8 is used as it is as an acoustic diaphragm. As this acoustic vibration diaphragm, in addition to a member for the interior of an automobile as shown in the figure, a wall plate of a living room is used, and such a panel member 8 is used.
etc. are made of a material such as compressed cardboard or plywood, and are generally rigidly fixed to the vehicle body etc. at their outer edges.

When the audio signal is energized to the coil 7, the magnet 4 side and the frame 1 side, that is, the excitation plate 2 side, vibrate relative to each other via the damper 6, and the vibration of the excitation plate 2 etc. is transmitted to the panel member 8. The low frequency range is reproduced.

However, in the conventional vehicle acoustic device as described above, the entire panel member 8 was used as an acoustic diaphragm, so the panel member 8
The plate vibrates around the fixed part on the outer periphery, and the lowest natural resonance point cannot be kept low enough, and as shown in the reproduction frequency characteristics in Figure 4, the lowest resonance frequency as a speaker _{is 0.}
The frequency becomes approximately several 100 Hz. Therefore, a peak appears in the desired bass reproduction range B, which takes advantage of the characteristics of this type of vehicle audio device, and the characteristics lack flatness, and the sound is sufficient to reach the desired low frequency range, for example, up to about 50 Hz. There was a problem in that it was not possible to output according to the pressure level. Further, there is a problem in that split vibration occurs in which each part of the panel member 8 vibrates in different phases, resulting in a lower output sound pressure level as a whole, lowering efficiency, and poor transient response characteristics.

This invention improves the output characteristics in the low frequency range found in conventional vehicle acoustic devices,
The object of the present invention is to provide a vehicle audio device that has predetermined low frequency characteristics and has good reproduction efficiency.

In order to achieve the above objective, a hole with a required area is drilled in the panel member, and a separate diaphragm member is supported by both opposing edges of this hole so as to face the hole. A slit corresponding to a clearance for vibration is provided between the vibration member and the opening, and a vibration excitation driver is attached to the vibration member.

The present invention will be explained below based on the drawings. Fifth
6 and 6 are diagrams showing an embodiment of the present invention. In each of the figures following FIG. 5, the same or equivalent members or parts as shown in FIGS. 1 to 3 are designated by the same reference numerals and redundant explanations will be omitted.

First, the configuration will be described. In this invention, a rectangular (rectangular) opening 8a having a required area is bored in the panel member 8 at the location where the driver is disposed. As an example, the opening area of the opening 8a is 130×
It is selected to be around 400mm. A diaphragm member 9 made of a material different from that of the panel member 8 is fixedly supported on both longitudinally opposing edges of the aperture 8a.
The vibrating driver D is mounted approximately at the center of the diaphragm member 9. That is, the driver D is supported by the rectangular diaphragm member 9 in the form of a beam on the main body of the panel member 8. The diaphragm member 9 is made of a material that functions appropriately as an acoustic diaphragm, such as urethane foam, for example, and has a thickness of approximately several mm and is formed in the same shape and size as the aperture 8a. In order to allow the diaphragm member 9 to face the opening 8a, an extremely narrow slit 11 corresponding to the clearance for vibration is provided between the vibrating side edges and the opening 8a. It's like this.

Next, the action will be explained. When an audio signal is energized to the coil 7, the magnet 4 side and the excitation plate 2 side are relatively displaced and vibrated within the driver D via the damper 6, and the diaphragm member 9 is excited by this vibration. . Then, vibration of the beam with a concentrated mass in a two-degree-of-freedom system occurs in the diaphragm member 9, generating sound pressure and reproducing a low frequency range. At this time, the material, shape, etc. of the diaphragm member 9 are selected so that the lowest resonant frequency ₀ is the desired frequency, so as explained in the following equation, the lowest resonant frequency ₀ is an example.
At about 50 Hz, the reproduction frequency characteristics shift as shown by the solid line in FIG. Therefore, the flatness of the characteristics increases within the desired bass reproduction range B that takes advantage of the characteristics of this type of vehicle acoustic device, and
Sufficient output sound pressure level can be obtained up to the desired low frequency range of about 50Hz, improving efficiency.

Next, the effect of lowering the lowest resonance frequency ₀ will be explained in more detail using an equation.

Now m ₁ ; Vibration system mass including the diaphragm member 9,
k ₁ : Spring constant of this vibration system, m ₂ : Mass of magnet system, k ₂ : Spring constant of driver (damper),
Let ω = 2π, and the magnetic mass m ₂ is Fcosωt,
Assuming that an excitation force of −Fcosωt acts on the vibrating system mass m ₁ , when examining the motion of the vibrating system mass m ₁ , the equation of motion is m ₁ d ² x ₁ /dt ² +k ₁ x ₁ +k ₂ (x ₁ −x ₂ )=−Fcosωt … m ₂ d ² x ₂ /dt ² +k ₂ (x ₂ −x ₁ )=Fcosωt …′. Also, assuming that the forced vibration is x ₁ = a ₁ cosωt, x ₂ = a ₂ cosωt (a ₁ , a ₂ : amplitude)... and substituting this into the equation ′, a ₁ (and a ₂ ) can be found. Then, a ₁ =Fm ₂ ω ² / [−m ₁ ω ² +k ₁ +k ₂ ) (−m ₂ ω ² +k ₂ )−K ₂ ² ] …. Here, the lowest resonance frequency ₀ is the frequency when the amplitude a ₁ becomes infinite (assuming there is no mechanical resistance), so the denominator of the above equation is set to zero as follows, (-m ₁ ω ² +k ₁ +k ₂ )(−m ₂ ω ² +k ₂ ) −k ₂ ² =0… Find ω (=2π) that satisfies this equation, and match the higher value of the two solutions. The following formula was obtained in this way.

Further, the spring constant k ₁ of the vibration system is expressed by the following equation, where L: length of the beam (diaphragm member), E: Young's modulus, and I: section coefficient of the beam.

k ₁ = L ³ / (192EI) ... From both equations above, the spring constant k ₁ of the vibration system is determined by the external dimensions of the beam, that is, the diaphragm member 9,
In addition, the lowest resonance frequency ₀ depends on this spring constant k ₁ and the mass m ₁ of the vibration system, that is, the material of the diaphragm member 9, etc., so the material of the diaphragm member 9 and its external dimensions are selected as described above. By doing so, the lowest resonant frequency ₀ can be defined to a desired value.

Next, FIGS. 8 and 9 show other embodiments of the present invention. In this embodiment, acoustic shields 12 are provided on both sides of the panel member 8 along the slits 11, 11.
a, 12b are planted. The height h of the acoustic shields 12a and 12b is set slightly higher than the maximum amplitude of the diaphragm member 9.

To explain the operation, as shown in FIG. 9, the diaphragm member 9 is excited and vibrates, and the opening area of the slit 11 is expanded. At this time, there is a tendency for vibrating air to enter and exit the front and back surfaces of the diaphragm member 9 through the enlarged slit 11, but the acoustic shields 12a, 12
b substantially restricts the expansion of the area of the slit 11 and suppresses the tendency of the vibrating air to enter and exit. Therefore, a decrease in the output sound pressure level due to cancellation of low-frequency out-of-phase sound waves caused by the inflow and outflow of vibrating air is prevented, and efficiency is improved. The characteristic shown by the solid line in the reproduced frequency characteristic in FIG. 10 shows the improvement in the sound pressure level in the low frequency range due to the above-mentioned effect.

As described in detail above, according to the present invention, an aperture having a required area is formed in a panel member, and a separate diaphragm member is supported at both opposing edges of the aperture, so that the aperture 8a vibrates. Since the diaphragm has an extremely narrow slit that corresponds to the clearance for This provides the effect that the characteristics of the vehicle audio device can be fully utilized. In addition, in order to reproduce the desired low frequency sound, it is economically advantageous because only the diaphragm member is made of a material suitable for this low frequency sound reproduction, and there is no need to replace the entire panel member with one made of such a material. is demonstrated.

Furthermore, according to an embodiment in which acoustic shields are installed on both sides of the panel member along the slits, in addition to the above-mentioned common effects, a decrease in the output sound pressure level due to the cancellation of out-of-phase sound waves in the low range can be prevented. The effect is that the low frequency characteristics can be improved.

[Brief explanation of the drawing]

Fig. 1 is a partially cross-sectional side view showing a driver section for excitation in a conventional vehicle acoustic device, Fig. 2 is a plan view showing a conventional vehicle acoustic device, and Fig. 3 is a side view of a conventional vehicle acoustic device. A side view, and FIG. 4 is a characteristic curve diagram showing the reproduction frequency characteristics of the same vehicle audio device.
FIG. 5 is a plan view showing an embodiment of the vehicle acoustic device according to the present invention, FIG. 6 is a cross-sectional view taken along the line -- in FIG. 5, and FIG. 7 is a characteristic showing reproduction frequency characteristics of the same vehicle acoustic device. 8 is a plan view showing another embodiment of the present invention, FIG. 9 is a cross-sectional view taken along the line -- in FIG. 8, and FIG. 10 is a characteristic curve diagram showing reproduction frequency characteristics of another embodiment of the same It is. 8: panel member, 8a: opening, 9: diaphragm member, 11: slit, 12a, 12b: acoustic shield, D: driver.

Claims (1)

[Claims] 1. A hole having a required area is bored in a panel member such as a vehicle interior material, and a separate diaphragm member is supported by both opposing edges of the hole, and a hole is formed between both side edges and the hole. 1. A vehicle acoustic device characterized in that a slit corresponding to a clearance for vibration is provided in the diaphragm member, and a driver for excitation is attached to the diaphragm member.