JPH08242498A - Electroacoustic transducer - Google Patents

Abstract

PURPOSE: To provide an electroacoustic transducer which can secure the excellent characteristic over a wide range including the low-pitched sounds through the high-pitched ones without increasing its size. CONSTITUTION: An electrode aggregate consists of the plural platy fixed electrodes 1 which are arranged in parallel to each other with spaces secured between them, and every vibration film 3 is held between plates 1 via a spacer 2 attached at the edge part of the film 3. A voice voltage generation means 21a applies the bias voltage to the film 3 and also generates the voice voltage at its both ends, and these two ends are alternately connected to the electrode 1. The spacer 2 includes an opening part P1 where the air is sent out and also taken in at one side and the other of the electrode aggregate when the film 3 vibrates toward the electrode 1. In such a holding structure of the film 3, many films 3 can be laminated on each other and the largest output sound pressure is secured. Furthermore, the air can be effectively pressurized and depressurized so that the excellent characteristic is secured in the low-pitched sound ranges.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speaker, a loudspeaker, and other electroacoustic transducers, and more particularly to an electroacoustic transducer capable of obtaining excellent frequency characteristics in the entire frequency band without increasing the size. .

[0002]

2. Description of the Related Art As an electroacoustic transducer such as a speaker, a capacitor type is known in the past. A capacitor-type speaker has a thin film-shaped vibrating membrane arranged close to a plate-shaped fixed electrode, and by applying an audio voltage to the fixed electrode with a bias voltage applied to the vibrating membrane, It vibrates and emits sound waves.

By the way, a condenser type speaker generally has a narrow sound frequency band, and a speaker of a size smaller than normal is usually used for high pitched sounds. In addition, although there is a speaker in which the frequency band is expanded to the low frequency range, such a speaker not only becomes considerably large, but also holds a vibrating membrane having a large area at a fixed distance from a fixed electrode. It was quite difficult. Further, in order to radiate the vibration of the vibrating film to the outside as a sound wave signal, it is necessary to use a component in which a large number of holes called pan ring metal are formed in the fixed electrode, resulting in a high manufacturing cost.

Therefore, a so-called heil type has been proposed as an electroacoustic transducer capable of improving the frequency characteristics of the entire frequency band without increasing the size. This electroacoustic transducer is disclosed in, for example, Japanese Patent Publication No. 55-42.
As disclosed in Japanese Patent No. 555, one diaphragm is bent so as to meander, both ends thereof are supported by a casing, and magnets are arranged on both sides of the diaphragm. In such an electroacoustic transducer, since the diaphragm is bent so as to meander, it is possible to increase the total area of the diaphragm without increasing the size, and it is possible to cover the low frequency range. .

[0005]

However, in the above-mentioned Heil type electroacoustic transducer, since only the both ends of the diaphragm are supported and the space between them is free, the diaphragm has a predetermined shape. There was a limit to its size in order to hold it. Therefore, in any case, it was not possible to sufficiently cover the bass range. In addition, since the magnets are arranged on both sides of the diaphragm, the distance between the magnets is long. Therefore, in order to form a strong magnetic field that vibrates the entire diaphragm, a fairly large magnet must be used. There was also the problem of not becoming.

The present invention has been made to solve the above problems, and an object thereof is to provide an electroacoustic transducer which can obtain excellent frequency characteristics over the entire frequency band without increasing the size. I am trying.

[0007]

The electroacoustic transducer according to claim 1 constitutes an electrode assembly in which a plurality of plate-shaped fixed electrodes are arranged in parallel with each other and spaced apart from each other. , Sandwiching the vibrating membrane via a spacer arranged at the edge thereof, and applying a bias voltage to the vibrating membrane,
Alternately connecting one end and the other end of the audio voltage generating means for generating an audio voltage to both ends to the fixed electrode,
The spacer is provided with an opening through which air is ejected from one side of the electrode assembly and at the same time air is sucked from the other side of the electrode assembly when the vibrating membrane is swung to the fixed electrode side. Is characterized by.

In the electroacoustic transducer according to a second aspect of the present invention, in addition to the features of the first aspect, the thickness of the spacer is 1/4 or less of the maximum length of the vibrating portion of the vibrating membrane. It is characterized by being.

[0009]

According to the electroacoustic transducer of claim 1,
When the potential of the fixed electrode on one side of the vibrating membrane becomes positive, the potential of the fixed electrode on the other side becomes negative. As a result, the vibrating film to which the bias voltage is applied is attracted to the side of the fixed electrode having a potential having a polarity opposite to that of the vibrating film, and receives the repulsive force from the other fixed electrode. As a result, the vibrating membrane swings to the fixed electrode side having the opposite polarity to this, air is discharged from the space between the two, and air is sucked into the space between the fixed electrode and the vibrating membranes separated from this. In this case, air is discharged from one side of the electrode assembly,
Since the opening portion of the spacer is arranged so as to suck air from the other side, a compression wave of air is generated at the side portion of the electrode assembly and becomes a sound wave.

The maximum output sound pressure in a speaker or the like is proportional to the amount of air discharged and sucked by the vibration of the vibrating membrane. In this electroacoustic transducer, since the vibrating membranes are held between the spacers, the vibrating membranes can be stacked in multiple layers. Therefore, in this electroacoustic transducer,
By forming the vibrating membrane in multiple layers, it is possible to increase the discharge amount and suction amount of air, and it is possible to obtain a large maximum output sound pressure without increasing the size of the vibrating membrane.

In order to improve the output sound pressure frequency characteristics in the low sound range in a speaker or the like, it is necessary to efficiently convert the vibration energy of the vibrating membrane into acoustic energy. This is because if the pitch of the compression wave of air is long, a larger amount of air must be pressurized and depressurized. In the electroacoustic transducer having the above structure, the space between the vibrating membrane and the fixed electrodes and the outside are communicated with each other by the opening provided in the spacer, so that the air flowing in and out of the space passes through the opening. Receive resistance at the time. Therefore, the pressurization and depressurization of the air are efficiently performed in the space between the vibrating membrane and the fixed electrodes, so that the characteristics in the low sound range can be improved.

Further, in the electroacoustic transducer having the above structure, since the compressional wave of air is not directly formed by the vibrating membrane, the shape of the vibrating membrane has little influence on the frequency characteristic. Therefore, the degree of freedom of the shape of the vibrating membrane is increased, and eventually the design restrictions of the cabinet and the like are reduced.

[0013]

【Example】

A. Configuration of Embodiment One embodiment of the present invention will be described below with reference to FIGS. 1 to 4. FIG. 1 is a perspective view showing a part of the speaker of the embodiment in an exploded manner in the vertical direction. Hereinafter, the configuration of the speaker will be described in order from the upper components. In the figure, reference numeral 1 is a fixed electrode. The fixed electrode 1 is composed of an aluminum plate having a length, width, and thickness of 50 mm × 100 mm × 0.5 mm. A spacer 2 is provided on the lower surface of the fixed electrode 1.
Are glued together. The spacer 2 is a U-shaped frame body made of PET resin, and one open side thereof serves as an opening of a space for generating a sound wave described later. The spacer 2 has the same vertical and horizontal dimensions (50 mm × 1) as the fixed electrode 1 in this embodiment.
00 mm) and has a thickness of 1 mm and a width of 5 mm. The vibrating film 3 is bonded to the lower surface of the spacer 1.

The vibrating membrane 3 has a length, width and thickness of 50 mm.
Aluminum is vapor-deposited to a thickness of 5000 angstrom on the surface of a polyimide film (Kapton) of × 100 mm × 15 μm. On the lower surface of the vibrating film 3, a second-stage spacer 2 is adhered in a direction opposite to the spacer 2. The fixed electrode 1 is adhered to the lower surface of the second-stage spacer 2, and the third-stage spacer 2 is adhered to the lower surface of the fixed electrode 1 in the same direction as the second-stage spacer 2.

As shown in FIG. 1, the spacers 2 and 2 adhered to the front and back surfaces of the fixed electrode 1 face in the same direction, and the spacers 2 and 2 adhered to the front and back surfaces of the fixed electrode 1 adjacent thereto are the above spacers. It faces in the opposite direction of 2,2. In this way, the pair of spacers 2 and 2 sandwiching the fixed electrode 1 are alternately reversed in direction for each fixed electrode 1.

A portion surrounded by the vibrating film 3, the spacer 2 and the fixed electrode 1 is a space for generating a sound wave.
In addition, one open side of the spacer 2 serves as openings P ₁ , P ₂ , ... P _n for allowing air to flow in and out of the space. Then, the unbonded portion of the vibrating film 3 inside the portion bonded to the spacers 2 and 2 vibrates in the vertical direction, whereby the air is pressurized or depressurized in the space, and the opening P ₁ , P ₂ , ... P _n passes into and out of the space.

The horizontal length of the vibrating portion of the vibrating membrane 3 is preferably 4 times or more the thickness of the spacer 2, and more preferably 10 times or more (90 in this embodiment).
Times). With such a configuration, pressurization and depressurization in the space can be performed more efficiently, and the frequency characteristic can be improved especially in the low sound range.

Next, FIG. 3 shows the fixed electrode 1 and the vibrating membrane 3.
2 shows a circuit for supplying an audio signal to the. In the figure, reference numeral 20 is an audio signal input circuit for inputting an audio signal to a speaker. The audio voltage signal supplied from the audio signal input circuit 20 is a step-up transformer (audio voltage generating means) 2
Amplified by 1. One end of the output side coil 21a of the step-up transformer 21 is connected to every other fixed electrode 1, ..., And the output side coil 21 is connected to the fixed electrodes 1 ,.
The other end of a is connected.

Further, the central portion of the output side coil 21a is grounded, so that the voltage at both ends of the output side coil 21a is evenly divided into plus and minus and is applied to the fixed electrodes 1, .... It That is, assuming that the voltage across the output side coil 21a is V ₀ , the voltage V _0/2 is applied to one fixed electrode 1 across the vibrating membrane 3 and the voltage −V is applied to the other fixed electrode 1. _0/2 is applied. On the other hand, when the voltage across the output side coil 21a is assumed to be -V _0, the voltage on one of the fixed electrode 1 the -
V _0/2 is applied, and the voltage V ₀ is applied to the other fixed electrodes 1, ...
/ 2 is applied.

A DC power source V is connected to each of the vibrating membranes 3, ... Through a protective resistor R. The negative side terminal of the DC power supply V is grounded, and the positive side terminal is each vibrating membrane 3, ...
It is connected to the. As a result, each vibrating membrane 3, ...
A positive bias voltage is applied. Therefore, when an audio voltage signal is input from the audio signal input circuit 20, the vibrating membrane 3 is attracted to the fixed electrode 1 to which a negative voltage is applied and the repulsive force from the fixed electrode 1 to which a positive voltage is applied. As a result, the vibrating membrane 3 swings toward the fixed electrode 1 having a negative polarity. Then, the polarities and potentials of the fixed electrodes 1, 1 change according to the sound voltage, and the sound voltage is converted into vibration of the vibrating membrane 3.

FIG. 2 is a perspective view showing a state where the speaker of the embodiment is assembled. Now, the fixed electrode 1 located at the top
When a negative voltage is applied to the fixed electrodes 1, the second fixed electrode 1 has a positive voltage, and the third fixed electrode 1 has a negative voltage. The polarities alternate. Due to the voltage polarities of the fixed electrodes 1, ..., The vibrating membrane 3 located at the uppermost stage is swung upward, and as a result, air is discharged from the opening P ₁ facing the front side in the drawing and the other side. Opened opening P ₂
Draws air from.

Further, since the vibrating membrane 3 in the second stage from the top swings downward, air is sucked from the opening P ₃ opened on the other side in the figure, and the opening P ₄ below it which faces the front side. From which air is discharged. In this way, the fixed electrode 1,
When the above voltage is applied to ..., Air is discharged from the openings P ₁ , P ₄ , P ₅ , ... P _n facing the front side, and the openings P ₂ , P ₃ opening toward the other side. , ... Air is sucked from P _n-1 . Further, when a voltage having the opposite polarity to the above is applied to the fixed electrodes 1, ..., The opening P ₁ facing the front side,
Air is sucked from P ₄ , P ₅ , ... P _n , and air is discharged from the opening portions P ₂ , P ₃ , ... P _n-1 opened on the other side.
In this way, compressional waves of air are formed on both sides of the speaker and become sound waves.

B. Actions and Effects of the Embodiment In the speaker having the above configuration, since the vibrating membranes 3, ... Are held between the spacers 2, 2, it is possible to stack the vibrating membranes 3 ,. it can. Therefore, in this speaker, the amount of air discharged and the amount of air sucked can be increased, and thus the output sound pressure level can be increased despite the compact configuration as described above. Specifically, thirty vibrating membranes 3, ... Are arranged in the speaker of the example, and the total area of the vibrating portions of the vibrating membranes 3, ... Is (50-10) mm × (100-10). m
m × 30 = 108000 mm ² = 1080 cm ² .
This is almost the same area as the 33 cm square area.
In the above speaker, a vibrating membrane with an area equivalent to this is 5 cm.
It is within the volume of × 10 cm × 8 cm.
Further, the total area of the openings P ₁ , ... Is 0.1 cm × 9 c
m × 30 = 27 cm ² , which is about 1/40 of the total area of the vibrating membranes 3, ... As described above, in the loudspeaker of the embodiment, the area of the portion that radiates sound waves is very small compared to the total area of the vibrating membranes 3, ...

Further, in the above-mentioned speaker, the air flowing in and out of the space between the vibrating membranes 3, ... And the fixed electrodes 1, ... Passes through the openings P ₁ ,. To resist. Therefore, the pressurization and depressurization of the air are efficiently performed in the space, so that the output sound pressure frequency characteristic in the low sound range can be improved. Further, since the speaker does not directly form the compressional wave of air by the vibrating membranes 3, ..., The shape of the vibrating membrane 3 has little influence on the frequency characteristic. Therefore, the degree of freedom in the shape of the vibrating membrane 3 is increased, and the restrictions on the design of the cabinet and the like are reduced.

In the speaker having the above structure, the vibrating membrane 3 is used.
Since the vibrating membrane 3 is vibrated by the fixed electrodes 1 and 1 arranged on the front and back sides, it is not necessary to dispose a large magnet on the side of the vibrating membrane unlike the Heil type speaker. in this way,
In the speaker of the embodiment, the space for the magnet is unnecessary, so that the structure becomes more compact.

In particular, in the above embodiment, since the thickness of the spacer 2 is set to 1/10 or less of the maximum length of the vibrating portion of the vibrating membrane 3, pressurization and depressurization of air in the space are more efficient. It is performed well, and the frequency characteristic in the low frequency range can be further improved.

Next, FIG. 4 shows a result of measuring the output sound pressure frequency characteristic of the speaker having the above-mentioned structure. In the speaker used for the measurement, the bias voltage applied to the vibrating membranes 3 was set to 1000V. In addition, for comparison, a direct-radiation speaker in which two punching metals as fixed electrodes are arranged in parallel to each other and the same vibrating membrane as above is arranged via a rectangular spacer between the punching metals is manufactured. did. The output sound pressure frequency characteristics of this speaker were also measured and are also shown in FIG. As shown in FIG. 4, in the speaker of the embodiment, a sufficient output sound pressure level is secured from about 50 Hz and is stable up to about 1 KHz. on the other hand,
It was found that in the speaker of the comparative example, the output sound pressure level was considerably low in the low sound range, and considerable undulation occurred also in the middle sound range and the high sound range.

C. Modifications The present invention is not limited to the above embodiments, and various modifications such as the following are possible. In the above embodiment, the sound waves are emitted from the two side surfaces on both sides of the speaker, but the sound waves may be emitted from the four side surfaces. However, in this case, in order to prevent the compressional waves of the air from being extinguished, air is simultaneously discharged from all the openings that are open to the side surface,
At the same time, it is necessary to be sucked at the same time. Although the spacer is formed in a U-shape, its shape is arbitrary. For example, a spacer bent at a right angle may be used as the vibration film 3
You may arrange | position at each corner part of. It is also possible to form plate portions extending from both ends of the spacer in a direction approaching each other so as to have a substantially C-shape so that the opening portion of the above-mentioned embodiment becomes narrower. By forming the spacers in this way, the resistance of air entering and exiting the space between the vibrating membrane and the fixed electrodes is further increased,
It is possible to further improve the output sound pressure frequency characteristic in the low sound range. Although the size of the openings of the spacers is constant in the above-described embodiment, openings having various sizes may be mixed. The present invention is not limited to the speaker as described above, and the subject such as headphones and loudspeaker is arbitrary.

[0029]

As described above, according to the present invention, since the vibrating membranes are held between the spacers, it is possible to stack the vibrating membranes in multiple layers. Therefore, by forming the vibrating membranes in multiple layers, A large maximum output sound pressure can be obtained without increasing the size. Also, since the space between the vibrating membranes communicates with the outside through the opening provided in the spacer,
When the air passes through the opening, it receives resistance, so that the air is efficiently pressurized and depressurized in the space. Therefore, the output sound pressure frequency characteristic in the low sound range can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view in which a part of a speaker according to an embodiment of the present invention is vertically disassembled.

FIG. 2 is a perspective view showing a state where the speaker of the embodiment is assembled.

FIG. 3 is a diagram showing wiring of the speaker of the embodiment.

FIG. 4 is a diagram showing output sound pressure frequency characteristics of a speaker of an example and a conventional example, respectively.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Fixed electrode 2 Spacer 3 Vibration film 21 Step-up transformer (sound voltage generating means) P ₁ , ... Opening

Claims (2)

[Claims] 1. An electrode assembly in which a plurality of plate-shaped fixed electrodes are arranged parallel to each other and spaced apart from each other, and a vibrating membrane is sandwiched between the fixed electrodes via a spacer arranged at an edge thereof. While applying a bias voltage to the vibrating membrane, one end and the other end of the audio voltage generating means for generating an audio voltage at both ends are alternately connected to the fixed electrode, and the spacer is When the vibrating membrane is swung to the fixed electrode side, air is ejected from one side of the electrode assembly and at the same time, an opening is provided to suck air from the other side of the electrode assembly. Acoustic transducer. 2. The electroacoustic transducer according to claim 1, wherein the thickness of the spacer is 1/4 or less of a maximum length of a vibrating portion of the vibrating film.