JP6153448B2 - Electret condenser headphone unit - Google Patents

Description

  The present invention relates to a so-called push-pull electret condenser headphone unit in which an insulating plate having independent electrodes on both sides is used as a fixed pole, and an electret layer is provided on the surface of the fixed pole.

  There is a capacitor type headphone that uses an electrostatic force to vibrate a diaphragm and converts an audio signal into a sound wave. The capacitor-type headphones have a structure in which a diaphragm and a fixed pole are arranged to face each other, and a high voltage such as 300 to 600 V is applied between the diaphragm and the fixed pole, and the diaphragm And a fixed pole are used to input an audio signal. The electrostatic force between the diaphragm and the fixed pole changes in accordance with the input audio signal, and the diaphragm vibrates in response to the change in electrostatic force to emit sound waves.

  The sound pressure of the sound wave radiated from the capacitor-type headphones depends on the polarization voltage applied between the diaphragm and the fixed pole and the voltage of the input audio signal. However, when the polarization voltage applied between the diaphragm and the fixed electrode becomes equal to or higher than the dielectric breakdown voltage of air, the discharge is caused between the diaphragm and the fixed electrode, so that it is limited to the dielectric breakdown voltage or less. Also, when the diaphragm vibrates in response to the input audio signal and the distance between the diaphragm and the fixed pole is narrowed, the input voltage of the audio signal is prevented so that no spark discharge occurs between the diaphragm and the fixed pole. Level is limited. Due to such factors, the sound pressure that can be output from the capacitor-type headphones is limited.

  Therefore, it is proposed that a condenser headphone element consisting of a diaphragm and a fixed pole should be arranged acoustically in series so that a sound pressure output approximately twice that of a certain input voltage level of the audio signal can be obtained. Has been. FIG. 5 shows an example.

  In FIG. 5, reference numeral 101 denotes a capacitor headphone element (hereinafter simply referred to as “element”). Two elements 101 are arranged in parallel with each other with an appropriate space to constitute a condenser headphone unit 100. Each element 101 includes a diaphragm 103 and a fixed pole 102 disposed on both sides of the diaphragm 103 so as to face each other. Therefore, the capacitor headphone unit 100 is configured by arranging the fixed pole 102, the diaphragm 103, the fixed pole 102, the fixed pole 102, the diaphragm 103, and the fixed pole 102 in this order. Each fixed pole 102 has a plurality of holes 124 through which sound waves pass. The outer peripheral edge of the diaphragm 103 is held by a holding ring 131.

  A high DC voltage is applied to the diaphragm 103 from the outside as a polarization voltage, and an audio signal is input to the fixed pole 102. The specific electrical connection is as follows. The audio signal 5 is boosted by the transformer 6 and input to the condenser headphone unit 100. The secondary coil of the transformer 6 has a center tap 61, and a DC voltage source 8 starting from the center tap 61 is connected to each diaphragm 103 through a high resistance 9. The DC voltage source 8 outputs a high voltage of about 500 V, for example, and this high voltage is applied to each diaphragm 103 as a polarization voltage. The positive side and the negative side of the audio signal are output from both ends of the secondary coil of the transformer 6. In the example shown in FIG. 5, the positive side of the audio signal is connected to the fixed pole 102 located on the right side of each diaphragm 103, and the negative side of the audio signal is connected to the fixed pole 102 located on the left side of each diaphragm 103. . In other words, an audio signal is input between the fixed poles 102 arranged on both sides of each diaphragm 103.

  In the conventional example shown in FIG. 5, when the audio signal 5 is input to the capacitor headphone unit 100 through the transformer 6, the electrostatic force is generated in the same direction in each element 101 corresponding to the audio signal 5. Therefore, the sound pressure generated in one element 101 is superimposed on the sound pressure generated in the other element 101, and a sound pressure output approximately twice the sound pressure generated in only one element 101 can be obtained.

  However, according to the above conventional condenser headphone unit, since the two fixed poles 102 are interposed between the two diaphragms 103, the volume of the air chamber existing between the two diaphragms 103 is increased. When the volume of the air chamber is increased, the acoustic capacity between the two diaphragms 103 is increased, so that the sound pressure superimposing effect by the two diaphragms 103 is reduced, and the sound pressure output of the capacitor headphone unit is lowered. .

  An example of a capacitor headphone provided with a circuit approximate to the polarization voltage application circuit of the capacitor headphone unit shown in FIG. The capacitor headphone described in Patent Document 1 is characterized in that a fixed electrode located on the user's ear side in use is connected to the ground so that the user does not get an electric shock from the polarization voltage.

  The conventional capacitor headphone unit shown in FIG. 5 needs to be provided with a high voltage power supply or a high voltage generation circuit in order to apply a high voltage polarization voltage between the diaphragm and the fixed pole. However, if the electret material is used, a high voltage such as 300 to 600 V can be generated between the diaphragm and the fixed pole, and a high voltage power supply or a high voltage generation circuit is not necessary. The electret material is a dielectric that can confine charges. When this dielectric is sandwiched between electrodes and a high voltage is applied between the electrodes, the charge moves to the electrode surface, and an electric dipole is formed inside the dielectric. Thereafter, even if the electrode plates are short-circuited, the electric dipole inside the dielectric remains and the electret state is maintained.

  Patent Document 2 describes a method of forming an electret layer on the surface of the fixed electrode. The invention described in Patent Document 2 relates to a method of manufacturing an electret condenser headphone unit, and forms an electret layer on the surface of a fixed pole by a unique method. According to the electret layer forming method described in Patent Document 2, for example, the fixed electrode can have a surface potential of about −600 V and the diaphragm about +600 V, and a voltage source applied between the diaphragm and the fixed electrode. Is no longer necessary.

  If two elements 101 are arranged acoustically in series as shown in FIG. 5 and an electret as described in Patent Document 2 is used, an electret condenser headphone with a high sound pressure output should be obtained. However, even if such an electret is applied to the electret condenser headphones shown in FIG. 5, the volume of the air chamber is increased as described above because two fixed poles are still interposed between the two diaphragms. Therefore, the sound pressure superimposing effect by the two diaphragms is lowered, and the sound pressure output is lowered.

Japanese Patent No. 4533778 Japanese Patent No. 4659703

  The present invention has been made in view of the conventional electret condenser headphone technology described above, and an object thereof is to provide a high output electret condenser headphone.

The present invention
A diaphragm and a fixed pole disposed opposite to the diaphragm and provided with an electret layer on the surface. The fixed pole is disposed on both sides of the diaphragm, and between the fixed poles on both sides. An electret condenser headphone unit to which an audio signal is input,
The fixed electrode includes an insulating plate, an electrode plate disposed independently on both surfaces of the insulating plate, and an electret material formed so as to cover the entire fixed electrode including the electrode plate and the insulating plate. And
Two diaphragms are arranged parallel to each other,
The fixed pole is arranged across the diaphragms,
The electret material on at least the surface of each fixed pole facing the diaphragm is charged into an electret layer,
The electret layer of each fixed pole is configured to synchronously drive the two diaphragms in the same direction when an audio signal is input to the electrode plate of each fixed pole. The most important feature.

  The fixed pole has electrode plates arranged independently on both sides of the insulating plate, and these electrode plates are covered with electret material. Further, another fixed pole can be arranged opposite to the outside of the plate. There are fixed poles on both sides of the two diaphragms, and the electret layer of each fixed pole is configured to drive the diaphragms synchronously in the same direction by the input of an audio signal. The sound pressure due to the vibration is superimposed on the sound pressure due to the vibration of the other diaphragm. A fixed pole for driving these diaphragms is arranged between the two diaphragms, and the volume of the air chamber between the two diaphragms is small. Efficiently superimposed.

It is the longitudinal cross-section and electric circuit diagram which show Example 1 of the electret condenser headphone unit which concerns on this invention. It is the longitudinal cross-section and electric circuit diagram which show Example 2 of the electret capacitor | condenser headphone unit which concerns on this invention. It is a longitudinal cross-sectional view which expands and shows the fixed pole in the said Example. It is a longitudinal cross-sectional view which expands and shows a part of said fixed pole further. It is a longitudinal section and an electric circuit diagram showing an example of a conventional capacitor headphone unit.

  Embodiments of an electret condenser headphone unit according to the present invention will be described below with reference to the drawings.

  In FIG. 1, reference numeral 1 denotes an electret condenser headphone unit. The electret condenser headphone unit 1 includes a diaphragm 3 and a fixed pole 2 that is disposed to face the diaphragm 3 at an appropriate interval and is provided with an electret layer 23 on the surface. In the example shown in FIG. 1, two diaphragms 3 and three fixed poles 2 are arranged in the order of a fixed pole 2, a diaphragm 3, a fixed pole 2, a diaphragm 3, and a fixed pole 2. One electret condenser headphone element is constituted by one diaphragm 3 and two fixed poles 2 arranged on both sides of the diaphragm 3, and substantially two elements are acoustically arranged in series. The central fixed pole 2 acts on the two diaphragms 3 in common.

  Although not shown, each fixed pole 2 has a disk shape, and each diaphragm 3 has a circular film shape, and FIG. 1 shows a longitudinal section thereof. Each diaphragm 3 is held by a retaining ring 31 at the peripheral edge in a state where an appropriate tension is applied.

  As shown in FIGS. 3 and 4, each fixed pole 2 includes an insulating plate 21, an electrode plate 22 disposed independently on both surfaces of the insulating plate 21, and a fixed pole 2 including the electrode plate 22 and the insulating plate 21. And an electret layer 23 formed so as to cover the whole. Each fixed electrode 2 can be configured based on a double-sided printed wiring board having conductive patterns formed on both sides. That is, the insulating substrate of the printed wiring board constitutes the insulating plate 21, and the conductive patterns formed on both surfaces of the insulating substrate constitute the electrode plate 22. The electrode plate 22 made of a conductive pattern is formed as a solid conductive pattern on one surface of the insulating plate 21 and the entire other surface. A plurality of holes 24 are formed in the fixed pole 2 so as to pass through the electrode plate 22 so that sound waves radiated by the vibration of the diaphragm 3 pass through the fixed pole 2.

  As described above, the electret layer 23 holds the high voltage even if there is no polarization voltage source because the electret material made of a dielectric is sandwiched between electrodes and a high voltage is applied between the electrodes to confine the charge. doing. In order to cover the entire fixed electrode 2 including the electrode plate 22 and the insulating plate 21 with the electret material, the entire fixed electrode 2 may be immersed in a liquid electret material having fluidity. The fixed electrode 2 is pulled up from the electret material, and the electret material is dropped to form an electret material layer on the entire surface of the double-sided printed wiring board constituting the fixed electrode 2. As a result, the wall surface around the hole 24 is also covered with the electret material.

  As electret materials, there are organic materials and inorganic materials, each having its own characteristics. In the present invention, since the entire fixed electrode is covered with the electret material, the thickness of the electret layer is not limited. Therefore, an organic electret material that can be easily thickened, such as a fluororesin, may be used. In the examples, CYTOP (CTL-107MK) manufactured by Asahi Glass Co., Ltd. was used as the electret material.

  An electret material covering the plane of the fixed electrode 2 is sandwiched between electrodes, and an electret layer 23 is formed by applying a high voltage between the electrodes. The electrode plate 22 can be used as one electrode when the electret layer 23 is formed. The polarity when forming the electret layer 23 is the same for all the fixed poles 2. For example, as shown in FIG. 4, the polarities of the left and right electret layers 23 in the longitudinal section of the fixed pole 2 are polarized so that the right side is − and the left side is +.

  As shown in FIG. 1, three fixed poles 2 in which the electret layer 23 is formed as described above are arranged, and two diaphragms 3 are arranged between the two fixed poles 2, respectively. Then, the positive side of the audio signal is input to the electrode plate 22 on the diaphragm 3 side of each fixed pole 2 positioned on the right side of each of the two diaphragms 3, and each of the positions on the left side of each of the two diaphragms 3. The negative side of the audio signal is input to the electrode plate 22 on the diaphragm 3 side of the fixed pole 2. In this embodiment, the audio signal 5 is boosted by the audio signal input transformer 6, and the + side and the − side of the audio signal output from the secondary winding of the transformer 6 are input as described above. Accordingly, the audio signals are connected between the fixed poles 2 on both sides arranged with the respective diaphragms 3 interposed therebetween.

  It is assumed that an audio signal is input to the electret layers 23 on both surfaces of each fixed pole 2 as shown in FIG. 1 in a state where charges are polarized as shown in FIG. Further, it is assumed that the two diaphragms 3 are positively charged. Considering the moment when a forward direction audio signal is input, a positive voltage is added to the electret layer 23 located on the right side of each of the two diaphragms 3, and a repulsive force is generated on each diaphragm 3 on the right side. On the other hand, a minus voltage is added to the electret layer 23 located on the left side of each of the two diaphragms 3, and an attractive force is generated on the left side of each diaphragm 3.

  Considering the moment when audio signals in opposite directions are input, a positive voltage is added to the electret layer 23 located on the left side of each of the two diaphragms 3, and a repulsive force is generated on each diaphragm 3 on the left side. On the other hand, a negative voltage is added to the electret layer 23 located on the right side of the two diaphragms 3, and an attractive force is generated on the right side of each diaphragm 3. 3 and 4 are applied through the secondary winding of the transformer 6 to the electrode plates 22 on both sides at the center fixed pole 2 disposed between the two diaphragms 3, respectively. The polarity of the audio signal 5 is shown.

  In this way, the two diaphragms 3 are synchronously driven in the same direction according to the audio signal 5, so that the sound pressure generated by the vibration of one diaphragm 3 is generated by the other diaphragm 3. It is added to the sound pressure generated by the vibration. Further, since the fixed pole 2 is interposed between the two diaphragms 3 and the volume of the space between the two diaphragms 3 is limited, the sound generated by one diaphragm 3 is limited. The pressure is efficiently added to the sound pressure generated by the vibration of the other diaphragm 3. Furthermore, since the fixed pole 2 interposed between the two diaphragms 3 generates a driving force for the two diaphragms 3, the sound pressure generated by driving the two diaphragms 3 is effectively increased. be able to.

  As described above, both the wall surface around the hole 24 formed for passing the sound wave to each fixed pole 2 and the corner portion where the surface is connected are covered with the electret material. Since the electret material is an insulator and has high volume resistivity and surface resistivity, it is possible to prevent spark discharge between the fixed electrodes 2 even if the fixed electrodes 2 are close to each other.

  Of the three fixed poles 2 arranged in parallel to each other, in the fixed poles 2 positioned on both outer sides, that is, the two fixed poles 2, no audio signal is input to the electrode plates 22 positioned on the outer sides. Is in a floating state and does not contribute to the electroacoustic conversion action. Therefore, it is not necessary to charge the electret material located outside the fixed pole 2 located on both outsides. In other words, it is only necessary that the electret material on the surface of each fixed pole 2 facing at least the diaphragm 3 is an electret layer.

  FIG. 2 shows a second embodiment of the electret condenser headphone unit according to the present invention. Since the structure of the electret condenser headphone unit according to the second embodiment is substantially the same as that of the first embodiment and only the electrical connection is different, the electrical connection portion will be described mainly. The same reference numerals are given to the same parts as those in the first embodiment.

  In FIG. 2, a transformer 6 that boosts an audio signal and inputs it to the electret condenser headphone unit 1 has a center tap 61 in the secondary winding. The center tap 61 is connected to and grounded to the electrode plates 22 located on the outer sides of the two fixed poles 2 located on the outermost side among the three fixed poles 2 arranged in parallel to each other. Except for such electrical connection, the configuration and operation are the same as those of the first embodiment.

  According to the second embodiment, since the electret layer of the fixed pole 2 located near the user's ear is grounded when the headphone is used, discharge is caused between the user's ear and the electret layer when the headphone is used. Can be prevented.

  The electret condenser headphone unit according to the present invention can be configured as an electret condenser headphone by incorporating it into an appropriate housing.

DESCRIPTION OF SYMBOLS 1 Electret condenser headphone unit 2 Fixed pole 3 Diaphragm 5 Sound signal source 6 Transformer 21 Insulating plate 22 Electrode plate 23 Electret layer 24 Hole 31 Retaining ring 61 Center tap

Claims (10)

A diaphragm and a fixed pole disposed opposite to the diaphragm and provided with an electret layer on the surface. The fixed pole is disposed on both sides of the diaphragm, and between the fixed poles on both sides. An electret condenser headphone unit to which an audio signal is input,
The fixed electrode includes an insulating plate, an electrode plate disposed independently on both surfaces of the insulating plate, and an electret material formed so as to cover the entire fixed electrode including the electrode plate and the insulating plate. And
Two diaphragms are arranged parallel to each other,
The fixed pole is arranged across the diaphragms,
The electret material on at least the surface of each fixed pole facing the diaphragm is charged into an electret layer,
The electret layer of each fixed pole is configured to drive the two diaphragms synchronously in the same direction when an audio signal is input to the electrode plate of each fixed pole. Headphone unit.   The electret condenser headphone unit according to claim 1, wherein the electret layer has the same polarity in all the fixed poles.   The electret condenser headphone unit according to claim 1 or 2, wherein the two diaphragms and the three fixed poles are arranged in the order of a fixed pole, a diaphragm, a fixed pole, a diaphragm, and a fixed pole.   4. The electret condenser headphone unit according to claim 3, wherein an audio signal is not input to the electrode plates located on the outer sides of the two fixed poles arranged on both outer sides.   4. The electret condenser headphone unit according to claim 3, wherein the electrode plates located on the outer sides of the two fixed poles arranged on both outer sides are grounded.   The electret condenser headphone unit according to any one of claims 1 to 5, wherein a hole for passing a sound wave is formed in each fixed pole, and a wall surface around the hole is covered with an electret material.   The electret condenser headphone unit according to any one of claims 1 to 6, wherein the electret material is made of an organic electret material.   The electret condenser headphone unit according to any one of claims 1 to 7, further comprising a sound signal input transformer, wherein a sound signal is input from a secondary winding of the transformer.   9. The electret condenser headphone unit according to claim 8, wherein the secondary winding has center taps, and the center taps are connected to electrode plates located on the outer sides of the fixed poles arranged on both outer sides. The fixed pole is configured based on a double-sided printed wiring board having conductive patterns formed on both sides, the conductive pattern forms an electrode plate, and the entire double-sided printed wiring board including the electrode plate is covered with an electret material. The electret condenser headphone unit according to any one of claims 1 to 9.

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