Electroacoustic transducer and headphones

Abstract

[Problem] To maintain stable performance. [Solution] An electroacoustic transducer 1 for transmitting vibration to a human body, including: a movable part 10 that vibrates according to an input signal; a gel-like material 30 connected to the movable part; and a fix part 20 that includes a coil 21 into which at least a part of the movable part is inserted, and is connected to the movable part via the gel-like material.

Description

Electroacoustic transducer and headphones

[0001] The present invention relates to an electroacoustic transducer and headphones that transmit vibration to the human body.

[0002] There is known a sound output device that listens to vibrations generated from the skull or the like as sound by bringing the outer wall surface into contact with the bones around the skull or the entrance of the external auditory canal.

[0003] Conventionally, for example, there is known a bone conduction vibration source device for a mobile phone or the like that acoustically processes an audio signal for bone conduction vibration and outputs a processed signal as a drive signal to a bone conduction vibration source (see, for example, Patent Document 1). In addition, there is disclosed a stereo earphone having a bone conduction part and a branch part having one end connected to the bone conduction part and serving as a vibration source (see, for example, Patent Document 2).

[0004] A sound output device using bone conduction has a movable part that vibrates according to an audio signal. There is a possibility that the movable part may run wild at the resonance point, that is, vibrate in an unintended direction and generate abnormal sounds associated therewith.

[0005] JP-A-2013-197730 JP-A-2014-116755

[0006] An object of the present invention is to provide an electroacoustic transducer and headphones that can maintain stable performance.

[0007] The electroacoustic transducer according to the present invention is an electroacoustic transducer that transmits vibration to the human body, and includes a movable part that vibrates according to an input signal, a gel-like material connected to the movable part, and a coil through which at least a part of the movable part is inserted, and a fixed part connected to the movable part through the gel-like material.

[0008] Further, the headphones according to another aspect of the present invention include a headband and a pair of electroacoustic transducers respectively held at both ends of the headband, and the electroacoustic transducer is the electroacoustic transducer described above.

[0009] According to the present invention, it is possible to provide an electroacoustic transducer and headphones that can maintain stable performance.

[0010] This is a schematic perspective view showing an embodiment of headphones according to the present invention. This is a schematic longitudinal cross-sectional view showing a portion of a component in cross-section, illustrating a first embodiment of the electroacoustic converter according to the present invention. This is a schematic perspective view showing a portion of a component of the above electroacoustic converter in cross-section. This is a schematic longitudinal cross-sectional view showing a portion of a component in cross-section, illustrating a second embodiment of the electroacoustic converter according to the present invention. This is a schematic longitudinal cross-sectional view showing a portion of a component in cross-section, illustrating a third embodiment of the electroacoustic converter according to the present invention. This is a schematic longitudinal cross-sectional view showing a portion of a component in cross-section, illustrating a fourth embodiment of the electroacoustic converter according to the present invention. This is a schematic oblique one-sided cross-sectional view showing a portion of a component in cross-section, illustrating a fifth embodiment of the electroacoustic converter according to the present invention. This is a schematic longitudinal cross-sectional view showing a portion of a component in cross-section, illustrating a sixth embodiment of the electroacoustic converter according to the present invention. This is a graph showing an example of the frequency characteristics of the above electroacoustic converter. This is a schematic oblique one-sided cross-sectional view showing an example of an electroacoustic converter according to related technology.

[0011] Hereinafter, embodiments of the electroacoustic converter according to the present invention will be described with reference to the drawings. In the following description, the axial direction of the electroacoustic converter 1 will also be referred to as the Y direction, and the directions perpendicular to the Y direction will also be referred to as the X direction and Z direction. Furthermore, the surface facing the +Y direction will also be referred to as the top surface, and the surface facing the -Y direction will also be referred to as the bottom surface. In addition, the surface facing the -X direction will also be referred to as the front, and the surface facing the +X direction will also be referred to as the back.

[0012] ●Headphones● As shown in Figure 1, the headphones 1000 mainly consist of a pair of electroacoustic transducers 1, a pair of housings 2, and a headband 3. Each of the pair of housings 2 is roughly rectangular and houses the electroacoustic transducers 1 inside. The headband 3 is roughly U-shaped. Both ends of the headband 3 are curved in a direction roughly perpendicular to the U-shape, so that they can be placed over the wearer's ears when worn. The housings 2 are connected to both ends of the headband 3. That is, the electroacoustic transducers 1 are held at both ends of the headband 3 via the housings 2. When worn, the headband 3 clamps onto the wearer's head, and the housings 2 are pressed against the ear area by the elastic force of the headband 3. As a result, vibrations from the electroacoustic transducers 1 are transmitted to the human body. In this embodiment, the electroacoustic transducer is described in which vibrations are mainly transmitted to the ear cartilage. However, the technical scope of the present invention is not limited thereto and includes headphones and electroacoustic transducers that transmit vibrations to any bone, including cartilage other than ear cartilage and hard bones such as the skull.

[0013] ●Electroacoustic transducer (1)● First, a first embodiment of the electroacoustic transducer of this embodiment will be described. The electroacoustic transducer 1 is, for example, a headphone unit. As shown in Figures 2 and 3, the electroacoustic transducer 1 is a substantially cylindrical member and is a pair of members that are attached to the left and right ears, respectively. The electroacoustic transducer 1 mainly comprises a movable part 10, a fixed part 20, and a gel-like material 30.

[0014] The movable part 10 is a component that vibrates vertically in the figure in response to an input signal.

[0015] The movable part 10 mainly comprises a cap yoke 11, a magnet 12, and a center yoke 13.

[0016] The cap yoke 11 is a bottomed cylindrical member that forms the upper and side surfaces of the movable part 10. The upper side (+Y side) of the cap yoke 11 is exposed to the upper surface (+Y side) of the electroacoustic transducer 1. The lower end of the cap yoke 11 on the -Y side faces the unit base 22 with a gap between them. The inner diameter of the cap yoke 11 is larger than the outer diameter of the coil 21. As a result, the cap yoke 11 covers a portion of the outer circumference of the coil 21.

[0017] The magnet 12 is a substantially cylindrical magnet and is disposed inside the cap yoke 11. The magnet 12 may also be connected to the inner bottom surface of the cap yoke 11. The center yoke 13 is a disc-shaped member that is at one end of the movable part 10 in the direction of vibration and is connected to the lower end of the magnet 12 in the figure. In this embodiment, the center yoke 13 faces the unit base 22, which will be described later, with a gap S between them.

[0018] The fixed part 20 mainly comprises a coil 21 and a unit base 22.

[0019] The coil 21 is an annular member, and the magnet 12 and the center yoke 13 are inserted through a hole 23 formed in the center of the coil 21. The outer diameters of the magnet 12 and the center yoke 13 are smaller than the inner diameter of the hole 23 in the coil 21. Therefore, the magnet 12 and the center yoke 13 are movable axially (y-direction) inside the hole 23. A Lorentz force is generated in the magnet 12 and the coil 21. As a result, the movable part 10 vibrates in the axial direction.

[0020] The unit base 22 is a component that forms the bottom surface of the electroacoustic transducer 1 and holds the coil 21. The unit base 22 may be a flat plate-shaped component, or it may have holes in the portion corresponding to the holes 23 of the coil 21.

[0021] The gel-like material 30 is a so-called gel-like component. The gel-like material 30 may be, for example, a resin material or a rubber-based material, such as silicone gel or RTV rubber (Room Temperature Vulcanizing rubber). The gel-like material 30 is a material that can be applied as an adhesive, and it adheres the movable part 10 and the fixed part 20 when it hardens. With this configuration, no separate component is required to adhere the gel-like material 30 to the movable part 10 and the fixed part 20, so the structure is simple and assembly is easy.

[0022] The gel-like material 30 is a component that is fluid before curing and elastic after curing. For example, the gel-like material 30 may be a so-called UV-curing resin that hardens when irradiated with ultraviolet light. Alternatively, the gel-like material 30 may be a two-part adhesive. If the gel-like material 30 is configured to be fluid before curing, assembly can be performed by injecting the gel-like material 30 into the gap between the movable part 10 and the coil 21, thus eliminating the need for shape control of the gel-like material 30. Furthermore, since the gap between the movable part 10 and the coil 21 is the region through which magnetic flux passes, efficiency increases as the distance is narrowed. On the other hand, if the gap between the movable part 10 and the coil 21 is made narrow, the possibility of contact between the movable part 10 and the coil 21 increases. In this regard, if the gap between the movable part 10 and the coil 21 is filled with the gel-like material 30, it is possible to sufficiently narrow the gap between the movable part 10 and the coil 21 while preventing contact.

[0023] The gel-like material 30 is connected to the movable part 10 and the fixed part 20. The gel-like material 30 is arranged in a cylindrical shape along the circumferential direction of the coil 21. Alternatively, the gel-like material 30 may be arranged intermittently at multiple locations along the circumferential direction of the coil 21. As a result, the gel-like material 30 controls the vibration of the movable part 10.

[0024] As explained above, the direction of vibration in which the movable part 10 vibrates in response to the signal is the Y direction, which is different from the vertical direction when worn. In other words, the movable part 10 is subjected to gravity in a direction different from the direction of vibration. The gel-like material 30 supports the movable part 10 by connecting it to the movable part 10 and the fixed part 20. That is, the gel-like material 30 can prevent the movable part 10 from sagging due to gravity.

[0025] The gel-like material 30 has a predetermined hardness and coefficient of restitution. As a result, the gel-like material 30 dampens and eliminates abnormal oscillations at the resonance point of the movable part 10, and suppresses displacement of the movable part 10 in a direction different from the vibration direction. Furthermore, because the gel-like material 30 is connected along the circumferential direction of the movable part 10, it suppresses displacement of the movable part 10 in the rotational direction. Displacement of the movable part 10 in a direction other than the vibration direction in which it vibrates in response to the signal causes abnormal noise. In this respect, the gel-like material 30 can suppress abnormal noise by preventing displacement in directions other than the axial direction, and thereby improve the sound quality of the electroacoustic transducer 1. The characteristics of the gel-like material 30, such as hardness or coefficient of restitution, are appropriately adjusted according to the desired sound quality and the mass or shape of the movable part 10.

[0026] Here, we will describe the electroacoustic transducer 1a of the related technology using Figure 10. The electroacoustic transducer 1a shown in Figure 10 mainly comprises a movable part 10a, a fixed part 20a, and a spring 40a.

[0027] The fixed part 20a mainly comprises a coil 21a and a unit base 22a. The unit base 22a has a flange portion 24a formed on its inner wall at the bottom. The movable part 10a mainly comprises a cap yoke 11a, a magnet 12a, a center yoke 13a, and a spacer 14a. The spring 40a is, for example, a metal leaf spring, and it abuts against the inside of the flange portion 24a and is connected to the spacer 14a which is located in the center of the movable part 10a. As a result, the movable part 10a is supported by the flange portion 24a via the spring 40a. Therefore, the pivot point for the vibration of the movable part 10a is the lower end of the spacer 14a, and the contact point between the spring 40a and the flange portion 24a is the point of action. In this way, the electroacoustic transducer 1a, in which the center of gravity of the movable part 10a and the pivot point for vibration are far apart, may experience unruly vibrations at the resonance point, i.e., vibrations in unintended directions. Vibration at the resonance point can cause abnormal noises.

[0028] Furthermore, in Figure 10, the vertical direction in the mounted state is the Z direction. That is, the vibration direction in which the movable part 10a vibrates in response to the signal is the Y direction, which is different from the vertical direction in the mounted state. Therefore, gravity acts on the movable part 10a in a direction different from the vibration direction. The first end of the movable part 10a is connected to the spring 40 approximately in the middle, while the second end is not supported and is in a cantilevered state. Also, because the center of gravity of the movable part 10a and the fixing position of the spring 40a are far apart, the balance of the movable part 10a tends to become unstable, which may cause irregular vibrations. In addition, since the second end of the movable part 10a hangs down in the direction of gravity, unwanted moments or twists may occur during resonance. These moments or twists may cause vibration or damage. Furthermore, since this electroacoustic transducer 1a does not have a structure to dampen vibrations, if the coefficient of restitution of the spring 40a is high, there is a risk of steep resonance occurring near the natural vibration frequency. Furthermore, since the spring 40a is a metal leaf spring, there is a risk of plastic deformation. If the spring 40a deforms, the movable part 10a and the coil 21a will come into contact, resulting in poor performance and abnormal noise. Also, the spring 40a is generally more expensive than the gel-like material. Moreover, there are limitations to how small a metal spring 40a can be made.

[0029] Furthermore, the mass of the movable part 10a in the electroacoustic transducer 1a, which transmits vibrations to the ear cartilage, is larger than that of a headphone unit that vibrates a diaphragm, because it vibrates the ear cartilage. As a result, the sagging and instability of the movable part 10a at the resonance point are even greater than in a headphone unit with a diaphragm, which can cause malfunctions.

[0030] Furthermore, the movable part 10a of the electroacoustic transducer 1a may vibrate due to external vibrations. In this case, the vibration of the movable part 10a generates an electromotive force in the coil 21a which is positioned opposite the movable part 10a. As a result, in a headphone unit having a movable part, the vibration may be mixed into the sound as an abnormal noise.

[0031] In this regard, the electroacoustic transducer 1 according to the present invention connects the movable part 10 and the fixed part 20 with a gel-like material 30 instead of a metal spring 40a. With the configuration in which the gel-like material 30 is filled between the coil 21 and the magnet 12, contact between the movable part 10 and the coil 21 does not occur, so the generation of abnormal noise can be reduced and good characteristics can be maintained. Furthermore, with the configuration in which the gel-like material 30 is arranged in the circumferential direction of the movable part 10, the connection part between the movable part 10 and the fixed part 20 is relatively close to the center of gravity of the movable part 10, so the operation of the movable part 10 is stable. Moreover, since the gel-like material 30 does not undergo plastic deformation, the risk of failure is small. Furthermore, since vibrations can be dampened by the gel-like material 30, the effects of resonance can be reduced. Furthermore, it can be manufactured at low cost. In addition, it is possible to construct a smaller electroacoustic transducer compared to the configuration with a spring 40a.

[0032] ●Electroacoustic Converter (2)● Here, we will describe a different embodiment of the electroacoustic converter of this embodiment, focusing on the parts that differ from the previously described form. Note that the same reference numerals are used for components that are the same as in the first embodiment. The electroacoustic converter 101 of the second embodiment shown in Figure 4 differs from the first embodiment in that the gel-like material 130 is connected to the outer circumferential surface of the coil 21 and the inner circumferential surface of the cap yoke 11. Even with this configuration, the gap between the movable part 10 and the fixed part 20 can be filled with the gel-like material 30, preventing contact between the movable part 10 and the fixed part 20, while maintaining a gap between the movable part 10 and the fixed part 20 that generates magnetic flux.

[0033] ●Electroacoustic transducer (3)● The electroacoustic transducer 201 of the third embodiment shown in Figure 5 is configured by adding the gel-like material 130 provided in the electroacoustic transducer 101 of the second embodiment to the electroacoustic transducer 1 of the first embodiment. Specifically, the gel-like material 30 is connected to the inner circumferential surface of the coil 21 and the outer circumferential surface of the movable part 10, and the gel-like material 130 is connected to the outer circumferential surface of the coil 21 and the inner circumferential surface of the cap yoke 11.

[0034] ●Electroacoustic transducer (4)● The electroacoustic transducer 301 of the fourth embodiment shown in Figure 6 differs from the previously described embodiment in that it further has a holding member 330 as a fixed part 20 at the end of the movable part 10 in the direction of vibration. The holding member 330 holds the movable part 10 between the center yoke 13 and the unit base 22. The holding member 330 is a member that exhibits elastic force due to a porous structure, for example, and more specifically, it is a urethane foam. The holding member 330 may also be formed from an appropriate sponge material. Furthermore, the holding member 330 may be composed of an elastic body such as rubber or gel material. Furthermore, the holding member 330 may be a leaf spring composed of an appropriate material such as metal or resin. With such a configuration, the holding member 330 assists the gel-like material 30 and appropriately dampens the vibration of the movable part 10, preventing resonance and the like. In addition, the holding member 330 prevents the movable part 10 from sagging downwards in the figure.

[0035] ●Electroacoustic Transducer (5)● The electroacoustic transducer 401 of the fifth embodiment shown in Figure 7 differs from the previously described embodiment in that it includes an elastic member 440 that connects the movable part 410 and the fixed part 420. The elastic member 440, or the elastic member 440 and the spacer 414, is another example of a holding member in the claims. It also differs from the electroacoustic transducer 1a in the related art (see Figure 10) in that the movable part 410 and the fixed part 420 are connected via a gel-like material 30.

[0036] The movable part 410 mainly comprises a cap yoke 11, a magnet 12, a center yoke 13, and a spacer 414. The spacer 414 is, for example, a substantially cylindrical member connected to approximately the center of the bottom surface of the center yoke 13. The elastic member 440 may have a configuration similar to the spring 40a shown in Figure 10. The elastic member 440 is a leaf spring made of an appropriate material such as metal or resin. The elastic member 440 abuts against a flange 424a formed on the inside of the bottom of the unit base 422 and holds the movable part 410 between the center yoke 13 and the unit base 422.

[0037] With this configuration, compared to the electroacoustic transducer 1a shown in Figure 10, the gel-like material 30 is disposed between the coil 21 and the magnet 12 or center yoke 13, so that interference between components does not occur during vibration. In this embodiment, the source of magnetic flux is the center yoke 13, so by bringing the center yoke 13 and the coil 21 as close together as possible, a high magnetic flux density is ensured and efficiency is improved, but there was a risk of interference between the center yoke 13 and the coil 21. In this respect, the presence of the gel-like material 30 prevents interference between components. In addition, the gel-like material 30 has a damping effect, which can suppress unwanted vibrations at the resonance point. Furthermore, depending on the viscosity and material of the gel-like material 30, it may be necessary to maintain the positional relationship for a long time before it solidifies. With the configuration that includes the elastic member 440, the positional relationship between the movable part 410 and the fixed part 420 can be mechanically restricted by assembling the elastic member 440 before injecting the gel-like material 30, making assembly easier compared to the configuration without the elastic member 440.

[0038] ●Electroacoustic Converter (6)● The electroacoustic converter 501 of the sixth embodiment shown in Figure 8 differs from the previously described embodiment in that the movable part 510 comprises two magnets 512a and 512b and a center yoke 513 disposed between the two magnets 512a and 512b. The two magnets 512a and 512b are arranged so that the same poles face each other. With this configuration, the magnetic flux can be concentrated on the central center yoke 513. The fixed part 520 comprises a coil 521 and a unit base 522. The gel-like material 530 is connected to the coil 521 and the movable part 510. In the figure, the gel-like material 530 is connected to the magnets 512a and 512b and the center yoke 513, but it is not limited to this embodiment, and may be connected to any or more of the magnets 512a and 512b and the center yoke 513. The unit base 522 is a bottomed cylindrical member that holds the coil 521 at the top. This configuration offers high sensitivity due to the presence of two magnets, 512a and 512b. Furthermore, the center of gravity of the movable part 510 and the fixed position of the gel-like material 530 almost coincide in the vibration direction (Y direction), enabling stable operation. Additionally, the absence of a cap yoke allows for a more compact design compared to other embodiments.

[0039] ●Frequency response characteristic figure 9 shows the frequency characteristics of the electroacoustic transducer 501. That is, the horizontal axis represents frequency, and the vertical axis represents output level (dBV). The frequency characteristics of the electroacoustic transducer 1 according to the present invention are low and smooth. Furthermore, while the primary resonance frequency of the prototype on which this frequency characteristic was measured is around 1030 Hz, it can be seen that a very flat characteristic is achieved at frequencies higher than 1030 Hz.

[0040] As described above, the present invention provides an electroacoustic converter and headphones that can maintain stable performance. Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of its gist.

[0041] 1 Electroacoustic transducer 10 Movable part 11 Cap yoke 12 Magnet 13 Center yoke 20 Fixed part 21 Coil 22 Unit base 30 Gel-like material 1000 Headphones

Claims

1. An electroacoustic transducer for transmitting vibrations to the human body, comprising: a movable part that vibrates in response to an input signal; a gel-like material connected to the movable part; and a fixed part having a coil through which at least a portion of the movable part is inserted, and connected to the movable part via the gel-like material.

2. The electroacoustic converter according to claim 1, wherein the gel-like material is connected to the inner circumferential surface of the coil and the movable part.

3. The movable part comprises a cap yoke that covers at least a portion of the outer circumferential surface of the coil, and the gel-like material is connected to the outer circumferential surface of the coil and the inner circumferential surface of the cap yoke, as described in claim 1.

4. The movable part comprises two magnets and a center yoke disposed between the two magnets, and the gel-like material is connected to the inner circumferential surface of the coil and the movable part, as described in claim 1.

5. The electroacoustic transducer according to claim 1, further comprising: a center yoke disposed at one end in the direction of vibration; a unit base facing the center yoke; and a holding member that holds the movable part between the center yoke and the unit base.

6. The electroacoustic transducer according to claim 1, wherein the gel-like material is arranged in a cylindrical shape over the circumferential direction of the movable part.

7. Headphones comprising a headband and a pair of electroacoustic transducers held at each end of the headband, wherein the electroacoustic transducers are the electroacoustic transducers described in any one of claims 1 to 6.

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