Electroacoustic transducer

Abstract

The purpose of the invention disclosed herein is to measure electrostatic capacitance in which a fluctuation corresponding to a change in a mounting state is suppressed.　This electroacoustic transducer includes: a hollow housing attached to an ear of a user; a cylindrical external ear canal insertion part which is a part of the housing and is provided to a part on an external ear canal side of the housing; a signal output driver which is provided inside the external ear canal insertion part and has a cylindrical metal housing; and a measurement unit which measures electrostatic capacitance with the metal housing as an electrode.

Description

electroacoustic transducer

[0001] The technology of the present disclosure relates to an electro-acoustic transducer.

[0002] Earphones that have the added function of a capacitance sensor have been known.

[0003] For example, it is known to have a cover made of an electrically conductive material that forms electrodes, receive a signal from the electrically conductive material, and measure capacitance using the electrically conductive material (US 2011 / 0007908 A1).

[0004] It is also known that a metal clip is used to connect the metal shell of the speaker to the main board, forming a touch electrode, which is then connected to the capacitance detection interface of the main board (CN102802099B).

[0005] There is a problem in that if the wearing state of the earphones changes due to vibration or other reasons, the capacitance fluctuates, resulting in erroneous sensing.

[0006] In consideration of the above, the technique of the present disclosure aims to provide an electroacoustic transducer that can measure capacitance with reduced fluctuations caused by changes in the wearing state.

[0007] One aspect of the present disclosure is an electro-acoustic transducer that includes a hollow housing that is worn on a user's ear, a cylindrical ear canal insertion portion that is a part of the housing and is provided on the ear canal side of the housing, a driver for signal output that has a cylindrical metal casing that is provided inside the ear canal insertion portion, and a measuring portion that measures capacitance using the metal casing as an electrode.

[0008] As described above, the electroacoustic transducer according to the technique of the present disclosure can measure capacitance with reduced fluctuations caused by changes in the wearing state.

[0009] FIG. 1 is a cross-sectional view showing the overall configuration of an electro-acoustic transducer according to an embodiment of the technology of the present disclosure. FIG. 2 is an exploded perspective view of a driver portion according to an embodiment of the technology of the present disclosure. FIG. 3 is an exploded perspective view of a driver portion according to an embodiment of the technology of the present disclosure. (a) is a top view of the driver, and (b) is a side view of the driver. FIG. 3 is a cross-sectional view showing the driver portion according to an embodiment of the technology of the present disclosure. FIG. 4 is a diagram showing a mounting method for measuring capacitance using a metal casing as an electrode. FIG. 5 is a diagram showing a mounting method for measuring capacitance using a metal casing as an electrode. FIG. 6 is a diagram showing a mounting method for measuring capacitance using a metal casing as an electrode. FIG. 7 is a diagram showing a mounting method for measuring capacitance using a metal casing as an electrode. FIG. 8 is a graph showing data recording fluctuations in capacitance in a comparative example. FIG. 9 is a graph showing data recording fluctuations in capacitance in a method described in an embodiment of the technology of the present disclosure. FIG. 10 is a cross-sectional view showing the overall configuration of an electro-acoustic transducer according to an example.

[0010] Hereinafter, embodiments of the technology of the present disclosure will be described in detail with reference to the drawings.

[0011] <Outline of Embodiments of Technique of the Present Disclosure> When providing earphones with a capacitance sensing function, the layout of the capacitance sensor pad is a major constraint for earphones that are required to be small in size.

[0012] Furthermore, in devices like conventional earphones, where capacitance sensor pads are laid out on the surface of the auricle or outside the ear canal (near the tragus), when the earphones vibrate or the wearing state changes due to body movement or user operation, even a small change can cause large fluctuations in capacitance, resulting in incorrect detection of whether the earphones are in place or not, which was an issue.

[0013] Furthermore, when adding a sensing function to earphones, there are many restrictions, particularly with regard to attachment / detachment and pulse sensing, and it is necessary to select an appropriate earphone according to the intended use or purpose.

[0014] When sensing whether the device is being worn or removed, the IR (infra-red) method requires that the transparent window and sensor be placed in a location that is less susceptible to external light and can properly capture reflections. The capacitance method requires that the capacitance sensor pad be placed in a location that comes into close contact with the skin when the device is worn. In both cases, the size of the window and pad is a few mm. ２ This required a space of about 100 mm, which was a constraint that made design difficult for earphones, which are becoming increasingly miniaturized.

[0015] When it comes to sensing pulse, the photoplethysmographic method is subject to the same "restrictions on placement" as the detachable IR method, and the passive acoustic sensing method has the restriction that "sensing is not possible unless the ear canal is securely sealed."

[0016] Therefore, in an embodiment of the technique of the present disclosure, in an ear canal insertion type electroacoustic transducer, in order to use the metal housing of the driver as a capacitance sensor pad, a part of the metal housing is shaped like a terminal, thereby imparting the function of a capacitance sensor that can be inserted into the ear canal, thereby enabling the capacitance fluctuations in the ear canal to be acquired.

[0017] 1, an electroacoustic transducer 100 according to an embodiment of the disclosed technique has a hollow housing 40 that houses various functional components and is worn on a user's ear. The electroacoustic transducer 100 also has a cylindrical ear canal insertion portion 42 that is part of the housing 40 and has a hollow portion 42A and is provided on the ear canal side of the housing 40 when worn on the user's ear.

[0018] The electroacoustic transducer 100 also has a driver 1 for signal output that is provided inside the ear canal insertion portion 42. It is sufficient that at least a portion of the driver 1 is provided inside the ear canal insertion portion 42, and it is preferable that more than half of the driver 1 is provided inside the ear canal insertion portion 42.

[0019] The electroacoustic transducer 100 also includes a reproduction unit 50, a measurement unit 48, a calculation unit 52, and an output unit 53. The reproduction unit 50 outputs a signal from the driver 1. The measurement unit 48 measures capacitance using the metal casing of the driver 1 as an electrode. The calculation unit 52 calculates biological information based on the capacitance measured by the measurement unit 48. The output unit 53 outputs the calculation result by the calculation unit 52.

[0020] The measurement unit 48 , reproduction unit 50 , calculation unit 52 , and output unit 53 are mounted on a printed circuit board (not shown) disposed within the housing 40 .

[0021] Next, a specific configuration of the driver 1 will be described.

[0022] Fig. 2 is an exploded perspective view of the driver 1 according to the embodiment of the disclosed technique as seen from one side in the direction of the central axis O, Fig. 3 is an exploded perspective view of the driver 1 according to the embodiment of the disclosed technique as seen from the other side in the direction of the central axis O, Fig. 4(a) is a top view of the driver 1, (b) is a side view of the driver 1, and Fig. 5 is a cross-sectional view along line IV-IV. The configuration of the driver 1 will be described below with reference to these figures.

[0023] The driver 1 mainly comprises a diaphragm assembly 3, a magnetic circuit 4, a plate member 5, a screen 6, and a terminal 7 provided inside a cylindrical metal housing 2 that forms the outer shell. The magnetic circuit 4 drives the diaphragm assembly 3. The plate member 5 is connected to the magnetic circuit 4. The screen 6 is provided inside the plate member 5. The terminal 7 is provided on the outer surface of the plate member 5. The metal housing 2 is made of a conductive material that forms an electrode.

[0024] Specifically, the cylindrical metal housing 2 has an outer shape such that the diameter of one end portion in the direction of the central axis O gradually decreases toward the tip, and a sound emitting opening 2a is formed in one end face, while the other end face of the metal housing 2 is left open.

[0025] In the diaphragm assembly 3, the periphery of a diaphragm 10 made of pulp, film, or the like is supported by an annular frame 11. The diaphragm 10 has a flat, circular central surface 10a in the center, and an annular edge portion 10b that rises to one side in the direction of the central axis O on the periphery of the central surface 10a. A voice coil 12 (coil) wound in a cylindrical shape coaxial with the central axis O is connected to the back surface (the surface on the other side in the direction of the central axis O) of the peripheral portion of the central surface 10a of the diaphragm 10, and vibrations of the voice coil 12 are transmitted to the diaphragm 10. Two lead wires 12a of a wire that forms a coil extend outward from the voice coil 12.

[0026] The magnetic circuit 4 is made up of a magnet 20, a pole piece 21 connected to one polarity of the magnet 20, and a yoke 22 connected to the other polarity. The pole piece 21 and the yoke 22 are made of a magnetic material.

[0027] The magnet 20 has a cylindrical shape with a diameter larger than that of the voice coil 12, and is disposed coaxially with the voice coil 12. The magnet 20 has polarities in the direction of the central axis O, with one polarity (e.g., an S pole) on one side of the direction of the central axis O and the other polarity (e.g., an N pole) on the other side of the direction of the central axis O.

[0028] The pole piece 21 has an annular shape and is disposed on the outer periphery of the voice coil 12. A stepped portion 21a is formed on the peripheral edge of one surface of the pole piece 21 in the direction of the central axis O, with which the frame 11 of the diaphragm assembly 3 engages. The pole piece 21 also has cutouts 21b formed therein for passing the two lead wires 12a of the voice coil 12 therethrough.

[0029] The yoke 22 is composed of a center pole 30 whose tip is positioned on the inner periphery of the voice coil 12 and extends along the central axis O, and a disk-shaped flat plate portion 31 that extends radially outward from the base of the center pole 30 and is connected to the magnet 20.

[0030] The center pole 30 is formed of a cylindrical portion 30a at the tip side and a conical portion 30b at the base side. The diameter of the conical portion 30b increases from the tip, which is the boundary with the cylindrical portion 30a, toward the base side (the other side in the direction of the central axis O) along the central axis O.

[0031] Specifically, the diameter of the conical portion 30b increases from the tip to the base, and although the diameter increases to a larger diameter than the voice coil 12, it is tilted within a range that prevents interference between the voice coil 12 and the center pole 30 even when the voice coil 12 vibrates due to current flow. More specifically, as shown in FIG. 5 , the tip of the conical portion 30b is located at approximately the same position as the other end of the voice coil 12 in the direction of the central axis O. Note that the tip position of the conical portion 30b is not limited to this position, and it may be located at a position that faces the inner peripheral surface of the voice coil 12 in the radial direction. The diameter of the base of the conical portion 30b is formed on the outer periphery side of the outer peripheral surface of the voice coil 12, and in this embodiment in particular, it is formed close to the inner diameter of the magnet 20.

[0032] The flat plate portion 31 is disk-shaped with a diameter slightly larger than the outer diameter of the magnet 20. Three air vents 31a are formed in the flat plate portion 31 at three locations spanning the base of the center pole 30. The air vents 31a connect space A on one side of the flat plate portion 31 connected to the magnet 20 (one side in the direction of the central axis O) with space B on the other side (the other side in the direction of the central axis O) opposite the one side. Each air vent 31a is a circular hole, and the base of the center pole 30 is partially cut out to fit the shape of each air vent 31a. The opening on one side of each air vent 31a is partially blocked by the magnet 20.

[0033] In addition, an arc-shaped notch 31b is formed in a part of the periphery of the flat plate portion 31 for passing two lead wires 12a of the voice coil 12 therethrough.

[0034] The plate member 5 is disk-shaped with a stepped periphery and is attached to the other side of the flat plate portion 31 of the yoke 22. As a result, the plate member 5 defines a space B that communicates with each of the vent holes 31a on the other side of the flat plate portion 31 of the yoke 22. An air vent 5a that communicates the internal space with the outside is formed at the center of the plate member 5. In addition, an arc-shaped notch 5b is formed in part of the periphery of the plate member 5 to allow the two lead wires 12a of the voice coil 12 to pass through.

[0035] The screen 6 is a circular, membrane-shaped, breathable acoustic resistance material, and is provided so as to cover the air holes 5a within the space formed by the plate member 5. An annular double-sided tape 6a is attached to the other surface of the screen 6, and the screen 6 is attached to the plate member 5 via the double-sided tape 6a.

[0036] The terminal 7 is a circular plate material with a central hole 7a formed therein, and one surface of the terminal 7 in the direction of the central axis O is bonded to the plate member 5, and an electrode 7b is formed on the surface of the terminal 7 in the direction of the central axis O. In addition, a circular arc-shaped notch 7c is formed in part of the periphery of the terminal 7 to pass two lead wires 12a of the voice coil 12 through.

[0037] The above-mentioned notch 21b of the pole piece 21, notch 31b of the flat portion 31 of the yoke 22, notch 5b of the plate member 5, and notch 7c of the terminal 7 are all positioned on approximately the same line parallel to the central axis O. Two lead wires 12a of the voice coil 12 pass through the respective notches 21b, 31b, 5b, and 7c and are connected to the electrode 7b of the terminal 7. Although not shown, a UV adhesive is applied along the circumferential direction to the annular gap between the metal housing 2 and the plate member 5, sealing the gap between the metal housing 2 and the plate member 5. The two lead wires 12a passing through the notch 5b of the plate member 5 are also bonded with the UV adhesive. Therefore, in the driver 1 configured in this manner, the space on the back side of the diaphragm 10 is closed up to the air vent 5a of the plate member 5 via the screen 6.

[0038] When an electrical signal is sent to the electrode 7b of the terminal 7 of the driver 1 configured as described above, electricity is passed through the voice coil 12 via the lead wire 12a, and the voice coil 12 vibrates in response to the electrical signal, causing the diaphragm 10 to vibrate, and sound is emitted from the sound-emitting opening 2a.

[0039] Next, a mounting method for measuring capacitance using the metal housing 2 as an electrode will be described.

[0040] 6A, in the first mounting method, lugs 60 that can be soldered to the metal housing 2 are formed. In this case, the measuring unit 48 measures the capacitance by the self-capacitance method, using the metal housing 2 as an electrode.

[0041] 6B, in addition to the first mounting method, a mounting board 62 has an insertion hole for inserting the driver 1, and electrodes 64 are printed around the insertion hole. In this case, the measuring unit 48 measures the capacitance by a mutual capacitance method using the metal housing 2 as RX and the electrodes 64 printed on the mounting board 62 as TX.

[0042] 6C , in addition to the first mounting method, the third mounting method involves printing electrodes 66 on a flexible substrate 65, and wrapping the flexible substrate 65 around a portion of the circumferential surface of the metal casing 2. As a result, the electrodes 66 are formed over a portion of the circumferential surface of the metal casing 2. In this case, the measuring unit 48 measures the capacitance by a mutual capacitance method using the metal casing 2 as RX and the electrodes 66 printed on the flexible substrate 65 as TX.

[0043] 6D , in the fourth mounting method, the metal housing 2 mounted by the first mounting method is divided in the circumferential direction. A lug 60 that can be soldered is formed on each of the divided metal housings 68. In this case, the measuring unit 48 measures the capacitance by the mutual capacitance method using the multiple metal housings 68 as TX and RX.

[0044] The calculation unit 52 calculates biological information based on the capacitance measurement results by the measurement unit 48. For example, blood flow rate and sweat rate are calculated as biological information.

[0045] The output unit 53 outputs the calculation results or measurement results of the biological information. For example, the calculation results or measurement results of the biological information are transmitted to another terminal via wireless communication. Alternatively, the calculation results or measurement results of the biological information are output as audio from the driver 1. Alternatively, the calculation results or measurement results of the biological information are transmitted to an external output device via wireless communication, and the calculation results or measurement results of the biological information are output as audio or displayed from the external output device.

[0046] <Operation of the electroacoustic transducer according to the embodiment of the technique of the present disclosure> When the housing 40 of the electroacoustic transducer 100 is worn on the ear of a user and an instruction to measure biological information is received via wireless communication from the user's terminal (not shown), the measurement unit 48 measures the capacitance using the metal casing 2 as an electrode. Then, the calculation unit 52 calculates the biological information based on the capacitance measurement result by the measurement unit 48, and the output unit 53 outputs the calculation result of the biological information.

[0047] First, as a comparative example, an electroacoustic transducer was configured so that a capacitance sensor pad formed of a flexible substrate was located outside the ear canal insertion portion. Data recording the capacitance fluctuations caused by attaching, vibrating, and removing the electroacoustic transducer in this comparative example are shown in Figure 7. In this data, the pressure and vibration during attachment appear as relatively large fluctuations in capacitance.

[0048] Specifically, in the comparative example, when the electroacoustic transducer moves, the ear canal insertion part moves as a fulcrum, and the distance between the capacitance sensor pad and the auricle changes, resulting in large fluctuations in the output value from the capacitance sensor.

[0049] Next, Fig. 8 shows the change in capacitance caused by the attachment of the electroacoustic transducer 100, the vibration of the electroacoustic transducer 100, and the removal of the electroacoustic transducer 100, in the method described in the embodiment of the technique of the present disclosure. The operations for acquiring data are generally similar to those in Fig. 7.

[0050] A comparison between FIG. 7 and FIG. 8 also reveals that the method described in the embodiment of the technique of the present disclosure reduces the influence of fluctuations in capacitance due to pressure or vibration when attached.

[0051] Specifically, even if the electroacoustic transducer 100 moves, the fulcrum and the metal housing are the same, so no large fluctuation in distance occurs. Also, even if the position of the metal housing displaces within the ear canal, if one side of the metal housing moves closer to the human body, the other side of the metal housing displaces away, so that ultimately the two movements are canceled out and no large fluctuation occurs.

[0052] Table 1 also shows the amount of change in the proximity sensor output value when worn for the method of the comparative example and the method described in the embodiment of the technique of the present disclosure.

[0053]

[0054] From Table 1, it can be seen that the method described in the embodiment of the technique of the present disclosure measures capacitance closer to the human body and has smaller individual differences.

[0055] As described above, according to the electroacoustic transducer according to the embodiment of the technique of the present disclosure, a driver for signal output having a cylindrical metal housing is provided inside the cylindrical ear canal insertion portion, and capacitance is measured using the metal housing as an electrode. This makes it possible to measure capacitance with reduced fluctuations caused by changes in the wearing state.

[0056] Furthermore, the metal housing that functions as a capacitance sensor pad can be positioned in a location that allows for reliable sensing, and the space occupied by the capacitance sensor pad can be eliminated. This makes it possible to minimize fluctuations in capacitance even when the wearing state changes due to vibration or other factors. Furthermore, by using an ear tip as shown in the examples below, the ear tip fits tightly against the inner surface of the ear canal, preventing the electro-acoustic transducer from changing its position within the ear canal. This allows the metal housing that functions as a capacitance sensor pad to be stably positioned in a location that allows for reliable sensing.

[0057] Furthermore, in electroacoustic transducers whose primary purpose is to hear sound, the state of fit of the cylindrical ear canal insertion portion inserted into the ear canal is a factor that is given priority in achieving the primary purpose. In this embodiment, by providing the metal housing of the driver placed inside the cylindrical ear canal insertion portion with the function of a capacitance sensor pad, it is possible to position the metal housing functioning as a sensor pad in a location that is expected to be reliably inserted into the ear canal. Furthermore, there is no need to provide a dedicated space for the capacitance sensor pad. Furthermore, because no optical attachment / detachment sensor / pulse wave sensor is used, there is no need to consider the placement of these optical windows or sensor ICs.

[0058] Furthermore, since the metal housing of the driver is inserted into the ear canal and the entire outer periphery is covered by the human body, it is possible to minimize fluctuations in capacitance value due to changes in the wearing state (changes in positional relationship with the human body).

[0059] As a method of sensing pulse waves, there is an acoustic sensing method that uses intra-aural sounds, which is different from the method that uses light. In this acoustic sensing method, it is necessary to sense extremely low-frequency pressure fluctuations, so it is necessary to seal the ear canal. In the method of this embodiment, the pulse wave is sensed based on changes in electrostatic capacitance, so the seal required in the acoustic sensing method is not necessary, and it is also possible to sense pulse waves using a semi-canal-type electro-acoustic transducer that is well-ventilated.

[0060] Furthermore, because fluctuations caused by changes in the wearing state are kept small, it is possible to acquire biometric information with high accuracy. This makes it possible to acquire minute fluctuations in capacitance due to changes in blood flow (see Non-Patent Document 1), and to estimate heart rate, stress level, brain activity, etc.

[0061] [Non-patent Document 1]: "Capacitive Sensing for Pulse Rate Monitoring." Conference: BIODEVICES 2010 - Proceedings of the Third International Conference on Biomedical Electronics and Devices, Valencia, Spain, January 20-23, 2010

[0062] 9, the housing 40 of the electro-acoustic transducer of this embodiment is formed by fitting a main housing 101a and a front housing 101b together.

[0063] The main housing 101a is a hollow member having an overall cylindrical shape, and its rear opening is closed by a cover 102. A printed wiring board 103 is disposed inside the main housing 101a, facing the opening. The printed wiring board 103 is a board on which electronic components that function as the measurement unit 48, the reproduction unit 50, the calculation unit 52, and the output unit 53 are mounted.

[0064] A battery 106 is disposed in front of the printed wiring board 103 via a battery cushion 107 and a battery cap 108 .

[0065] 9, the outer periphery of the main housing 101a is provided with housing rubber 109. Housing rubber 109 is a cylindrical elastic member fitted to the outer periphery of the main housing 101a, which reduces contact with the ear and prevents water from entering the housing 40.

[0066] 9, the front housing 101b is disposed so as to close the front opening of the cylindrical main housing 101a. The front housing 101b has an overall oblique truncated cone shape, with part of the periphery slightly raised toward the eardrum.

[0067] An ear canal insertion portion 42 is provided in front of the front housing 101b, protruding from the apex of the oblique truncated cone toward the eardrum. The ear canal insertion portion 42 is cylindrical and provided in a portion of the front housing 101b. It is open at both the front and rear, allowing communication between the inside and outside of the front housing 101b. A driver 1 having a cylindrical case is installed inside the ear canal insertion portion 42. Therefore, a positioning portion 111 for the driver 1 is provided near the front opening of the ear canal insertion portion 42, and the front end of the driver 1 engages with this positioning portion 111, thereby fixing the driver 1 to the inner surface of the ear canal insertion portion 42. The rear end of the driver 1 is positioned near the front end of the front housing 101b. The driver 1 includes a magnetic circuit for generating an output signal, a diaphragm, and the like, within a cylindrical case, and an appropriate well-known structure is used.

[0068] As shown in FIG. 9 , an earpiece 113 is fixed to the outer periphery of the ear canal insertion portion 42. The earpiece 113 is also called an eartip, earpad, or earcap, and is made of an elastic material such as silicone rubber. The earpiece 113 has a cylindrical portion 113b that fits around the outer periphery of the ear canal insertion portion 42, and a hemispherical portion 113a at the tip of the cylindrical portion 113b that fits around the ear canal wall. An earpiece attachment groove 412 is provided on the outer periphery of the ear canal insertion portion 42, and as shown in FIG. 9 , a fitting portion 113c is provided on the inner periphery of the cylindrical portion 113b of the earpiece 113, and the fitting portion 113c engages with the earpiece attachment groove 412. This secures the earpiece 113 to the ear canal insertion portion 42.

[0069] The present invention is not limited to the above-described embodiment, and various modifications and applications are possible without departing from the spirit and scope of the present invention.

[0070] The disclosure of Japanese Patent Application No. 2024-106775 is incorporated herein by reference in its entirety.

[0071] All publications, patent applications, and technical standards mentioned in this specification are herein incorporated by reference to the same extent as if each individual publication, patent application, or technical standard was specifically and individually indicated to be incorporated by reference.

Claims

1. An electro-acoustic transducer comprising: a hollow housing to be worn on a user's ear; a cylindrical ear canal insertion portion that is a part of the housing and is provided on the ear canal side of the housing; a driver for signal output having a cylindrical metal housing that is provided inside the ear canal insertion portion; and a measuring portion that measures electrostatic capacitance using the metal housing as an electrode.

2. The electroacoustic transducer according to claim 1, wherein the measuring section measures the electrostatic capacitance by a self-capacitance method using the metal casing as an electrode.

3. An electro-acoustic transducer as described in claim 1, further comprising a substrate having an insertion hole for inserting the driver, the substrate having electrodes printed around the insertion hole, wherein the measuring unit measures the electrostatic capacitance by a mutual capacitance method using the metal casing and the electrodes printed on the substrate.

4. An electro-acoustic transducer as described in claim 1, further comprising a substrate wrapped around a portion of the periphery of the metal housing and having electrodes printed over the entire periphery, wherein the measuring unit measures capacitance using a mutual capacitance method that uses the metal housing and the electrodes printed on the substrate.

5. An electro-acoustic transducer according to claim 1, wherein the metal housing is a plurality of metal housings divided in the circumferential direction, and the measuring unit measures the electrostatic capacitance by a mutual capacitance method using the plurality of metal housings.

6. The electroacoustic transducer according to claim 1, further comprising a calculation unit that calculates bioinformation based on the capacitance measured by said measurement unit.

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