Speaker

Abstract

To provide a speaker for measuring a movement state of a vibration part including a diaphragm so as to perform feedback control.SOLUTION: A speaker 1 includes a detection part for detecting the vibration of a vibration part. The detection part includes: a fixed magnet 11 constituting a magnetic circuit 10; and a mobile magnet 22 and magnetic sensor 21 arranged under a cap 8. A fixed magnetic field component H1 directed in a Z2 direction acts on the magnetic sensor 21 by a leak magnetic flux from the magnetic circuit 10, and a mobile magnetic component H2 acts on the magnetic sensor 21 from the mobile magnet 22 in a Y2 direction. The magnetic sensor 21 detects the change of an angle θ of a detection magnetic field component Hd being the synthetic vector of the magnetic field components H1, H2 from the two directions, and an active position of the mobile magnet 22 is measured in response to the detection output.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a speaker capable of measuring the operation of a vibration part including a diaphragm with high accuracy by a magnetic sensor. [Background technology]

[0002] Conventional speakers in audio equipment simply receive the audio signal output from the amplifier and process it to reproduce the sound pressure, and the speaker itself does not control the audio signal. Therefore, the sound is easily distorted and the sound quality is easily varied. Furthermore, when the amplitude of the diaphragm becomes excessive, the diaphragm and damper can be damaged.

[0003] In order to solve the above problems, Patent Document 1 describes a speaker system that performs feedback control by detecting the movement of a diaphragm with a magnetic sensor.

[0004] This speaker system has a plate that constitutes a magnetic circuit, and a Hall element, which is a magnetic sensor, is supported on the plate facing the voice coil. The effective magnetic flux density in the gap of the magnetic circuit is detected by the Hall element, and the detection signal is amplified and fed back to the power amplifier. When a driving current is applied from the power amplifier to the voice coil and the bobbin vibrates together with the voice coil, the effective magnetic flux density in the gap changes due to the current flowing through the voice coil and the back electromotive force generated in the voice coil. This change in effective magnetic flux density is detected by the Hall element and fed back to the power amplifier, thereby correcting the distortion of the driving current applied to the voice coil. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 57-184397 Summary of the Invention [Problem to be solved by the invention]

[0006] The feedback control of the speaker system described in Patent Document 1 uses a Hall element, which is smaller than an optical detector or a coil, as the detector element, and therefore can prevent the speaker from becoming excessively large in size and can also prevent an increase in power consumption. However, the method of detecting the change in effective magnetic flux density in the gap of the magnetic circuit section with a Hall element cannot directly detect the movement of the voice coil or bobbin, making it difficult to accurately correct sound distortion and variations in sound quality.

[0007] Furthermore, the speaker system of Patent Document 1 has a structure in which the Hall element is embedded in the portion of the plate facing the voice coil, so that the mounting structure for the Hall element is complicated and the assembly work is inefficient.

[0008] The present invention is devised to solve the above-mentioned problems in the conventional art, and aims to provide a speaker that can detect the vibration of a vibrating part with high accuracy using a magnetic sensor that detects magnetic field components in two directions. [Means for solving the problem]

[0009] The present invention relates to a speaker having a vibration section including a diaphragm, a bobbin fixed to the diaphragm, and a voice coil provided on the bobbin, a support section supporting the vibration section so as to be capable of vibrating freely, and a magnetic circuit section included in the support section, the magnetic circuit unit has a magnetic gap in which the voice coil is located, an inner yoke located inside the magnetic gap, and a fixed magnet that forms a driving magnetic flux that crosses the magnetic gap and flows within the inner yoke along the vibration direction of the vibration unit, a movable magnet that forms a movable magnetic flux in a direction intersecting the vibration direction is fixed to the vibration section, and a magnetic sensor that is located inside the magnetic gap when viewed in a plane perpendicular to the vibration direction is fixed to the support section; The magnetic sensor detects a fixed magnetic field component acting in the vibration direction based on leakage magnetic flux from the magnetic circuit section, and a moving magnetic field component acting in a direction intersecting the fixed magnetic field component based on the moving magnetic flux, and is characterized in that the operation of the vibration section is measured based on changes in intensity of the moving magnetic flux component.

[0010] In the speaker of the present invention, the magnetic sensor detects the direction of a resultant vector of the magnetic field components from two directions, or detects a ratio of intensities of the magnetic field components from two directions.

[0011] In the speaker of the present invention, it is preferable that the inner yoke has a central hole aligned with the vibration direction, and the magnetic sensor is located within the area of ​​the central hole when viewed in a plane perpendicular to the vibration direction.

[0012] The speaker of the present invention has a sensor support member fixed to the inner yoke, the magnetic sensor supported by the sensor support member, and wiring connected to the magnetic sensor extending to the outside through the central hole.

[0013] The speaker of the present invention may have a structure in which the central hole is blocked by the sensor support member.

[0014] In the speaker of the present invention, it is preferable that the vibrating portion is provided with a cap that covers the bobbin from the diaphragm side, and the movable magnet is fixed to the cap. Effect of the Invention

[0015] In the speaker of the present invention, a magnetic sensor fixed to a support detects magnetic field components in two mutually intersecting directions, namely, a fixed magnetic field component which is a leakage magnetic flux from a magnetic circuit section, and a moving magnetic field component from a moving magnet which moves with a vibrating section. For example, by determining the change in the direction of the resultant vector of the two magnetic field components, or by determining the relative value of the two magnetic field components, the operation of the vibrating section can be measured with high accuracy without being affected by surrounding noise. Based on this measurement, it becomes possible to perform high-accuracy feedback control to correct the operation of the vibrating section.

[0016] The fixed magnetic field component is a magnetic field component leaking from the inner yoke of the magnetic circuit in the direction along the vibration direction. The magnetic sensor is disposed inside the magnetic gap in a plan view, and is preferably positioned in the center hole of the inner yoke in a plan view. This makes it possible to detect the fixed magnetic field component leaking from the magnetic circuit in the direction along the vibration direction with a stable intensity, and to obtain a stable detection output from the magnetic sensor. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1A is a half-sectional perspective view of a speaker according to a first embodiment of the present invention, taken along a cutting plane parallel to the XZ plane and including a central axis O; FIG. 1B is a partial perspective view illustrating two magnetic field components acting on a magnetic sensor; [Diagram 2] FIG. 11 is a cross-sectional view showing a modified example of the speaker of the first embodiment, taken along a cutting plane parallel to the XZ plane and including a central axis O; [Diagram 3] FIG. 11 is a cross-sectional view showing a speaker according to a second embodiment of the present invention, taken along a cutting plane parallel to the XZ plane and including a central axis O; [Figure 4] FIG. 11 is a cross-sectional view showing a speaker according to a third embodiment of the present invention, taken along a cutting plane parallel to the XZ plane and including a central axis O; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] In the speaker 1 of the first embodiment of the present invention shown in Fig. 1(A), the Z1-Z2 direction is the front-rear direction, with the Z1 direction being the front and the Z2 direction being the rear. The Z1-Z2 direction is the vibration direction of the vibration part. The speaker 1 may be used such that the Z1 direction is the sound generation direction due to the vibration of the vibration part, or the Z2 direction is the sound generation direction.

[0019] Fig. 1(A) shows a central axis O extending in the front-rear direction (Z1-Z2 direction). The main part of the speaker 1 has a structure that is almost rotationally symmetrical about the central axis O. The central axis O passes through the center of the diaphragm 3, the center of the bobbin 6, and the center of the magnetic circuit part 10. Fig. 1(A) shows an X1-X2 axis and a Y1-Y2 axis that are perpendicular to each other on a plane perpendicular to the central axis O.

[0020] The speaker 1 shown in Fig. 1(A) has a frame 2. The frame 2 is made of a non-magnetic or magnetic material, and has a tapered shape with a diameter that gradually increases toward the front (Z1 direction). A magnetic circuit section 10 is fixed to the rear (Z2 direction) of the frame 2 by means of adhesion, screws, or other such means. The frame 2 and the magnetic circuit section 10 form a "support section."

[0021] The magnetic circuit section 10 has a ring-shaped fixed magnet 11 centered on a central axis O, a ring-shaped opposing yoke 12 joined to the front of the fixed magnet 11, and a rear yoke 13 joined to the rear of the fixed magnet 11. An inner yoke 14 is formed integrally with the rear yoke 13. The inner yoke 14 is located inside the fixed magnet 11 and the opposing yoke 12, and is formed by protruding forward (in the Z1 direction) from the rear yoke 13. The inner yoke 14 may be formed separately from the rear yoke 13, and the rear yoke 13 and the inner yoke 14 may be joined together. The opposing yoke 12, the rear yoke 13, and the inner yoke 14 are formed of a magnetic material, i.e., a magnetic metal material.

[0022] Between the outer peripheral surface of the inner yoke 14 and the inner peripheral surface of the opposing yoke 12, a magnetic gap G is formed along a circumference centered on the central axis O. The inner yoke 14 is located inside the magnetic gap G. In the embodiment shown in FIG. 1(A), the surface facing forward (Z1 direction) of the fixed magnet 11 located outside the magnetic gap G is magnetized to the N pole, and the surface facing backward (Z2 direction) is magnetized to the S pole. Therefore, the driving magnetic flux Φ1 generated from the fixed magnet 11 flows toward the central axis O in the opposing yoke 12 and crosses the magnetic gap G. The driving magnetic flux Φ1 that crosses the magnetic gap G flows in the inner yoke 14 in a direction along the central axis O, i.e., in the Z2 direction along the vibration direction of the vibration part, and circulates to return to the fixed magnet 11 via the rear yoke 13. The magnetic circuit part 10 may be magnetized so that the surface facing backward (Z2 direction) of the fixed magnet 11 is the N pole and the surface facing forward (Z1 direction) is the S pole.

[0023] A diaphragm 3 is provided inside the front portion of the frame 2. The diaphragm 3 has a conical shape. A front end peripheral portion 2a of the frame 2 and an outer peripheral edge 3a of the diaphragm 3 are joined via an elastically deformable edge member 4. The edge member 4 and the front end peripheral portion 2a, and the edge member 4 and the outer peripheral edge 3a are fixed with an adhesive. An inner peripheral fixing portion 2b is formed on the inner surface of the middle portion of the frame 2, and an outer peripheral portion 5a of an elastically deformable damper member 5 having a corrugated cross section is fixed to the inner peripheral fixing portion 2b with an adhesive.

[0024] A bobbin 6 is provided inside the frame 2. The bobbin 6 has a cylindrical shape centered on a central axis O. An inner peripheral end 3b of the diaphragm 3 is fixed to the outer peripheral surface of the bobbin 6 with an adhesive, and an inner peripheral portion 5b of the damper member 5 is also fixed to the outer peripheral surface of the bobbin 6 with an adhesive. A dome-shaped cap 8 that protrudes forward is provided at the center of the diaphragm 3. The cap 8 covers and closes the front opening of the bobbin 6, and a peripheral portion 8a of the cap 8 is fixed to the front surface of the diaphragm 3 with an adhesive.

[0025] A voice coil 7 is provided on the outer circumferential surface of the rear end portion of the bobbin 6 facing rearward (Z2 direction). The coated conductor wire that constitutes the voice coil 7 is wound a predetermined number of turns on the outer circumferential surface of the bobbin 6. The voice coil 7 is located within the magnetic gap G of the magnetic circuit section 10. The magnetic circuit section 10 and the voice coil 7 constitute a "magnetic drive section."

[0026] The diaphragm 3 and bobbin 6 are supported so as to be able to vibrate freely in the front-to-back direction (Z1-Z2 direction) relative to the frame 2 (relative to the "support part") due to the elastic deformation of the edge member 4 and damper member 5, which are elastic support members. The diaphragm 3, cap 8, bobbin 6, and voice coil 7 constitute a "vibration part" that vibrates in the front-to-back direction relative to the "support part" including the frame 2. In addition, the parts of the edge member 4 and damper member 5 that vibrate back-to-back together with the diaphragm 3 also constitute part of the "vibration part."

[0027] A detection unit (vibration detection unit) that detects vibration of the vibration unit is provided in the speaker 1. The detection unit is composed of the magnetic circuit unit 10, a movable magnet 22 that faces the movable unit and vibrates together with the diaphragm 3, and a magnetic sensor 21 fixed to the support unit side.

[0028] As shown in FIG. 1(A), in the magnetic circuit unit 10, a central hole 15 is formed in the inner yoke 14. The central hole 15 is a hole with a circular cross section in which the central axis O is located at the center, and is formed penetrating the inner yoke 14 from front to back. A sensor support member 26 is fitted into the central hole 15. The sensor support member 26 is made of a non-magnetic material such as a synthetic resin material or synthetic rubber. A protective cap 23 is fixed to the front end of the sensor support member 26. The protective cap 23 is made of a non-magnetic material such as a non-magnetic metal material or a synthetic resin material. A sealed support space is formed between the sensor support member 26 and the protective cap 23. In the support space, a circuit board 24 is fixed to a support protrusion 26b formed integrally with the sensor support member 26, and the magnetic sensor 21 is mounted on the circuit board 24. Wiring material 25 is connected to circuit board 24, and wiring material 25 and terminal portion 21a (see FIG. 1(B)) of magnetic sensor 21 are electrically connected by a conductor pattern formed on the surface of circuit board 24. Wiring material 25 passes through the inside of sensor support member 26, passes through center hole 15, and extends into the space behind speaker 1.

[0029] The sensor support member 26, the protective cap 23, the circuit board 24, the magnetic sensor 21, and the wiring material 25 can be preassembled and made into a unit. In the unitized state, the protective cap 23 is facing forward, and is inserted into the center hole 15 from the rear, and the flange portion 26a formed at the rear end of the sensor support member 26 is abutted against the rear surface 13a of the rear yoke 13, so that the magnetic sensor 21 and the wiring material 25 can be positioned and assembled inside the magnetic circuit section 10, which is a part of the support body. The sensor support member 26 is pressed into the center hole 15 and fixed to the magnetic circuit section 10. Alternatively, the sensor support member 26 is fixed to the magnetic circuit section 10 by a fixing means such as adhesive or screwing. Even if the magnetic sensor 21 or the circuit board 24 breaks down, the unitized sensor support member 26 and the magnetic sensor 21 can be pulled out rearward from the center hole 15 without disassembling the vibration section or the support section, so that maintenance work can be easily performed.

[0030] As shown in Fig. 1(A), a magnet support member 27 is fixed to the center of the cap 8. A fixing portion 27a is formed at the front end of the magnet support member 27, and the fixing portion 27a is adhered and fixed to the cap 8. The magnet support member 27 extends rearward (in the Z2 direction) from the cap 8 toward the inner space of the bobbin 6. A movable magnet 22 is adhered and fixed to the rear portion of the magnet support member 27. The movable magnet 22 is located approximately on the central axis O.

[0031] The movable magnet 22 is magnetized so that the surface facing the Y1 side is the north pole and the surface facing the Y2 side is the south pole. Therefore, the direction of the movable magnetic flux Φ2 emitted from the movable magnet 22 is the Y1 direction. In the magnetic circuit section 10, the direction of the driving magnetic flux Φ1 flowing within the inner yoke 14 is the front-rear direction (Z1-Z2 direction) which is the vibration direction of the vibration section, that is, the direction along the central axis O. The magnetization direction of the movable magnet 22 and the direction of the moving magnetic flux Φ2 emitted from the movable magnet 22 intersect with each other, and are preferably perpendicular to the driving magnetic flux ΦF1 flowing within the inner yoke 14.

[0032] 1, the center of the magnetic sensor 21 and the center of the movable magnet 22 are both located on the central axis O. In addition, the movable magnet 22 is disposed at a distance forward from the protective cap 23 so as not to hit the protective cap 23 when the vibrating part operates at the maximum amplitude in the front-rear direction.

[0033] When viewed on a plane perpendicular to the vibration direction of the vibrating part, i.e., a plane perpendicular to the central axis O, the magnetic sensor 21 is located inside the magnetic gap G and inside the bobbin 6 and the voice coil 7. As shown in FIG. 1B, a fixed magnetic field component H1 based on leakage magnetic flux from the magnetic circuit part 10 and a movable magnetic field component H2 based on the movable magnetic flux Φ2 generated by the movable magnet 22 act on the magnetic sensor 21. Since the driving magnetic flux Φ1 flows in the Z2 direction along the central axis O in the inner yoke 14, the fixed magnetic field component H1 acts on the magnetic sensor 21 in the Z2 direction due to the leakage magnetic flux of the fixed magnetic flux Φ1. The magnetization direction of the movable magnet 22 is the Y direction, and the movable magnetic flux Φ2 coming out of the N pole of the movable magnet 21 in the Y1 direction circulates in space and returns to the S pole of the movable magnet 22, so that the movable magnetic field component H2 based on the movable magnetic flux Φ2 acts on the magnetic sensor 21 in the Y2 direction. The intensity of the fixed magnetic field component H1 is a vector quantity directed in the Z2 direction, and the intensity of the movable magnetic field component H2 is a vector quantity directed in the Y2 direction. The intensity of the fixed magnetic field component H1 acting on the magnetic sensor 21 is substantially constant, but the intensity of the movable magnetic field component H2 changes according to the vibration of the vibrating part.

[0034] The magnetic sensor 21 can detect two magnetic field components H1 and H2, which are vector quantities, in the YZ plane including the central axis O. The magnetic sensor 21 has at least one magnetoresistance effect element. The magnetoresistance effect element is a GMR element or a TMR element having a fixed magnetic layer and a free magnetic layer. The magnetization direction of the fixed magnetic layer is fixed in a predetermined direction in the YZ plane, for example, in the Y2 direction. The free magnetic layer is made into a single magnetic domain by a bias magnetic field, and the magnetization direction of the free magnetic layer changes in the YZ plane following the direction of the magnetic field acting from the outside. The electrical resistance value of the magnetoresistance effect element changes according to the change in the relative angle between the magnetization direction of the fixed magnetic layer and the magnetization direction of the free magnetic layer.

[0035] 1B, the magnetic sensor 21 is acted upon by a fixed magnetic field component H1, which is a vector quantity directed in the Z2 direction, and a movable magnetic field component H2, which is a vector quantity directed in the Y2 direction, so that the magnetization direction of the free layer of the magnetoresistance effect element follows the direction of the detection magnetic field component Hd, which is the vector sum of the fixed magnetic field component H1 and the movable magnetic field component H2. When the movable magnet 22 fixed to the vibration part moves forward (Z1 direction) and away from the magnetic sensor 21, the strength of the movable magnetic field component H2 acting on the magnetic sensor 21 decreases, so that the angle θ of the vector of the detection magnetic field component Hd with respect to the Y2 direction, which is the magnetization direction of the fixed magnetic layer, increases, and the electrical resistance of the magnetoresistance effect element increases. When the movable magnet 22 moves backward (Z2 direction) and approaches the magnetic sensor 21, the strength of the movable magnetic field component H2 increases, so that the angle θ of the vector of the detection magnetic field component Hd decreases, and the electrical resistance of the magnetoresistance effect element decreases.

[0036] Alternatively, the magnetic sensor 21 may be configured with two directional detection elements, such as Hall elements, arranged with their detection directions crossing, preferably perpendicular to each other, in the YZ plane. In the magnetic sensor 21, one detection element with directionality in the Z-axis direction detects the intensity of the fixed magnetic field component H1, and the other detection element with directionality in the Y-axis direction detects the intensity of the moving magnetic field component H2. In a detection circuit (not shown), a detection output equivalent to that obtained by determining the change in the angle θ of the vector of the detection magnetic field component Hd can be obtained by determining the ratio between the intensity of the fixed magnetic field component H1, which is a substantially constant value, and the intensity of the moving magnetic field component H2, which changes in response to the vibration of the moving part.

[0037] Next, the sound generation operation of the speaker 1 will be described. In sound generation, a driving current is applied to the voice coil 7 based on an audio signal output from an audio amplifier. As the driving magnetic flux Φ1 generated from the magnetic circuit section 10 crosses the voice coil 7, the electromagnetic force excited by the driving magnetic flux Φ1 and the driving current causes the vibration section including the diaphragm 3, bobbin 6, and voice coil 7 to vibrate in the front-rear direction, generating sound pressure according to the frequency of the driving current, and sound is emitted forward (Z1 direction) or backward (Z2 direction).

[0038] The circuit section provided in the speaker 1 constitutes a detection circuit and a control section, and the detection output of the magnetic sensor 21 is detected by the detection circuit and provided to the control section. The control section performs feedback control based on the detection output from the magnetic sensor 21. By detecting a change in the angle θ of the vector of the detected magnetic field component Hd by the magnetic sensor 21, the control section can measure the position of the vibration section including the diaphragm 3 in the front-rear direction and the change therein. For example, the control section calculates the deviation between the ideal position of the vibration section in the front-rear direction and the change therein assumed by application of an audio signal and the actual position of the vibration section measured from the detection output of the magnetic sensor 21 and the change therein. When the deviation exceeds a threshold value, a correction signal (offset signal) for correcting the deviation is superimposed on the drive signal (voice current) and provided to the voice coil 7. This feedback control corrects distortion and sound deviation of the sound produced by the speaker 1, and further prevents the diaphragm 3 from vibrating excessively in the front-rear direction.

[0039] The magnetic sensor 21 measures the change in the intensity of the moving magnetic field component H2 based on the intensity of the fixed magnetic field component H1, which is a substantially constant value, and detects the change in the inclination of the detection magnetic field component Hd, which is a composite vector, or detects the ratio of the intensity of the fixed magnetic field component H1 to the intensity of the moving magnetic field component H2. Since the intensity of the fixed magnetic field component H1, which is a substantially constant value, is used as the reference, it is less susceptible to the influence of external noise, and the position and operation of the vibration unit can be measured with high accuracy. In addition, the leakage magnetic flux from the magnetic circuit unit 10, which may otherwise cause noise in the detection operation, is used for the detection operation, and this leakage magnetic flux is detected as the fixed magnetic field component H1, which is the reference, so it is less susceptible to the influence of external noise, and feedback control with high accuracy and sensitivity can be performed at all times.

[0040] When the structure of the detection unit is viewed in a plane perpendicular to the vibration direction, i.e., a plane (XY plane) perpendicular to the central axis O, or when the structure of the detection unit is viewed by projecting it onto the XY plane, the magnetic sensor 21 is located inside closer to the central axis O than the magnetic gap G. As is clear from the embodiment shown in FIG. 2 and subsequent figures, the inner yoke 14 has a length dimension in the Z1-Z2 direction greater than a thickness dimension (radial thickness dimension) in the X1-X2 direction, and inside the inner yoke 14, the path length of the driving magnetic flux Φ1 is shorter in the X1 direction (direction toward the central axis O) and longer in the Z2 direction. Therefore, inside the magnetic gap G, the density of the leakage magnetic flux from the magnetic circuit unit 10 is relatively larger and more stable in the Z2 direction than in the X1 direction. Since the intensity of the fixed magnetic field component H1, which is the reference value, is large and stable, it is possible to obtain a stable detection output that is less susceptible to noise.

[0041] In particular, when the magnetic sensor 21 is located within the range of the central hole 15 of the inner yoke 14 when viewed on the XY plane or projected onto the XY plane, the magnetic flux density in the Z1 direction of the leakage magnetic flux in the area where the magnetic sensor 21 is provided can be increased, and the detection strength of the fixed magnetic field component H1 detected by the magnetic sensor 21 can be stabilized. Furthermore, in the embodiment shown in FIG. 1(A), the magnetic sensor 21 is located inside the central hole 15 in the front-rear direction as well, and is further located on the central axis O located at the center of the central hole 15. Inside the central hole 15 and further near the central axis O, the density of the leakage magnetic flux in the Z1 direction becomes high, so the strength of the fixed magnetic field component H1 detected by the magnetic sensor 21 is stabilized. Since the strength of the fixed magnetic field component H1 can be stably detected, the relative strength ratio of the fixed magnetic field component H1 and the movable magnetic field component H2 can be detected with low noise.

[0042] A modified example of the speaker 1 of the first embodiment of the present invention is shown in Fig. 2. This speaker 1 has a cap 108 which differs from the cap 8 shown in Fig. 1(A). The cap 108 is made of a synthetic resin material or the like, and is fitted onto the end of the bobbin 6 facing forward (Z1 direction) and fixed thereto with an adhesive or the like. A magnet support member 127 is formed integrally with the cap 108, and a movable magnet 22 is fixed to the magnet support member 127.

[0043] 2, the cap 108 and the movable magnet 22 can be easily fixed to the front end of the bobbin 6 in the final stage of assembly work. Therefore, after fixing the magnetic circuit section 10 to the frame 2, and further assembling the diaphragm 3, edge member 4, bobbin 6 and voice coil 7, the fixed magnet 11 of the magnetic circuit section 10 can be magnetized before attaching the cap 108, and then the cap 108 and the movable magnet 22 can be easily attached. In this assembly work, the magnetizing magnetic field used in the magnetizing work of the fixed magnet 11 does not affect the magnetized state of the movable magnet 22.

[0044] In speaker 101 according to the second embodiment of the present invention shown in Fig. 3, sensor support member 126 is fitted and fixed to the front end (Z1 direction) of central hole 15 formed in inner yoke 14. Circuit board 24 and magnetic sensor 21 are fixed to the front of sensor support member 126. When viewed on an XY plane perpendicular to the front-rear direction which is the vibration direction of the vibrating part, or when projected onto the XY plane, magnetic sensor 21 is located within the area of ​​central hole 15 and is located approximately on central axis O. However, magnetic sensor 21 is not located inside central hole 15 but in the space in front of central hole 15.

[0045] In this speaker 101, when viewed on the XY plane or when projected onto the XY plane, the magnetic sensor 21 is located within the area of ​​the central hole 15 and is located approximately on the central axis O, so that the fixed magnetic field component H1 detected by the magnetic sensor 21 can be stably detected as a strong magnetic field.

[0046] In addition, the sensor support member 26 shown in Figures 1(A) and 2 or the sensor support member 126 shown in Figure 3 blocks the central hole 15 of the inner yoke 14, thereby preventing dust and moisture from entering the space sandwiched between the front end of the inner yoke 14 and the caps 8, 108.

[0047] In speaker 201 of the third embodiment of the present invention shown in Fig. 4, sensor support member 226 is fixed to the edge of central hole 15 of inner yoke 14, and magnetic sensor 21 supported by sensor support member 226 is disposed at a position offset radially outward from central axis O. The front end of bobbin 6 is covered by cap 208, and movable magnet 22 is supported by magnet support member 227 formed integrally with cap 208. Movable magnet 22 is also positioned radially outward from central axis O. However, magnetic sensor 21 and movable magnet 22 are preferably positioned on the same axis parallel to central axis O.

[0048] In this speaker 201, when viewed on the XY plane or when projected onto the XY plane, the magnetic sensor 21 is located within the area of ​​the central hole 15, so that the fixed magnetic field component H1 detected by the magnetic sensor 21 can be stably detected as a strong magnetic field. [Explanation of symbols]

[0049] 1,101,201 Speakers 2 Frames 3 Vibration plate 6 Bobbin 7 Voice coil 10 Magnetic circuit section 11 Fixed magnet 12 opposing yoke 13 Rear Yoke 14 Inner Yoke 15 center hole 21 Magnetic Sensor 22 Moving magnet 26,126,226 Sensor support member Φ1 driving magnetic flux Φ2 moving magnetic flux H1 Fixed magnetic field component H2 Mobile magnetic field component Hd Detected magnetic field component O center axis

Claims

1. A speaker having a vibration section including a diaphragm, a bobbin fixed to the diaphragm, and a voice coil provided on the bobbin, a support section supporting the vibration section so as to be capable of vibrating freely, and a magnetic circuit section included in the support section, the magnetic circuit unit has a magnetic gap in which the voice coil is located, an inner yoke located inside the magnetic gap, and a fixed magnet that forms a driving magnetic flux that crosses the magnetic gap and flows within the inner yoke along the vibration direction of the vibration unit, a movable magnet that forms a movable magnetic flux in a direction intersecting the vibration direction is fixed to the vibration section, and a magnetic sensor that is located inside the magnetic gap when viewed in a plane perpendicular to the vibration direction is fixed to the support section; A speaker characterized in that the magnetic sensor detects a fixed magnetic field component acting in the vibration direction based on leakage magnetic flux from the magnetic circuit section, and a moving magnetic field component acting in a direction intersecting the fixed magnetic field component based on the moving magnetic flux, and the operation of the vibration section is measured based on changes in intensity of the moving magnetic flux component.

2. 2. The speaker according to claim 1, wherein the magnetic sensor detects a direction of a resultant vector of magnetic field components from two directions.

3. 2. The speaker according to claim 1, wherein said magnetic sensor detects a ratio of intensities of said magnetic field components from two directions.

4. 4. A speaker as described in any one of claims 1 to 3, wherein the inner yoke has a central hole aligned with the vibration direction, and the magnetic sensor is positioned within the area of ​​the central hole when viewed in a plane perpendicular to the vibration direction.

5. 5. A speaker according to claim 4, wherein a sensor support member is fixed to the inner yoke, the magnetic sensor is supported by the sensor support member, and wiring electrically connected to the magnetic sensor extends to the outside through the central hole.

6. 6. The speaker according to claim 5, wherein the center hole is closed by the sensor support member.

7. 7. The speaker according to claim 1, wherein the vibrating portion is provided with a cap for covering the bobbin from the diaphragm side, and the movable magnet is fixed to the cap.

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