Speaker

Abstract

To provide a speaker which is capable of feedback control by detecting a movement state of a movable part including a diaphragm.SOLUTION: In a speaker 1, a vibration part includes a diaphragm 3 and a bobbin 6, and a voice coil 7 is fixed to the bobbin 6. A detection part 20 has a movable magnet 21 and a magnetic sensor 22. The magnetic sensor 22 is located within a space surrounded by the bobbin 6, and the movable magnet 21 is fixed to the outer face of the bobbin 6. Because the magnetic sensor 22 is located inside the bobbin 6, the movable magnet 21 and the damper member 5 do not come into contact with the magnetic sensor 22 even when the movable magnet 21 and damper member 5 greatly move rearward.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a speaker capable of detecting the operation of a vibrating part having a diaphragm and a bobbin 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 using a magnetic sensor.

[0004] In this speaker system, a Hall element, which is a magnetic sensor, is supported on the portion of the plate that constitutes the magnetic circuit section that faces the voice coil, and the effective magnetic flux density in the gap of the magnetic circuit section 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] In addition, the speaker system of Patent Document 1 has a structure in which the Hall element is embedded on the surface of the plate facing the voice coil, so the mounting structure for the Hall element is complicated and the assembly work is inefficient. If the Hall element were mounted on the top surface of the plate as shown in the figure, it would be unable to adequately detect changes in the effective magnetic flux density in the gap of the magnetic circuit, and there would also be a problem that the vibrating diaphragm and the damper member supporting it would be more likely to hit the Hall element.

[0008] The present invention is intended to solve the above-mentioned problems in the conventional technology, and has an object to provide a speaker that can detect the vibration of a vibrating part with high accuracy. [Means for solving the problem]

[0009] The present invention provides a speaker including a frame, a vibration section supported by the frame, a magnetic drive section that drives the vibration section, and a detection section that detects the movement of the vibration section, the vibration section has a vibration plate supported by the frame so as to be capable of vibrating freely and a bobbin fixed to the vibration plate, the magnetic drive section has a voice coil fixed to the bobbin and a magnetic circuit section that forms a magnetic flux that crosses the voice coil, the detection unit has a movable magnet fixed to the vibration unit and a magnetic sensor that detects magnetic flux emitted from the movable magnet, A base is fixed to an end surface of a center yoke constituting the magnetic circuit portion,The magnetic sensor is disposed in a space surrounded by the bobbin. and attached to the base at a position away from the end surface. It is characterized by being fixed.

[0013] In the speaker of the present invention, it is preferable that a hole is formed in the center yoke that constitutes the magnetic circuit unit, penetrating in the front-to-rear direction, which is the vibration direction of the vibration unit, and a wiring cable connected to the magnetic sensor passes through the hole and is pulled out to the outside of the magnetic circuit unit.

[0014] In the speaker of the present invention, a direction of the magnetic flux applied from the magnetic circuit portion to the magnetic sensor intersects with a direction of the magnetic flux applied from the movable magnet to the magnetic sensor, It is preferable that the magnetic sensor provides a detection output based on a change in the direction of a resultant vector of the two magnetic fluxes.

[0015] Furthermore, in the speaker of the present invention, it is preferable that the movable magnet is provided on the outside of the bobbin. Effect of the Invention

[0016] The speaker of the present invention detects the magnetic flux from the movable magnet provided in the vibration section with a magnetic sensor, so that the movement of the vibration section can be directly detected. This enables highly accurate feedback control to correct the movement of the vibration section. In addition, by obtaining a detection output from the magnetic sensor based on the change in the magnetic field of the resultant vector of the driving magnetic flux from the magnetic circuit section and the moving magnetic flux from the movable magnet, it becomes possible to detect the movement of the vibration section with high accuracy without being affected by the strength of the driving magnetic flux generated from the magnetic circuit section.

[0017] Furthermore, by arranging the magnetic sensor in the space surrounded by the bobbin, the magnetic sensor can be arranged without being affected by a damper member that vibrates back and forth outside the bobbin, and the degree of freedom in arranging the magnetic sensor can be ensured. For example, the magnetic sensor can be arranged at a position away from the magnetic circuit section to bring the distance to the moving magnet closer. Furthermore, by arranging the magnetic sensor at a position away from the magnetic circuit section, the moving magnet can also be arranged at a position away from the voice coil, and if the moving magnet is arranged outside the bobbin, it becomes easier to prevent the moving magnet from hitting the magnetic circuit section when the vibrating section vibrates. [Brief description of the drawings]

[0018] [Figure 1] FIG. 1 is a half-sectional perspective view of a speaker according to a first embodiment of the present invention; [Diagram 2] FIG. 1 is a half cross-sectional view of a speaker according to a first embodiment; [Diagram 3] FIG. 2 is a half cross-sectional view of a speaker according to a second embodiment of the present invention; [Figure 4] 1 is a half sectional view of a speaker according to a third embodiment of the present invention; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] In the speaker 1 according to the first embodiment of the present invention shown in Fig. 1 and Fig. 2, the Z1-Z2 direction is the front-rear direction, the Z1 direction being the front and the sound generation direction, and the Z2 direction being the rear. Fig. 1 and Fig. 2 show 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. Fig. 1 shows an X-axis and a Y-axis that are perpendicular to each other on a plane perpendicular to the central axis O. The X-axis coincides with the direction of the magnetic field H1 to be detected by the magnetic sensor 22 among the driving magnetic flux F1 formed by the magnetic circuit section 10. The Y-axis coincides with the direction of the magnetic field H2 to be detected by the magnetic sensor 22 among the moving magnetic flux F2 formed by the moving magnet 21.

[0020] The speaker 1 shown in FIG. 1 and FIG. 2 has a frame 2. The frame 2 is made of a non-magnetic material or a magnetic material, and has a tapered shape with a diameter gradually increasing toward the front (Z1 direction). A magnetic circuit unit 10 is fixed to the rear of the frame 2 by means of adhesion, screwing, or the like. The magnetic circuit unit 10 has a ring-shaped driving magnet 11 centered on a central axis O, a ring-shaped opposing yoke 12 joined to the front of the driving magnet 11, and a rear yoke 13 joined to the rear of the driving magnet 11. A center yoke 14 is integrally formed with the rear yoke 13. The center yoke 14 is located inside the driving magnet 11 and the opposing yoke 12, and is formed by protruding from the rear yoke 13 toward the front (Z1 direction). The center yoke 14 may be formed separately from the rear yoke 13, and the rear yoke 13 and the center yoke 14 may be joined together. The center yoke 14 has a hole 15 penetrating in the front-rear direction (Z1-Z2 direction). The opposing yoke 12, the rear yoke 13 and the center yoke 14 are made of a magnetic material, that is, a magnetic metal material.

[0021] The center yoke 14 is cylindrical, and a magnetic gap G is formed between its outer peripheral surface and the inner peripheral surface of the opposing yoke 12 along a circumference centered on the central axis O. In the magnetic circuit unit 10, the driving magnetic flux F1 generated from the driving magnet 11 travels from the opposing yoke 12 across the magnetic gap G and circulates around the center yoke 14 and the rear yoke 13.

[0022] 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.

[0023] 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 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.

[0024] At the rear end of the bobbin 6, a voice coil 7 is provided on its outer circumferential surface. 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 a magnetic gap G of a magnetic circuit unit 10. The magnetic circuit unit 10 and the voice coil 7 constitute a magnetic drive unit.

[0025] The diaphragm 3 and the bobbin 6 are supported so as to be able to vibrate freely in the front-back direction (Z1-Z2 direction) due to the elastic deformation of the edge member 4 and the damper member 5. The diaphragm 3, the cap 8, the bobbin 6 and the voice coil 7 constitute a vibrating part that vibrates in the front-back direction within the frame 2.

[0026] The speaker 1 is provided with a detection section (vibration detection section) 20 that detects vibration of the movable section. The detection section 20 is composed of a movable magnet 21 and a magnetic sensor 22. The movable magnet 21 is provided on the outer peripheral surface of the bobbin 6, rearward of the bonding location of the inner peripheral section 5b of the damper member 5. The movable magnet 21 is bonded and fixed to the outer peripheral surface of the damper member 5. The magnetic sensor 22 is provided in the space inside the bobbin 6. A base 23 is bonded and fixed to the front end surface 14a of the center yoke 14. The base 23 is a block or plate-shaped material made of a non-magnetic material such as synthetic resin. A wiring board 24 is fixed to the base 23, and the magnetic sensor 22 is mounted on the wiring board 24. The wiring board 24 constitutes a part of the base, and the magnetic sensor 22 is disposed at a position away from the front end surface 14a of the center yoke 14 by these bases. A wiring cable 25 that is electrically connected to the magnetic sensor 22 is connected to the wiring board 24. The wiring cable 25 passes through the inside of the hole 15 of the center yoke 14 and is drawn out to the outside behind the magnetic circuit portion 10.

[0027] 1 and 2 show a cross section of the speaker 1 cut along a plane parallel to the XZ plane including the central axis O. The center of the movable magnet 21 and the center of the magnetic sensor 22 are located in the same cross section including the central axis O. As a result, the driving magnetic flux F1 generated by the magnetic circuit unit 10 acts on the magnetic sensor 22 in the radial direction (X direction). As shown in FIG. 1, the magnetized end face 21a of the movable magnet 21 is oriented in the tangential direction (parallel to the Y direction) of the bobbin 6, and the two end faces 21a are magnetized with polarities opposite to each other. As a result, the movable magnetic flux F2 generated by the movable magnet 21 acts on the magnetic sensor 22 in the approximate tangential direction (parallel to the Y direction) of the bobbin 6.

[0028] The magnetic sensor 22 can detect a change in the direction of the magnetic field, which is a vector quantity, in a plane (a plane parallel to the XY plane) that is perpendicular to the central axis O and passes through the center of the magnetic sensor 22. The driving magnetic flux F1 generated by the magnetic circuit unit 10 acts on the magnetic sensor 22 in the radial direction (X direction). In FIG. 1, the magnetic field, which is a vector quantity acting on the magnetic sensor 22 based on the driving magnetic flux F1, is indicated by H1. The movable magnetic flux F2 generated by the movable magnet 21 acts on the magnetic sensor 22 in the Y direction. In FIG. 1, the magnetic field, which is a vector quantity acting on the magnetic sensor 22 based on the movable magnetic flux F2, is indicated by H2. The magnetic sensor 22 detects the direction of the detection magnetic field Hd, which is a composite vector of the magnetic fields H1 and H2. Since the relative positions of the magnetic sensor 22 and the magnetic circuit unit 10 do not change, the strength of the magnetic field H1 acting on the magnetic sensor 22 does not change. In contrast, the strength of the magnetic field H2 detected by the magnetic sensor 22 changes with the vibration of the movable part in the front-rear direction (Z1-Z2 direction). Therefore, the direction θ (angle in a plane perpendicular to the central axis O) of the detected magnetic field Hd, which is a resultant vector, changes in response to the vibration of the movable part.

[0029] The magnetic sensor 22 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, the magnetic field direction of the free magnetic layer follows the change in the direction of the detection magnetic field Hd, and the electric resistance value changes according to the change in the relative angle between the fixed magnetic field of the fixed magnetic layer and the magnetization of the free magnetic layer. Alternatively, the magnetic sensor 22 can detect the change in the direction θ of the detection magnetic field Hd by arranging two Hall elements so that their detection directions cross each other, preferably orthogonal, in a plane perpendicular to the central axis O. In this case, one Hall element detects the strength of the magnetic field H1, and the other Hall element detects the strength of the magnetic field H2, thereby obtaining a detection output based on the change in the vector direction of the detection magnetic field Hd.

[0030] 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 F1 generated from the magnetic circuit section 10 crosses the voice coil 7, the electromagnetic force excited by the driving magnetic flux F1 and the driving current causes the vibration section including the bobbin 6 and the diaphragm 3 to vibrate in the front-rear direction, generating sound pressure according to the frequency of the driving current and emitting sound forward.

[0031] The control unit attached to the speaker 1 performs feedback control based on the detection output from the magnetic sensor 22. By detecting a change in the direction θ of the detected magnetic field Hd by the magnetic sensor 22, the control unit can know the position of the vibration unit including the diaphragm 3 in the front-rear direction and the change in the position. For example, the control unit calculates the deviation between the ideal position of the vibration unit in the front-rear direction and the change in the position, which is assumed by applying an audio signal, and the actual position of the vibration unit determined from the detection output of the magnetic sensor 22 and the change in the position, and if the deviation exceeds a threshold value, a correction signal (offset signal) for correcting the deviation is generated. The correction signal is superimposed on the drive signal (voice current) given to the voice coil 7, and this feedback control corrects distortion and sound delay of the sound produced by the speaker 1, and further prevents the diaphragm 3 from vibrating excessively in the front-rear direction.

[0032] The magnetic sensor 22 detects the position of the vibration part from the angular change of the vector of the detection magnetic field Hd obtained from both the driving magnetic flux F1 from the magnetic circuit part 10 and the movable magnetic flux F2 from the movable magnet 21. In other words, since the detection output is obtained using the driving magnetic flux F1 from the magnetic circuit part 10, the driving magnetic flux F1 does not interfere with the detection of the position of the movable part, and the driving magnetic flux F1 does not become a source of noise, and feedback control with high precision and high sensitivity can always be performed.

[0033] In the speaker 1 of the first embodiment shown in FIG. 1 and FIG. 2, the magnetic sensor 22 is located in a space surrounded by the bobbin 6. Therefore, the position of the magnetic sensor 22 in the front-rear direction (Z1-Z2 direction) can be freely set to be optimal. For example, by providing a base 23 (the wiring board 24 is also a substantial base), the magnetic sensor 22 can be located at a position away from the front end surface 14a of the center yoke 14 forward, and the distance in the front-rear direction between the magnetic sensor 22 and the movable magnet 21 can be shortened. By shortening this distance, the magnetic sensor 22 can easily detect the moving magnetic flux F2 emitted from the moving magnet 21, and the vibration of the moving part can be detected with high sensitivity. In addition, by arranging the magnetic sensor 22 away from the front end surface 14a of the center yoke 14 forward, the moving magnet 21 can also be arranged away from the magnetic circuit part 10 forward (Z1 direction). Therefore, even if the amplitude of the moving part increases in the front-rear direction, the moving magnet 21 is less likely to hit the magnetic circuit part 10.

[0034] Furthermore, when the magnetic sensor 22 is located within the space surrounded by the bobbin 6 and the movable magnet 21 is located on the outer surface of the bobbin 6, the amplitude of the vibration part becomes large, and even if the movable magnet 21 and the damper member 5 move back significantly to the position shown by (m) in Figure 2, it becomes possible to prevent the movable magnet 21 and the damper member 5 from coming into contact with the magnetic sensor 22.

[0035] From the above, it is possible to increase the amplitude in the front-rear direction of the vibrating part including the diaphragm 3, and it is possible to increase the sound output.

[0036] FIG. 3 shows a speaker 101 according to a second embodiment of the present invention. The speaker 101 is provided with a plurality of magnetic sensors. In this embodiment, two magnetic sensors 22, 32 are provided. The centers of the two magnetic sensors 22, 32 and the center of the movable magnet 21 are located in the same cross section including the central axis O. The magnetic sensors 22 and 32 are supported by the base 23 with an interval therebetween in the front-rear direction (Z1-Z2 direction), and both are disposed at positions forward and away from the front end surface 14a of the center yoke 14.

[0037] In the speaker 101 shown in FIG. 3, the two magnetic sensors 22, 32 arranged at a distance from each other in the front and rear direction can each detect the moving magnetic flux F2 from the moving magnet 21, so that the detection range in the front and rear direction of the moving part can be expanded. Since the magnetic sensor detects the change in the direction θ of the detected magnetic field Hd of the composite vector shown in FIG. 1, when the moving magnet 21 moves far forward from the magnetic sensor and the magnetic field H2 becomes weak, the angle θ indicating the direction of the detected magnetic field Hd becomes almost zero, and the position of the moving magnet 21 moving further forward cannot be detected. In addition, when the moving magnet 21 moves rearward (in the Z2 direction) from the magnetic sensor, the direction of the magnetic field H2 is reversed, so that the magnetic sensor 22 cannot detect the angle θ. Therefore, there is a limit to the range in which the position of the moving magnet 21 in the front and rear direction can be detected by one magnetic sensor. However, by arranging multiple magnetic sensors 22, 32 at a distance from each other in the front and rear direction as shown in FIG. 3, it is possible to ensure a wide detection range in the front and rear direction of the moving part.

[0038] FIG. 4 shows a speaker 201 according to a third embodiment of the present invention. In this speaker 201, a phase plug 41 is fixed in front of the center yoke 14 of the magnetic circuit section. A wiring board 24 is fixed to the phase plug 41, and a magnetic sensor 22 is mounted on the wiring board 24. In this embodiment, the magnetic sensor 22 can be disposed in a position away from the front end 14a of the center yoke 14 forward within the space surrounded by the bobbin 6 without using a base 23 other than the wiring board 24. Note that instead of the phase plug 41, a tweeter can be fixed in front of the center yoke 14, and the magnetic sensor 22 can be fixed to the tweeter.

[0039] In the speaker 201 shown in FIG. 4 as well, a plurality of magnetic sensors 22, 32 can be provided, and a plurality of movable magnets 21 can also be provided. [Explanation of symbols]

[0040] 1,101,201 Speakers 2 Frames 3 Vibration plate 6 Bobbin 7 Voice coil 10 Magnetic circuit section 14 Centre York 15 holes 20 Detection unit 21 Moving Magnet 22,32 Magnetic Sensor 25 Wiring cable 41 Phase Plug F1 Driving magnetic flux F2 moving magnetic flux H1,H2 magnetic field Hd detection magnetic field O center axis

Claims

1. A speaker including a frame, a vibration unit supported by the frame, a magnetic drive unit that drives the vibration unit, and a detection unit that detects the movement of the vibration unit, the vibration section has a vibration plate supported by the frame so as to be capable of vibrating freely and a bobbin fixed to the vibration plate, the magnetic drive section has a voice coil fixed to the bobbin and a magnetic circuit section that forms a magnetic flux that crosses the voice coil, the detection unit has a movable magnet fixed to the vibration unit and a magnetic sensor that detects a magnetic flux emitted from the movable magnet, A speaker characterized in that a base is fixed to an end face of a center yoke that constitutes the magnetic circuit portion, and the magnetic sensor is fixed to the base at a position within the space surrounded by the bobbin and away from the end face.

2. 2. The speaker of claim 1, wherein a hole is formed in a center yoke constituting the magnetic circuit section, penetrating in the front-to-rear direction which is the vibration direction of the vibration section, and a wiring cable connected to the magnetic sensor passes through the hole and is pulled out to the outside of the magnetic circuit section.

3. a direction of the magnetic flux applied from the magnetic circuit portion to the magnetic sensor intersects with a direction of the magnetic flux applied from the movable magnet to the magnetic sensor, 3. The speaker according to claim 1, wherein the magnetic sensor provides a detection output based on a change in the direction of a resultant vector of the two magnetic fluxes.

4. 4. The speaker according to claim 1, wherein the movable magnet is provided on the outside of the bobbin.

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