Speaker

Abstract

To provide a speaker for performing feedback control by detecting a movement state of a movable part including a diaphragm.SOLUTION: In a speaker, a vibration part includes a diaphragm and a bobbin 6 having a voice coil 7, and a partially ring-shaped movable magnet 21 is fixed to an inner peripheral surface 6a of the bobbin 6. A magnetic sensor 22 is arranged in a support part including a frame and a magnetic circuit part. The magnetic sensor 22 detects a fixed magnetic component H1 from a fixed magnetic field generation member (the magnetic circuit part) arranged in the support part, and a movable magnetic field component H2 from the movable magnet 21, so as to measure a vibration position of the vibration part from detection outputs of the two magnetic field components H1, H2.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a speaker capable of detecting the operation of a vibration part having a diaphragm and a voice coil 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] 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 of the conventional technology, and aims to provide a speaker that can detect the vibration of the vibrating part with high accuracy by providing a movable magnetic field generating member in the vibrating part and using a magnetic sensor provided in the support part to detect the movable magnetic field component from the movable magnetic field generating member and the fixed magnetic field component from the fixed magnetic field generating member as magnetic fields in directions that intersect with each other. [Means for solving the problem]

[0009] The present invention provides a speaker including a vibration section having a voice coil and a diaphragm that vibrates together with the voice coil, and a support section to which a magnetic circuit section that applies magnetic flux to the voice coil is fixed, The vibration section is provided with a movable magnetic field generating member having two magnetic pole ends with opposite polarities, the support is provided with a magnetic sensor that detects a fixed magnetic field component directed in a first direction generated from a fixed magnetic field generating member provided on the support and a mobile magnetic field component directed in a second direction generated from the mobile magnetic field generating member as magnetic fields in directions intersecting each other; When viewed in a plane perpendicular to the vibration direction of the vibration unit, The two magnetic pole tips are positioned on either side of a first reference line that extends in a first direction through the magnetic sensor, and each of the magnetic pole tips is positioned equidistant from the first reference line in a second direction.

[0010] In the speaker of the present invention, the vibration section is provided with a cylindrical bobbin around which the voice coil is wound, and the movable magnetic field generating member is disposed in a space inside the bobbin, The two magnetic pole tips may be configured to be disposed at positions farther inwardly of the bobbin than an intersection point between the first reference line and the inner surface of the voice coil.

[0011] In the speaker of the present invention, the two magnetic pole ends are arranged so as to face the center of the bobbin. Through It is preferable that the intersection point is located between a second reference line extending in the second direction and the intersection point.

[0012] Furthermore, in the speaker of the present invention, it is preferable that the two magnetic pole ends are located between a third reference line extending in a second direction through the intersection side end of the sensor substrate on which the magnetic sensor is mounted, and the second reference line.

[0013] In the speaker of the present invention, the movable magnetic field generating member has a partial ring shape that fits along the inner circumferential surface of the bobbin.

[0014] In the speaker of the present invention, the magnetic pole end is a magnetic pole end surface along a radial line extending from the center of the bobbin.

[0015] Alternatively, in the speaker of the present invention, the magnetic pole end is a magnetic pole end surface that is parallel to the second direction.

[0016] Alternatively, in the speaker of the present invention, the magnetic pole tip is a magnetic pole tip surface that is parallel to the first direction.

[0017] In this case, Moving magnetic field generating member It is preferable that a curved portion facing the magnetic sensor is formed on the inner surface of the magnetic pole and a magnetic pole tip surface is formed on an end of the curved portion.

[0018] In other words, in the speaker of the present invention, it is preferable that the magnetic pole tip face, which is the magnetic pole end, is set to any orientation within a range from an orientation along a radial line extending from the center of the bobbin around which the voice coil is wound to an orientation parallel to the first direction.

[0019] The speaker of the present invention may be configured such that the fixed magnetic field generating member also serves as the magnetic circuit section, or the fixed magnetic field generating member may be provided separately from the magnetic circuit section. Effect of the Invention

[0020] The speaker of the present invention detects the moving magnetic field component from the moving magnetic field generating member provided in the vibrating section and the fixed magnetic field component from the fixed magnetic field generating member composed of a magnetic circuit section etc. as magnetic fields that intersect with each other in a magnetic sensor, thereby making it possible to detect the movement of the vibrating section. By detecting the relative change in intensity between the moving magnetic field component and the fixed magnetic field component, the speaker becomes less susceptible to the effects of external noise, and enables highly accurate control to correct the operation of the vibrating section.

[0021] In addition, since the two magnetic pole ends of the movable magnetic field generating member are positioned at a distance on either side of the magnetic sensor in the second direction, the ratio of vector components of the movable magnetic field components acting on the magnetic sensor that face in the second direction increases, making it possible to maintain a high level of linearity between the actual position of the movable magnetic field generating member and the information on the position of the movable magnetic field generating member based on the detection output of the magnetic sensor. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a half-sectional perspective view showing an overall structure of a speaker according to an embodiment of the present invention; [Diagram 2] FIG. 2A is an exploded perspective view showing a bobbin and a movable magnetic field generating member provided in the speaker shown in FIG. 1; FIG. 2B is a perspective view showing the relative positions of the movable magnetic field generating member fixed to the bobbin and a magnetic sensor; [Diagram 3]FIG. 2 is a plan view showing a comparison of the relative positions of a plurality of types of movable magnetic field generating members having different positions of the magnetic pole end and a magnetic sensor on a plane perpendicular to the vibration direction; [Figure 4] FIG. 4 is a diagram showing a comparison of changes in detection output of a magnetic sensor when different types of movable magnetic field generating members shown in FIG. 3 are used; [Diagram 5] FIG. 4 is an explanatory diagram showing a simulation comparing the distribution of magnetic field lines when magnet A, magnet D, and magnet H are used among the multiple types of movable magnets shown in FIG. 3; [Figure 6] FIG. 2 is a plan view showing a comparison of the relative positions of a plurality of types of movable magnetic field generating members having different orientations of magnetic pole ends and a magnetic sensor; [Figure 7] FIG. 7 is a diagram showing a comparison of changes in detection output of the magnetic sensor when each of the movable magnets shown in FIG. 6 is used; [Figure 8] FIG. 7 is an explanatory diagram showing a simulation comparing changes in magnetic field lines when the multiple types of movable magnets shown in FIG. 6 are used; [Figure 9] FIG. 13 is a plan view showing a modified example of the movable magnetic field generating member; [Figure 10] FIG. 13 is a plan view showing a modified example of the movable magnetic field generating member; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] In the speaker 1 of the first embodiment of the present invention shown in FIG. 1, the Z1-Z2 direction is the front-rear direction, with the Z1 direction being the front and the Z2 direction being the rear. Either the Z1 direction or the Z2 direction is the main sound-producing direction. The Z1-Z2 direction is the vibration direction of the vibration part. FIG. 1 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. FIG. 1 also 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-direction is the first direction, and the Y-direction is the second direction.

[0024] The speaker 1 shown in Fig. 1 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."

[0025] 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 forward (Z1 direction) from the rear yoke 13. 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 formed of a magnetic material, i.e., a soft magnetic metal material.

[0026] 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 Fd generated from the driving magnet 11 traverses the magnetic gap G from the opposing yoke 12 and circulates around the center yoke 14 and the rear yoke 13. In this speaker 1, the magnetic circuit unit 10 functions as a "fixed magnetic field generating member," and a leakage magnetic field from the magnetic circuit unit 10 is detected as a fixed magnetic field component H1 acting on a magnetic sensor 22, which will be described later, in a first direction (X direction).

[0027] 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.

[0028] 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.

[0029] As shown in Fig. 2, 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 that constitutes the voice coil 7 is wound a predetermined number of turns on the outer circumferential surface of the bobbin 6. As shown in Fig. 1, the voice coil 7 is located within the magnetic gap G of the magnetic circuit unit 10. The magnetic circuit unit 10 and the voice coil 7 constitute a magnetic drive unit.

[0030] 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. 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. The Z1-Z2 direction is the vibration direction of the "vibration part".

[0031] The speaker 1 is provided with a detection section (vibration detection section) that detects vibration of the movable section. The detection section is composed of a movable magnet 21 provided in the space inside the front end of the bobbin 6 constituting the "vibration section", a magnetic sensor 22 provided in the "support section", and a magnetic circuit section 10. The movable magnet 21 functions as a "movable magnetic field generating member", and the magnetic circuit section 10 functions as a "fixed magnetic field generating member". Leakage magnetic flux from the magnetic circuit section 10, which is a fixed magnetic field generating member, acts on the magnetic sensor 22. As shown in FIG. 1 and FIG. 2(B), the magnetic sensor 22 mainly detects the intensity of the fixed magnetic field component H1 acting in the first direction (X direction) of the magnetic field of the leakage magnetic flux. In addition, leakage magnetic flux from the movable magnet 21, which is a movable magnetic field generating member, acts on the magnetic sensor 22. The magnetic sensor 22 mainly detects the intensity of the mobile magnetic field component H2 acting in the second direction (Y direction) of the magnetic field of the leakage magnetic flux. In addition, as the "fixed magnetic field generating member", a fixed magnet separate from the driving magnet 11 of the magnetic circuit section 10 may be provided in close proximity to the magnetic sensor 22, and the component of the magnetic field emitted from this fixed magnet that faces the first direction (X direction) may be detected by the magnetic sensor 22 as the fixed magnetic field component H1.

[0032] As shown in FIG. 1, the magnetic sensor 22 constituting the detection unit is provided in the space inside the bobbin 6. A base 27 is adhered and fixed to the front end surface 14a of the center yoke 14. The base 27 is in the shape of a block made of a non-magnetic material such as synthetic resin. A sensor board 28 is fixed to the front surface of the base 27, and the magnetic sensor 22 is mounted on the front surface of the sensor board 28. A wiring cable 25 that is electrically connected to the magnetic sensor 22 is connected to the sensor board 28. The wiring cable 25 passes through a hole formed in the center of the base 27 and the inside of the hole 15 of the center yoke 14, and is drawn out to the outside behind the magnetic circuit unit 10.

[0033] 2 shows the movable magnet 21 that functions as a movable magnetic field generating member. The movable magnet 21 has a partial ring shape that fits along the inner peripheral surface 6a of the bobbin 6, that is, a curved shape that forms part of a ring. The curvature of the outer peripheral surface of the movable magnet 21 almost matches the curvature of the inner peripheral surface 6a of the bobbin 6, and the movable magnet 21 is joined to the inner peripheral surface 6a without any gaps and fixed with an adhesive.

[0034] The movable magnet 21, which is a movable magnetic field generating member, is provided with two magnetic pole ends 21a and 21b. The movable magnet 21 shown in FIG. 2 is formed entirely of a material that becomes a magnet, i.e., a hard magnetic material, and the magnetic pole ends 21a and 21b are magnetized magnetic pole end surfaces, i.e., magnetized surfaces. The magnetic pole end 21a and the magnetic pole end 21b have opposite polarities, with the magnetic pole end 21a being the N pole and the magnetic pole end 21b being the S pole. FIG. 9 shows a modified movable magnetic field generating member 21A. This movable magnetic field generating member 21A has a partial ring shape. The movable magnetic field generating member 21A has a permanent magnet 121 and two yokes 122 and 123. The yokes 122 and 123 are formed of a soft magnetic material that is iron or an alloy mainly made of iron. The yoke 122 is joined to the N pole magnetized surface of the permanent magnet 121, and the yoke 123 is joined to the S pole magnetized surface of the permanent magnet 121. As a result, the other end of yoke 122 becomes N-pole magnetic pole end (magnetic pole end surface) 21a, and the other end of yoke 123 becomes S-pole magnetic pole end (magnetic pole end surface) 21b.

[0035] 2(A) and (B), the balancer 23 is adhered and fixed to the inner peripheral surface 6a of the front end of the bobbin 6 together with the movable magnet 21. The balancer 23 is preferably made of a non-magnetic material. The balancer 23 made of a non-magnetic material is preferably shaped to be in contact with the movable magnet 21 so that no gap is formed between the balancer 23 and the magnetic pole ends 21a, 21b of the movable magnet 21.

[0036] 2B shows the first reference line L1. In a plan view projected onto a plane (XY plane) perpendicular to the front-rear direction (Z1-Z2 direction) which is the vibration direction of the vibration part, the first reference line L1 is a virtual line extending in the first direction (X direction) through the magnetic sensor 22. It is preferable that the first reference line L1 is set as a virtual line passing through the center of the magnetic sensor 22, i.e., the center of the sensing part of the magnetic sensor 22. In the plan view, the two magnetic pole ends 21a, 21b of the movable magnet 21 are located on both sides of the first reference line L1, and the magnetic pole end 21a and the magnetic pole end 21b are located at the same distance from the first reference line L1 in the second direction (Y direction).

[0037] 1 is a cross-sectional view of the speaker 1 cut in an XZ plane including the central axis O. The center of the magnetic sensor 22 and a first reference line L1 shown in FIG. 2(B) are located in the same cross section including the central axis O. The magnetic circuit section 10 constitutes a fixed magnetic field generating member, and a part of the leakage magnetic flux appearing in front of the magnetic circuit section 10 among the driving magnetic flux Fd circulating inside the magnetic circuit section 10 acts on the magnetic sensor 22 as a fixed magnetic field. In addition, a part of the leakage magnetic flux appearing between the magnetic pole end 21a and the magnetic pole end 21b of the movable magnet 21, which is a movable magnetic field generating member, acts on the magnetic sensor 22 as a movable magnetic field.

[0038] The magnetic sensor 22 can detect the intensity of the magnetic field in the first direction (X direction) and the change in the intensity of the magnetic field in the second direction (Y direction) in the XY plane. Therefore, the magnetic sensor 22 can detect the intensity of the fixed magnetic field component H1 acting in the first direction (X direction) due to the leakage magnetic flux from the magnetic circuit unit 10, and the intensity of the mobile magnetic field component H2 acting in the second direction (Y direction) due to the leakage magnetic flux from the movable magnet 21. Since the relative position between the magnetic sensor 22 and the magnetic circuit unit 10 does not change, the intensity of the fixed magnetic field component H1 acting on the magnetic sensor 22 is basically constant. On the other hand, since the movable magnet 21 is provided in the vibration unit and vibrates in the Z1-Z2 direction together with the bobbin 6 during sound generation, the intensity of the mobile magnetic field component H2 acting on the magnetic sensor 22 always changes according to the change in the distance between the movable magnet 21 and the magnetic sensor 22. As a control operation by the control unit associated with the speaker 1, the change in the position of the movable magnet 21, i.e., the change in the position of the vibrating unit, can be known from the ratio of the intensity of the fixed magnetic field component H1 to the intensity of the moving magnetic field component H2 detected by the magnetic sensor 22. By using the relative value of the intensity of the fixed magnetic field component H1 to the intensity of the moving magnetic field component H2, highly accurate vibration detection that is less susceptible to the effects of external noise is possible.

[0039] 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. In the GMR element or the TMR element, the magnetization direction of the fixed magnetic layer is fixed, the magnetization direction of the free magnetic layer changes according to the magnetic field acting from the outside, and the electric resistance value changes according to the change in the relative angle between the fixed magnetization direction of the fixed magnetic layer and the magnetization direction of the free magnetic layer. As shown in FIG. 2B, when the fixed magnetic field component H1 and the mobile magnetic field component H2 act on the magnetic sensor 22, the magnetization direction of the free magnetic layer changes to match the direction of the detection magnetic field Hd, which is the composite vector of the fixed magnetic field component H1 and the mobile magnetic field component H2. The intensity of the fixed magnetic field component H1 is almost constant, and the intensity of the mobile magnetic field component H2 changes according to the position of the mobile magnet 21 in the front-rear direction (Z1-Z2 direction), so that the angle θ of the detection magnetic field Hd changes according to the change in the position of the mobile magnet 21. By detecting the change in the electrical resistance value of the magnetoresistance effect element, it is possible to know the change in angle θ of the detected magnetic field Hd, and thus to know the change in the forward / backward position of the movable magnet 21. When the magnetic sensor 22 is composed of a magnetoresistance effect element, it is possible to know the relative strength ratio between the fixed magnetic field component H1 and the movable magnetic field component H2 by detecting the change in the angle θ.

[0040] The magnetic sensor 22 can be configured with elements other than magnetoresistance effect elements as long as it can detect the strength of the magnetic field in the first direction (X direction) and the strength of the magnetic field in the second direction (Y direction). For example, the magnetic sensor 22 may include two Hall elements. One Hall element has a directivity that can detect the change in the magnetic field strength in the first direction (X direction), and the other Hall element has a directivity that can detect the change in the magnetic field strength in the second direction (Y direction). These two Hall elements can detect the strength of the fixed magnetic field component H1 facing the first direction and the strength of the movable magnetic field component H2 facing the second direction, and the change in the position of the movable magnet 21 in the front-rear direction can be detected from the ratio of the two intensities.

[0041] 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 Fd generated from the magnetic circuit unit 10 crosses the voice coil 7, the vibration unit including the bobbin 6 and the diaphragm 3 vibrates in the front-rear direction due to an electromagnetic force excited by the driving magnetic flux Fd and the driving current, generating a sound pressure according to the frequency of the driving current and emitting sound forward or backward.

[0042] The control unit attached to the speaker 1 performs feedback control based on the detection output from the magnetic sensor 22. By obtaining a detection output based on the change in angle θ in the plane of the detection magnetic field Hd from the magnetic sensor 22, or by obtaining the ratio of the intensity of the fixed magnetic field component H1 to the intensity of the movable magnetic field component H2, the control unit can obtain information on the position in the front-rear direction of the vibration unit including the diaphragm 3 and its change. For example, the control unit calculates the deviation between the ideal position in the front-rear direction of the vibration unit and its change, which is assumed by applying an audio signal, and the actual position of the vibration unit and its change, which is determined from the detection output of the magnetic sensor 22, 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 deviation of the sound produced by the speaker 1, and further prevents the diaphragm 3 from vibrating excessively in the front-rear direction.

[0043] The magnetic sensor 22 detects the change in the position of the vibrating part based on the relative strength ratio between the fixed magnetic field component H1 due to the leakage magnetic flux from the magnetic circuit part 10 which is a fixed magnetic field generating member, and the mobile magnetic field component H2 due to the leakage magnetic flux from the mobile magnetic field generating member. Therefore, it is possible to perform highly accurate feedback control which is less susceptible to the influence of external noise.

[0044] Next, a description will be given of the relationship between the shape of the movable magnet 21, i.e., the positions and orientations of the magnetic pole ends 21a and 21b, and the detection output from the magnetic sensor 22. In the following, the movable magnet 21 will be described as an example of the movable magnetic field generating member, but the relationship between the positions and orientations of the magnetic pole ends 21a and 21b, and the detection output from the magnetic sensor 22 is the same when the movable magnetic field generating member 21A composed of the permanent magnet 121 and yokes 122 and 123 shown in FIG.

[0045] 3 shows the relative positions of multiple types of movable magnets 21 with different dimensions and magnetic sensors 22 in a plan view projected onto an XY plane perpendicular to the central axis O. FIG. 3 also shows an intersection P between a first reference line L1 extending in a first direction (X direction) passing through the center of the magnetic sensor 22 and an inner peripheral surface 6a of the bobbin 6. FIG. 3 shows magnet A as a comparative example. Magnet A of the comparative example is magnet 221 having a rectangular planar shape. In this magnet 221, magnetized surface 221a magnetized to the N pole and magnetized surface 221b magnetized to the S pole are parallel to the first direction (X direction) and parallel to the XZ plane.

[0046] The magnets B, C, D, E, F, G, and H shown in Fig. 3 are partial ring-shaped movable magnets 21 according to an embodiment of the present invention, each having a different circumferential length and different positions of the magnetic pole ends 21a and 21b. In Fig. 3, the symbols B, C, D, E, F, G, and H indicating the difference in the length of the magnet are written near the magnetic pole end 21b of each movable magnet 21. The magnetic pole ends 21a and 21b of the magnets B, C, D, E, F, G, and H are magnetic pole end surfaces along a radial line R extending in the radial direction around the central axis O located at the center of the bobbin 6. In other words, the magnetic pole ends 21a and 21b are magnetic pole end surfaces formed along a plane including the respective radial lines R and the Z axis.

[0047] In FIG. 3, the positions of the edges of the magnetic pole ends 21a and 21b of the movable magnets 21 classified as B, C, D, E, F, G, and H facing the intersection point P are indicated by b, c, d, e, f, g, and h. All of b, c, d, e, f, g, and h are located farther away from the intersection point P toward the inside of the bobbin 6 in the first direction (X direction). That is, all of the magnetic pole ends 21a and 21b of the movable magnets 21 classified as B, C, D, E, F, G, and H are located farther away from the intersection point P toward the inside of the bobbin 6 in the first direction. Also, the magnetic pole ends 21a and 21b are located farther away from the magnetized surfaces 221a and 221b of the magnet A of the comparative example toward the inside of the bobbin 6 in the first direction. Therefore, the ratio of vector components in the second direction (Y direction) of the magnetic field acting on the magnetic sensor 22 due to the leakage magnetic flux from the magnetic pole end 21a to the magnetic pole end 21b of each of the movable magnets 21 classified as B, C, D, E, F, G, and H is higher than the ratio of vector components in the second direction (Y direction) of the magnetic field acting on the magnetic sensor 22 due to the leakage magnetic flux from the magnetized surface 221a to the magnetized surface 221b of magnet A, which is the comparative example.

[0048] In addition, the magnetized surfaces 221a and 221b of the magnet A as the comparative example are parallel to the first reference line L1, whereas the magnetic pole end 21a of each of the movable magnets 21 classified as B, C, D, E, F, G, and H is inclined clockwise from the magnetized surface 221a of the magnet A in a plan view, and the magnetic pole end 21b is inclined counterclockwise from the magnetized surface 221b of the magnet A. That is, the magnetic pole end 21a and 21b of the movable magnets 21 are inclined so as to rotate along the circumference of the bobbin 6. This also makes the ratio of the vector component in the second direction (Y direction) of the magnetic field acting on the magnetic sensor 22 by the leakage magnetic flux from the magnetic pole end 21a toward the magnetic pole end 21b of each movable magnet 21 higher than the ratio of the vector component in the second direction (Y direction) of the magnetic field acting on the magnetic sensor 22 by the leakage magnetic flux from the magnetized surface 221a toward the magnetized surface 221b of the magnet A as the comparative example.

[0049] 5 shows the results of a simulation of the direction and distribution of magnetic field lines due to leakage magnetic flux from a magnet, as viewed on an XY plane including the magnetic sensor 22. (A-1) shows the distribution of magnetic field lines when magnet A, which is a comparative example, is used, and (A-2) shows an enlarged view of the area of ​​the magnetic sensor 22 in the distribution of (A-1). (B-1) shows the distribution of magnetic field lines when the movable magnet 21 of the embodiment shown by D in FIG. 3 is used, and (B-2) shows an enlarged view of the area of ​​the magnetic sensor 22 in the distribution of (B-1). (C-1) shows the distribution of magnetic field lines when the movable magnet 21 of the embodiment shown by H in FIG. 3 is used, and (C-2) shows an enlarged view of the area of ​​the magnetic sensor 22 in the distribution of (C-1).

[0050] 5, in speaker 1 using movable magnet 21 of the embodiment of the present invention, the ratio of vector components in the second direction (Y direction) of the magnetic field acting on magnetic sensor 22 due to leakage magnetic flux from magnetic pole end 21a to magnetic pole end 21b of movable magnet 21 is higher than when magnet A of the comparative example is used. This improves the detection accuracy of magnetic sensor 22. In addition, the linearity of the change in detection output of magnetic sensor 22 when movable magnet 21 moves in the front-back direction (Z1-Z2 direction) together with the vibration part can be maintained with high accuracy.

[0051] 4 shows a diagram illustrating the relationship between the position of the magnet and the information on the position of the magnet detected by the magnetic sensor 22 in the speaker 1 using the magnet A of the comparative example and the movable magnet 21 of each embodiment classified as B, C, D, E, F, G, and H. The horizontal axis shows the distance that the movable magnet moves forward to +10 mm and the distance that it moves backward to -10 mm, with the neutral support position of the bobbin 6 set to zero, and the vertical axis shows the position information of the movable magnet 21 detected by the magnetic sensor 22. FIG. 4 shows the simulation results when the magnetization amount of each magnet classified as A, B, C, D, E, F, G, and H is 0.2 T, and the magnetization amount of the drive magnet 11 of the magnetic circuit unit 10, which is a fixed magnetic field generating member, is 0.4 T.

[0052] 4, it can be seen that when magnet A, which serves as a comparative example, is used, it is difficult to ensure linearity between the actual change in magnet position and the change in magnet position information detected by magnetic sensor 22. On the other hand, it can be seen that in a speaker using magnets B, C, D, E, F, G, and H, which are movable magnet 21 according to an embodiment of the present invention, the linearity between the actual change in magnet position and the change in magnet position information detected by magnetic sensor 22 can be significantly improved compared to when magnet A, which serves as a comparative example, is used.

[0053] According to the simulation results in Fig. 4, when the movable magnets 21 classified as G and H are used, the linearity is improved, but the rate of change of the magnet position information detected by the magnetic sensor 22 decreases with respect to the rate of change of the actual magnet position, and the detection sensitivity of the magnetic sensor 22 is effectively reduced. This is expected to be because, as shown in Figs. 5(C-1) and (C-2), the magnetic pole ends 21a and 21b approach each other at a position distant from the magnetic sensor 22, so that the magnetic flux density is high at the opposing portion between the magnetic pole ends 21a and 21b, and the magnetic flux density in the vicinity of the magnetic sensor 22 decreases accordingly. On the other hand, in the speaker 1 using the movable magnets 21 classified as B, C, D, E, and F, the linearity of the detection output is excellent, and the detection sensitivity of the magnetic sensor 22 is also relatively high.

[0054] 3, it is necessary that the two magnetic pole ends 21a, 21b are located between a second reference line L2 extending in a second direction (Y direction) passing through the center O of the bobbin 6 and the intersection P, on the premise that the magnetic sensor 22 is located between an intersection P between the first reference line L1 and the inner peripheral surface of the bobbin 6 and the center O of the bobbin 6. In addition, to obtain the movable magnet 21 classified into B, C, D, E, F, it is necessary that the two magnetic pole ends 21a, 21b are located between the second reference line L2 and the third reference line L3 when a virtual line extending in the second direction passing through an end of the sensor substrate 28 facing the intersection P is defined as a third reference line L3, or a virtual line extending in the second direction passing through an end of the magnetic sensor 22 facing the intersection P is defined as a third reference line L3. 4, speakers using moving magnets 21 classified as B, C, D, and E are better in both linearity of detection output and sensitivity. In order to obtain moving magnets 21 classified as B, C, D, and E, it is necessary that the two magnetic pole ends 21a, 21b and the magnetic sensor 22 are both located between the second reference line L2 and the intersection point P, and that the two magnetic pole ends 21a, 21b are disposed in positions substantially opposite the magnetic sensor 22 in the second direction (Y direction).

[0055] FIG. 6 shows a further modified example of the movable magnet 21. FIG. 6(A) shows a magnet D. This magnet D is the same as the one classified in FIG. 3. The movable magnet 21 shown by the magnet D has magnetic pole ends 21a and 21b that are magnetic pole end surfaces formed along a radial line R extending from the center O of the bobbin 6. The magnet J shown in FIG. 6(B) has a relative position between the magnetic pole ends 21a and 21b and the magnetic sensor 22 that is almost the same as that of the magnet D. However, in the magnet J, the magnetic pole ends 21a and 21b are parallel to the second direction (Y direction). That is, the magnetic pole ends 21a and 21b are magnetic pole end surfaces that are parallel to the YZ plane. The magnet K shown in FIG. 6(C) and the magnet L shown in FIG. 6(D) are both formed at positions where the magnetic pole ends 21a and 21b face the magnetic sensor 22 from the second direction (Y direction). In addition, in magnets K and L, magnetic pole ends 21a and 21b are parallel to the first direction (X direction). That is, magnetic pole ends 21a and 21b are magnetic pole end surfaces parallel to the XZ plane. Furthermore, in magnet L shown in Fig. 6(D), curved portions 21c and 21d bent toward magnetic sensor 22 are formed at both ends of partial ring-shaped movable magnet 21, and magnetic pole ends 21a and 21b are end faces of curved portions 21c and 21d.

[0056] Fig. 7 shows a diagram illustrating the positions of magnets and the information on the positions of magnets detected by magnetic sensor 22 in speaker 1 using movable magnets 21 classified as D, J, K, and L. Fig. 7 is the same diagram as Fig. 4, but the range of the vertical axis of Fig. 7 is slightly enlarged compared to the vertical axis of Fig. 4. Fig. 8 is an explanatory diagram similar to Fig. 5, simulating the direction and distribution of magnetic field lines due to leakage magnetic flux acting on magnetic sensor 22 in the XY plane including magnetic sensor 22. Fig. 8(A) shows the distribution of magnetic field lines of magnet D, and Figs. 8(B), (C), and (D) show the distribution of magnetic field lines of magnets J, K, and L, respectively.

[0057] The simulation results in FIG. 7 show that the speaker 1 using the moving magnet 21 classified as D, J, or L has excellent linearity in the change in the information on the position of the moving magnet 21 detected by the magnetic sensor 22 with respect to the change in the position of the moving magnet 21 in the forward / rearward direction, and has high detection sensitivity. As a result, the detection output of the magnet K is reversed when the moving magnet 21 approaches the magnetic sensor 22. As shown in FIG. 8(C), the magnet K has a high density of magnetic flux that is attracted from the magnetic pole ends 21a and 21b parallel to the first direction (X direction) to the ring-shaped portion of the moving magnet 21. Therefore, it can be predicted that when the magnet K approaches the magnetic sensor 22, the magnetic flux that is attracted by being wound in the ring-shaped portion affects the detection portion of the magnetic sensor 22.

[0058] From the simulation results shown in Fig. 7, it is preferable that the orientation of the magnetic pole end surface which becomes the magnetic pole ends 21a and 21b starts from a plane parallel to the radial line R extending from the center O shown in Fig. 6(A), tilts toward the magnetic sensor 22, becomes a surface parallel to the second direction (Y direction) shown in Fig. 6(B), and further, is set to be oriented at any angle within the range of rotation angles until it becomes a surface parallel to the first direction (X direction) and facing the magnetic sensor 22 as shown in Fig. 6(C) and (D). In addition, when the magnetic end surface is parallel to the first direction (X direction), it is preferable that curved portions 21c and 21d are formed at both ends of the movable magnet 21 as shown in Fig. 6(D).

[0059] In addition, in the present invention, the planar shape of the movable magnet may be U-shaped or V-shaped as long as the positions of the magnetic pole tips 21a and 21b and the orientation of the magnetic pole tip faces are the same as those of the magnets B, C, D, E, F, G, H, J, K, and L in the above-mentioned embodiments. Also, as shown in Fig. 10, movable magnets 221A and 221B having symmetrical shapes may be arranged on both sides of the magnetic sensor 22 in a plan view seen on a plane perpendicular to the central axis O. In this case, in the second direction (Y direction), the magnetic pole tips of the movable magnets 221A and 221B are located with the same polarity, and the movable magnets 221A and 221B are arranged symmetrically in the first direction (X direction) with the magnetic sensor 22 in between. [Explanation of symbols]

[0060] 1 Speaker 2 Frames 3 Vibration plate 6 Bobbin 7 Voice coil 10 Magnetic circuit section (fixed magnetic field generating component) 11 Drive magnet 12 opposing yoke 13 Rear Yoke 14 Centre York 21 Movable magnet (movable magnetic field generating component) 21a,21b magnetic pole tip 21A Movable magnetic field generating member 22 Magnetic Sensor 28 Sensor board Fd Driving magnetic flux H1 Fixed magnetic field component H2 Mobile magnetic field component Hd detection magnetic field L1 1st reference line L2 Second Reference Line L3 3rd reference line O center axis P intersection

Claims

1. A speaker including a vibration section having a voice coil and a diaphragm that vibrates together with the voice coil, and a support section to which a magnetic circuit section that applies a magnetic flux to the voice coil is fixed, The vibrating section is provided with a movable magnetic field generating member having two magnetic pole ends with opposite polarities, a magnetic sensor is provided on the support portion to detect a fixed magnetic field component in a first direction generated from a fixed magnetic field generating member provided on the support portion and a movable magnetic field component in a second direction generated from the movable magnetic field generating member as magnetic fields in directions intersecting each other; When viewed in a plane perpendicular to the vibration direction of the vibration unit, A speaker characterized in that the two magnetic pole ends are arranged on either side of a first reference line extending in a first direction through the magnetic sensor, and each of the magnetic pole ends is positioned equidistant from the first reference line in a second direction.

2. the vibration section is provided with a cylindrical bobbin around which the voice coil is wound, and the movable magnetic field generating member is disposed in a space inside the bobbin, 2. The speaker according to claim 1, wherein the two magnetic pole tips are disposed at positions toward the inside of the bobbin away from an intersection of the first reference line and the inner surface of the voice coil.

3. 3. The speaker according to claim 2, wherein the two magnetic pole tips are located between the intersection point and a second reference line that passes through the center of the bobbin and extends in a second direction.

4. A speaker as described in claim 3, wherein the two magnetic pole ends are located between a third reference line extending in a second direction through the intersection side end of the sensor substrate on which the magnetic sensor is mounted and the second reference line.

5. 5. The speaker according to claim 2, wherein the movable magnetic field generating member is in the shape of a partial ring that fits along the inner circumferential surface of the bobbin.

6. 6. A speaker according to claim 1, wherein the magnetic pole end is a magnetic pole end surface along a radial line extending from the center of a bobbin around which a voice coil is wound.

7. 6. The speaker according to claim 1, wherein the magnetic pole tip is a magnetic pole tip surface parallel to the second direction.

8. 6. The speaker according to claim 1, wherein the magnetic pole tip is a magnetic pole tip surface parallel to a first direction.

9. 9. The speaker according to claim 8, wherein the movable magnetic field generating member is formed with a curved portion facing the magnetic sensor, and a magnetic pole tip surface is formed at an end of the curved portion.

10. A speaker as described in any one of claims 1 to 5, wherein the magnetic pole end surface, which is the magnetic pole end, is set in any direction within a range from an orientation along a radial line extending from the center of a bobbin around which the voice coil is wound to an orientation parallel to a first direction.

11. 11. The speaker according to claim 1, wherein a fixed magnetic field generating member is also used as the magnetic circuit portion.

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