JP7650606B2 - Speaker - Google Patents

Description

The present invention relates to a speaker that can detect the operation of a vibration part having a diaphragm and a voice coil using a magnetic sensor.

Conventional speakers in audio equipment simply accept the audio signal output from the amplifier and process it to reproduce sound pressure, but the speaker itself does not perform control operations in accordance with the audio signal. This makes it easy for distortion to occur in the sound produced, and the sound quality is prone to variation. Furthermore, when the amplitude of the diaphragm becomes excessive, the diaphragm or damper can be damaged.

To solve the above problem, Patent Document 1 describes a speaker system that uses a magnetic sensor to detect the movement of the diaphragm and perform feedback control.

This speaker system has a plate that constitutes a magnetic circuit section, and a Hall element, which is a magnetic sensor, is supported on the part of this plate facing the voice coil. 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 drive 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, correcting the distortion of the drive current applied to the voice coil.

Japanese Unexamined Patent Publication No. 57-184397

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

In addition, the speaker system of Patent Document 1 has a structure in which the Hall element is embedded in the part of the plate facing the voice coil, so the mounting structure for the Hall element is complicated and the assembly work is inefficient.

The present invention aims to solve the above-mentioned problems of the conventional technology by providing 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.

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 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,
The two magnetic pole tips are positioned on either side of a first reference line extending 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.

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 a position farther toward the inside of the bobbin than an intersection of the first reference line and the inner surface of the voice coil.

In the speaker of the present invention, it is preferable that 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.

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

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

In the speaker of the present invention, the magnetic pole end is a magnetic pole end surface that follows a radial line extending from the center of the bobbin.

Or, in the speaker of the present invention, the magnetic pole end is a magnetic pole end surface that is parallel to the second direction.

Alternatively, in the speaker of the present invention, the magnetic pole end is a magnetic pole end surface that is parallel to the first direction.

In this case, it is preferable that the movable magnetic field generating member is formed with a curved portion facing the magnetic sensor, and that a magnetic pole tip surface is formed at an end of the curved portion.

In other words, in the speaker of the present invention, it is preferable that the magnetic pole end surface, 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.

The speaker of the present invention can be configured, for example, so that the fixed magnetic field generating member also serves as the magnetic circuit section. Alternatively, the fixed magnetic field generating member can be provided separately from the magnetic circuit section.

The speaker of the present invention detects the moving magnetic field component from the moving magnetic field generating member provided in the vibrating part and the fixed magnetic field component from the fixed magnetic field generating member composed of a magnetic circuit part or the like as magnetic fields that intersect with each other in a magnetic sensor, making it possible to detect the movement of the vibrating part. 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, making it possible to perform highly accurate control to correct the operation of the vibrating part.

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 acting on the magnetic sensor that face in the second direction increases, making it possible to maintain a high degree 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.

FIG. 1 is a half-sectional perspective view showing an overall structure of a speaker according to an embodiment of the present invention; 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; 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; FIG. 4 is a diagram showing a comparison of changes in detection output of the magnetic sensor when different types of movable magnetic field generating members shown in FIG. 3 are used; FIG. 4 is an explanatory diagram showing a simulation comparing distributions 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; 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; FIG. 7 is a diagram showing a comparison of changes in detection output of the magnetic sensor when the respective movable magnets shown in FIG. 6 are used; 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; FIG. 13 is a plan view showing a modified example of the movable magnetic field generating member; FIG. 13 is a plan view showing a modified example of the movable magnetic field generating member;

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 generation direction. The Z1-Z2 direction is also the vibration direction of the vibration part. A central axis O extending in the front-rear direction (Z1-Z2 direction) is shown in FIG. 1. The main part of the speaker 1 has a structure that is almost rotationally symmetrical about the central axis O. An X-axis and a Y-axis that are perpendicular to each other on a plane perpendicular to the central axis O are shown in FIG. 1. The X-direction is the first direction, and the Y-direction is the second direction.

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, screwing, or other means. The frame 2 and the magnetic circuit section 10 form a "support section."

The magnetic circuit unit 10 has a ring-shaped drive magnet 11 centered on the central axis O, a ring-shaped opposing yoke 12 joined to the front of the drive magnet 11, and a rear yoke 13 joined to the rear of the drive magnet 11. A center yoke 14 is integrally formed with the rear yoke 13. The center yoke 14 is located inside the drive 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 center yoke 14 may be joined. A hole 15 is formed in the center yoke 14, penetrating in the front-rear direction (Z1-Z2 direction). The opposing yoke 12, rear yoke 13, and center yoke 14 are formed of a magnetic material, i.e., a soft magnetic metal material.

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 the leakage magnetic field from the magnetic circuit unit 10 is detected as a fixed magnetic field component H1 acting on the magnetic sensor 22 (described later) in a first direction (X direction).

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

A bobbin 6 is provided inside the frame 2. The bobbin 6 has a cylindrical shape centered on the central axis O. The inner peripheral end 3b of the diaphragm 3 is fixed to the outer peripheral surface of the bobbin 6 with adhesive, and the inner peripheral portion 5b of the damper member 5 is also fixed to the outer peripheral surface of the bobbin 6 with 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 the peripheral portion 8a of the cap 8 is fixed to the front surface of the diaphragm 3 with adhesive.

As shown in FIG. 2, a voice coil 7 is provided on the outer peripheral surface of the rear end 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 peripheral 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 section 10. The magnetic circuit section 10 and the voice coil 7 constitute the magnetic drive section.

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 form a "vibration part" that vibrates in the front-to-back direction relative to the "support part" that includes the frame 2. The Z1-Z2 direction is the vibration direction of the "vibration part".

The speaker 1 is provided with a detection unit (vibration detection unit) that detects the vibration of the movable part. The detection unit is composed of a movable magnet 21 provided in the space inside the front end of the bobbin 6 constituting the "vibration part", a magnetic sensor 22 provided in the "support part", and a magnetic circuit unit 10. The movable magnet 21 functions as a "movable magnetic field generating member", and the magnetic circuit unit 10 functions as a "fixed magnetic field generating member". Leakage magnetic flux from the magnetic circuit unit 10, which is a fixed magnetic field generating member, acts on the magnetic sensor 22. As shown in Figures 1 and 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 this 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 this leakage magnetic flux. In addition, as the "fixed magnetic field generating member," a fixed magnet separate from the drive magnet 11 of the magnetic circuit unit 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.

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 glued and fixed to the front end surface 14a of the center yoke 14. The base 27 is a block shape 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 conductive 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.

Figure 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, i.e., a curved shape that forms part of a ring. The curvature of the outer peripheral surface of the movable magnet 21 is approximately the same as the curvature of the inner peripheral surface 6a of the bobbin 6, and the movable magnet 21 is bonded to the inner peripheral surface 6a without any gaps and fixed with an adhesive.

The movable magnet 21, which is a movable magnetic field generating member, has two magnetic pole ends 21a and 21b. The movable magnet 21 shown in FIG. 2 is formed of a material that becomes a magnet in its entirety, 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 the N pole end (magnetic pole end surface) 21a, and the other end of yoke 123 becomes the S pole end (magnetic pole end surface) 21b.

As shown in Figures 2(A) and (B), the balancer 23 is glued and fixed to the inner circumferential 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 so that it is in contact with the movable magnet 21 so that no gap is formed between the magnetic pole ends 21a and 21b of the movable magnet 21.

The first reference line L1 is shown in FIG. 2(B). In a plan view projected onto a plane (X-Y 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 either side of the first reference line L1, and the magnetic pole ends 21a and 21b are located equidistant from the first reference line L1 in the second direction (Y direction).

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

The magnetic sensor 22 can detect the strength of the magnetic field in the first direction (X direction) and the change in the strength of the magnetic field in the second direction (Y direction) in the X-Y plane. Therefore, the magnetic sensor 22 can detect the strength 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 strength 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 strength 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 production, the strength of the mobile magnetic field component H2 acting on the magnetic sensor 22 always changes depending on the change in the distance between the movable magnet 21 and the magnetic sensor 22. The control operation by the control unit associated with the speaker 1 can detect the change in the position of the movable magnet 21, i.e., the change in the position of the vibrating unit, from the ratio of the strength of the fixed magnetic field component H1 to the strength of the movable magnetic field component H2 detected by the magnetic sensor 22. By using the relative values of the strength of the fixed magnetic field component H1 and the strength of the movable magnetic field component H2, highly accurate vibration detection that is less susceptible to the effects of external noise is possible.

The magnetic sensor 22 has at least one magnetoresistance effect element. The magnetoresistance effect element is a GMR element or TMR element having a fixed magnetic layer and a free magnetic layer. In the GMR element or 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 electrical 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 strength of the fixed magnetic field component H1 is almost constant, and the strength of the mobile magnetic field component H2 changes according to the position of the movable magnet 21 in the front-back direction (Z1-Z2 direction), so the angle θ of the detection magnetic field Hd changes according to the change in the position of the movable magnet 21. By detecting the change in the electrical resistance value of the magnetoresistance effect element, it is possible to know the change in the angle θ of the detected magnetic field Hd, and 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.

The magnetic sensor 22 can be composed of elements other than magnetoresistance effect elements, so 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 be equipped with two Hall elements. One Hall element has a directivity that can detect changes in the magnetic field strength in the first direction (X direction), and the other Hall element has a directivity that can detect changes 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 forward and backward directions can be detected from the ratio of the two intensities.

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. The driving magnetic flux Fd generated from the magnetic circuit section 10 crosses the voice coil 7, and the driving magnetic flux Fd and the driving current excite an electromagnetic force, causing the vibration section including the bobbin 6 and the diaphragm 3 to vibrate in the front-rear direction, generating a sound pressure according to the frequency of the driving current, and sound is emitted forward or backward.

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 and change in the forward/backward direction of the vibration unit including the diaphragm 3. For example, the control unit calculates the deviation between the ideal position and change in the forward/backward direction of the vibration unit assumed by application of an audio signal and the actual position and change of the vibration unit 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 forward/backward direction.

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. This allows for highly accurate feedback control that is less susceptible to the effects of external noise.

Next, the relationship between the shape of the movable magnet 21, i.e., the position and orientation of the magnetic pole ends 21a and 21b, and the detection output from the magnetic sensor 22 will be described. In the following, the movable magnet 21 will be described as an example of a movable magnetic field generating member, but the relationship between the position and orientation of the magnetic pole ends 21a and 21b and the detection output from the magnetic sensor 22 is the same when using the movable magnetic field generating member 21A composed of the permanent magnet 121 and yokes 122 and 123 shown in Figure 9.

Figure 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 the X-Y plane perpendicular to the central axis O. Figure 3 also shows the intersection P between a first reference line L1 that extends in a first direction (X direction) through the center of the magnetic sensor 22 and the inner peripheral surface 6a of the bobbin 6. Figure 3 shows magnet A as a comparative example. Magnet A of the comparative example is magnet 221 with a rectangular planar shape. This magnet 221 has magnetized surface 221a magnetized to the N pole and magnetized surface 221b magnetized to the S pole that are parallel to the first direction (X direction) and parallel to the X-Z plane.

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 the radial line R that extends radially from the central axis O located at the center of the bobbin 6. In other words, each magnetic pole end 21a and 21b is a magnetic pole end surface formed along a plane that includes the respective radial line R and the Z axis.

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 P are indicated by b, c, d, e, f, g, and h. b, c, d, e, f, g, and h are all located further inward of the bobbin 6 in the first direction (X direction) than the intersection P. That is, the magnetic pole ends 21a and 21b of the movable magnets 21 classified as B, C, D, E, F, G, and H are all located further inward of the bobbin 6 in the first direction than the intersection P. The magnetic pole ends 21a and 21b are also located further inward of the bobbin 6 in the first direction than the magnetized surfaces 221a and 221b of the magnet A of the comparative example. Therefore, the ratio of the 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 the 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.

In addition, the magnetized surfaces 221a and 221b of the magnet A, which is 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 more clockwise than the magnetized surface 221a of the magnet A in a plan view, and the magnetic pole end 21b is inclined more counterclockwise than the magnetized surface 221b of the magnet A. In other words, the magnetic pole end 21a and 21b of the movable magnet 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 to 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 to the magnetized surface 221b of the magnet A, which is the comparative example.

Figure 5 shows the results of a simulation of the orientation and distribution of magnetic field lines due to leakage magnetic flux from a magnet when viewed in the X-Y 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 Figure 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 Figure 3 is used, and (C-2) shows an enlarged view of the area of the magnetic sensor 22 in the distribution of (C-1).

As shown in FIG. 5, in the speaker 1 using the movable magnet 21 of the embodiment of the present invention, the ratio of the vector component 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 the movable magnet 21 is higher than when the magnet A of the comparative example is used. This improves the detection accuracy of the magnetic sensor 22. In addition, the linearity of the change in the detection output of the magnetic sensor 22 when the movable magnet 21 moves in the forward/backward direction (Z1-Z2 direction) together with the vibration part can be maintained with high accuracy.

Figure 4 shows a diagram showing the relationship between the magnet position and the magnet position information detected by the magnetic sensor 22 in the speaker 1 using the comparative magnet A and the movable magnet 21 of each embodiment classified as B, C, D, E, F, G, and H. The horizontal axis shows the distance the movable magnet moves forward to +10 mm and the distance 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. Figure 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.

The simulation results in Figure 4 show 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, in a speaker using magnets B, C, D, E, F, G, and H, which are movable magnets 21 according to an embodiment of the present invention, it is clear that 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.

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 compared to the rate of change of the actual magnet position, and the detection sensitivity of the magnetic sensor 22 is effectively reduced. This is predicted to be because, as shown in FIG. 5 (C-1) and (C-2), the magnetic pole ends 21a and 21b approach each other at a position away from the magnetic sensor 22, so the magnetic flux density is high at the opposing portion of 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.

3, it is necessary that the two magnetic pole ends 21a and 21b are located between the second reference line L2 extending in the second direction (Y direction) through the center O of the bobbin 6 and the intersection P, assuming that the magnetic sensor 22 is located between the 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, in order to obtain the movable magnets 21 classified as B, C, D, E, and F, when a virtual line extending in the second direction through the end of the sensor board 28 facing the intersection P is set as the third reference line L3, or a virtual line extending in the second direction through the end of the magnetic sensor 22 facing the intersection P is set as the third reference line L3, it is necessary that the two magnetic pole ends 21a and 21b are located between the second reference line L2 and the third reference line L3. According to FIG. 4, speakers using movable magnets 21 classified as B, C, D, and E are better in both linearity of detection output and sensitivity. To obtain movable 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 positioned almost opposite the magnetic sensor 22 in the second direction (Y direction).

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

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

The simulation results in FIG. 7 show that the speaker 1 using the moving magnets 21 classified as D, J, and L has excellent linearity in the change in the information on the position of the moving magnet 21 detected by the magnetic sensor 22 in response 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 to the ring-shaped portion of the moving magnet 21 from the magnetic pole ends 21a and 21b parallel to the first direction (X direction) and wrapped around it. Therefore, it can be predicted that when the magnet K approaches the magnetic sensor 22, the magnetic flux that is attracted by being wrapped around the ring-shaped portion affects the detection portion of the magnetic sensor 22.

From the simulation results shown in FIG. 7, it is preferable that the orientation of the magnetic pole end surface, which is the magnetic pole end portion 21a, 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, and becomes a surface parallel to the second direction (Y direction) shown in FIG. 6(B), and further, as shown in FIG. 6(C)(D), 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. In addition, when the magnetic end surface is parallel to the first direction (X direction), it is preferable that curved portions 21c, 21d are formed at both ends of the movable magnet 21, as shown in FIG. 6(D).

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 ends 21a and 21b and the orientation of the magnetic pole end 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, in a plan view seen on a plane perpendicular to the central axis O, symmetrical movable magnets 221A and 221B may be arranged on both sides of the magnetic sensor 22. In this case, in the second direction (Y direction), the magnetic pole ends 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.

1 Speaker 2 Frame 3 Diaphragm 6 Bobbin 7 Voice coil 10 Magnetic circuit section (fixed magnetic field generating member)
11 Drive magnet 12 Opposed yoke 13 Rear yoke 14 Center yoke 21 Movable magnet (movable magnetic field generating member)
21a, 21b Magnetic pole tip 21A Movable magnetic field generating member 22 Magnetic sensor 28 Sensor substrate Fd Driving magnetic flux H1 Fixed magnetic field component H2 Movable magnetic field component Hd Detection magnetic field L1 First reference line L2 Second reference line L3 Third reference line O Central axis P Intersection

Claims (11)

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. 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. 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. The speaker according to claim 3, wherein the two magnetic pole ends are located between a third reference line that extends in the second direction through the end of the sensor board on which the magnetic sensor is mounted on the intersection side, and the second reference line. A speaker according to any one of claims 2 to 4, wherein the movable magnetic field generating member is a partial ring shape that fits along the inner peripheral surface of the bobbin. A speaker according to any one of claims 1 to 5, wherein the magnetic pole end is a magnetic pole end surface along a radial line extending from the center of a bobbin around which the voice coil is wound. A speaker according to any one of claims 1 to 5, wherein the magnetic pole end is a magnetic pole end surface parallel to the second direction. A speaker according to any one of claims 1 to 5, wherein the magnetic pole end is a magnetic pole end surface parallel to the first direction. 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. A speaker according to any one of claims 1 to 5, in which the magnetic pole end surface is set in a direction within a range from a direction along a radial line extending from the center of the bobbin around which the voice coil is wound to a direction parallel to the first direction. A speaker according to any one of claims 1 to 10, in which the fixed magnetic field generating member is also used as the magnetic circuit section.

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