Speaker

Abstract

To provide a speaker capable of highly accurately detecting a position of a voice coil.SOLUTION: A speaker comprises: a yoke for forming a magnetic circuit; a first magnet to be fixedly arranged; a voice coil arranged in a gap through which the magnetic flux of the magnetic circuit passes; a diaphragm connected to the voice coil so as to be oscillated together with the voice coil; a second magnet arranged in an oscillation part including the voice coil and the diaphragm; and a magnetic sensor arranged at a position through which magnetic fluxes of both of a first magnetic flux generated by the first magnet and a second magnetic flux generated by the second magnet pass. The direction of the first magnetic flux is different from the direction of the second magnetic flux.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a speaker. [Background technology]

[0002] Conventionally, there is a speaker that detects the capacitance formed between a center pole and a voice coil bobbin having a bobbin made of an insulating layer and a non-magnetic conductive layer, and outputs it as an electric signal. The detected capacitance is used to eliminate sound distortion in a motional feedback (MFB) circuit (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-020153 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, conventional speakers are designed to make the capacitance to be detected less susceptible to the effects of disturbance noise. However, the change in capacitance due to disturbance noise is likely to be greater than the actual detection value, making it difficult to detect the zero point, and the detection accuracy of the voice coil position is not at a level that can fully eliminate sound distortion in the MFB circuit.

[0005] It is therefore an object of the present invention to provide a speaker that is capable of detecting the position of a voice coil with high accuracy. [Means for solving the problem]

[0006] A speaker according to an embodiment of the present invention includes a yoke that forms a magnetic circuit, a fixedly arranged first magnet, a voice coil that is arranged in a gap through which the magnetic flux of the magnetic circuit passes, a diaphragm that is connected to the voice coil and vibrates together with the voice coil, a second magnet that is provided in a vibration section that includes the voice coil and the diaphragm, and a magnetic sensor that is provided at a position where both a first magnetic flux generated by the first magnet and a second magnetic flux generated by the second magnet pass, and the direction of the first magnetic flux and the direction of the second magnetic flux are different. Effect of the Invention

[0007] It is possible to provide a speaker that is capable of detecting the position of the voice coil with high accuracy. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a speaker 100. [Diagram 2] 1 is a diagram showing a magnetic sensor 120 and the direction of magnetic flux. [Diagram 3] 2 is a diagram showing the displacement of the voice coil 105 of the speaker 100 relative to the voltage applied to the voice coil 105. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment to which a speaker of the present invention is applied will be described.

[0010] <Embodiment> FIG. 1 is a diagram showing a speaker 100. FIG. 1(A) shows a cross section taken along the line AA in FIG. 1(B). FIG. 1(B) is a plan view showing the speaker 100 as viewed from above with the diaphragm and damper removed. Here, the explanation will be given using the up-down relationship in FIG. 1(A), but this does not represent a universal up-down relationship. The up-down side is the front side of the speaker 100, and is the side from which sound is output. The down-down side is the back side of the speaker 100.

[0011] In the following description, a plan view refers to a view from the top or bottom. Words such as right angle, perpendicular, vertical, up and down, etc., allow for deviations that do not impair the effects of the embodiments.

[0012] The speaker 100 includes a frame 101, a diaphragm 102, an edge 103, a bobbin 104, a voice coil 105, a damper 106, a yoke 107, a first magnet 108, a top plate 109, a second magnet 110, a magnetic sensor 120, and a base 130. The bobbin 104, the voice coil 105, and the diaphragm 102 are an example of a vibrating part. The speaker 100 is circular in a plan view, and a central axis C of the speaker 100 is shown in Fig. 1(A) and Fig. 1(B).

[0013] Frame 101 is a housing of speaker 100, and is made of metal, resin, or the like in a generally conical shape. Frame 101 has holding portion 101A on the lower side as shown in Fig. 1(B). Holding portion 101A is fixed to the upper surface of top plate 109. Note that holding portion 101A is omitted in Fig. 1(A).

[0014] Diaphragm 102 is made of paper, resin, or a thin metal plate, and is vibrated by the upward and downward vibrations of voice coil 105 to generate sound. Diaphragm 102 is generally conical in shape, and has a circular ring shape in plan view, with its outer periphery connected to frame 101 via edge 103 made of an elastic material such as rubber, and its inner periphery connected to bobbin 104. The center of the circular ring shape of diaphragm 102 coincides with central axis C in plan view.

[0015] The bobbin 104 is a cylindrical member made of paper, resin, or the like, and its upper end is connected to the inner periphery side of the diaphragm 102 and is also connected to the inner periphery side of the damper 106. A voice coil 105 is wound around the outer periphery of the lower part of the bobbin 104, and the bobbin 104 and the voice coil 105 are inserted from above into a gap 107G, which will be described later. The center of the cylindrical shape of the bobbin 104 coincides with the central axis C in a plan view. The bobbin 104 may be formed integrally with the inner periphery side of the diaphragm 102.

[0016] The yoke 107 is provided on the back side of the speaker 100. The yoke 107 is a member made of a magnetic material that is circular in plan view and has an arm-like shape in cross section as shown in FIG. 1(A). An outer peripheral end 107A of the yoke 107 holds a first magnet 108. An inner peripheral upper end 107B of the yoke 107 faces the inner peripheral surface of the top plate 109 with a gap 107G therebetween. That is, an annular gap 107G that is a magnetic gap is formed between the outer peripheral surface of the upper end 107B of the yoke 107 and the inner peripheral surface of the top plate 109. The center of the circular shape of the yoke 107 coincides with the central axis C in plan view.

[0017] The first magnet 108 is an annular permanent magnet as shown in FIG. 1B. The center of the annular shape of the first magnet 108 coincides with the central axis C in plan view. The first magnet 108 is magnetized so that one of the upper and lower sides is an N pole and the other is an S pole. The magnetic flux generated by the first magnet 108 passes through the top plate 109, the gap 107G, and the yoke 107 and returns to the first magnet 108. At the vertical height position where the magnetic sensor 120 is located, the direction of the magnetic flux generated by the first magnet is toward the central axis C in plan view, as indicated by eight arrows B in the center of FIG. 1B. The magnetic flux generated by the first magnet 108 is an example of the first magnetic flux.

[0018] Top plate 109 is a member made of a magnetic material and has a circular ring shape in a plan view, and is fixed onto first magnet 108. The center of the circular ring shape of top plate 109 coincides with central axis C in a plan view. Top plate 109, together with yoke 107 and first magnet 108, constitutes a magnetic circuit.

[0019] The second magnet 110 is attached to a position above the voice coil 105 on the outer circumferential surface of the bobbin 104. The second magnet 110 is attached to one location in the circumferential direction of the bobbin 104, and is arranged to face a magnetic sensor 120 described later in a plan view, or to overlap the magnetic sensor 120 in the vertical direction. The second magnet 110 is a permanent magnet having an N pole and an S pole, and generates a magnetic flux having a direction indicated by an arrow D. The magnetic flux of the second magnet 110 is an example of the second magnetic flux. The magnetic flux of the second magnet 110 is a tangent direction of a circle formed by the outer circumferential surface of the bobbin 104 in a plan view. Here, the direction of the magnetic flux that passes through the center of the second magnet 110 in a plan view of the magnetic flux generated by the first magnet 108 is indicated by an arrow B1. The direction of the magnetic flux of the first magnet 108 indicated by the arrow B1 and the direction of the magnetic flux of the second magnet 110 indicated by the arrow D are orthogonal in a plan view. Such a second magnet 110 only needs to provide a magnetic flux of a predetermined density (magnetic field of a predetermined strength) to the magnetic sensor 120 in order to detect the position of the voice coil 105, and therefore may be a magnet smaller than the first magnet .

[0020] The magnetic sensor 120 is provided on the top plate 109 via a pedestal 130. The pedestal 130 is provided to adjust the height of the magnetic sensor 120, and is made of, for example, resin. The magnetic sensor 120 is located on a straight line connecting the central axis C and the center of the second magnet 110 in a plan view. Therefore, the position of the magnetic sensor 120 is a position where the magnetic flux of the first magnet 108 and the magnetic flux of the second magnet 110 are orthogonal to each other.

[0021] The magnetic sensor 120 is a sensor capable of detecting the direction of magnetic flux in a plane, and is arranged so as to detect the direction of magnetic flux in a plane perpendicular to the central axis C. When an audio signal current flows through the voice coil 105, the bobbin 104 and the voice coil 105 vibrate in the direction of the central axis C as indicated by the double arrow, and the magnetic sensor 120 can detect the direction of the composite magnetic flux of the magnetic flux of the first magnet 108 and the magnetic flux of the second magnet 110 in a plane perpendicular to the vibration direction of the bobbin 104 and the voice coil 105. As an example, the magnetic sensor 120 can be a sensor including an MR (Magneto Resistance) element, such as an AMR (Anisotropic Magneto Resistance) element, a GMR (Giant Magnetic Resistance) element, or a TMR (Tunnel Magneto Resistance) element. Here, an embodiment in which the magnetic sensor 120 is a sensor including a GMR element will be described as an example.

[0022] 2 is a diagram showing the magnetic sensor 120 and the direction of magnetic flux. FIG. 2 shows the direction B1 of the magnetic flux of the first magnet 108 that exists at the position of the magnetic sensor 120, and the direction D of the magnetic flux of the second magnet 110. FIG. 2 also shows an XYZ coordinate system that is an orthogonal coordinate system. The X direction coincides with the direction D, and the Y direction coincides with the direction B1. The Z direction coincides with the direction of the central axis C shown in FIG. 1.

[0023] Since the voice coil 105 vibrates in the direction of the central axis C (Z direction), when the voice coil 105 is driven in accordance with an audio signal to vibrate in the Z direction, the second magnet 110 also vibrates in the Z direction. If the direction D is considered to indicate a certain magnetic flux generated by the second magnet 110, when the second magnet 110 moves in the Z direction due to the vibration in the Z direction, the position of the certain magnetic flux in the Z direction changes as shown by the thick arrow in Fig. 2. The density of the magnetic flux of the second magnet 110 detected by the magnetic sensor 120 decreases as the second magnet 110 moves away in the Z direction (upward in Fig. 1(A)), so when the second magnet 110 moves in the Z direction due to the vibration in the Z direction, the density of the magnetic flux (strength of the magnetic field) penetrating the magnetic sensor 120 in the X direction changes.

[0024] Since the magnetic sensor 120 is attached to the magnetic circuit (fixed body side) and not to the vibrating part, the density (strength of the magnetic field) of the magnetic flux of the first magnet 108 penetrating the magnetic sensor 120 in the Y direction is constant. Therefore, when the density of the magnetic flux penetrating the magnetic sensor 120 in the X direction changes, the direction of the composite magnetic flux of the magnetic flux of the first magnet 108 and the magnetic flux of the second magnet 110 in the XY plane passing through the magnetic sensor 120 changes. Therefore, the magnetic sensor 120 can detect the change in the direction of the composite magnetic flux accompanying the vibration of the voice coil 105 in the Z direction.

[0025] Since the displacement of the voice coil 105 in the Z direction represents the displacement of the diaphragm 102, the displacement of the diaphragm 102, the bobbin 104, and the voice coil 105 in the Z direction can be detected by detecting a change in the direction of the composite magnetic flux with the magnetic sensor 120. The relationship between the direction of the composite magnetic flux detected by the magnetic sensor 120 and the position or displacement of the voice coil 105 in the Z direction may be measured in advance and acquired as data, and stored in a memory of a control unit consisting of a microcomputer or the like, and the position or displacement of the voice coil 105 in the Z direction corresponding to the direction of the composite magnetic flux detected by the magnetic sensor 120 may be output. The control unit may be disposed inside the speaker 100, or may be connected to the speaker 100 from the outside.

[0026] The magnetic sensor 120 is a sensor that detects the direction of magnetic flux (magnetic field) in the XY plane, and has the characteristic that the magnetic resistance changes only depending on the magnetic field direction. The magnetic resistance of the magnetic sensor 120 does not change depending on the magnitude of the magnetic field. Therefore, the magnetic sensor 120 is not easily affected by external noise, etc., and can detect the direction of the magnetic flux with high accuracy.

[0027] Therefore, it is possible to provide a speaker 100 capable of detecting the position of the voice coil 105 with high accuracy. By being able to detect the position of the voice coil 105 with high accuracy, by performing feedback control using the output of the microcomputer representing the direction of the resultant magnetic flux detected by the magnetic sensor 120 in adaptive signal processing (output representing the position or displacement of the voice coil 105 in the Z direction), it is possible to reduce sound distortion in the audio signal input to the voice coil 105.

[0028] The speaker 100 is a device that passively outputs sound according to the audio signal output from the amplifier at all times, and the output distortion for the audio signal is very large and varies widely, so that the device may be damaged due to overexcitation. Although technology for feeding back the amplitude of the voice coil has been considered in the past, there was no sensor that could minimize noise and the burden on the speaker, and it was difficult to correct the output distortion for the audio signal with high precision.

[0029] Sensors that have been tried in the past include sensors that detect lasers, light, or eddy currents, differential sensors, and moving coils, but all of them had issues such as being unable to accurately identify the position of the voice coil, being noisy, putting a heavy burden on vibrating components such as the bobbin and voice coil, being unable to withstand temperature changes, and being too expensive.

[0030] In contrast, speaker 100 using magnetic sensor 120 that detects the direction of the composite magnetic flux as described above can accurately identify the position of voice coil 105, has low noise, imposes little strain on vibrating members such as bobbin 104 and voice coil 105, can adapt to temperature changes, and can be realized at low cost.

[0031] Furthermore, since the first magnet 108 is a magnet that forms a magnetic circuit together with the yoke 107, it is possible to provide the speaker 100 that can detect the position of the voice coil 105 with high accuracy by utilizing the existing magnet in the speaker 100.

[0032] Furthermore, since the second magnet 110 is attached to the bobbin 104 around which the voice coil 105 is wound, the position of the voice coil 105 can be accurately detected by the second magnet 110, thereby providing a speaker 100 that can detect the position of the voice coil 105 with high accuracy.

[0033] Furthermore, since the magnetic sensor 120 is provided on the outer periphery of the bobbin 104, it can be easily arranged close to both the first magnet 108 (magnetic circuit) and the second magnet 110, thereby providing a speaker 100 capable of detecting the position of the voice coil 105 with high accuracy.

[0034] The magnetic sensor 120 detects changes in the direction of the composite magnetic flux of the magnetic flux of the first magnet 108 and the magnetic flux of the second magnet 110 in a plane perpendicular to the vibration direction of the voice coil 105, so that the displacement due to the vibration of the voice coil 105 can be reflected to the composite magnetic flux to the maximum extent possible, improving the detection accuracy of the position of the voice coil 105.

[0035] Furthermore, at the position where the magnetic sensor 120 is provided, the magnetic flux of the first magnet 108 and the magnetic flux of the second magnet 110 are perpendicular to each other, so that the change in the magnetic flux density (change in the magnetic field strength) of the second magnet 110 can be reflected to the maximum extent possible in the composite magnetic flux, improving the detection accuracy of the position of the voice coil 105.

[0036] 3 is a diagram showing the displacement of the voice coil 105 with respect to the voltage applied to the voice coil 105 of the speaker 100. When the absolute value of the voltage applied to the voice coil 105 increases, the absolute value of the current of the audio signal input to the voice coil 105 also increases, although not linearly.

[0037] 3 indicates the characteristic in which sound distortion relative to the applied voltage is corrected by performing feedback control with adaptive signal processing based on the direction of the resultant magnetic flux detected by the magnetic sensor 120. The characteristic in which the solid line indicates the characteristic in which sound distortion is adjusted by adaptive signal processing without performing feedback control based on the direction of the resultant magnetic flux detected by the magnetic sensor 120.

[0038] As shown in FIG. 3, the characteristics indicated by the solid line when feedback control based on the direction of the composite magnetic flux detected by the magnetic sensor 120 is not performed show large distortion in the operating region where the absolute value of the applied voltage is large, whereas the characteristics indicated by the dashed line when feedback control based on the direction of the composite magnetic flux detected by the magnetic sensor 120 is performed show that the displacement of the voice coil 105 changes linearly with respect to the applied voltage.

[0039] Since the magnetic sensor 120 can detect the direction of the resultant magnetic flux with high accuracy, it is possible to linearly correct the distortion of the displacement of the voice coil 105 with respect to the voltage applied to the voice coil 105 in this manner. In other words, the distortion rate in the displacement of the voice coil 105 can be improved.

[0040] In addition, since the displacement of the voice coil 105 can be detected with high accuracy based on the direction of the resultant magnetic flux detected by the magnetic sensor 120, the resonance of the voice coil 105 (voice coil 105 and diaphragm 102) can be controlled, and the vibration of the voice coil 105 can be controlled with high accuracy even outside the resonance band.

[0041] In addition, since the displacement of the voice coil 105 can be detected with high accuracy based on the direction of the composite magnetic flux detected by the magnetic sensor 120, damage to the diaphragm 102, the edge 103, the bobbin 104, the damper 106, etc. can be detected with high accuracy. If any of these members is damaged, an error notification can be sent to the source of the audio signal.

[0042] Furthermore, since the displacement of voice coil 105 can be detected with high accuracy based on the direction of the resultant magnetic flux detected by magnetic sensor 120, it may be possible to electrically control the damping of diaphragm 102 without using damper 106.

[0043] In addition, since the displacement of the voice coil 105 can be detected with high accuracy based on the direction of the resultant magnetic flux detected by the magnetic sensor 120, the power input to the amplifier that amplifies the audio signal can be optimized, the input power to the amplifier can be reduced, and the amplifier can be made smaller.

[0044] Furthermore, since the displacement of the voice coil 105 can be detected with high accuracy based on the direction of the resultant magnetic flux detected by the magnetic sensor 120, distortion can be suppressed by feedback control based on the position information of the voice coil 105.

[0045] In addition, since the displacement of the voice coil 105 can be detected with high accuracy based on the direction of the resultant magnetic flux detected by the magnetic sensor 120, damage to the speaker 100 due to excessive input can be prevented, and the margin (room to spare) provided in the input signal to the speaker 100 can be reduced.

[0046] Although the above describes a mode in which the second magnet 110 is attached to the bobbin 104, the second magnet 110 may be attached to the voice coil 105. In addition, the second magnet 110 may be attached to a portion that vibrates together with the voice coil 105, other than the bobbin 104 and the voice coil 105.

[0047] In the above, a form has been described in which the magnetic sensor 120 is placed on the base 130 provided on the top plate 109, but the magnetic sensor 120 may be placed anywhere on the fixed part side such as the magnetic circuit or the frame 101 as long as it is in a position where it can detect the magnetic flux of the second magnet 110.

[0048] Also, in the above description, the magnetic sensor 120 is positioned at a position where the magnetic flux of the first magnet 108 and the magnetic flux of the second magnet 110 are orthogonal to each other. However, since it is sufficient for the magnetic sensor 120 to detect the direction of the composite magnetic flux, the magnetic flux of the first magnet 108 and the magnetic flux of the second magnet 110 do not have to be orthogonal to each other. It is sufficient that the magnetic sensor 120 is positioned at a position where the magnetic flux of the first magnet 108 and the magnetic flux of the second magnet 110 are different in direction.

[0049] Also, in the above, a configuration has been described in which the magnetic sensor 120 detects the direction of the composite magnetic flux of the magnetic flux of the first magnet 108 and the magnetic flux of the second magnet 110 in a plane that perpendicularly intersects with the vibration direction of the bobbin 104 and the voice coil 105. However, the plane in which the magnetic sensor 120 detects the direction of the composite magnetic flux of the magnetic flux of the first magnet 108 and the magnetic flux of the second magnet 110 does not have to be perpendicular to the vibration direction of the bobbin 104 and the voice coil 105, but only needs to intersect with it. This is because, if it intersects with it, a change in the direction of the composite magnetic flux of the magnetic flux of the first magnet 108 and the magnetic flux of the second magnet 110 due to the vibration of the bobbin 104 and the voice coil 105 can be detected.

[0050] In the above, the magnetic sensor 120 detects the direction of the composite magnetic flux of the magnetic flux of the first magnet 108 and the magnetic flux of the second magnet 110. The first magnet 108 is fixed, and the second magnet 110 moves with the vibration of the bobbin 104 and the voice coil 105. Instead of the first magnet 108, a magnet fixedly disposed in the speaker 100 may be provided and used as the first magnet, and the magnetic sensor 120 may detect the direction of the composite magnetic flux of the magnetic flux of the first magnet and the magnetic flux of the second magnet 110. This is because the displacement of the voice coil 105 can be detected with high accuracy based on the direction of the composite magnetic flux detected by the magnetic sensor 120. The magnetic sensor 120 may also detect the direction of the composite magnetic flux of the magnetic flux of the magnet fixedly disposed in the speaker 100, the magnetic flux of the first magnet 108, and the magnetic flux of the second magnet 110.

[0051] Although a speaker according to an exemplary embodiment of the present invention has been described above, the present invention is not limited to the specifically disclosed embodiment, and various modifications and variations are possible without departing from the scope of the claims. [Explanation of symbols]

[0052] 100 Speakers 102 Vibration plate 104 Bobbin 105 Voice Coil 107 York 108 First Magnet 110 Second Magnet 120 Magnetic Sensor

Claims

1. A yoke that forms a magnetic circuit; A first magnet that is fixedly disposed; a voice coil disposed in a gap through which the magnetic flux of the magnetic circuit passes; a diaphragm connected to the voice coil and vibrating together with the voice coil; a second magnet provided in a vibration section including the voice coil and the diaphragm; a magnetic sensor provided at a position through which both a first magnetic flux generated by the first magnet and a second magnetic flux generated by the second magnet pass; The direction of the first magnetic flux is different from the direction of the second magnetic flux, The vibrating section includes a cylindrical bobbin around which the voice coil is wound, the second magnet is attached to an outer circumferential surface of the bobbin at a position above the voice coil, The magnetic flux of the second magnet is directed in a tangent direction to a circle formed by an outer circumferential surface of the bobbin in a plan view, A speaker, wherein the magnetic sensor is located on a straight line connecting a central axis of the cylindrical shape of the bobbin and a center of the second magnet in a plan view.

2. The speaker according to claim 1 , wherein the first magnet forms the magnetic circuit together with the yoke.

3. 3. The speaker according to claim 1, wherein the second magnet is provided on one of the bobbin, the voice coil, and the diaphragm.

4. The speaker according to claim 3 , wherein the magnetic sensor is provided on an outer periphery of the bobbin or the voice coil.

5. The speaker according to claim 1 , wherein the magnetic sensor detects a change in the direction of a resultant magnetic flux of the first magnetic flux and the second magnetic flux in a plane intersecting a vibration direction of the vibration section.

6. 6. The speaker according to claim 5, further comprising a control unit that calculates a displacement amount of the vibration unit from a change in a direction of a resultant magnetic flux of the first magnetic flux and the second magnetic flux detected by the magnetic sensor.

7. The speaker according to claim 1 , wherein a direction of the first magnetic flux and a direction of the second magnetic flux are perpendicular to each other at a position where the magnetic sensor is provided.

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