THIN SPEAKER

Abstract

A damper has an inner circumference including a curve descending in a bow shape. A wave section extends from the outer circumferential end of the curve to the outer circumference of the damper. The inner circumference of the damper is shorter than the wave section.

Claims

1. A thin speaker comprising: a voice coil bobbin including a voice coil and having an upper end to which a back surface of a diaphragm body is attached; the diaphragm body having an outer circumference attached to a thin frame with an edge interposed therebetween; the thin frame having a bottom including a magnetic circuit having a magnetic gap; the magnetic gap including the voice coil, the voice coil bobbin to which an inner circumference of a damper is attached, and the damper having an outer circumference attached to a mount for the outer circumference of the damper in the thin frame; and the inner circumference of the damper including a curve descending in a bow shape, and a wave section extending from an outer circumferential end of the curve to the outer circumference of the damper, the inner circumference of the damper being shorter than the wave section.

2. The thin speaker of claim 1, wherein the inner circumference of the damper includes a bend protruding upward and having a flat upper surface in contact with and attached to the back surface of the diaphragm body.

3. The thin speaker of claim 1, wherein the wave section includes at least two or more waves each having a vertex at a height equal to or lower than an outer circumferential end of the outer circumference of the damper.

4. The thin speaker of claim 1, wherein the curve includes a fold that orients the curve downward and increases rigidity.

5. The thin speaker of claim 2, wherein an outer circumferential end of the outer circumference of the damper is located lower than the bend.

6. The thin speaker of claim 2, wherein the damper is shaped to pass through a point lower than an outer circumferential end of the damper between the bent and the outer circumferential end.

7. The thin speak of claim 1, wherein the outer circumferential end of the curve is located lower than an upper end of a yoke of the magnetic circuit.

8. The thin speaker of claim 3, wherein the two or more waves include at least a first inner wave on an inner circumference and a second outer wave on an outer circumference, and the vertex of the first wave is located lower than the vertex of the second wave.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0052] FIG. 1 is a half-sectional side view of a thin speaker according to an embodiment of the present disclosure.

[0053] FIG. 2 is an enlarged illustration of a main part of the thin speaker.

[0054] FIG. 3 is an exploded perspective view of the thin speaker according to the present disclosure.

[0055] FIG. 4 illustrates an adhesion of a lead wire of a voice coil in the thin speaker according to the present disclosure.

[0056] FIG. 5 is a perspective view of the voice coil and the lead wire according to the present disclosure.

[0057] FIG. 6 illustrates results of simulating displacements in a vibration system of the thin speaker according to the present disclosure.

[0058] FIG. 7 shows a result of measuring the amplitude of a damper of the thin speaker according to the present disclosure.

[0059] FIG. 8 shows a vibration system in a normal state (without any signal) of the thin speaker according to the present disclosure.

[0060] FIG. 9 shows a downward movement of the vibration system.

[0061] FIG. 10 shows frequency characteristics with respect to a sound pressure according to the present disclosure.

[0062] FIG. 11 shows a schematic half-sectional view of a prototype prepared prior to the present disclosure.

[0063] FIG. 12 shows a result of measuring the amplitude of a damper of the prototype.

[0064] FIG. 13 illustrates a simulation result in a vibration system of the prototype.

[0065] FIG. 14 illustrates a movement of a voice coil with respect to a magnetic circuit in the prototype in one period.

[0066] FIG. 15 is a conceptual diagram of a vehicle emergency notification system.

[0067] FIG. 16 illustrates an overhead console on the ceiling of a vehicle.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT

[0068] In order to develop a speaker for a vehicle emergency notification system satisfying the specifications described above, the present inventor prepared a prototype of a thin speaker as shown in FIG. 11.

[0069] In FIG. 11, reference character 1′ denotes a damper that vibratably supports a voice coil bobbin 4b. This damper 1′ has an inner circumferential end 1a′ attached to the outer circumferential surface of the voice coil bobbin 4b by an adhesive. The damper 1′ has an outer circumferential end 1g′ whose lower surface is attached to the upper surface of a thin frame 10 on the right in the figure.

[0070] The thin frame 10 of this prototype has an aperture of, for example, 40 mm that matches an emergency notification system of an eCall system. The thin speaker S′ has an overall height of 10 mm. In an operation, upon receipt of an audio current, a voice coil 4a in a magnetic field vibrates so that a diaphragm 2A coupled to the voice coil bobbin 4b including the voice coil 4a moves back and forth (or up and down).

[0071] The damper 1′ of this thin speaker S′ has corrugations extending substantially linearly from its inner to outer circumference. The inner circumferential end 1a′ of the damper is attached to the voice coil bobbin 4b at substantially the same height as the outer circumferential end 1g′ of the damper attached to the mount for the outer circumference of the damper.

[0072] FIG. 12 shows the amplitude characteristics of the prototype. The amplitude is asymmetric between the forward movement (“UP”) and the backward movement (“DOWN”) opposite to the forward movement, and greater in the backward movement. The vibration system tends to move downward, which affects the distortion. This is because the damper 1′ is corrugated uniformly over its entire surface and has a lower rigidity.

[0073] FIG. 13 shows simulation results in the vibration system (i.e., the diaphragm 2A and damper 1′) described above.

[0074] In each lower graph in FIG. 13, the vertical axis represents a load and the horizontal axis represents a displacement.

[0075] The curve A shows a forward “UP-SIDE” movement, and the curve B shows a backward “DOWN-SIDE” movement.

[0076] FIG. 13 includes the illustrations (a) to (c) respectively showing relationships between a load and a displacement of an edge 3 on the outer circumference of the diaphragm 2A, the damper 1′, and (the total displacement of) the vibration system of the thin speaker S′ as the integration thereof.

[0077] It is found from the simulation results that the “DOWN-SIDE” requires a lower load than the “UP-SIDE” to cause the same displacement, and both the edge 3 of the diaphragm 2A and the damper 1′ tend to move downward.

[0078] Accordingly, when the vibration system moves downward, the voice coil abuts onto the bottom.

[0079] In FIG. 14, the illustrations (a) to (d) show a movement of the voice coil bobbin 4b in one period of the forward and backward movement of the diaphragm 2A. In FIG. 14, reference character C denotes the bottom of a magnetic circuit 5, and 4b denotes the voice coil bobbin.

[0080] In this one period, at a downward movement, the voice coil bobbin 4b abuts on the bottom C of the magnetic circuit 5 as surrounded by a circle in (b) to cause an abnormal sound. In FIG. 14, the lower graph illustrates the occurrence of the abnormal sound.

[0081] In the prototype, as shown in FIG. 11, the space b between the back surface of the inner circumferential end 1a′ of the damper and the front end of a yoke 6 is narrow. The inner circumferential end 1a′ of the damper may abut on the upper end of the yoke 6.

[0082] In such the thinned prototype, the voice coil bobbin 4b abuts onto the bottom at a high input level. That is, the prototype cannot withstand a high input level. To address the problem, there is a need to reduce the abutting of the voice coil bobbin 4b onto the bottom and the abutting of the damper onto the yoke even at a high input level.

[0083] The prototype has the asymmetric amplitude between the forward and backward movement. There is also a need to improve the amplitude symmetricity of the diaphragm.

[0084] The present disclosure was made in view of the foregoing. It is an objective of the present disclosure to provide a thin speaker meeting the specifications of an ACN system having a highly symmetric amplitude, reducing the abutting of the voice coil onto the bottom, and reducing an increase in the lowest resonance frequency fo.

Example

[0085] FIG. 1 is a half-sectional side view of a thin speaker according to an embodiment of the present disclosure. FIG. 2 illustrates the main part of the above thin speaker.

[0086] The present disclosure has a main feature in the cross-sectional shape of a damper 1 that supports a vibration system.

[0087] The vibration system includes, for example, a diaphragm 2A, a voice coil 4, and the damper 1. The diaphragm 2A includes a cone-shaped diaphragm body 2, and a ring-shaped edge 3 on the outer circumference of the diaphragm body 2. The voice coil 4 is located at the center of the back surface of the diaphragm 2A to vibrate the diaphragm 2A. This voice coil 4 with a voice coil 4a wound around the outer circumference of a cylindrical voice coil bobbin 4b may be simply referred to as a “voice coil 4” in the speaker industry. With the inner circumferential end (i.e., a bend 1a) of the inner circumference L1 of the damper attached to the voice coil bobbin 4b, the voice coil 4 is located in a magnetic gap.

[0088] In FIG. 1, reference character 5 denotes a magnetic circuit. This magnetic circuit 5 includes a yoke 6, a magnet 7, and a plate 8. The yoke 6 has a bottomed cylindrical shape. The magnet 7 is located on the bottom of the yoke 6 and has a cylindrical shape. The plate 8 is located on the upper surface of the magnet 7 and has a circular shape in a plan view. Interposed between the outer circumferential surface of the plate 8 and the corresponding inner circumferential surface of the yoke 6 is a magnetic gap 9. The magnetic circuit 5 is located on the bottom of the thin frame 10. The magnetic circuit 5 is of an inner magnetic type, but may be of an outer magnetic type.

[0089] Reference character 10 denotes the thin frame with a small aperture of 40 mm or smaller, which is prepared in a size according to a specification required for an automatic vehicle notification system. The thin frame 10 has, at its inner circumferential end, a step-shaped frame mount 10a corresponding to the outer circumferential end 6a of the yoke 6 to integrate the thin frame 10 and the yoke 6.

[0090] The thin frame 10 has, on the outer circumference of its inner surface, a step-like mount 10b for the outer circumference of the damper and a step-like mount 10c for the outer circumference of an edge. The mount 10c is located above and outside the mount 10b.

[0091] The mount 10b is located slightly higher than the upper end 6b (see FIG. 2) of the yoke 6, as can be seen from the state shown in the figure. The mount 10c is located higher than the mount 10b. The thin frame 10 has a dust-proof fabric 13 on its back surface.

[0092] The lower surface of the outer circumference 3a of the edge is attached to the mount 10c of the thin frame 10 by an adhesive. The outer circumference 3a of the edge includes a ring 11 and a gasket 12 on its upper surface. The length (or an overall height Ht) between the upper surface of the gasket 12 and the back surface of the yoke 6 is set to 10 mm or lower (but not 0 mm) so that the frame 10 has a smaller thickness.

[0093] The inner circumference 3b of the edge is bonded to the outer circumference of the diaphragm body 2 by an adhesive. Accordingly, the outer circumference of the diaphragm body 2 is attached via the edge 3 to the thin frame 10.

[0094] An upper end of the voice coil bobbin 4b including the voice coil 4a is bonded to the back surface of a voice coil mount 2a of the diaphragm body 2 by an adhesive.

[0095] The damper 1 has, on the inner end of its inner circumference (i.e., the inner circumference L1 of the damper), the bend 1a protruding upward and having a flat upper surface which is in contact with and attached to the back surface of the voice coil mount 2a of the diaphragm body 2 by an adhesive. The outer circumferential end 1g, which is the outer end of the outer circumference of the damper, is attached to the mount 10b of the thin frame 10 by an adhesive.

[0096] As shown in detail in FIG. 2, the outer circumference of the bend 1a of the damper 1 has a curve 1b descending in a bow shape toward the back surface of the speaker. This configuration increases the rigidity of the inner circumference of the damper 1, reduces deformations and downward movements of the damper, and reduces the abutting of the voice coil bobbin 4b onto the bottom.

[0097] In the shown example, this curve 1b has two folds. These serve to orient the inner circumference L1 of the damper downward and to increase the rigidity. Note that the curve 1b may have only one fold a. Alternatively, the curve 1b may have no fold a.

[0098] The inner end of the bend 1a on the inner circumference L1 of the damper is attached to the upper end of the voice coil bobbin 4b. The curve 1b secures a space b between the back surface of the inner circumference L1 of the damper and the upper end 6b of the yoke 6 to reduce the abutting of the voice coil 4 onto the bottom when the damper 1 moves downward in accordance with a downward movement of the diaphragm 2A and to reduce the abutting of the damper 1 onto the upper end 6b of the yoke 6.

[0099] In this manner, the curve 1b serves to increase the shape rigidity while securing the space b with the yoke 6.

[0100] The damper 1 has the inner circumference L1 in the area including the bend 1a and the curve 1b, and a wave section L2 on its outer circumference. L2 is longer than L1, that is, L1<L2. This configuration reliably provides the softness of the damper 1 at a usually reproduced acoustic level to reduce an increase in the lowest resonance frequency fo.

[0101] The damper is rigid on its inner circumference L1 due to its bow-shaped curve 1b, and soft in the wave section L2.

[0102] Specifically, the area from the outer circumferential end 1e of the bow-shaped curve 1b, which is the outer circumference of the inner circumference L1 of the damper, to the outer circumferential end 1f of the wave section L2 is soft to reduce an increase in the lowest resonance frequency fo, operate at a required lowest resonance frequency fo, and provide desired frequency characteristics.

[0103] The mount 10b for the outer circumference of the damper is located lower than the inner circumferential end of the bend 1a which is the mount for the inner circumference of the damper 1. The wave section L2 is located lower, that is, closer to the back surface of the thin frame 10 with a space interposed between. This secures a sufficient space between the diaphragm 2A and the damper to easily arrange a lead wire and thus reduces the contact between the lead wire and the damper when the vibration system moves downward. This also secures a sufficient distance between the lead wire and the wave section L2, that is, a sufficient space for placing the wave section L2, which increases the flexibility in designing the damper. This configuration further reduces the thickness of the speaker.

[0104] The wave section L2 may have at least two or more waves, for example, a first wave 1c on the inner circumference and a second wave 1d on the outer circumference of the first wave 1c.

[0105] The first wave 1c is gently inclined forward from the outer circumferential end 1e of the curve 1b, and has a substantially L-shaped cross section that is gently inclined backward (toward the back surface of the frame) from its vertex. The second wave 1d continuous with and on the outer circumference of the first wave 1c has a convex cross section steeper than the first wave 1c. The first wave 1c on the inner circumference has a greater curvature radius than the second wave on the outer circumference.

[0106] The first wave 1c has a lower vertex than the second wave 1d. The first wave 1c is located lower than the second wave 1d to adjust the displacement characteristics. By lowering the vertex of the first wave 1c, the damper is more easily stretched and less likely to move under the voice coil 4 than in the case where the vertexes are at the same height. This configuration reliably reduces the abutting of the voice coil onto the bottom when the vibration system moves downward.

[0107] The positions of the bend 1a, at which the inner circumference of the damper 1 is attached to the voice coil 4 and the mount 10b, on which the outer circumferential end 1g of the damper is attached to the thin frame 10 are compared. In the shown state, the outer circumferential end 1g of the damper is located lower than the bend 1a. In this manner, the bend 1a is located higher than the mount 10b, while the wave section L2 is located lower than the bend 1a. The vertexes of the first and second waves 1c and 1d are at heights equal to or lower than the outer circumferential end 1g of the damper.

[0108] The damper 1 is shaped to pass through a point lower than the outer circumferential end 1g between the bend 1a and the outer circumferential end 1g. In FIG. 2, the curve 1b has, at the lowest point of the damper 1, the outer circumferential end 1e which leads through the waves of the first and second waves 1c and 1d to the outer circumferential end 1g of the damper which is higher than the outer circumferential end 1e. That is, it can also be said that the damper does not linearly connect the bend 1a and the outer circumferential end 1g, but bends, for example, to pass through a point lower than the outer circumferential end 1g even once in this cross section and is bridged to the mount 10b for the outer circumference of the damper. With this configuration, the damper has a greater radial length even in a tiny space between the thin frame 10 and the lead wire or the diaphragm 2A than in a linear connection between the bend 1a and the outer circumferential end 1g. This allows efficient arrangement of the curve 1b and the wave section L2, improves the flexibility in designing the damper, and reduces the thickness of the speaker.

[0109] The outer circumferential end 1e of the curve 1b is located lower than the upper end 6b of the yoke 6. This allows efficient arrangement of the curve 1b and the wave section L2 and further reduces the thickness of the speaker.

[0110] FIG. 3 is an exploded perspective view of the thin speaker according to the present disclosure.

[0111] The diaphragm 2A includes the diaphragm body 2 made of paper and the edge 3 made of a fabric on the outer circumference of the diaphragm body 2. Located under the diaphragm 2A is the voice coil 4. The bend 1a of the damper 1 is coupled to the lower surface of the diaphragm body 2, while the outer circumferential end 1g of the damper is coupled to the mount 10b for the outer circumference of the damper in the thin frame 10. Reference character 14 denotes a terminal of the thin frame 10. Located under the thin frame 10 is the magnetic circuit 5 including the plate 8, the magnet 7, and the yoke 6. The thin frame 10 has the dust-proof fabric 13 on the back surface.

[0112] The lead wire of the voice coil 4 is connected to the terminal 14 of the thin frame 10. FIG. 4 shows an arrangement of a lead wire 4c of the voice coil 4.

[0113] The lead wire 4c out of the voice coil 4a is led out from the outer circumference of the upper end of the voice coil bobbin 4b along the back surface of the diaphragm body 2.

[0114] That is, the lead wire 4c is sandwiched between the back surface of the diaphragm body 2 and the bend 1a of the damper 1. The diaphragm body 2, the bend 1a, the voice coil bobbin 4b, and the lead wire 4c of the voice coil 4a are collectively bonded at four points by an adhesive as indicated by an adhesive section AG surrounded by the broken line.

[0115] The lead wire 4c is directly drawn out of the adhesive section AG to the outer circumference and has the outer end connected to the terminal 14 by an adhesive (not shown).

[0116] FIG. 5 shows how to draw out the lead wire 4c. In order to reduce the thickness of the lead wire 4c, no relay lead wire is used, but a stress-concentrated portion is formed into an L-shape to disperse the stress. The outer end of the portion is connected to the terminal 14 by an adhesive.

[0117] In this manner, the thin speaker S of the present disclosure is configured.

[0118] Results of simulating displacements of the vibration system and the amplitude characteristics of the thin speaker S configured as described above as follows.

[0119] FIG. 6 includes the illustrations (a) to (c) respectively showing results of simulating displacements of the edge 3 of the diaphragm 2A, the damper 1, and the vibration system of the thin speaker S as the combination and integration thereof.

[0120] In the illustrations (a) to (c) of FIG. 6, the lower graphs show their characteristics. In each graph, the vertical axis represents a load and the horizontal axis represents the displacement. The curve A represents the forward “UP-SIDE” movement, and the curve B represents the backward “DOWN-SIDE” movement.

[0121] It is found from the comparison between the relationships between the load and the displacement of (i) the damper 1 according to the present disclosure in the illustration (b) of this FIG. 6 and (ii) the damper 1′ of the prototype in the illustration (b) of FIG. 13 that there is an improvement in the characteristics.

[0122] The following is also found from the comparison between the relationships between the load and the displacement of (i) the edge 3 and the damper 1′ of the prototype (see the illustration (c) of FIG. 13) and (ii) the present disclosure in the illustration (c) of FIG. 6. The forward “UP-SIDE” and the backward “DOWN-SIDE” have substantially the same shape in the present disclosure.

[0123] FIG. 7 shows a result of measuring a displacement with respective to the frequency. In the present disclosure, the non-linearity of the amplitude characteristics of the edge 3 of the diaphragm 2A is cancelled by the non-linearity of the amplitude characteristics of the damper 1. This causes a symmetrical amplitude of the forward “UP-SIDE” displacement and the backward “DOWN-SIDE” displacement, and reduces distortions.

[0124] FIG. 8 shows a stationary state of the vibration system, whereas FIG. 9 shows a deformation of the damper 1 when an audio current flows through the voice coil 4a and the diaphragm 2A moves downward. The present disclosure reduces the abutting of the voice coil bobbin 4b onto the bottom of the yoke 6, that is, abutting of the voice coil onto the bottom.

[0125] As described above, the damper 1 according to the present disclosure reduces the tendency of the vibration system to move downward and abutting of the voice coil bobbin 4b onto the bottom of the yoke 6, thereby coping with a high input level.

[0126] As shown in FIG. 10, the present disclosure provides flat and excellent frequency characteristics from low to middle frequencies.

[0127] While an example has been described above where the thin speaker S according to the present disclosure is used in an automatic vehicle emergency notification system, the thin speaker S is also applicable for other purposes.

[0128] The size of the damper 1 is set to be fitted into the thin frame 10 according to a specification but is not limited thereto. The size may correspond to even a larger size of the thin frame 10.

DESCRIPTION OF REFERENCE CHARACTERS

[0129] 1 Damper [0130] 1a Bend [0131] 1b Curve [0132] 1c First Wave [0133] 1d Second Wave [0134] 1e Outer Circumferential End (of Curve) [0135] 1f Outer Circumferential End (of Wave Section) [0136] 1g Outer Circumferential End of Damper [0137] 2 Diaphragm Body [0138] 2a Voice Coil Mount [0139] 2A Diaphragm [0140] 3 Edge [0141] 4 Voice Coil [0142] 4a Voice Coil [0143] 4b Voice Coil Bobbin [0144] 4c Lead Wire [0145] 5 Magnetic Circuit [0146] 6 Yoke [0147] 6a Outer Circumference of Yoke [0148] 7 Magnet [0149] 8 Plate [0150] 9 Magnetic Gap [0151] 10 Frame [0152] 10a Frame Mount [0153] 10b Mount for Outer Circumference of Damper [0154] 10c Mount for Outer Circumference of Edge [0155] 13 Dust-Proof Fabric [0156] 14 Terminal [0157] S, S″ Speaker [0158] L1 Inner Circumference of Damper [0159] L2 Wave Section [0160] a Fold [0161] b, b″ Space [0162] AG Adhesive Section