SK11142001A3 - Vibration exciter for creating bending wave vibration - Google Patents

Abstract

A moving coil vibration exciter (1) for exciting a resonant diaphragm comprising a magnet assembly defining an annular gap (2), a voice coil assembly (5) arranged in the annular gap, a mounting member (8) by which the exciter is mounted on the diaphragm and to which the voice coil assembly is fixedly attached, and a resilient suspension (12) on the mounting member and coupled to the magnet assembly to permit axial movement of the voice coil assembly (5) in the annular gap, the arrangement being such that the footprint of the resilient suspension is contained within that of the mounting member or is co-extensive therewith.

Description

The invention relates to vibration exciters. More particularly, the present invention relates to moving coil vibratory exciters for producing a bending wave in a bending member for producing an acoustic output. Thus, these drivers can form drivers in loudspeakers in the form of an acoustic resonant member. Loudspeakers in the form of an acoustic resonant member are described in the international application 'WO 97/09842 and are known as distributed mode loudspeakers.

BACKGROUND OF THE INVENTION

EP-A-0 160 478 discloses a piston cone excitation unit with an excitation coil comprising a ring incorporated with the voice coil assembly and adapted to connect the rear star hinge to the coil body and connect the piston cone diaphragm to the voice coil.

In a known embodiment of a moving coil vibratory exciter used to excite a loudspeaker in the form of a resonant acoustic member, the magnet assembly is coupled to the voice coil assembly by a resilient hinge disposed between the flange of the magnet socket and the outer edge of the voice coil. This elastic hinge can be made from a corrugated fabric or other suitable elastic material in a known manner.

A disadvantage of this arrangement is that a cavity is formed between the acoustic resonant member and the adjacent flange, which results in the air filling the cavity generating cavity modes within an audible frequency range. These cavity modes are emitted from the open edge of the flange and can cause an undesirable acoustic output, the absorption of which may be difficult. Said arrangement can be improved by sealing the area between ·········································· The pole piece and the acoustic resonant element by leaving the voice coil region without a gap, but the outer part of the flange has so far generated hollow modes in an audible frequency range.

The alignment of the voice coil in the annular gap of the magnet assembly is critical to performance, and notwithstanding the loss of efficiency due to large air gaps, it is obvious that even a very small violation of the voice coil alignment will cause the voice coil to swing in the air gap.

An important parameter of efficient exciters is the gap size, which cannot be easily reduced unless the lateral play of the voice coil is severely limited. Foam rubber systems make vertical and lateral movement straight, laterally increasing stiffness to maintain a good alignment capability of the voice coil, and increase the stiffness of the hinge in the operating plane of the voice coil motion, limiting the low frequency range.

Obviously, in some applications, miniature exciters require suspension systems that allow the voice coil to move freely in and out of the air gap, but which severely restrict the movement of the voice coil in other directions, thereby reducing the air coil. and thus increase the efficiency of the drivers.

The two-plane hinge ensures the reciprocating movement of the voice coil and reduces swing of the voice coil to a minimum. However, this requirement is slightly adapted for distributed mode loudspeaker operations. The need for an exciter that controls the bending wave reflections has resulted in the requirement that the hinge at the rear end of the voice coil (i.e., behind the magnet) be more laterally more flexible than the hinge at the magnet end, so side to side movement at the rear end of the guided bending wave it does not push the outer pole piece sideways. This also implies the requirement that the front hinge element be, if possible3

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arranged as close to the acoustic resonant element as possible.

SUMMARY OF THE INVENTION

The subject of the invention is a vibration exciter with a movable coil for exciting an acoustic, e.g. a resonant member capable of bending a wave, the principle being that the vibration exciter comprises a magnet assembly defining an annular gap; a voice coil assembly arranged in an annular gap; a fastening element by which the vibration exciter is attached to the acoustic resonant member and to which the voice coil assembly is attached; and a resilient hinge disposed on the fastening element and associated with the magnet assembly to allow axial movement of the voice coil assembly within the annular gap, the arrangement being such that the trace of the resilient hinge is contained within the fastening element or coincides with the fastening element. Preferably, the track of the resilient hinge is contained within the magnet assembly. The vibration exciter may be a inertial exciter.

The magnet assembly may comprise an inner pole piece and an outer pole piece in the form of a housing, both pole pieces being associated with the magnet. The circumference of the outer pole piece may be without a flange. The edge of the outer pole piece is tapered to form a sharp end.

The fastening element may coincide with the outer pole piece. The fastening element may be in the form of a ring or disc.

The hinge may be arranged entirely at the wall thickness of the outer pole piece. The hinge may associate an inner pole piece with a fastening element mounted within the voice coil assembly. Alternatively, the hinge may associate an outer pole piece with a fastening element.

The resilient hinge may take the form of blocks of resilient material secured between the axial projections of the fastener and the notch in the outer pole piece. Alternatively, the hinge includes a resilient hinge. The element is arranged on the axis of the disc-shaped fastener and the inner pole piece. In another embodiment, the resilient hinge may comprise an annular spring element. The annular spring element may further include tongues whose free ends are attached to the outer edge of the outer pole piece.

The outer pole piece may include a detachable disc-shaped rear portion and a tubular portion. The vibration exciter may further comprise a second resilient hinge axially spaced from said hinge and associating the voice coil assembly with the magnet assembly. The second flexible hinge may be inserted into a groove defined between the rear portion and the tubular portion of the outer pole piece. The second hinge may be a resilient annular hinge and may further be inserted into a groove extending along the circumference of the magnet.

The voice coil assembly preferably comprises an voice coil wound on the frame. The hinge may include electrical contacts for connecting the voice coil assembly to an electrical power source to power the voice coil assembly.

Placing the hinge in a plane perpendicular to the resonant acoustic member eliminates the need for a flange on the outer pole piece to support the hinge, thereby preventing the residual air from being blocked. Said embodiments reduce any potential flange area that, if present, may cause undesired cavity modes.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand the invention, a description of exemplary embodiments of the invention is given in the following part of the invention, with reference to the accompanying drawings, in which FIG. 1 shows an exploded perspective view of a first embodiment of a inertia vibration exciter with a movable coil for driving a bending wave in an acoustic resonant element, FIG. Fig. 4 Fig. 7 Fig. 1a shows a perspective view of the assembled vibration exciter shown in FIG. 1, FIG. Fig. 2 shows an exploded perspective view of a second embodiment of an inertia vibration exciter with a movable coil for driving bending waves in an acoustic resonant member; 2a shows a cross-section of the exciter shown in FIG. 2, FIG. 2b shows a cross-section of an exciter generally similar to that shown in FIG. 2a, but incorporating a modified hinge arrangement; FIG. 3 is a cross-sectional view of another embodiment of a inertia vibration exciter with a movable coil for driving bending waves in an acoustic resonant member;

Fig. 4 shows a cross-section of a vibrating exciter with a moving wave in an acoustic resonance another member coil, embodiment inertial bending on the alarm Fig. 5 shows a cross-section another embodiment inertial vibrating exciter with movable coil on the alarm bending waves in acoustic resonance member, Fig. 6 shows a cross-section another embodiment inertial vibrating exciter with movable coil on the alarm bending waves in acoustic resonance member, and Fig. 7 shows a cross-section another embodiment inertial vibrating exciter with movable coil on the alarm bending waves in acoustic resonance member.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 and 1a, an inertial vibration exciter 1 with a movable coil for driving bending waves in an acoustic resonant member, e.g. an acoustic resonant element described by: · · · · · · t · t · t · t · t · t · t · In the patent application WO 97/09842, to form a loudspeaker. This inertial vibratory exciter 1 comprises a magnet assembly having a magnet 2 interposed between a disc-shaped inner pole piece 3 and an outer pole piece 4 in the form of a cover for defining an annular gap (not shown); a voice coil assembly 5 having a tubular body 6 on which the voice coil 7 is wound; and a suspension and fastening assembly 8 to which the voice coil is mounted to connect the magnet assembly and the voice coil assembly 5 to allow axial movement of the voice coil in the annular gap, and by which the exciter is mounted on an acoustic resonant member (not shown) that to wake up.

As shown in FIG. 1, three notches 9 are formed in the housing of the outer pole piece 4 and are equally spaced from each other along the periphery of the outer pole piece 4, the hinge and fastening assembly 8 comprising a fastening ring 10 having an inner and outer diameter substantially coincident with the inner and outer diameters of the outer pole piece 6. The attachment ring 10 is provided with three projections 11 extending in the axial direction and equally spaced from each other along the periphery of the attachment ring 10. A prism-shaped resilient hinge 12, e.g. of rubber, the projections 11 and hinges 12 being arranged to engage the slots 9 of the outer pole piece 4, and each hinge 12 is an end opposite to the end by which each hinge 12 is attached to a respective projection 11 attached to the walls of the respective notch. 9th

In this arrangement, each hinge 12 is located within the wall thickness of the housing of the outer pole piece 4, as a result of which the outer pole piece 6 need not be provided with a flange extending around the periphery of the pole piece, thereby solving the above problem.

The exciter embodiment shown in FIG. 2 and 2a is basically ······································· Similar to the embodiment of the inertia vibration exciter shown in FIG. 1, that is, like the inertial vibration exciter 1, it comprises a magnet assembly having a magnet 2 interposed between a disc-shaped inner pole piece 3 and an outer pole piece 6 in the form of a cover to define an annular gap 20; an voice coil assembly having a tubular body 6 on which the voice coil 7 is wound; and the suspension and attachment assembly E3. However, in the embodiment of the driver shown in FIG. 2 and 2a, the hinge is formed by a spring element 13 in the form of a spring ring 14 made e.g. of stainless steel, and attached to the fixing ring 10, wherein certain portions of the spring ring 14 define three curved spring tongues 15 which are equally spaced from each other along the periphery of the spring ring 14, each free end 16 of each spring tongue 15 being fixed to the wall outer sleeve housing. It should be noted that the spring element 13 is shown in FIG. 2a is shown only schematically.

As shown in FIG. 2 and 2a, the voice coil assembly is secured to the attachment ring 10 so that the spring ring 14 forms a hinge between the voice coil assembly 5 and the outer pole piece 4 of the magnet assembly. As shown in FIG. 2, the spring tongues 15 extend along the outer edge of the spring ring 14, however, it will be understood that the spring tongues 15 may also extend along the inner edge of the spring ring 14.

In the alternative embodiment shown in FIG. 2b, the hinge formed by the spring element may be disposed between the inner pole piece 3 and the attachment disc 30 attached to the carcass 6. The spring ring 14 is concentrically arranged on the inner pole piece 3, which is achieved e.g. forming a hole (not shown) in the spring ring into which the projection on the inner pole piece 3 can fit. The concentric arrangement is transferred to the voice coil by locating the spring ring 14 concentrically inside the voice coil frame 6

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and by providing a tight fit of the spring ring 14 within the carcass 6. This exciter structure is therefore self-aligning and the lateral compliance of the hinge is sufficiently low to achieve a relatively small air gap.

Fig. 3 illustrates another embodiment of an inertial vibration exciter similar to that shown in FIG. 2b. However, in the embodiment of FIG. 3, the outer pole piece 4 is formed of two parts, one of which is a detachable disc-shaped rear part 4a and the other of the tubular part 4b, the two parts joined together defining a recess 23 providing space for the star hinge 17 arranged at the rear end of the oscillating a coil 7 for achieving a hinge acting in two planes and having different lateral compliance between the front and rear planes.

This embodiment has two additional features which lead to a simple self-alignment assembly. One of these two features is that the spring hinge 13 is attached to the fastening disc 30 by a bayonet connection, which allows the exciter to be easily assembled and unfolded, the other of these two features being that the coil terminals T can be connected to electrical contacts 16 on the mounting disc 30, which are in turn inside the driver contact contact system in contact with the conductors (not shown) on the acoustic resonant member (not shown) when the driver is contacted with the surface of the acoustic resonant member. This eliminates the use of conductors connecting the thin coil wires to the outer conductors and improves the balance of the magnet assembly. In addition, this excludes the use of conductors led to or in the acoustic resonant element, since the conductors may be encapsulated in the coating of the acoustic resonant element and made in the form of a thin copper plate or conductive coating.

The adoption of the principle of assembling the outer pole piece of the two-piece magnet assembly opens the way to a very high degree of excitement. * Compact integrated suspension system, especially suitable for small exciters. · · · • e e e * * * * * * * * * * * * Fig. 4 shows a further embodiment of the inertia vibration exciter 3, which is generally similar to the embodiments of the inertia vibration exciter shown in FIG. 2b and 3, except that in the embodiment of FIG. 4, the magnet 2 comprises two slots (not shown) extending along the circumference of the magnet and associated with a single double planar suspension system using flat spring washers 19 disposed between the magnet 2 and the frame 6. This has the advantage of a wider annular gap 24 between the magnet 2 and the side of the tubular member 4b. It should be noted that both the inner pole piece 3 and the rear piece 4a are centered to the center of the magnet 2 so that the exciter as a whole comprising the voice coil is self-aligning. In this embodiment, the front hinge is formed by a suspension block 18 made of soft rubber and concentrically arranged on the attachment disc 30 and the inner pole piece 3.

Fig. 5 shows an alternative with respect to the embodiment of the inertial vibration exciter 1 shown in FIG. 4, which uses a standard unmodified, i.e., unscrewed magnet 2. In the embodiment of FIG. 5, the outer pole piece 6 is made up of three self-aligning parts formed by the bottom part 4a, the middle part 4b and the top part 4c and manufactured, e.g. These parts meet in planes in which recesses for hinges are formed, which makes it possible to pre-assemble the spring washer 19 on the voice coil frame 6. In this embodiment, the tubular top portion 4c is used to terminate the outer pole piece 4, wherein the end 21 of the top portion 4c is sharp, to improve the acoustic cavity effect, and a true air gap 20 is created only where necessary to align the pole pieces .

The embodiment of the inertial vibration exciter 1 in FIG. 6 is generally similar to the embodiment shown in FIG. 5 and provides smaller assemblies, but can also be used with larger exciters,

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especially where very strong lateral alignment resulting from the distance between the front and rear hinges helps to accomplish the application. The maximum penetration of the voice coil into the external pole piece shall be limited to prevent the front end of the pole piece from striking the acoustic resonant element. A foam stop can be used for this purpose.

As shown in FIG. 7, further simplifying the embodiment of the inertial vibratory exciter 1 can be achieved by providing an annular foam rear hinge 22 disposed around the magnet housing 2 and in contact with the voice coil body 6. Proper selection and correct tolerance of the annular rear hinge 22 allows the voice coil assembly 5 to be easily pushed and self-aligning at the rear end of the assembly. The front end of the voice coil assembly 5 is aligned by a suspension block 18 which is concentrically arranged on the fixing disc 30 and the inner pole piece 2. The fixing disc 30 is supported by the fixing ring 10.

Claims (7)

1/7 A movable coil vibratory exciter for exciting an acoustic resonant member capable of bending waves, comprising a magnet assembly defining an annular gap; a voice coil assembly arranged in an annular gap; a fastening element by which the vibration exciter is attached to the acoustic resonant member and to which the voice coil assembly is attached; and a resilient hinge disposed on the fastening element and associated with the magnet assembly to allow axial movement of the voice coil assembly within the annular gap, the arrangement being such that the trace of the resilient hinge is contained within the fastening element or coincides with the fastening element. 2/7 ············· I ··········································· L · Vibration exciter according to claim 1, characterized in that the magnet assembly comprises an inner pole piece and an outer pole piece in the form of a housing, both pole pieces being associated with a magnet. 3/7 ·························· Vibration exciter according to claim 2, characterized in that the periphery of the outer pole piece is free of a flange. 4/7 Τ \ ΙΉΜ-ΟΊ ·· ······················ The vibratory exciter according to claim 3, wherein the periphery of the outer pole piece is tapered to form a sharp end. 5/7 FIG. 3 4α -θ ') · · • β · · · • · • • · • • • • 0 β • • · · · • • • · • • · · • • • · • • · • · • · • • • • · · • · · · · · · · ·· ···· ·· ·· ·· 9 · ························· · FIG. 7 Vibration exciter according to any one of claims 2 to 4, characterized in that the fastening element coincides with the outer pole piece. Vibrating exciter according to any one of claims 2 to 5, characterized in that the hinge is completely arranged in the wall thickness of the outer pole piece. ·········································································· ·· · Vibrating exciter according to one of the preceding claims, characterized in that the fastening element is in the form of a ring. Vibration exciter according to any one of claims 2 to 6, characterized in that the hinge associates an inner pole piece with a fastening element fixed within the voice coil assembly. Vibrating exciter according to any one of claims 2 to 8, characterized in that the resilient hinge is in the form of blocks of resilient material attached between the axial projections of the fastener and the notch in the outer pole piece. Vibration exciter according to any one of claims 1 to 7, characterized in that the fastening element is disc-shaped. 11. The vibratory exciter of claim 10, wherein the hinge comprises a resilient element disposed on the axis of the disc-shaped fastener and the inner pole piece. Vibrating exciter according to any one of the preceding claims, characterized in that the resilient hinge comprises an annular spring element. Vibrating exciter according to any one of the preceding claims, characterized in that the resilient hinge comprises electrical contacts for connecting the voice coil assembly to a power source for supplying the voice coil assembly with electrical power. Vibration exciter according to any one of the preceding claims, • · • · ···· ·· • · · í ·· · · • · · · 13 • · • · · ·· · · • · • · • · · · ·· · · · v y z learning m that includes the second flexible hang up axially offset from said hinge and associating assembly kmi- tace j coils with magnet assembly. 15th Vibration exciter according to claim 14, s n a č u j ú - wherein the second hinge is a resilient annular hinge. 16. The vibration exciter of claim 15, wherein the second hinge is inserted into a groove extending along the circumference of the magnet. Vibrating exciter according to any one of claims 2 to 16, characterized in that the outer pole piece comprises a detachable disc-shaped rear part and a tubular part. A vibratory exciter according to claim 17, wherein the rear portion and the tubular portion define recesses for receiving the second hinge. An exciter according to any one of the preceding claims, characterized in that the vibration exciter is formed by an inertial exciter. Vibrating exciter according to any one of the preceding claims, characterized in that the track of the resilient hinge is contained within the magnet assembly. TV4 <H -CM ······················································ · ···· · · ·· ·· ·· ·· ·· FIG. 1 7/7