SK25498A3 - Inertial vibration transducers - Google Patents

Abstract

An inertial vibration transducer (9) characterised by a motor coil assembly comprising a tubular member (18) and a coil (13) rigidly fixed to the tubular member, and by a magnet assembly (15) disposed concentrically within the motor coil, and resilient means (19) supporting the magnet assembly for axial movement relative to the motor coil, the motor coil and tubular member being adapted to be rigidly mounted to a distributed mode radiator (2).

Description

Technical field

The invention relates to a transducer, in particular a vibration transducer of loudspeakers comprising panel acoustic radiating elements.

BACKGROUND OF THE INVENTION

GB-A-2262861 discloses a panel loudspeaker comprising a resonant multi-mode radiator consisting of a uniform composite plate comprising a core having a transverse chamber structure surrounding the two shells, the plate having a bending strength ratio (b) in all directions to a cubic power of a panel weight per unit area (μ) of at least 10, a fastener carrying or supporting said plate to the support body in a free, non-damped manner, and an electromechanical excitation means designed to drive multi-mode resonance in the radiating an electrical input board within the working frequency range of the speakers.

US-A-4,506,117 discloses an electroacoustic transducer comprising a flywheel adapted to be attached to a base plate of a panel to be vibrated.

SUMMARY OF THE INVENTION

Individual embodiments of the invention use elements having properties, e.g. the structure and configuration generally and / or specifically described in WO 97/09842 relating to this application. Thus, these elements have the ability not to dampen and propagate the input vibration energy by bending waves in the functional surface or functional surfaces that extend transversely to the thickness of the element, often but not necessarily at the edge of said element or elements. They have a configuration with or without anisotropy of bending strength so that the resonant modes of bending vibration vibrations distributed over the entire surface of the element favorably affect the acoustic connection with the ambient air, and have predetermined preferred positions or locations for the converter means, in particular functionally active or movable parts effective depending on the acoustic vibration activity in said area and on signals, usually electric, corresponding to the acoustic measure of such vibration activity. In co-pending international patent application WO 97/09842, which has the same priority, the above-mentioned elements for passive acoustic devices without converter means, such as e.g. reverberation or acoustic filtering equipment, or acoustic sounding of a room or room, as well as active acoustic equipment with transducers, including sound sources or loudspeakers with a remarkably wide frequency range, where input signals are applied to that sound, or microphones that are exposed to sound they transmit to other signals.

In particular, the invention relates to active acoustic devices in the form of loudspeakers. The above elements in these devices are referred to as distributed mode acoustic radiators and have the characteristics described in patent application WO 97/09842 or other characteristics described in this patent application.

SUMMARY OF THE INVENTION The present invention provides an inertial vibration transducer for driving an element having the ability to dampen and propagate input vibration energy by bending waves in at least one functional area extending transversely to its thickness such that resonant bending vibration modes are distributed over said at least one area and predetermined preferred positions and a transducer mounted on said element in a single position to vibrate said element to achieve resonance of said acoustic radiator element which provides acoustic output during its resonance, said inertial vibration transducer comprising a motor coil assembly with a transducer. a coil mounted on the tubular member, a magnet assembly arranged concentrically with respect to the motor coil assembly, and a resilient means for carrying the magnet assembly to achieve axial movement of the assembly relative to the motor coil assembly. In this case, said tubular element is adapted to be directly attached to the element to be vibrated by means of adhesive means. The resilient means may comprise mutually opposed elastomeric members disposed on opposite sides of said magnet assembly. Caps may be used to close the axial ends of the tubular member to which the resilient means may be attached. These caps may comprise a resilient means. Each of said lids may further have an annular resilient groove edge. In addition, magnetic shielding can be provided through these caps. The coil may be attached to the inside of the tubular member. The motor coil assembly may be adapted to be positioned within a cavity of the radiator, the shape of which corresponds to that of the assembly. In addition, the motor coil assembly may be adapted to be attached to the front face of said radiator. The magnet assembly may comprise opposing generally disc-shaped pole extensions, the edge of one of these extensions being arranged within the motor coil assembly and adjacent to the motor coil assembly, and the edge of the other pole piece being formed by a flange disposed adjacent the motor coil assembly and surrounding the coil assembly. motor coil. A resilient element may be inserted between one of the pole pieces and the front surface of the radiator. The magnet assembly may comprise a pair of opposing magnets interposed between the pole pieces. Complementary assemblies, each including a motor coil assembly and a magnet assembly, may be provided on opposite faces of the emitter, further providing means for attaching the magnet assemblies to each other for dual-action operation.

In another aspect, the present invention provides a loudspeaker comprising a flywheel converter as described above.

Brief description of the figures

The subject matter of the invention will become more apparent from the description of exemplary embodiments of the invention, with reference to the accompanying drawings, in which FIG. 1 shows a distributed mode loudspeaker that has been described and claimed in WO 97/09842, which is related to this application, FIG. 2a shows a partial cross-section along the line A-A shown in FIG. 1, FIG. 2b shows an enlarged cross-section of a distributed mode radiator of the same kind as shown in FIG. 2a, wherein this figure also shows two alternative structures of the emitter, FIG. 3 shows a cross-section of a first embodiment of a converter, FIG. 4 shows a cross-section of a second embodiment of the converter, FIG. 5a shows a cross-section through a third embodiment of the converter; FIG. 5b shows a cross-section through a fourth embodiment of the converter; FIG. 5c shows a cross-section through a fifth embodiment of the converter, and FIG. 6 shows a cross-section of a sixth embodiment of the converter.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1, there is shown a panel loudspeaker 81 of the same type as described and claimed in the related application WO 97/09842 with the same priority, the loudspeaker comprising a rectangular frame 1 carrying a flexible hinge 2 around the inner edge carrying a sound emitting panel 2 with distributed modes . Converter 9, e.g. the transducer described in detail in the related patent applications WO / 09859, WO97 / 09861, WO9709858 with the same priority is mounted wholly and exclusively to panel 2 or panel 2 at a predetermined position defined by the coordinates x and y, which coordinates are. calculated as described in related application WO97 / 09842 with the same priority to generate a bending waveform in the panel to cause resonance of the panel forming the radiator providing acoustic power during its resonance.

Said transducer 9 is driven by a signal amplifier 10, e.g. a low frequency amplifier coupled to the transducer by means of conductors 28; The amplifier load and power requirements can be quite normal, i. as with conventional conical loudspeakers, with a sensitivity of the order of 86 to 88 dB / W under ambient load conditions. The impedance load of the amplifier has a strong resistive character at 6 Ω and a load rating of 20 to 80 W. If the core of the panel and / or its sheath are made of metallic material, they serve as heat dissipation of the converter to dissipate heat from the converter's coil and improve performance.

In FIG. 2a and 2b show typical cross-sections of the loudspeaker 81 in FIG. 1. FIG. 2a, it is evident that the frame 1, the flexible hinge 2 and the panel 2 are connected to each other in the joints 20 by means of adhesive means. Said frame may be a lightweight frame, e.g. an image extruded frame of metallic material, e.g. aluminum alloy or plastic. Suitable materials for the flexible hinge may be flexible materials, e.g. foam rubber and foam plastic. Suitable adhesives for the joints 20 may be epoxy, acrylate and cyanoacrylate resins, or other adhesives.

FIG. 2b, the panel 2 is formed by a rigid lightweight panel having a core 22 made e.g. of rigid plastic foam 97, such as e.g. cross-linked polyvinyl chloride, or a core structure 98 with a cellular structure such as e.g. a core with a honeycomb structure made of metal foil, plastic, mass or other similar material, the chambers of said structure extending transversely to the panel surface and closed by opposing shells 21 made of a material such as e.g. paper, plastic or metal foil. In case the casings are made of plastic, the casings can be reinforced in a known manner to increase their modules, e.g. carbon, glass, Kevlar fibers, and the like.

Thus, the envisaged sheathing materials and reinforcements include carbon, glass, Kevlar (RTM), Nomex (RTM), i.e., carbon, glass, and liner. aramid fibers in different layers and bonds, as well as paper, laminated paper, melamine and various synthetic plastic films with high modules, such as e.g. Mylar (RTM)

Captan (RTM), a plastic reinforced plastic and the quality of Vectra liquid thermoplastics have been found to be used for molding very ie.

Polycarbonate, phenol, or related plastic metal foils can be used based on polymer thermoplastic research.

crystals on that polymer-thin sheaths of small size, with a diameter of about 30 cm by injection molding. This material constitutes the oriented crystal structure itself in the injection direction, which is an advantageous direction for good propagation of high sound frequencies from the excitation point towards the edge of the panel.

The additional shaping of said or other thermoplastics allows the molding tools to have locating and registration features, such as grooves or rings, to precisely locate the parts of the transducer, e.g. excitation coil and / or magnet hinge. In addition, in the case of a weaker core material, it is preferable to locally increase the thickness of the sheath, e.g. in a surface or ring with a diameter of up to 150% of the diameter of the sensor, to enhance said surface and advantageously couple the vibration energy in the panel. In this way, the high-frequency response can be improved by some softer foam materials.

The envisaged core layer has a honeycomb structure or a corrugated structure formed of aluminum alloy foil, Kevlar (RTM), Nomex (RTM), unpainted paper or paperboard and sheets of various synthetic plastics, also cellular or foamed plastic or fiber materials, even aerogel metals if they have a suitably low density. Some suitable core layer materials have a self-sheathing capability in manufacture and / or have sufficient strength to be sandwiched between the sheath layers without the use of lamination. The core-material with a high-performance cellular structure is known under the trade name Rohacell, which material is suitable for a radiant panel to be provided with a jacket. In practical terms, the aim is to achieve overall lightness and strength suitable for specific purposes, which in particular includes optimizing the contributions of the core, the skin layers and the transitions therebetween.

In several preferred embodiments of the panel, sheaths of metal and metal alloys, or alternatively carbon fiber reinforced materials, have been used. These panel designs as well as panel designs in which the Aerogel alloy is used or in which the core has a honeycomb structure of metallic material have a high frequency shielding capability that is important for the compatibility of the electromagnetic energy emitting device. Conventional cone-type panels or loudspeakers do not have the capability of said shielding.

In addition, preferred forms of piezoelectric transducers and electrodynamic transducers have negligible electromagnetic radiation or stray magnetic fields. Conventional loudspeakers have a large magnetic field, up to a distance of up to 1 m, unless specific compensatory countermeasures are taken.

Where it is important to provide or maintain shielding in a given application, the electrical connections may be made such that the conductive portions of a suitable DML panel, the electrically conductive foam, or similar interfaces can be used for attachment in the edge region.

The hinge 3 may damp the edges of the panel 2 to prevent excessive movement of the edges of the panel. In addition, additional buffering means, e.g. means in the form of patches associated with the panel at selected positions to damp the excessive movement of the panel to achieve a uniform resonance distribution across the panel surface. These patches may be made of bitumen-based material typically used in conventional loudspeaker enclosures or a flexible or rigid polymeric sheet material. Some materials, especially paper and board and some types of core materials, may be self-limiting. If desired, damping can be enhanced in the construction of the panels using adhesives that are flexible and not only rigid when cured.

Said effective selective damping comprises specific panel applications comprising a sheet material of the composition permanently associated with the panel. The edges and corners may be particularly important for the dominant and in the context of less dispersed low frequency modes of bending vibration of the panel described in this application. The edge fastening of the damping means may advantageously lead to a panel with a completely framed sheet material, although at least its corners may often be relatively free for the necessary elongation of the panel in low frequency panel operation. The attachment can be carried out by means of adhesive or self-adhesive materials. Other forms of useful damping, particularly with respect to several minor effects and / or intermediate and higher frequencies, may be accomplished by means of a suitable mass or masses attached to the sheet material at predetermined effective center positions in said area.

The above panel is indeed two-dimensional. The sound energy from the rear of the panel is not strongly phase related to the sound energy from the front of the panel. This brings the advantage of space, frequency, in the total sum of the sound energy, the limited effect of the acoustic power given with a uniform distribution reflecting standing waves and good reproduction of natural space.

While the sound or radiation from the acoustic panel is largely non-directional, the percentage of phase-related information outside the speaker axis increases. To improve the focusing of artificial stereo listening, positioning the speaker at a height at which images are usually hung, i.e. at the usual height of a standing person, gives the normal seated listener optimal stereo listening even when in a position slightly deviated from the axis speaker. This triangular geometry left / right relative to the listener provides an additional angular component. This gives a good stereo effect.

This is another advantage for a group of listeners compared to conventional loudspeaker reproduction. Given the truly dispersed nature of the acoustic panel of the acoustic panel, the acoustic panel provides a loud volume, to which the rule of the loss of square distance to the equivalent point source in no way applies. As a result, for a listener sitting off the axis of the speakers, or at a location not very suitable for listening, the panel speaker field strength enhances a better stereo effect compared to conventional speakers. This is because the listener located outside the center of action of all speakers does not suffer from two drawbacks, which are usually applied near the speakers. The first of these is that the perceived loudness of the nearby speaker is excessively increased and, as a result of the latter, the perceived loudness of the other speakers.

Another advantage of the flat, lightweight panel loudspeaker is its visual attractiveness, good sound quality, and the requirement for only one transducer, and this loudspeaker does not require a switch over the entire sound range per panel diagram.

Fig. 3 shows an embodiment of a voice coil converter 9 disposed entirely within a fixed light-weight distributed panel 2 comprising a core 22 coated on both sides with sheaths 21 to generate bending waves in the panel 2.

The transducer comprises a coil 13 embedded in a fastening means 16 made, e.g. of an epoxy resin, and arranged in the cavity 29 in the core 22 of the panel 2, and surrounding the cylindrical coil frame 18, the coil 13 and its frame 18 being fixed in the panel 2.

In the part of the cavity 29 defined by the coil frame 18, a magnet assembly is mounted which includes a pair of opposing magnets 15 separated by a pole element 14 and is attached to the inside of the skins 21 of the panel 2 by opposing flexible hinges 19 made of a rubber material such as foam rubber. and adhesively coupled to the magnet assembly and the inner surfaces of the respective shells 21 of the panel 2. The magnet assembly 14, 15 is thus concentrically disposed relative to the coil 13 and is movable in the axial direction on the hinges 19 of the assembly.

During operation of the transducer, due to the axial movement of the magnet assembly relative to the coil, there is local elastic deformation of the panel in the region between the magnet assembly and the coil, and thus the bending wave in the panel 2 is excited.

In operation of the transducer, at least at high frequencies, due to the mass of the magnet assembly being relatively greater than that of the panel, the inertia of the magnet assembly tends to keep the magnet assembly in a stationary state and keep the panel relative to the magnet assembly in a vibrating state.

Fig. 4 shows a further embodiment of an oscillating coil converter 9 similar to the one shown in FIG. 3 and arranged entirely within the inner portion of the solid light emitting panel 2 comprising the core 22 coated with sheaths 21 to induce bending waves in the panel 2. To allow assembly of the transducer 9 with the panel 2, the transducer takes the form of a modular assembly. As can be seen from this picture, in the panel

2, a suitable cavity 120 is provided for receiving the transducer 9.

Said transducer comprises a coil 13 attached to the inner wall of the cylindrical coil frame 18 by means of, e.g. a rigid adhesive casting 20, wherein the coil former 18 provides an outer housing of the transducer and is closed at opposite axial ends by light end caps 119 which are fixed to the coil former in any desired manner, e.g. using adhesive bonds 220.

Said inverter module assembly is adapted. for placement in the cavity 120 in the distributed mode panel 2 by moving in the direction of the arrow A. This transducer assembly is secured in the cavity by adhesives.

In the cavity 29 defined by the coil frame 18, a magnet assembly comprising a pair of opposing magnets 15 separated by a pole member 14 is secured to the end caps 119 of the coil frame 18 by means of opposing resilient hinges 19 made of a rubber material such as e.g. foam rubber, and adhesively bonded to the magnet assembly and the inner surfaces of the respective end caps.

Thus, the magnet assembly 14, 15 is mounted concentrically relative to the coil 13 and is axially movable on its hinge 19. During operation of the transducer 9, local elastic deformation of the panel and thus vibration of the panel occurs, as is the case of the transducer shown in FIG. 3, so the inverter drives bending waves in panel 2. ·

In the embodiment of FIG. 5a, the transducer 9 comprises complementary double-acting exciters located on opposite sides of the panel 2 to induce bending waveform in the fixed light-emitted light emitter 2, which comprises a core 22 surrounded by opposite shells 21 to cause panel resonance.

In this embodiment, the coils 13 are attached, e.g. by means of adhesives, on the outside of the coil frame 18 intended to form motor coil assemblies that are rigidly connected, e.g. The magnets 15 are closed by pairs of poles 14, one of which has the shape of a disc and its edge is near the inner part of each coil frame 18 and the other has a peripheral flange 162 arranged so as to: that it surrounds the coil 13.

The fastener 93, which is generally cylindrical in shape, is arranged so that it freely extends through an opening 29 in the panel 2. This fastener 93 comprises opposed generally complementary portions each provided with a head 95 which acts against the axial end of the respective exciter. from said pair of transducer drivers 9 to interconnect said transducers. Said complementary portions of the fastening element 93 are rigidly connected to each other by complementary threaded portions 160, 161. The fastener may be made of any suitable material, such as e.g. plastic.

In the embodiment of FIG. 5a, the panel 2 is not firmly clamped to the panel 2 at a location adjacent to the opening 29, but is coupled to the panel via resilient pads 17, e.g. of foam rubber and arranged near the opening 29 in the panel 2 in the same manner as described with reference to FIGS. 3 and 4, whereby the transducer 9, due to the inertia effects induced by the combined mass of the respective exciters, induces bending waves in the panel 2.

The embodiment of the converter 9 in FIG. 5b is generally similar to the embodiment of FIG. 5a except that in the embodiment of FIG. 5b, the transducer 9 is intended to be fastened on only one side of the panel 2. Thus, the magnet assembly 14, 15 is fastened to the surface of the panel 2 by means of a flexible hinge 17 made, e.g.

of rubber and attached to the edge of the flange 162 of the outer pole piece 14.

Fig. 5c shows an embodiment of a transducer 9 of the same kind as shown in FIG. 5b, and intended to be simply applied to the panel surface. The transducer 9 is thus fixed by means of a coil former 18 and a resilient hinge 17 on a thin substrate 147 provided on the outside with a self-adhesive layer by means of which the transducer can be fixed to the panel 2 in the desired position.

The transducer 9 in FIG. 6 is a low profile device and may be substantially concealed within the distributed mode panel 2. The exciter comprises a coil cylindrical body 18 adapted to be attached, e.g. by means of adhesives, in the corresponding aperture 29 in panel 2- To form the motor coil assembly, e.g. The opposite axial ends of the carcass 18 are closed by disc elastic hinges 59 made, e.g. of rubber and other similar materials, and provided with an annular groove 136 arranged at the edge of said hinges to form a groove-like edge similar to that used in conventional conical loudspeaker drive units. The edges of said hinges 59 are attached to the axial ends of the carcass 18. e.g. by clipping the respective parts of these elements, using adhesives or some other suitable means. The central portions of the hinges 59, which are delimited by annular grooves 136, carry a magnet assembly therebetween comprising a pair of opposing magnets 15 between which a pole piece 14 is inserted. The outer faces of the magnets 15 are attached to the central portions of the hinges 59, thereby the magnet assembly 14, 15 is disposed concentrically relative to the coil 13 and is capable of limited axial movement relative to the coil.

The magnet assembly is shielded by disc-shaped screens 121 mounted on annular resilient members 17 supported on the panel 2 to prevent or limit the scattering magnetic field surrounding the panel at a location adjacent to said transducer.

Although in the above embodiments of the transducer, the motor coil assembly is shown to be attached to the panel 2, and the magnet assembly is shown to be resiliently attached to the panel, it is understood that this arrangement can be reversed so that the magnet assembly is attached to said panel and the motor coil assembly is hinged. In this case, to increase the excitation effect, the magnet assembly will be made relatively light, and the motor coil assembly will be made relatively heavy.

Claims (14)

PATENT CLAIMS 1. Inertial vibration transducer for excitation of an element having the ability to • damp in a. propagating the input vibration energy by bending at least one functional surface extending transversely to a thickness such that the resonant modes of bending vibration are distributed over said at least one surface and predetermined positions within said surface for the transducer means, and a transducer mounted on said resonance element forming an acoustic radiator which provides an acoustic output during its resonance, characterized in that it comprises a motor coil assembly (13, 18), the coil (13) of which is mounted on the tubular element (18), a magnet assembly (15) arranged concentrically relative to a motor coil assembly and a resilient means (19, 136) supporting the magnet assembly for axially moving the magnet assembly relative to the motor coil assembly, wherein the tubular member (18) is adapted to be directly attached to the member (2) to be vibrated by adhesion means (16, 20). An inertia vibratory transducer according to claim 1, characterized in that said resilient means (19, 136) comprises mutually opposed elastomeric elements arranged on opposite sides of said magnet assembly. An inertia vibratory transducer according to claim 1 or 2, characterized in that it comprises caps (59, 119) closing the axial ends of the tubular element (18), said resilient means (19, 136) being fixed to said caps. The inertia vibratory transducer according to one of claims 1 to 3, characterized in that the coil (13) is attached to the inside of the tubular element (18). The inertia vibratory transducer according to any one of the preceding claims, characterized in that the motor coil assembly (13, 18) is adapted to be inserted into a cavity (120) in the radiator (2) having a shape corresponding to the shape of the assembly. An inertia vibratory transducer according to claim 3, 4 or 5, if the claim is dependent on claim 3, characterized in that the caps (59) comprise resilient means (136). An inertia vibratory transducer according to claim 6, characterized in that each of the caps (59) comprises an annular resilient flute (136). The inertia vibratory transducer according to claim 6 or 7, characterized in that it comprises a magnetic shield (121) arranged over the caps (59). The inertia vibratory transducer according to one of claims 1 to 4, characterized in that the motor coil assembly (13, 18) is adapted to be fastened to the front face of the radiator (2). An inertia vibratory transducer according to claim 9, characterized in that the magnet assembly (15) comprises opposing generally disc-shaped pole extensions (14), the edge of one of these pole extensions being located within the motor coil assembly (13, 18) and in place. adjacent the assembly, and the edge of the second pole piece forms a flange (162) located adjacent the motor coil assembly and surrounding the motor coil assembly. An inertia vibratory transducer according to claim 10, characterized in that a resilient element (17) is interposed between one of the pole pieces and the front surface of the radiator. The inertia vibratory transducer according to one of claims 1 to 9, characterized in that the magnet assembly (15) comprises a pair of opposing magnets (15) between which a pole piece (14) is inserted. The inertia vibratory transducer according to any one of the preceding claims, characterized in that it comprises two complementary assemblies, a magnet / motor coil assembly arranged on opposite sides of the radiator, and means (93) for securing the magnet assemblies to each other for dual-action operation. A loudspeaker comprising an inertia converter according to any one of the preceding claims.