SK25698A3 - Vibration transducers - Google Patents

Abstract

A vibration transducer (9) to vibrate a member (2) having a face, characterised by a motor coil assembly having a coil (13) rigidly fixed to a tubular member (18), the assembly being adapted to be fixed to the said face of the member, and by a magnet assembly (15) comprising opposed disc-like pole pieces, the periphery of one of which pole pieces is arranged to be disposed with and adjacent to the motor coil assembly, and the periphery of the other of which pole pieces is formed with a surround flange (90) adapted to surrounding and to be disposed adjacent to the motor coil assembly, and characterised in that the magnet assembly is adapted to be secured at its centre to the said member to be vibrated.

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 panel weight per unit area (μ) equal to at least 10, a fastening means which carries said plate or fastens said plate to a support body in a free, non-damped manner, and an electromechanical excitation means designed to drive multi-mode resonance in a radiating board in response to an electrical input 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 the bending strength so that the resonant modes of the bending wine vibration 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 moving parts effective depending on the acoustic vibration activity in said area and on signals, usually electrical, 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.

It is an object of the present invention to provide a vibration transducer for driving an element having a face, the ability to dampen and propagate input vibration energy by bending waves in at least one functional surface extending transversely to its thickness so that resonant bending vibration modes are distributed over at least one surface and and a transducer mounted on said element in one said position to vibrate said element to achieve resonance of said acoustic radiator element which provides acoustic output during its resonance. The transducer comprises a motor coil assembly with a coil mounted on a tubular member and adapted to be fastened to the face of the element, a magnet assembly having opposing disc pole extensions. An edge of one of the pole pieces is disposed within the motor coil assembly and at a location adjacent to the motor coil assembly, and an edge of the other pole piece is formed by a surrounding flange adapted to surround the motor coil assembly and disposed adjacent the motor coil assembly. The magnet assembly is adapted to be attached at its center to the element to be vibrated. An attachment means may be used to attach the magnet assembly to the member. The fastening means may comprise a fastening member adapted to engage in a cavity in said element. The fastening member may include a spacer for offsetting the edges of the pole pieces from the element. The vibration transducer may comprise a complementary motor coil assembly / magnet assembly, the parts of which are adapted to be fastened on opposite faces of the member and means for mutually fastening the centers of the magnet assemblies to dual action. Thus, the attachment member may have heads at opposite ends adapted to engage respective magnet assemblies, the attachment member further comprising a pair of interlocking portions, one of which is formed by a threaded projection and the other by a threaded recess. The spacer is adapted to be arranged at a location adjacent to said attachment means and to be interposed between respective magnet assemblies and opposing faces of the element.

According to another aspect, the invention is a loudspeaker with a characterized element having the ability not to dampen and propagate the input vibration energy by bending waves in at least one functional area extending transversely to its thickness so that the resonant modes of bending wave vibrations are distributed over at least one area. determined positions for the transducer means, and a vibration transducer mounted on said element in one of the positions to achieve vibration of the resonance causing element of the acoustic radiator element which provides acoustic output during its resonance.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, exemplary embodiments of the invention are illustrated in the accompanying drawings, in which: FIG. 1 shows a distributed mode loudspeaker as described in related application WO 97/09842; FIG. 2a shows a partial cross-section along the line A-A shown in FIG. 1, FIG. 2b shows an enlarged cross-sectional view of a distributed mode radiator of the type shown in FIG. 2a, showing two alternative designs of the radiator of FIG. 3 shows a cross-section of a first embodiment of a converter according to the invention, and FIG. 4 shows a cross-section of a second embodiment of a converter according to the invention.

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 3 around an inner edge carrying a sound radiating panel 2 with distributed DM operable. Inverter 9, e.g. the transducer described in detail in the related patent applications WO / 09859, WO97 / 09861, WO97 / 09858 with the same priority is mounted wholly and exclusively on panel 2 or panel 2 at a predetermined position defined by x and y coordinates, these coordinates being calculated so as described in co-pending application WO97 / 09842 with the same priority to generate 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 idle 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 clear that the frame 1, the elastic hinge 3 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 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), Kaptan (RTM), polycarbonate, phenolic, polyester or related plastics, fiber reinforced plastics and metal foils. On the basis of the Vectra quality research of liquid thermoplastics, it has been found that polymer thermoplastics can be used to form very large polymer-based crystals of thin coatings of small size, i.e., in the case of thermoplastics. with a diameter of about 30 cm by injection. This material forms the oriented crystal structure itself in the injection direction, which is an advantageous direction for good propagation of high sound frequencies from the driving 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 for 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 and is suitable for a radiant panel without having 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 in the panel construction may be enhanced by the use of adhesives that are flexible and not 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 less dispersible low frequency modes of the 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 during 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 a number of minor effects and / or intermediate and higher frequencies, may be performed 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, in the total sum of the sound energy of the frequency, the limited effect of the acoustic power in a given with a uniform distribution reflecting the 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 speaker axis. 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, which does not require a full-range crossover per panel diagram.

Fig. 3 shows an embodiment of a transducer 9 for driving bending waves in a fixed light emitting panel 2 with distributed modes, e.g. a panel of the same type as shown in FIG. 1 and 2, wherein the panel comprises a core 22 enclosed by opposing shells 21 to cause panel resonance.

The transducer comprises a coil 13 mounted, e.g. by means of adhesive means, to the outside of the coil former 18 which is fixedly connected to the surface of the sheath 21 of the radiating panel 2, e.g. by means of epoxy adhesive connections 16. The magnet 15 is surrounded by a pair of pole pieces 14, one of which is in the form of a disc, the edge of which is close to the inner part of the coil frame 18, and the other is in the form of a flange 90.

The magnet assembly comprising the magnet 15 and the pole pieces 14 is fixed to the panel 2 by means of a fastening means 93 made, e.g. The fastening means 93 comprises a pair of complementary threaded elements 91, 92 and each has a head 95. The head 95 of one element 91 of said pair of elements acts against the external surface of the transducer 9 and the head 95 of the second element 92 of said pair of elements opposes the face of the panel

2. on the side of the panel opposite to the side on which the converter 9 is attached to the panel. To offset the transducer 9 from the panel 2, a spacer 127 is inserted between the transducer 9 and the panel 2.

To generate a bending waveform in the panel 2 to cause its resonance in the event that an acoustic signal is supplied to the transducer 9, the transducer 9 shown in FIG. 3 operates such that there is a local elastic bending in the region between the fastening means and the coil former 18.

The embodiment of the transducer 9 shown in FIG. 4 is similar to the embodiment of the converter 9 shown in FIG. 3, except that in this embodiment, the transducer comprises complementary dual-acting exciters of the same type as shown in FIG. 3, and arranged on opposite sides of the panel. To attach the two transducers to each other and to the transducers to the panel, a fastening element 93 extends through an aperture 29 formed in the panel 2. This fastening element 93 comprises two opposing complementary portions 9.4, 96 each having a head 95 which opposes the outer face of the respective surface. converter 9 for coupling the exciters together. To attach the complementary portions 94, 96 to each other, both portions are provided with threaded means, e.g. threaded projection, respectively. threaded recess. The fastener 93 may be. made of any suitable material, such as e.g. plastic or metal.

In this embodiment, the converter device 9 is firmly clamped to the panel 2 by means of fixed washers 19 made, e.g. of rigid plastic, and arranged between the panel and the pole pieces 14 at a location adjacent to the aperture 29, thereby causing a local elastic bending of the panel in the region between the washers 19 and the coil frame 18 during operation of the transducer causing the bending wave in the panel.

Claims (7)

1. A vibration converter for driving an element having a face; ability to wave in at thickness not to dampen and propagate the input vibration energy by bending at least one functional surface running transversely so that it has resonant modes of bending vibration distributed over at least one surface and predetermined positions within said surface for the transducer means, and a transducer mounted on an element at one of said vibration positions of said element to achieve vibration of said acoustic radiator element providing an acoustic output during its resonance, characterized in that it comprises a motor coil assembly (13, 18), the coil (13) of which is fixedly attached to the tubular element (18), the assembly being adapted to be fastened to the face of the element (2), and the magnet assembly (15) having opposing disc poles (14), an edge of one of said poles extending inside the motor coil assembly and at a location adjacent to the motor coil assembly, and a peripheral flange (90) adapted to surround the motor coil assembly at the edge of the other and an arrangement at a location adjacent to said motor assembly the coil, the magnet assembly being adapted to be attached at its center to the element (2) to be vibrated. Vibration transducer according to claim 1, characterized in that it comprises fastening means (93) for fastening the magnet assembly (15) to the element (2). Vibration transducer according to claim 2, characterized in that the fastening means (93) comprises a fastening member (91, 92) adapted to engage in a cavity (29) formed in the element (2). Vibration converter according to claim 3, characterized in that the fastening member (91, 92) comprises a spacer (127) for offsetting the edges of the pole pieces (14) from the element (2). Vibration transducer according to any one of the preceding claims, characterized in that it comprises a pair of complementary systems comprising a motor coil assembly (13, 18) and a magnet assembly (15) adapted to be mounted on opposite faces of the member (2). , and means (93) for rigidly interconnecting the centers of the magnet assemblies (15) to achieve dual operation of the vibrating transducer. Vibration transducer according to claim 5, characterized in that the fastening member (91, 92) has heads (95) at opposite ends and is adapted to engage a respective magnet assembly, the fastening member (91, 92) comprising complementary parts ( 94, 96), which are threaded and interlocked, and a spacer (19) adapted to be disposed adjacent to said fastening member and to be interposed between the respective magnet assembly and opposing faces of the member (2). A loudspeaker comprising an element (2) having the ability to dampen and propagate the input vibration energy by bending waves in at least one functional area extending transversely to the thickness of the member so as to have resonant bending vibration modes distributed over at least one a surface and predetermined preferred positions within said area for the transducer means, and a vibration transducer (9) according to the preceding claims mounted on the element (2) in a single vibration position of the element (2) to achieve resonance of the radiator element providing acoustic output during his resonance.