EA000376B1 - Vibration transducer - Google Patents

Abstract

1. A vibration transducer (9) for exciting a member (2) having a face and comprising a motor coil assembly (13, 18) having a coil (13) rigidly fixed to a tubular member (18), the motor coil assembly being adapted to be fixed to the said face of the member (2), and a magnet assembly (15), having opposed disc-like pole pieces (14), the periphery of one of which pole pieces is arranged to be disposed within and adjacent to the motor coil assembly, and the periphery of the other of which pole pieces is formed with a surrounding flange (90) adapted to surround and to be disposed adjacent to the motor coil assembly, and wherein the magnet assembly is adapted to be secured at its centre to the said member (2) to be vibrated. 2. A vibration transducer according to Claim 1, characterised by fixing means (93) to secure the magnet assembly (15) to the member (2). 3. A vibration transducer according to Claim 2, characterised in that the fixing means (93) comprises a fastener (91, 92) adapted to engage in a cavity (29) in the member (2). 4. A vibration transducer according to Claim 3, characterised in that the fastener (91, 92) comprises a spacer (127) for spacing the peripheries of the pole pieces (14) from the said member (2). 5. A vibration transducer according to any preceding Claim, characterised by complementary motor coil assemblies (13, 18) and magnet assemblies (15) adapted for mounting on opposed faces of the said member (2), and by means (93) tying the centres of the magnet assemblies (15) together for push/pull operation. 6. A vibration transducer according to Claim 5, characterised in that the fastener (91, 92) has heads (95) at opposite ends and adapted to engage the respective magnet assemblies, the fastener (91, 92) comprising a pair of interengaging screw-threaded portions (94, 96), and by spacer means (19) adapted for disposition adjacent to the fastener and adapted for sandwiching between the respective magnet assemblies and the opposed faces of the said member (2). 7. A loudspeaker (81) characterised by a member (2) having capability to sustain and propagate input vibrational energy by bending waves in at least one operative area extending transversely of thickness to have resonant mode vibration components distributed over said at least one area and have predetermined preferential locations or sites within said area for transducer means and having a vibration transducer (9) as claimed in any preceding Claim mounted on said member (2) at one of said locations or sites to vibrate the member to cause it to resonate forming an acoustic radiator which provides an acoustic output when resonating.

Description

The invention relates to transducers and, mainly, to transducers of oscillations for loudspeakers, including acoustic radiating elements in the form of a panel.

Known proposed in GB-A-2262861 loudspeaker in the form of a panel, which includes:

- resonant multi-mode radiating element, which is a single multi-layer panel formed by two surface layers of material with an intermediate core with a cellular transverse structure, in which the panel has a bending stiffness ratio (B) in all directions to the cube mass of the panel per unit surface area (μ) equal to at least 10;

- mounting means that supports the panel or attaches to it a carrying case in a free, undamped manner;

- and electromechanical driving means connected to the panel, which serves to excite a multi-mode resonance in the radiating panel in response to an input electrical signal in the working frequency range of the loudspeaker.

MULTIPHONIE US-A-4,506,117 discloses an electroacoustic transducer containing an inertial mass capable of being rigidly fixed with its base plate to a panel subjected to vibrations.

Embodiments of the present invention utilize elements that are able to maintain and propagate in the work area (s) the input vibrational energy through bending waves propagating transversely to thickness, often but not necessarily towards the edges of the element (s); they are configured with or without bending stiffness anisotropy so that the components of the resonant vibration mode are distributed over the specified area (s) favorable for acoustic interaction with the ambient air; they have in the specified area specified preferred positions or locations for the means of conversion, in particular, its operationally active (s) or moving part (s), effective (s) with respect to the acoustic oscillatory motion in the specified area (s) (s) and to signals, usually electrical, corresponding to the acoustic part of this vibrational energy.

This invention, in particular, concerns active acoustic devices in the form of loudspeakers. The above elements are called here acoustic emitters of distributed oscillations.

The invention is an oscillation transducer for excitation of an element having a surface and configured to maintain and propagate the input vibrational energy in at least one working area by means of bending waves propagating transversely to thickness, so that the components of the resonant mode of oscillation are distributed at least , on one specified area, and having specified preferential positions or locations of the means of transformation within the specified area, and A transducer mounted on the specified element in one of the specified positions or locations to cause the element to oscillate, causing it to resonate, thereby forming an acoustic emitter, which at resonance provides an acoustic output containing a motor winding unit whose winding is rigidly attached to the tubular element, while the motor winding assembly itself is designed to be mounted on the surface of the element, and the magnetic assembly, having opposite poles in the idea of disks, the edge of one of these poles is set so as to be located inside and close to the motor winding node, and the edge of the other pole is formed as a girdle flange designed to surround and lie close to the motor winding node in which the magnetic node is made with the possibility of mounting in its center to the specified element, subject to vibration. Anchoring means may be provided for attaching the magnet assembly to the element. The fastening means may be a clip adapted to engage in the cavity of the element. The clamp may contain a gasket to accommodate the edges of the poles at a distance from the specified element. The vibration transducer may contain additional nodes of the excitation winding and magnetic nodes, made with the possibility of installation on opposite surfaces of the specified element, and means connecting the centers of the magnetic nodes with each other for push-pull action. Thus, the clamp may have heads at opposite ends and is adapted to engage the respective magnetic assemblies, the clamp comprises a pair of threaded parts engaged with each other, and separation means designed to be placed close to the clamp and serving as a gasket between the respective magnetic assemblies and opposite surfaces of the specified element .

On the other hand, the invention is a loudspeaker, characterized by an element that is able to maintain and propagate the input vibrational energy in at least one working area by means of bending waves propagating transversely to thickness, so that the components of the resonant mode of oscillation are distributed over at least one specified area and having specified preferred positions or locations within the specified area for the conversion means and having a converter to as described above, installed on the specified element in one of the specified positions or locations to cause the element to vibrate, causing it to resonate, thus forming an acoustic emitter, which provides an acoustic output at resonance.

The invention is schematically illustrated by way of examples and the accompanying drawings, in which:

FIG. 1 is a schematic representation of a loudspeaker with a distributed mode of vibration;

FIG. 2a is a partial sectional view of FIG. 1 on line

A-A;

FIG. 2b is an enlarged cross section of a radiator of a distributed type of oscillations of the same type as shown in FIG. 2a, and demonstrates two alternative constructions;

FIG. 3 is a diagram of a first embodiment of a converter according to the present invention; and FIG. 4 is a diagram of a second embodiment of the converter according to the present invention.

FIG. 1 shows a loudspeaker (81) in the form of a panel, which is a rectangular frame (1) carrying an elastic suspension 3 along its inner perimeter, which supports panel 2 emitting sound in a distributed mode. The transducer 9 is installed entirely and exclusively on or in panel 2 at a given location, defined by the x and y coordinates, in order to excite bending waves in the panel causing resonance and emission of the acoustic output.

Converter 9 is controlled by a signal amplifier 10, for example, a sound amplifier connected to the converter by conductors 28. The load and power requirements of the amplifier can be quite ordinary, similar to those applied to traditional diffuser type loudspeakers, and the sensitivity is about 86-88 dB / W in the conditions of the loaded room. The load impedance of the amplifier is largely active on the order of 6 Ω, the power is adjustable from 20 to 80 W. If the panel core and / or its coating is metallic, they can be used as a heat sink for the converter to remove heat from the motor winding of the converter and, thus, improve power control.

FIG. 2a and 2b are characteristic partial transverse sections of the loudspeaker 81 of FIG. 1. FIG. 2a shows that the frame 1, the suspension 3 and the panel 2 are joined together by corresponding gluing seams 20. A light border is suitable as a frame, for example, a border of pictures made of extruded metal, for example, an aluminum alloy or plastic. Elastic materials such as foam rubber or foam are suitable as materials for the suspension. For the joints 20 are suitable adhesives: epoxy, acrylic, cyano-acrylic, etc.

FIG. 2b shows on an enlarged scale that panel 2 is a rigid light panel having a core 22, for example, of rigid plastic foam 97, for example, a cross-linked polyvinyl chloride or a cellular matrix 98, i.e. honeycomb matrix of metal foil, plastic, etc., the cells of which go transversely to the plane of the panel and are closed with opposite coatings 21 of, for example, paper, cardboard, plastic, metal foil or sheet. Plastic membranes can be reinforced with fibers, such as carbon, glass, Kevlar (RTM), etc., in a manner that is known per se to increase their elastic modulus.

Coating layer materials and amplifiers such as carbon, glass, Kevlar (RTM), Nomex (RTM), i.e. aramid, etc. fibers of diverse nature and weaving, in addition, paper, paper laminates, melamine and various synthetic plastic films with a high modulus of elasticity, for example, Milar (RTM), Captan (RTM), polycarbonate, phenolics, polyester or related plastics, and plastics, reinforced with fibers, etc., as well as sheet metal or foil. A study of the Vectra index of liquid crystal polymer thermoplastics shows that they can be useful for injection molding of ultra-thin coatings or shells of small size, for example, up to 30 cm in diameter. This material itself creates a crystal structure oriented in the direction of injection — a preferential orientation for a good propagation of triple energy from the point of excitation to the perimeter of the panel.

In addition, such extrusion of a thermoplastic allows the molding tool to apply signs to determine the location and alignment, for example, a groove or ring for precise installation of parts of the converter, for example, the motor winding and magnetic suspension. In addition, it was calculated that when using some less durable core materials, it would be useful to locally increase the thickness of the coating, for example, in an area or ring to 150% of the diameter of the transducer, in order to strengthen this area and transfer vibrational energy to the panel. In this way, the high frequency response will be improved due to softer foams.

Core layer materials offered include stamped honeycombs or corrugated sheets or aluminum alloy foil or Kevlar (RTM), Nomex (RTM), plain or laminated paper, various synthetic plastic films, and expandable or foamy plastics or crushed materials, even airgel metals - as long as they are of sufficiently low density. Some materials suitable for the core layer effectively show, during their manufacture, the useful ability of self-formation of the coating and / or, in other words, have sufficient intrinsic rigidity to be used without lamination between the coating layers. A high-quality, uncoated cellular core material, known under the trade name “Rohacell”, may be suitable for use in a radiating panel. In practice, the task is to achieve the utmost ease and rigidity that meets the requirements of a particular task, in particular, the presence of an optimizing interaction of the core and coating layers and transitions between them.

In some advantageous panel designs, metal or metal alloy coatings or reinforcement by carbon fibers are used. Both of these, as well as structures with a rod made of cellular material or Airgel alloy, are capable of substantially shielding radio frequencies, which is important for some EMC applications. Conventional panel or tapered loudspeakers are not capable of shielding EMC.

In addition, preferred forms of piezo or electrodynamic transducers have negligible electromagnetic radiation or scattered magnetic fields. Ordinary loudspeakers have a large magnetic field at a distance of up to 1 meter, unless special compensatory countermeasures are taken.

In an application where it is important to maintain shielding, electrical connection can be made to the conductive parts of the corresponding DML panel, or conductive foam or similar contact means can be used to set the edge.

Suspension 3 can dampen the edges of panel 2 to prevent excessive edge movement of the panel. Additionally or alternatively, additional damping can be applied, for example, jumpers attached to the panel in selected positions to dampen the excess movement in order to evenly distribute the resonance across the panel. The jumpers can be made of bitumen-based material, as is usually done in the case of a conventional loudspeaker, or they can be made of elastic or rigid polymeric sheet material. Some materials, especially paper and cardboard, as well as some cores can be self-damping. If necessary, the damping can be strengthened by using an elastic bonding glue instead of a rigid bonding glue in the panel construction.

In order for the said selective damping to be effective, it is necessary to use in the panel, including its sheet material, a special means indissolubly associated with it. The edges and corners of the panels can be extremely important for the main and less scattered low-frequency modes. Transverse fixing of the damping means may be useful for a panel in which the specified sheet material is completely enclosed in a frame, although its corners can often be relatively free, for example, for stretching them when working at lower frequencies. Attaching can be done with glue or self-adhesive materials. Other methods of useful damping, especially when applied to finer effects and / or for medium and high frequencies, can be carried out using a suitable mass or masses attached to the sheet material in given effective localized middle positions of the specified area.

The acoustic panel described above is bidirectional. The sound energy emitted by the back surface is not very tightly coupled in phase with the energy emitted by the front surface. This has the following advantages: complete summation of the sound power in the room, uniform frequency distribution of sound energy, reduction of the effects of reflected and standing waves, and a great impression of natural space and environment when playing sound recordings.

Despite the fact that the radiation of the acoustic panel is highly non-directional, the proportion of phase-related information increases with distance from the axis. Placing loudspeakers like pictures at the usual height of human growth expands the area of stereo perception, which gives an advantage to a normally seated listener seeking to achieve the best stereo effect, located at a moderate distance from the axis. In addition, the triangle formed by the left and right columns in relation to the listener gives an additional corner component. Thus, a good stereo sound is achieved.

Compared to playing through ordinary loudspeakers, in this case there is an additional advantage for a group of listeners. The substantially dispersed nature of the acoustic radiation of acoustic panels leads to the fact that the loudness of the sound does not obey the inverse square law for the distance to an equivalent point source. Since the intensity decreases with distance much slower than prescribed by the inverse square law, respectively, for listeners who are outside the center at a disadvantageous position, the intensity field created by the panel loudspeakers gives an excellent stereo effect in comparison with ordinary loudspeakers. The reason is that the listener located outside the center does not face the problem of doubling caused by the neighborhood with the nearest column; at first, the sound coming from the near speaker is too loud, and then, accordingly, a quieter sound coming from the second speaker.

Undoubtedly, it is also an advantage of a flat, lightweight loudspeaker made in the form of a panel that is attractive from an aesthetic point of view, good sound quality, the need for only one transducer and the absence of intersections for completeness of sound from each membrane of the panel.

FIG. 3 shows an embodiment of a converter 9 for exciting bending waves in a rigid, lightweight panel 2 of a radiator with a distributed mode, for example, of the type shown in FIG. 1 and 2, consisting of a core 22, enclosed between opposite coatings 21, causing the panel to resonate.

The Converter is a winding 13, rigidly fixed, for example, with glue on the outer side of the winding frame 18, which is rigidly connected to the surface coating 21 of the radiating panel 2, for example, by means of epoxy glue 16. Magnet 15 is enclosed between two poles 14, one of which made in the form of a disk, the edge of which is located close to the inner surface of the frame (18) of the winding, and the other has a surrounding side (90), which serves to surround the winding 13.

A magnetic assembly comprising a magnet 1 5 and poles 1 4 is mounted on panel 2 by means of a fastening 93, made, for example, of metal or hard plastic, which passes through an opening (29) made through panel 2. The fastening 93 is an additional a pair of threaded elements 91, 92, each of which has a head 95, one of which rests against the outer surface of the transducer 9, and the other rests against the surface of the panel 2 on the side opposite to that on which the transducer is mounted. The gasket 127 is clamped between the transducer 9 and the panel 2 to separate the transducer from the panel.

The converter 9 in FIG. 3 controls by local elastic bending of the panel between mount 93 and frame 18 when an acoustic signal is fed to the transducer to excite bending waves in the panel in order to make it resonate.

The transducer device 9 of FIG. 4 is similar to the device described in FIG. 3, except that in this embodiment, the transducer comprises mating push-pull actuators of the same type as in FIG. 3, located on opposite sides of the panel. The fastening element 93 is arranged to pass through the opening 29 in panel 2, and to connect the two transducers with each other and with the panel. The fastening element 93 consists of opposing mating parts, each of which is made with a head 95, which is pressed along the axis of the corresponding pair of transducer 9, in order to fasten the drive with each other. The mating parts of the fastening element 93 are fastened to each other by means of the mating threaded portions 94, 96. The fastening element may be made of any suitable material, for example, plastic or metal.

In this embodiment, the transducer 9 is rigidly pressed to the panel 2 by means of rigid pads 1 9, for example, made of hard plastic, located between the panel and the poles 14 closest to the opening 29, which ensures the operation of the transducer, which consists in exciting bending waves in the panel by local elastic bending of the panel between the gaskets and frame 1 8 winding.

Claims (7)

CLAIM 1. An oscillation transducer (9) for exciting acoustic vibrations in a panel-type element, comprising a motor winding assembly (13, 18) having a winding (13) rigidly attached to the tubular element (18) and adapted to be attached to the surface of the element ( 2), a magnetic assembly (15) having opposite poles (14) in the form of disks, the edge of one of which is installed so as to be located inside and close to the motor winding assembly, and the edge of the other pole is formed in the form of a girdle (90) made with the possibility of vatyvaniya and location adjacent to the motor coil assembly, the magnet assembly is adapted to mount at its center to an element (2) is subjected to vibrations. 2. The oscillation transducer according to claim 1, characterized in that the fastening means (93) serves to fasten the magnetic assembly to the element (2). 3. The oscillation transducer according to claim 2, characterized in that the fastening means (93) comprises a clamp (91, 92) made with the possibility of engagement in the hole (29) of the element (2). 4. The oscillation transducer according to claim 3, characterized in that the clamp (91, 92) includes a gasket (127) for placing the edges of the poles at a distance from the element (2). 5. The oscillation transducer according to any one of the preceding paragraphs, characterized in that it contains the conjugate nodes of the motor winding (13, 18) and magnetic nodes (15) made with the possibility of installation on opposite surfaces of the element (2), and means (93) of fastening, connecting the centers of the magnetic nodes (15) with each other for push-pull action. 6. The oscillation transducer according to claim 5, characterized in that the clamp (91, 92) comprises heads (95) at opposite ends and is configured to engage the corresponding magnetic assemblies, the clamp (91, 92) comprising a pair of engaging threaded parts (94 , 96) and a release agent (1 9) made with the possibility of placement close to the clamp and serving as a gasket between FIG. 1 by the corresponding magnetic nodes and opposite surfaces of the element (2). 7. Loudspeaker (81), characterized in that it contains an element (2) configured to support and propagate the input vibrational energy in at least one working region by means of bending waves propagating transversely to the thickness so that the components of the resonant vibration mode are distributed at least one specified area, and having inside the specified area specified preferred position or location of the conversion means, and the oscillation transducer according to any one of the preceding points installed on the indicated element (2) in one of the indicated positions or locations to cause vibrations of the element causing its resonance, forming an acoustic emitter providing an acoustic output during resonance.