DE102018211426A1 - Acoustic panel for optimal transmission of sound frequencies and method of manufacturing the same - Google Patents

Abstract

An acoustic panel for a vehicle, comprising an exciter for providing vibration for a trim part, a transmitter between the exciter and the trim part for transmitting the vibration from the exciter to the trim part, the transmitter at least one stiffening fiber embedded in a polymer matrix material, and extends anisotropically in directions parallel to the trim part, which is curved in the area in which the transmitter is arranged thereon.

Description

This patent application relates to the field of vehicle audio systems based on excitation-based loudspeakers. More specifically, the subject matter of this patent application relates to an acoustic panel that enables the optimum acoustic performance of a loudspeaker based on an exciter using an intermediate transformer, an interior part of a vehicle having such an acoustic panel and a method for producing the same.

A loudspeaker based on an exciter has an electromagnetic actuator (exciter) which is attached to a radiation panel which generates tones through the vibrations of the panel caused by the actuator. Unlike a speaker driver, in which the cone moves substantially in accordance with the voice coil, most surfaces are not rigid enough to evenly direct the force of the exciter over their entire surface area, so they often vibrate in a disorderly manner , when longitudinal sound waves move through the surface itself. The type of material, the pathogen arrangement and the edge termination of the surface all influence the tonal properties of a surface.

Most loudspeakers based on an exciter are currently used without transmission parts to the panel by simply connecting the exciter to the panel. With such use on the relatively soft decorative interior panels of a vehicle, the problems outlined above may arise. Thus, the main solving problem is that the stiffness of a decorative interior part in a vehicle is too low to produce a sound quality that is competitive compared to conventional speakers.

One way to solve this problem is to use an intermediate transmitter panel between the exciter and the decorative surface for the optimal transmission of vibrations. The in EP 2819432 A1 and WO 2004110096 A1 The prior art illustrated corresponds to a flat intermediate transfer panel between an exciter and the decorative surface. The prior art acoustic panels are flat panels with a uniform thickness. Such panels have a stiffness, in particular a bending stiffness, which does not or only varies slightly with the direction of the bend perpendicular to the panel. In other words, these panels are more or less isotropic.

However, given that the trim parts, such as decorative surfaces, in vehicles are often not flat and have varying stiffness across the shape of the panel, with different edge termination points, the prior art solution would not provide optimal tone distribution over the areas lead to a decorative surface. Thus, there is a problem in providing an improved sound experience when using excitation-based speakers in vehicles.

The subject of this patent application offers this solution. The main object of the subject matter of this patent application is to provide a transmitter and to provide a method of manufacturing the same in order to achieve optimal acoustic performance of the acoustic panel in a wide frequency range, the transmitter being made of a material which is considerably stiffer than the decorative part while anisotropically extending in directions parallel to the decorative surface. The transmitter preferably has at least one stiffening fiber which is embedded in a polymer matrix material. The stiffening fiber or stiffening fibers improve the stiffness considerably, while the polymer matrix enables the exciter to be shaped appropriately. The polymer matrix can be a thermoplastic polymer or thermosetting. The stiffening fiber can be provided with a coating to improve the adhesion between the polymer matrix and the fiber. Anisotropic stretching in directions parallel to the decorative surface means that when viewed from the front or the back of the trim part, the contour of the transmitter is anisotropic. For example, the transmitter can be shaped as a plurality of fingers that extend in different directions from a central part. This allows the transducer to mechanically distribute vibrations to improve the overall acoustic performance of the exciter-based speaker over the surface of the decorative part. With the anisotropic transducer, the rigidity of the transducer and the cladding part is better adapted to the requirements for good acoustic performance of the acoustic panel than the cladding part alone. This applies in particular to curved trim parts, which can have a lower rigidity in the direction of the curvature than in a transverse direction. in particular, this aim is achieved by the subject matter of independent claims 1 and 10 of this patent application.

A first example of the exemplary embodiments of the subject matter of this patent application is an acoustic panel which comprises: a trim part (e.g. a decorative inner part of the Vehicle); an exciter used to generate sound vibrations; and an intermediate transmitter part that transmits the vibrations from the exciter to the trim part. The trim parts, for example decorative interior parts of a vehicle, are usually soft and have low rigidity, and therefore the transducer must be stiffer than the material of the panel in order to optimize the transmission of vibrations between the exciter and the trim part. At the same time, it must be light in weight. For this reason, the transmitter is a fiber-reinforced composite material that has at least one stiffening fiber in a polymer matrix material. Therefore, when the transmitter is placed on the panel, it extends anisotropically in directions parallel to the trim part.

Trim parts have a thickness that is much less than their dimensions in the transverse directions. Often the cladding parts are not flat, but curved. It is preferred that the transducer follow the surface of the trim part in order to obtain optimal acoustic performance. It can be provided that the trim part is an inner door panel with an uneven surface, a back shelf or a ceiling, the back of a headrest or, for example, a part in an instrument panel. The transmitter is designed so that it can be adapted to any type of decorative inner surface (e.g. trim part) in a vehicle.

A second example uses the shape of the acoustic panel according to the previous example, in which the stiffening fiber is a carbon fiber. In a preferred embodiment, the transmitter comprises a carbon fiber material embedded in a polymer matrix, the carbon fiber content in the transmitter being greater than 50% by volume. This composition of the transducer material ensures a high rigidity of the transducer, which means that the transducer absorbs less energy through deformation, which in turn leads to better acoustic energy transfer to the vibrating surface, i. H. the trim part. The carbon fiber material preferably has long carbon fibers. The carbon fiber material can also consist of small fibers that are randomly distributed in the polymer matrix.

A third example uses the shape of the acoustic panel according to one of the preceding examples, in which the covering part has natural fibers and / or glass fibers which are embedded in a polymer matrix.

This polymer matrix can consist of a different matrix material than the matrix material of the transmitter. The polymer binder of the trim part is preferably a thermoplastic matrix, for example polypropylene. Trim parts that have natural fibers are advantageous in terms of support and contribute to a reduction in weight compared to other materials. Furthermore, parts of this type can bring about a specific visual appearance and a tactile sensation.

A fourth example uses the shape of the acoustic panel according to each of the preceding examples, the transducer having glass fiber embedded in the polymer matrix. Glass fiber composites may be preferred in terms of rigidity and / or price. Glass fiber composites are less expensive than carbon fiber composites, but still offer greater flexibility. The use of glass fibers for the transmitter may be required if the transmitter is to be placed on a cladding surface that is strongly curved.

A fifth example uses the shape of the acoustic panel according to each of the preceding examples, in which the transducer is designed in the form of at least two arms which have a different stiffness and point in different directions so that the angle between two of the arms is more than 5 Degrees and less than 175 degrees. Different stiffness of an arm can be realized in several ways. Among other things, changing the length of an arm or its thickness determines stiffness. However, it is preferred that the bending strength of the material of the arms is adapted to the specific requirements. The angle between two arms also defines the area of the trim part on which the arms act. The angle between the arms can be adapted to the rigidity or curvature of the trim part in the corresponding direction. In this way it is possible, for example, to obtain a more uniform distribution of the rigidity of the acoustic panel. The arms can follow a curvature of the trim part in the area of the transmitter. The geometry and design of the arms therefore have a direct impact on the acoustic performance of the panel.

A sixth example uses the shape of the acoustic panel according to the fifth example, the bending strength of the arms being adapted to a frequency or a frequency range so that they can transmit between 15 Hertz and 20 Kilohertz. This frequency range ensures that the transmitter transmits vibrations from the exciter to the trim part that are audible to a human listener.

A seventh example uses the shape of the acoustic panel after each of the previous ones Examples where the exciter is preferably bonded to the transmitter using a polymer adhesive to form a clamping arrangement. An adhesive can provide good contact between the exciter and the transmitter and thus enables an optimized arrangement for ensuring a firm interface and a strong connection between the two parts. The greater the clearance of the exciter on the transmitter, the lower the efficiency of the vibration transmission.

An eighth example uses the shape of the acoustic panel according to each of the preceding examples, the transmitter being an integral part of the cladding part. This means that the transmitter can be inside or partially inside the trim part. In such a panel, the exciter is an inseparable part of the cladding part. This has the advantage that the vibrations are optimally transmitted and that the loss of acoustic energy from the exciter to the trim part is limited.

A ninth example uses the shape of an interior part of a vehicle having the acoustic panel according to one of the preceding examples. This means that the interior of the vehicle can be designed to have the acoustic panel.

A tenth example relates to a method, which is preferably applied to an acoustic panel according to one of the preceding examples, according to which the transmitter and the covering part are molded together to form a new integrated part and the exciter is attached to the new integrated part becomes. Ideally, the transmitter and the trim part are integrated with one another in order to obtain a better transmission of vibrations from the exciter via the transmitter to the trim part, and the molding can achieve this optimal integration.

An eleventh example is an exemplary embodiment of the method according to the ninth example, which contains, in every possible order, at least the following steps: pre-impregnating the transmitter and the covering part with resin; correct positioning of the pre-impregnated transmitter and trim part in a printing form; Compressing the pre-impregnated transmitter and trim part, thereby forming an integrated part; and attaching the exciter to the integrated part. Due to the pressure molding, the transmitter is integrated into the covering part and is compatible with compressed natural fibers.

A twelfth example is an exemplary embodiment of the method according to the tenth example, which contains at least the following steps in every possible sequence: forming an injection mold for the trim part; correctly positioning the fiber structure of the transmitter (fibers only) in the cavity of the injection mold for the trim part; Performing the injection molding process to integrate the transmitter and the trim part together, forming an integrated part; and attaching the exciter to the integrated part. By performing injection molding, the transmitter is integrated into the trim part, and during the molding process, the transmitter is handled as a semi-finished product.

• 1 einen herkömmlichen Lautsprecher in dem Türpaneel eines Fahrzeugs mit einer dedizierten Oberfläche illustriert.
• 2 ein Fahrzeuginneres mit an verschiedenen Verkleidungsteilen angeordneten Erregern illustriert, wodurch eine Umgebungstonwahrnehmung bereitgestellt wird.
• 3 verschiedene weiche, gekrümmte Verkleidungsteile in einem typischen Fahrzeuginneren illustriert.
• 4 ein Ausführungsbeispiel des Gegenstands dieser Patentanmeldung illustriert. Genauer gesagt zeigt sie einen Übertrager in der Form von Armen mit einem darüber befestigten Erreger, der auf der Oberfläche eines Verkleidungsteils zum Übertragen von Vibrationen von dem Erreger zu dem Verkleidungsteil angeordnet sind.
• 5a - 5c die verschiedenen Arten illustrieren, in denen der Übertrager auf dem Verkleidungsteil angeordnet werden kann.

The disclosure may be more fully understood by considering the following description of various illustrative embodiments in conjunction with the accompanying drawings, in which:

• 1 illustrates a conventional loudspeaker in the door panel of a vehicle with a dedicated surface.
• 2 illustrates a vehicle interior with pathogens arranged on different trim parts, whereby an ambient sound perception is provided.
• 3 Various soft, curved trim parts illustrated in a typical vehicle interior.
• 4 an embodiment of the subject of this patent application illustrated. More specifically, it shows a transducer in the form of arms with an exciter attached above them, which are arranged on the surface of a covering part for transmitting vibrations from the exciter to the covering part.
• 5a - 5c illustrate the various ways in which the transmitter can be placed on the trim panel.

While the disclosure is capable of various modifications and alternative forms, specific features thereof are shown by way of example in the drawings and are described in detail here. It should be noted, however, that there is no intent to limit aspects of the disclosure to the particularly illustrative embodiments described. On the contrary, the intention is to cover all modifications, equivalents and alternatives that fall within the spirit and scope of the revelation.

As in 1 As shown, conventional loudspeakers used in vehicles require a dedicated space within the decorative parts (or trim parts) of the vehicle, such as a door panel. Furthermore, such speakers produce directional sound narrow scattering angles, and their vibrations are limited to the area of their membranes. Therefore, the use of conventional loudspeakers in vehicles suffers from various disadvantages, including a) occupying space in a vehicle; b) often requiring a hole to be cut through the trim panels of the vehicle to allow the sound energy generated by the speaker to pass through; and c) providing a spatially limited sound projection, due to which several loudspeakers have to be used in order to give the vehicle users a good sound sensation.

Excitation speakers transform every surface on which they are arranged into a vibrating surface. They are also much lighter than conventional speakers and take up significantly less volume. As in 2 is shown, suitably arranged excitation loudspeakers on different trim parts of the vehicle can provide better ambient sound perception. Furthermore, since speakers can be placed directly on the surface of the trim parts, particularly on the back of the trim parts, which cannot be seen by a vehicle occupant, there is no need for a dedicated space or cutting holes through the trim parts. As an additional advantage, the use of pathogens in this way can make the audio system of a vehicle completely invisible to a vehicle occupant.

However, there are two practical problems with the above proposal. 3 shows the various trim parts, in particular the instrument panel, on which pathogens can be arranged. The first problem is that the rigidity of the trim parts in a vehicle is too low to produce a competitive sound quality compared to conventional speakers. A second problem relates to the curved trim part surfaces as in FIG 3 on which the arrangement of pathogens in such a way that an optimal sound distribution is obtained over the entire surface of the trim part becomes difficult. Thus, conventional speakers have the advantage of dedicated spaces, holes and outlets for projecting their sound and avoiding the above problems. However, this is not possible with loudspeakers based on pathogens, since the sound from a pathogen must be transmitted from the pathogen to the trim part, which is both soft and is not conducive to the attachment of a pathogen to produce an optimal sound distribution.

4 shows an embodiment for the subject of this patent application that tries to overcome the aforementioned problems. It shows a panel part ( 5 ), a pathogen ( 6 ) and a transformer in the form of arms ( 8.1 . 8.2 . 8.3 . 8.4 ) is designed. The exciter is attached to the transmitter, while the transmitter is arranged on the trim part. The transmitter is thus arranged between the exciter and the trim part. The stiffness of the arms of the transmitter is preferably greater (e.g. twice) than the stiffness of the material of the covering part in order to optimize the transmission of vibrations between the exciter and the covering part. In particular, each of the arms can be stiffer than the area of the trim part covered by the arm. Ideally, this stiffness should be at least as great as is required for the transmission of acoustic energy from an exciter to a vibrating surface, that is to say for an acceptable hearing sensation, which can be, for example, greater than 40 gigapascals. The audio frequency ( 7 ) which is transmitted through one of the arms to the vibrating surface is in 4 shown as an example.

Furthermore, the material and design of the transmitter arms should be such that they can be modified to fit any surface (flat or curved). This is necessary because the area on which the transmitter (and thus the exciter) has to be arranged on the cladding part can be strongly curved, which makes an ideal arrangement of exciters for optimal sound distribution difficult. The arms of the transmitter can be adapted to curved surfaces. For example, the arms can be curved, or the arms can be shaped, for example by molding, in such a way that the arms are adapted to the curvature of the trim part.

The arms (e.g. 8.1-8.4 in 4 ) have or consist of a fiber-reinforced polymer composite material. Several fiber materials that increase the stiffness of the polymer can be used, such as carbon fibers, glass fibers and other fillers. Although glass fibers or other stiffening fibers such as metal fibers can be used, the use of carbon fibers is preferred. Such materials result in great rigidity and flexibility in design and also provide a low damping factor. The fibers in the reinforced polymer can be short fibers, typically of the order of millimeters in length, for example between 0.5 and 5 mm, which are randomly distributed in the polymer. However, the inventors have found that the use of long fibers is advantageous, especially fibers that extend in the longitudinal direction of an arm. Typically, the length of the long fibers can range from several centimeters to a few tens of centimeters, depending on the size and geometry of the pathogen. This anisotropic property enables the transducer to create a local anisotropic area in relation to the shape of the trim part to which it is attached: such a design enables optimal acoustic performance of the panel. A change in the stiffness, in particular the bending stiffness of a transmitter arm (see e.g. arms of different lengths 8.1 . 8.2 . 8.3 . 8.4 in 4 ), allows adaptation of the combined rigidity of the covering part and the transmitter to specific requirements. The angle between two arms also allows adaptation to a specific curvature of the trim part. Furthermore, as stated above, the arms can be modified to fit any surface, flat or curved.

It can be seen that the above embodiment solves the problems discussed above: lack of rigidity of the trim part and the curved nature of the trim part surface area. The arms can be uniform from a central area to the tip. However, the arms can have a varying width or thickness. The arms can become narrower and / or thinner in the outward direction, for example, in the direction towards the tip. Additionally or alternatively, the distribution of the stiffening fibers can be different in order to obtain a different stiffness.

However, there are a few tweaks that can still be made. The loss of acoustic energy between the exciter and the transmitter and the transmitter and the cladding part should be limited as much as possible. The 5a . 5b and 5c represent three different ways of assembling the exciter, transmitter and trim part. In all three figures, the exciter is fixedly attached to the transmitter so that the arrangement between the two is a clamp arrangement. This can be achieved by using a polymer-based adhesive between the exciter and the transmitter.

On the other hand, the method of connecting the transmitter to the trim part is different in all three figures (5a, 5b and 5c). These are three methods of connecting the transmitter and the trim part. In 5a the transmitter ( 10 ) simply on the panel ( 12 ) glued (11). According to this method, the transmitter is manufactured with its own design and process, while the trim part is also manufactured alone (e.g. by classic thermoplastic injection molding). The exciter is attached to the transducer by gluing or, for example, clips or screws, and then the transducer and exciter assembly is glued directly to the surface of the trim member. In a slightly alternative method, the transmitter is glued to the trim part, and then the exciter is attached to the transmitter, either by gluing or, for example, by clips or screws. Such an integration process enables a high degree of compatibility between the transmitter and any type of surface.

5b represents a method in which the transmitter and the trim part are preferably pre-impregnated with resin. The pre-pregs (transmitter and trim part) are correctly positioned in a printing form and the two parts are pressed together so that they form a new integrated part. The exciter is then attached to this integrated part.

5c represents a method in which the fiber structure (fibers only) of the transmitter is positioned in the cavity of the injection mold of the trim part. The classic injection molding process takes place and at the same time the transmitter structure is completed and the cladding part is created (whereby both parts share the same matrix). This creates a new integrated part on which the exciter is attached. In this embodiment, the arms are actually formed by the distribution of the stiffening fibers in the trim part. The arms can form projections on the surface, in particular the rear surface of the trim part. However, the areas forming the arms can also be completely embedded.

List of reference numbers:

1.

Vehicle door panel (a panel)

Second

Conventional speaker with its dedicated space

Third

Pathogens, which are arranged on different cladding parts

4th

Curved surfaces of trim parts

5th

cowling

6th

pathogen

7th

Tone frequency transmitted through one of the arms to the trim part

8.1 - 8.4

Arms of the transmitter

9th

pathogen

10th

exchangers

11th

adhesive

12th

cowling

13th

New integrated part (formed by printing forms)

14th

Transformer (fibers only)

15th

New integrated part (formed by injection molding)

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• EP 2819432 A1 [0004]
• WO 2004110096 A1 [0004]

Claims (12)

Acoustic panel for a vehicle, comprising: an exciter (1) for providing a vibration, a covering part (2), a transmitter (3) between the exciter and the covering part for transmitting the vibration from the exciter to the covering part, the transmitter at least comprises a stiffening fiber embedded in a first polymer matrix material; and the transmitter extends anisotropically in directions parallel to the trim part, characterized in that the trim part is curved in the region in which the transmitter is arranged on the trim part. Acoustic panel according to any one of the preceding claims, in which the stiffening fiber is a carbon fiber; and the carbon fiber content is greater than 50% by volume of the transmitter. Acoustic panel according to one of the preceding claims, in which the covering part has natural fibers and / or glass fibers which are embedded in a second polymer matrix. Acoustic panel according to one of the preceding claims, in which the transmitter has glass fibers embedded in the first polymer matrix. Acoustic panel according to one of the preceding claims, in which the transmitter is designed in such a way that it has at least two arms (8.1-8.4) with different bending strengths; and an angle between the two arms (8.1, 8.2) is more than 5 degrees and less than 175 degrees. Acoustic panel after Claim 5 , at which the arm (3a) is adapted to a frequency in the range between 15 Hertz and 20 Kilohertz, which is transmitted from the arm to the trim part. Acoustic panel according to any one of the preceding claims, in which the exciter is glued to the transducer, preferably by means of a polymer adhesive, to form a clamping arrangement. Acoustic panel according to one of the preceding claims, wherein the transmitter is an integrated part of the trim part. Interior part of a vehicle, comprising the acoustic panel according to one of the preceding claims. Method for producing an acoustic panel, preferably an acoustic panel according to one of the Claims 1 - 9 , which has at least the following steps in every possible order: i. Molding the transmitter and the trim part together to form an integrated part; and ii. Attach the pathogen to the integrated part. Method of manufacturing an acoustic panel according to Claim 9 , which has at least the following steps in every possible order: i. Pre-impregnating the transmitter and the trim part with resin; and ii. correct positioning of the pre-impregnated transmitter and trim part in a printing form; and iii. Compressing the pre-impregnated transmitter and trim part together, thereby forming an integrated part; and iv. Attach the pathogen to the integrated part. Method of manufacturing an acoustic panel according to Claim 8 , which has at least the following steps in every possible order: i. Forming an injection mold for the trim part; and ii. correctly positioning the transmitter in the cavity of the injection mold for the trim part; and iii. Performing the injection molding process for integrating the transmitter and the trim part with each other, thereby forming an integrated part; and iv. Attach the pathogen to the integrated part.

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