JP7374631B2 - Acoustic panels and their manufacturing method for optimal transmission of sound frequencies - Google Patents

Description

The present patent application relates to the field of vehicle audio systems based on exciter-based speakers. In particular, the subject matter of the present patent application is an acoustic panel that allows optimal acoustic performance of exciter-based loudspeakers using an intermediate transmission body, an interior part of a vehicle equipped with such an acoustic panel, and the manufacture thereof. Regarding the method.

Exciter-based speakers consist of an electromagnetic actuator (exciter) fixed to a radiating panel, which generates sound through vibrations of the panel imposed by the actuator. Unlike loudspeaker drivers, where the cone moves essentially in unison with the voice coil, most surfaces are not rigid enough to transmit exciter forces evenly over their surface area, and therefore directional sound waves vibrate chaotically as they travel across the surface itself. Material type, exciter placement, and surface edge termination all affect the acoustic properties of the surface.

Most exciter-based speakers today are intended to be used without any transmission components to the panel, simply by bonding the exciter to the panel. When used in this manner on relatively soft upholstery panels of vehicles, the problems outlined above can occur. Therefore, the main problem to be solved is that the stiffness of vehicle upholstery parts is too low to produce competitive sound quality compared to conventional loudspeakers.

One way to solve this problem is to use an intermediate transmitter panel between the exciter and the decorative surface for optimal transmission of vibrations. The prior art exemplified in US Pat. Acoustic panels according to the prior art are flat panels with uniform thickness. Such panels have a stiffness, especially a bending stiffness, that does not change or only changes slightly with the direction of bending perpendicular to the panel. In other words, such panels are more or less isotropic.

European Patent Application No. 2819432 International Publication No. 2004/110096

However, since trim sections such as automotive decorative surfaces are often not flat and have a stiffness that varies across the shape of the panel and have different edge termination points, solutions in the prior art have does not provide a good acoustic distribution. Therefore, the problem is to provide an improved user experience when using exciter-based speakers in a vehicle.

The subject matter of the present patent application provides this solution. The main objective of the subject matter of the present patent application is to provide a transmitter and a method of making the same for optimal acoustic performance of acoustic panels over a wide range of frequencies, the transmitter comprising decorative surfaces and It is made of a material that is significantly stiffer than the decorative part, while extending anisotropically in parallel directions. Preferably, the transmission body includes at least one reinforcing fiber embedded in a polymeric matrix material. The reinforcing fiber or fibers significantly improve the stiffness, while the polymer matrix allows for proper shaping of the exciter. The polymer matrix may be a thermoplastic polymer or a thermoset. The reinforcing fibers may be coated with a coating to improve adhesion between the polymer matrix and the fibers. Extending anisotropically in a direction parallel to the decorative surface means that the contour of the transmitter is anisotropic when viewed from the front or back side of the trim section. For example, the transmission body may be shaped as several arms or fingers extending in different directions from the central part. This allows mechanical vibration distribution by the transmitter and improves the overall acoustic performance of the exciter-based speaker over the surface of the decorative component. With an anisotropic transmitter, the stiffness of the transmitter and trim section is better suited to the needs of good acoustic performance of the acoustic panel than the trim section alone. This is particularly true for curved trim sections which may be less stiff in the curvature direction than in the transverse direction. In particular, this object is achieved by the subject matter of independent claims 1 and 10 of the present patent application.

The acoustic behavior of curved panels is different from flat panels, especially when the panels are curved in more than one direction. For example, a door panel or other trim portion may be shaped to include a curvature in the panel, more specifically to provide storage space on the visible front side. For example, the acoustic panel or portion of the acoustic panel may have a spherical curvature having a first radius of curvature in a first direction and a second radius of curvature in a second direction perpendicular to the first direction; One or both of the first and second radii of curvature may be finite (a finite radius of curvature meaning that the acoustic panel or a portion of the acoustic panel is curved). The first radius of curvature may be equal to or different from the second radius of curvature, including having the same or opposite sign, the sign of the radius of curvature depending on whether the curvature is convex or concave. shows. For example, the curvature of the acoustic panel or part of the acoustic panel may be convex when viewed from one side, for example from inside the vehicle if the trim portion of the acoustic panel is a door or other part of the vehicle interior. and/or may be concave. Different regions or portions of the acoustic panel may have different curvatures.

Such curvature affects the local stiffness and thus the acoustic behavior of the acoustic panel. An anisotropic transmitter comprising at least one reinforcing fiber embedded in a polymer makes it possible to locally adapt the transmission of vibrations from the exciter to the trim part. The polymer may be selected from a variety of polymers with different mechanical properties. The length of the at least one reinforcing fiber and the manner in which the fiber or fibers are embedded in the polymer provide parameters for adapting the acoustic behavior to the particular shape of the trim section. Preferably, the vehicle looks like a spider, but has arms of different shapes and/or lengths. The inventors have discovered that it is possible to obtain good acoustic characteristics of a trim part with a complex shape using such a transmitter. The process of adapting the transmitter to the actual shape of the trim portion can be an empirical process by varying different characteristics and parameters as described above.

The arms or fingers of the transmission body according to certain preferred embodiments of the subject matter of the present application may be formed as elongated projections projecting in different directions from the central part of the transmission body, for example radially, thereby It will look like this. In other words, the contour of the transmitter may enclose a non-convex geometric region.

A first example of an embodiment of the subject matter of the present patent application comprises a trim part (e.g. an upholstery part of a vehicle), an exciter used to generate sound vibrations, and a vibration from the exciter to the trim part. It is an acoustic panel including an intermediate transmitting body portion for transmitting information. Since trim parts, such as car interior parts, are usually soft and non-rigid, the transmitter must be stiffer than the panel material to optimize vibration transmission between the exciter and the trim part. At the same time it must be lightweight. For this reason, the transmission body is a fiber-reinforced composite material comprising at least one reinforcing fiber in a polymeric matrix material. Therefore, when the transmission body is placed on the transmission body, it extends anisotropically in a direction parallel to the trim portion.

The trim parts have a thickness that is much smaller than their extension in the lateral direction. In many cases, the trim portion is curved rather than flat. For optimal acoustic performance, it is preferred that the transmitter follow the surface of the trim portion. It can be envisaged that the trim part is an inner panel of a door with a textured surface, a rear shelf or a ceiling, a rear part of a headrest or for example part of an instrument panel. The transmission body is designed such that it can fit into any type of interior decorative surface (i.e. trim section) within the vehicle.

A second example takes the form of the acoustic panel of the previous example in which the reinforcing fibers are carbon fibres. In a preferred embodiment, the vehicle body includes carbon fiber material embedded in a polymer matrix, and the carbon fiber content within the vehicle body is greater than 50% by volume. This composition of the transmitter material ensures a high stiffness of the transmitter, which means that the transmitter absorbs less energy through distortion, and it better transfers acoustic energy to the vibrating surface, i.e. the trimmed part. means transmission. The carbon fiber material preferably includes long carbon fibers. The carbon fiber material may be small fibers randomly distributed within a polymer matrix.

A third example takes the form of an acoustic panel of any of the previous examples, where the trim portion comprises natural fibers and/or glass fibers embedded in a polymer matrix. The polymer matrix may be a different matrix material than the matrix material of the transmitter. Preferably, the polymeric binder of the trim portion is a thermoplastic matrix, such as polypropylene. Trim sections containing natural fibers have sustainability advantages compared to other materials and contribute to weight reduction. Furthermore, such components can provide a particular optical appearance and tactile experience.

A fourth example takes the form of an acoustic panel of any of the previous examples, where the transmitter comprises glass fibers embedded in a polymer matrix. Glass fiber composite materials are preferred in terms of stiffness and/or cost. Glass fiber composites are less expensive than carbon fiber composites, but still offer greater flexibility. If the transmitter is placed in a highly curved trim region, it may be necessary to use fiberglass in the transmitter.

A fifth example is that the transmission body is designed in the shape of at least two arms, the at least two arms have different stiffnesses, and the angle between two of the arms is greater than 5 degrees and less than 175 degrees. take the form of the acoustic panels of any of the preceding examples, oriented in different directions as shown. Different stiffnesses of the arms can be achieved in several ways. Among other things, changes in arm length and thickness determine stiffness. However, it is preferred that the bending strength of the material of the arm is adapted to the specific requirements. The angle between the two arms also defines the area of the trim portion that the arms affect. The angle between the arms can be matched to the stiffness or curvature of the trim section in the corresponding direction. In this way, it is possible, for example, to obtain a more uniform distribution of the stiffness of the acoustic panel. The arm may follow the curvature of the trim portion within the region of the transmitter. Therefore, the arm geometry and design will directly impact the acoustic performance of the panel.

In one embodiment of the acoustic panel, the transmitter includes an arm that is integrated into the trim portion. The arms may be defined primarily by regions of the trim portion that include one or more reinforcing fibers. In other words, the one or more fibers are part of the trim part that have different mechanical properties than other parts of the trim part.

The trim portion may include fibers of the same or different material as the transmitter. In embodiments where the radiator includes multiple fibers, these fibers may be longer than the fibers of the trim portion.
The length of the fibers in the reinforcing polymer can be selected from a wide range of lengths. For example, the fibers can have typical lengths on the order of millimeters, such as 0.5 mm to 5 mm, randomly distributed within the polymer. However, the inventors have found that it is advantageous to use long fibers, especially fibers longer than 5 mm. A non-random arrangement in which the fibers are preferentially aligned with each other may also be advantageous, especially when combined with long fibers. Typically, the length of the long fibers can be from a few centimeters up to tens of centimeters, depending on the size and shape of the exciter. If the transmission body comprises arms, long fibers extending along the long axis of such arms may be preferred. In such cases, the individual fibers may be, for example, longer than half the length of an arm, longer than an arm, or half, two-thirds, or longer than the combined length of two or more arms. It may even be long enough to extend over 80 percent of the length.

A sixth example takes the form of an acoustic panel of the fifth example, in which the bending strength of the arms is adapted to a frequency or frequency range capable of transmitting between 15 Hz and 20 kHz. This frequency range ensures that the transmitter relays vibrations audible to a human listener from the exciter to the trim section.

A seventh example takes the form of an acoustic panel according to any of the preceding examples, in which the exciter is glued to the transmitter, preferably by means of a polymeric adhesive, to form a clamped assembly. The adhesive can provide good contact between the exciter and the transmitter, thus allowing an optimized assembly to ensure a solid interface and strong fixation between both parts do. The looser the exciter fits into the transmitter, the less efficient the vibration transmission.

An eighth example takes the form of an acoustic panel as in any of the previous examples, where the transmitter is an integral part of the trim section. This means that the transmission body is inside or partially inside the trim part. In such panels, the exciter is an integral part of the trim section. This has the advantage that there is an optimal transmission of vibrations and that losses of acoustic energy from the exciter to the trim part are limited.

A ninth example takes the form of an interior part of a vehicle comprising the acoustic panel of any of the preceding examples. This means that the interior parts of a vehicle can be constructed such that it includes acoustic panels.

A tenth example is an acoustic panel of any of the preceding examples, in which the transmitter and the trim portion are molded together to form a new integrated part, and the exciter is attached to the new integrated part. The present invention relates to a method preferably applied to. Ideally, the transmitter and trim section are integrated together to provide better transmission of vibrations from the exciter through the transmitter to the trim section, and molding can result in this optimal integration. can.

An eleventh example includes at least the steps of pre-impregnating the transmission body and trim portion with a resin, correctly positioning the pre-impregnated transmission body and trim portion in a compression mold, and The method in the ninth example, comprising compressing the body and trim portion together, thereby forming an integrated part, and attaching an exciter to the integrated part, in any possible order. This is an embodiment. By performing compression molding, the transmission body is integrated with the trim portion, which is compatible with compressed natural fibers.

The twelfth example includes at least the steps of constructing an injection mold for the trim section, correctly positioning the fiber structure (fiber only) of the transmitter in the cavity of the injection mold for the trim section, and injecting the trim section. performing a molding process to integrate the transmission body and the trim portion together to form an integrated part; and attaching an exciter to the integrated part, in any possible order; 10 is an embodiment of the method in the tenth example; By injection molding, the transmission body is integrated into the trim part, and during the molding process the transmission body is treated as a semi-finished product.

The present disclosure will be more fully understood upon consideration of the following description of various exemplary embodiments in conjunction with the accompanying drawings.
1 shows a conventional speaker in a vehicle door panel with a dedicated surface; FIG. 1 shows the interior of a vehicle with exciters placed on different trim parts providing a surround sound perception; FIG. FIG. 2 illustrates various soft curved trim sections in a typical vehicle interior. An embodiment of the subject matter of the present patent application is shown, in particular an arm-shaped device mounted on top of which is an exciter placed on the surface of the trim part, for transmitting vibrations from the exciter to the trim part. It is a figure showing a transmission body. Figures 1 and 2 illustrate various ways in which the transmitter can be placed on the trim portion. Figures 1 and 2 illustrate various ways in which the transmitter can be placed on the trim portion. Figures 1 and 2 illustrate various ways in which the transmitter can be placed on the trim portion.

While the disclosure is amenable to various modifications and alternative forms, details thereof are shown by way of example in the drawings and will be described in detail. However, it should be understood that it is not intended to limit aspects of the present disclosure to the particular exemplary embodiments described. On the contrary, the intent is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure.

As shown in FIG. 1, conventional speakers used in vehicles require dedicated space inside a decorative part (or trim) of the vehicle, such as a door panel. Furthermore, such speakers produce directional sound with a narrow dispersion angle and also their vibrations are limited to the area of their diaphragm. Therefore, the use of conventional speakers in vehicles a) takes up space inside the vehicle and b) often requires holes to be drilled in the trim of the vehicle to allow the sound energy generated by the speakers to pass through. c) provide a narrow sound projection, thereby suffering from various disadvantages, including having to use a large number of speakers to provide a good sound experience to the vehicle user.

Exciter speakers turn the surface on which they are placed into a vibrating surface. They are also substantially lighter than conventional speakers and require much less volume. As shown in FIG. 2, a more surround sound perception can be provided by appropriately placing exciter speakers in various trim parts of the vehicle. Furthermore, since the speaker can be mounted directly on the surface of the trim section, particularly on the back side of the trim section that is not visible to the vehicle occupants, there is no need for a dedicated space or for drilling holes through the trim section. As an additional advantage, using the exciter in this manner allows the vehicle's audio system to be completely invisible to the vehicle's occupants.

However, the above proposal has two practical problems. FIG. 3 shows various trim parts, more specifically instrument panels, on which the exciter can be placed. The first problem is that the stiffness of the trim within the vehicle is too low to produce competitive sound quality compared to conventional speakers. The second problem, as shown in Figure 3, is related to the curved surface of the trim section, on which it becomes difficult to position the exciter in such a way as to provide optimal sound distribution over the entire surface of the trim section. Become. Therefore, conventional speakers can have the advantage of being able to utilize dedicated spaces, holes and ejection parts to emit sound and avoid the above problems. However, this is not possible with exciter-based speakers, since the sound from the exciter is what should be transmitted from the exciter to the trim section, and the trim section is soft, for the generation of optimal sound distribution. It is almost certainly not suitable for installing an exciter.

FIG. 4 shows an embodiment of the subject matter of the present patent application, which aims to overcome the above problems. It shows a transmission body designed in the form of a trim part (5), an exciter (6) and an arm (8.1, 8.2, 8.3, 8.4). The exciter is attached to the top of the transmitter, and the transmitter is located in the trim section. In that way, the transmitting body is arranged between the exciter and the trim part. In order to optimize vibration transmission between the exciter and the trim section, the stiffness of the arms of the transmitter is preferably greater (eg, more than twice) than the stiffness of the material of the trim section. More particularly, each of the arms may be stiffer than the area of the trim portion covered by the arm. Ideally, this stiffness should be at least as strong as that required for an acceptable auditory experience and for the transfer of acoustic energy from the exciter to the vibrating surface, for example 40 gigapascals. It can be exceeded. The frequency (7) of the sound transmitted to the vibrating surface by one of the arms is shown in FIG. 4 by way of example.

Furthermore, the material and design of the transmitter arm should be able to be modified to accommodate any flat or curved surface. This is because the area above the trim section where the transmitter (and thus the exciter) needs to be placed is very curved, which can make ideal placement of the exciter for optimal sound distribution difficult. Therefore, it is required. The arms of the transmitter can be adapted to curved surfaces. For example, the arms can be bent or shaped, such as by molding, so that they match the curvature of the trim portion.

The arms (eg, 8.1-8.4 in Figure 4) include or are made from fiber-reinforced polymer composite material. Multiple fibrous materials that increase the stiffness of the polymer can be used, such as carbon fibers, glass fibers, and other filler materials. Although other reinforcing fibers such as glass or metal fibers may be used, the use of carbon fibers is preferred. Such materials offer great stiffness and flexibility in design, as well as low damping factors. The fibers in the reinforcing polymer can be short fibers with typical lengths on the order of millimeters, eg 0.5-5 mm, randomly distributed in the polymer. However, the inventors have found that it is advantageous to use long fibers, especially fibers that run the length of the arm. Typically, the length of the long fibers can be from a few centimeters up to tens of centimeters, depending on the size and shape of the exciter. This anisotropic property allows the transmitter to give rise to regions of local anisotropy with respect to the shape of the trim part to which it is fixed, and such a design allows for optimal acoustic performance of the panel. do. By varying the stiffness, more specifically the bending stiffness of the transmitter arms (see e.g. arms 8.1, 8.2, 8.3, 8.4 of different lengths in Fig. 4), the trim section and the transmission body joint stiffness can be adapted to specific requirements. Also, the angle between the two arms allows adaptation to the specific curvature of the trim part. Additionally, as mentioned above, the arms can be modified to accommodate any flat or curved surface.

It can be seen that the above embodiments solve the problems discussed above, namely the lack of stiffness of the trim section and the curved nature of the trim section surface area. The arms may be uniform in shape from the central region to the tips. However, the arms can have different widths or thicknesses. The arms may, for example, be smaller and/or thinner in the outward direction and thus in the direction of the tip. Additionally or alternatively, the distribution of reinforcing fibers may be different to obtain different stiffnesses.

However, there are still some optimizations that can be performed. The loss of acoustic energy between the exciter and the transmitter and between the transmitter and the trim section should be limited as much as possible. Figures 5a, 5b and 5c show three different types of exciter, transmitter and trim section assemblies. In all three figures, the exciter is rigidly fixed to the transmission body such that the assembly between the two is a fixed assembly. This can be achieved by applying a polymer-based adhesive between the exciter and the transmitter.

On the other hand, the method of joining between the transmission body and the trim part is different in all three figures (Fig. 5a, Fig. 5b, Fig. 5c). These are three methods for joining the transmission body and trim portion. In Figure 5a, the transmission body (10) is simply glued (11) onto the trim part (12). According to this method, the transmission body is manufactured alone with its own design and process, while the trim part is also manufactured alone (for example by classical thermoplastic injection molding). The exciter is attached to the transmitter by gluing or, for example, clipping or screwing, and then the transmitter and exciter assembly are glued directly to the surface of the trim section. In a slightly alternative method, the transmission body is glued to the trim part and the exciter is subsequently attached to the transmission body by gluing or, for example, by clipping or screwing. Such an integration process allows high compatibility between the carrier and all kinds of surfaces.

Figure 5b shows a method of pre-impregnating the transmission body and trim portion with resin. The prepreg (transmission body and trim portion) is properly placed in a compression mold and the two parts are compressed together to form a new integrated part. Next, an exciter is attached to this integrated part.

Figure 5c shows how the fiber structure (fibers only) of the transmitter is placed in the cavity of the injection mold of the trim section. A classic injection process is carried out, simultaneously completing the structure of the transmission body and creating the trim part (both parts share the same matrix). This creates a new integrated part to which the exciter is attached. In this embodiment, the arms are actually formed by the distribution of reinforcing fibers within the trim section. The arm may form a protrusion on the surface, in particular on the back side of the trim part. However, the areas forming the arms may also be completely recessed.

1 Vehicle door panel (trim part)
2. Conventional loudspeakers with dedicated space 3. Exciters arranged in various trim sections 4. Curved surface of the trim section 5. Trim section 6. Exciter 7. Frequency of sound transmitted to the trim section by one of the arms 8.1-8 .4 Transmitter arm 9 Exciter 10 Transmitter 11 Adhesive 12 Trim section 13 New integrated part (formed by compression molding)
14 Transmitter (fiber only)
15 New integrated parts (formed by injection molding)

Claims (12)

An acoustic panel for a vehicle,
an exciter (1) for providing vibration;
a trim part (2);
a transmission body (3) between the exciter and the trim part for transmitting the vibrations from the exciter to the trim part, the transmission body comprising at least one of the following: embedded in a first polymeric matrix material; Contains one reinforcing fiber,
The transmitter extends anisotropically in a direction parallel to the trim portion, the trim portion is curved in a region where the transmitter is disposed on the trim portion , and the reinforcing fibers are curved in a region where the transmitter is disposed on the trim portion. An acoustic panel for a vehicle, characterized in that the acoustic panel is made of carbon fiber, and the content of the carbon fiber exceeds 50% of the volume of the transmitter . 2. The acoustic panel of claim 1 , wherein the trim portion comprises natural fibers and/or glass fibers embedded in a second polymer matrix. 3. An acoustic panel according to claim 1 or 2 , wherein the transmitter comprises glass fibers embedded in a first polymer matrix. the transmission body is designed in a shape with at least two arms (8.1-8.4) with different bending strengths;
Acoustic panel according to any one of claims 1 to 3, wherein the angle between the two arms (8.1, 8.2) is greater than 5 degrees and less than 175 degrees. Acoustic panel according to claim 4 , wherein the arm (3a) is adapted to a frequency in the range of 15 Hz to 20 kHz that is transmitted from the arm to the trim part. 6. An acoustic panel according to any preceding claim, wherein the exciter is glued to the transmitter to form a fixed assembly. 7. An acoustic panel according to any one of the preceding claims, wherein the exciter is adhered to the transmitter by means of a polymeric adhesive to form a fixed assembly. 8. An acoustic panel according to any one of claims 1 to 7, wherein the transmitter is an integral part of the trim section. A vehicle interior component comprising the acoustic panel according to any one of claims 1 to 8. A method for manufacturing an acoustic panel according to any one of claims 1 to 9, comprising:
i. molding the transmission body and the trim portion together to form an integral part;
ii. and attaching the exciter to the integrated component in any possible order. A method of manufacturing an acoustic panel according to claim 9, comprising at least:
i. impregnating the transmission body and the trim portion with resin in advance;
ii. properly positioning the pre-impregnated transmission body and trim portion in a compression mold;
iii. compressing the pre-impregnated transmission body and trim portion together to form an integral part;
iv. and attaching the exciter to the integrated component in any possible order. 9. A method of manufacturing an acoustic panel according to claim 8, comprising:
i. constructing an injection mold for the trim portion;
ii. correctly positioning the transmission body within the injection mold cavity of the trim portion;
iii. performing an injection molding process to integrate the transmission body and the trim portion to form an integrated part;
iv. and attaching the exciter to the integrated component in any possible order.