Patent Application
20100314193
The invention relates to sound transmission devices for conducting engine sound towards or into the passenger compartment of a motor vehicle and, more particularly, to apparatus and methods for attenuating undesired frequency components of the transmitted sound.
Devices configured to conduct engine sound from the engine compartment of a motor vehicle into the passenger compartment are known. In one known configuration a sound transmission device includes a flexible tube or pipe in which one end is connected into the air intake tract of the engine and an opposing end positioned near or extending through the firewall into the passenger compartment.
As a drive unit, modern motor vehicles have internal combustion engines that operate very smoothly so that the engine operating sound may be barely audible within the interior of the motor vehicle. The operating sound of the internal combustion engine may be obscured by other secondary noises such as road noises, vehicle HVAC systems, etc.
Under certain circumstances it can be desirable to transmit the operating sound of the internal combustion engine to the interior of the motor vehicle. Engine sound may be channeled through the sound transmission device to provide a “sporty” engine sound experience to the driver and passengers. In some cases the sound output of the sound transmission device is relatively low in volume with the result that it is sometimes desirable to extend the sound transmission device tube into the vehicle interior from the engine compartment to thereby improve the transmitted engine sound amplitude level for an improved driver experience.
It is known to provide a flexible diaphragm in the sound transmission tube to provide air flow isolation, thereby preventing air flow through the sound transmission tube. Even if the sound tube is not extended into the passenger compartment, it is undesirable to permit air flow back into the engine air intake tract through a sound transmission tube for which the purpose is strictly to conduct sound. This is especially undesirable if the sound tube is connected to the clean side of the air filter as any air flow through the tube would be introduced as unfiltered air into the air intake tract.
It is known to provide tuning of a transmitted sound spectrum in a vehicle sound transmission device by the addition of a quarter wave tuner or a resonator chamber in the sound transmission tubing. A quarter wave tuner is a useful to attenuate or cancel a selected transmitted sound frequency. The quarter wave tuner may be positioned and connected to the sound transmission tubing so as to extend outwards from the tubing in a branch configuration, typically (although not necessarily) at about 90 degrees relative to the axis of the sound transmission tubing. Alternately, when it is desired to amplify a selected transmitted sound frequency then an inline resonator chamber may be provided in the sound transmission tubing. If the inline resonator is configured with a duct length L, then the amplified sound wavelength will be a function of L/2. The use of quarter wave tuners and inline resonators, alone or in combination, permit the transmitted sound to be tailored using only passive devices rather than by the application of more expensive and complicated active electronic devices.
U.S. patent application Ser. No. 12/061703 discloses a device for noise transmission in a motor vehicle. In this device sound is transmitted along a transmission line having an enlarged mouth at one end and a diaphragm fitted to close off the mouth. A protective device is fitted at the end to protect the diaphragm.
U.S. Pat. No. 6,600,408 B1 discloses a device for sound transmission for a motor vehicle. In this device, the sound is transmitted along a pipe conduit and a chamber in which a diaphragm is arranged toward the interior of the motor vehicle. The chamber that surrounds the diaphragm is comprised of several assembled parts.
German patent publication DE 101 16 169 A1 discloses a resonator chamber in which the diaphragm is arranged.
German patent DE 44 35 296 discloses a diaphragm for noise transmission in a motor vehicle in which the diaphragm is clamped in a holder.
U.S. published patent application 2006/0283658 A1 discloses a system for noise increase of an intake system of a motor vehicle. Various possibilities of noise introduction into the interior of the motor vehicle are illustrated wherein the diaphragm is arranged in a pipe conduit for noise transmission.
In the German publication DE 199 30 025 A1 a sound transmission body is illustrated in which the diaphragm is clamped between two transmission members.
A sound transmission device according to prior art may have a sound transmission tube that includes a flexible membrane or diaphragm covering an end of the tube or dividing the tube into two portions. A sound transmission device so configured is a passive device that can be tuned by changing the length of the interconnecting duct, by adding resonator chambers. In the present invention the membrane is selectively tuned by the addition of ribbing and/or a dampening member configured to selectively stiffen portions of the membrane to attenuate undesired sound frequency components.
Advantageously, the present invention results in improved tuning of the engine sound transmitted to the vehicle interior and results in improved material savings when compared to adding other countermeasures such as a quarter wave tuner or a side branch resonator.
In one aspect of the invention, a sound transmission device for transmitting an engine rumble sound into an interior of a motor vehicle while attenuating at least one undesired sound frequency includes a transmission line in acoustic communication with an air intake tract of the engine. A flexible membrane is arranged at and closing off an opposing second end of the transmission line, the membrane is tensioned to tune the transmitted sound spectrum. The membrane is provided with one or more countermeasures shaped, configured and secured to the membrane to attenuate transmission of one or more undesired frequencies by limiting flexure of a portion of the membrane at the undesired frequencies. The sound transmission device has a length selected to tune the sound transmission device to a desired target transmission frequency.
In another aspect of the invention, the sound transmission device includes a broadcast duct having a mouth at a first end. The mouth is sized and configured to close off against a side of the membrane in an air-tight fashion. The duct is arranged to transmit the engine rumble sound towards the interior of the motor vehicle.
In another aspect of the invention, the broadcast duct extends into the vehicle interior to deliver the engine rumble sound therein.
In another aspect of the invention, the countermeasures include at least one radially arranged rib secured to and extending across portions of the sound transmitting portion of the membrane.
In another aspect of the invention, the countermeasures include a dampening member secured to the membrane and having a position on the membrane as well as a size selected to restrict flexure of portions of the membrane responsive to the undesired frequencies.
In another aspect of the invention, at least a portion of the ribs have an end joined to and tensibly connected to the dampening member. The ribs cooperate with the dampening member to substantially attenuate the undesired frequencies.
In another aspect of the invention, a sound transmission device has a sound spectrum for transmitting an engine rumble sound into an interior of a motor vehicle while attenuating at least one undesired sound frequency includes a lower trumpet having at a first end a mouth portion and an opposing end in air tight connection with a second end of the transmission line. The lower trumpet includes a circumferential flange arranged at the mouth portion and extending radially outwards therefrom. The flexible membrane is secured to the mouth portion and tensioned to close off the mouth portion. The membrane having one or more countermeasures shaped, configured and secured to the membrane to attenuate transmission of one or more undesired sound frequencies by limiting flexure of a portion of the membrane according to a predicted modal shape of the membrane at the undesired frequencies. An upper trumpet includes a circumferential flange sized and configured to closeable mate with the flange of the lower trumpet.
In another aspect of the invention, a method of transmitting a desired engine rumble sound spectrum into an interior of a motor vehicle while attenuating at least one undesired sound frequency in the spectrum is disclosed. The method includes the steps of providing a transmission line having a first end and a second end, wherein the first end is in air tight acoustic communication with an air intake tract of the engine. Positioning and tensioning a flexible membrane having a sound transmitting portion to close off an opposing second end of the transmission line. Determining and establishing the membrane tensioning to tune the sound spectrum. Determining undesired frequency components of the tuned sound spectrum. Determining regions of the membrane responsive to the undesired frequencies to be damped. Providing and configuring a dampening member to selectively dampen the responsive membrane regions, the dampening member secured to the membrane. Providing at least one rib on the membrane, the ribs having an end joined to the dampening member and cooperating with the dampening member to attenuate the undesired frequencies.
In another aspect of the invention, the method includes determining or calculating a required length of the transmission line to establish a target engine sound transmission frequency Tf.
In the present invention, the diaphragm is tuned to remove or attenuate a desired sound frequency by adding countermeasures such as ribbing onto the membrane to eliminate specific membrane mode shapes.
The accompanying Figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention.
Features of the present invention, which are believed to be novel, are set forth in the drawings and more particularly in the appended claims. The invention, together with the further objects and advantages thereof, may be best understood with reference to the following description, taken in conjunction with the accompanying drawings. The drawings show a form of the invention that is presently preferred; however, the invention is not limited to the precise arrangement shown in the drawings.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
Before describing in detail embodiments that are in accordance with the present invention, it should be observed that the embodiments reside primarily in apparatus and methods relating to devices for transmitted engine rumble sounds into a vehicle interior that include countermeasures to remove or substantially attenuate undesired frequency components from the transmitted sound spectrum. Accordingly, the apparatus components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.
In this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element preceded by “comprises . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises the element.
The opposing end 24 of the first transmission line 12 is in airtight connection with a lower trumpet 26. A flexible membrane 28 is secured and tensioned to close off the trumpet rim 30 at a first side 34 of the flexible membrane 28. An upper trumpet 32 in configured and adapted to seal against an opposing second side 36 of the flexible membrane 28. The trumpets 26 and 32 define cavities 38A and 38B in which the flexible membrane 28 is free to deflect in response to acoustic pressure pulsations transmitted along first transmission line 12 from the engine 16.
The upper trumpet 32 may connect to a broadcast duct 40 that may in some aspects extend into the passenger compartment 42 through the firewall 44. In other aspects of the invention the broadcast may terminate inside the engine compartment and proximate to the firewall 44. In still other aspects of the invention, the broadcast duct may be omitted and the diaphragm 28 instead positioned to radiate sound within the engine compartment towards the interior 42 of the motor vehicle. In additional aspects of the invention, the trumpet 26 and 32 may be omitted and the sound transmitting membrane closes over the end 24 of the transmission line 12. The end 24 of the transmission line 12 may be of larger diameter than the transmission line 12 so as to form an enlarged diameter mouth over which the membrane 28 is closeably tensioned. In further aspects of the invention the transmission line 12 and the lower trumpet 26 may be formed as a unitary component by a plastic molding process such as injection molding. Similarly, in additional aspects of the invention the upper trumpet 32 and broadcast duct 40 may be formed as a unitary component by a plastic molding process such as injection molding. Components may be configured and arranged in other ways utilizing the principles taught in the present disclosure without deviating from the inventive concepts and present invention disclosed herein.
In accordance with at least one aspect of the present invention,
In some aspects of the present invention throttles 50 may be provided at either the lower or upper trumpet. Throttles 50 further restrict acoustic air pressure pulsations through sound transmission device 10 and are operable to further tune the transmitted sound spectrum. Acoustic pressure pulsations in the air intake tract are communicated by the first transmission line 12 to into the cavity 38A where they act to sympathetically displace or flex the membrane 28. Flexure of the membrane 28 re-transmits acoustic pressure pulsations into the otherwise isolated cavity 38B where they may then be transmitted to the driver and passengers of the vehicle interior 42 through the broadcast duct 40.
Advantageously, in the present invention the membrane 28 may be provided with countermeasure features of the present invention. Countermeasure features may be provided, secured onto or formed with the membrane and configured such that sound amplitude vs. frequency spectrum of the pressure pulsations in cavity 38B (as experienced by the driver/passengers in vehicle interior 42) deviates in intentional and advantageous ways from the sound amplitude vs. frequency spectrum of the pressure pulsations in the cavity 38A. This is discussed in more detail below.
Depending on the application, for obtaining the corresponding mechanical properties, the flexible membrane 28 may be made of rubber film, fabric or plastic film or may also be a metal foil or a thin sheet metal. In a preferred embodiment in the present invention, the diaphragm 28 is comprised of a rubber material, for example, ethylene propylene diene rubber (EPDM), silicon rubber (VMQ), fluorosilicone rubber (FVMQ), fluoropolymer rubber (FPM or FKM) or other suitable flexible materials as are known to those skilled in the art.
Particularly for elastic diaphragm materials such as varieties of rubber, the height of the rim 30 relative to the flange 48 may be configured to result in a specific desired (intentional) tension in the membrane 28. The tension in the membrane 28 may be selected to tune the acoustic flexure properties of the membrane 28 and therefore is one means of adjusting how the sound amplitude vs. frequency spectrum in cavity 38B may intentionally deviate from the sound amplitude vs. frequency spectrum in cavity 38A.
Another way in which the acoustic flexure properties of the membrane 28 may be tuned or adjusted is by varying the thickness (and therefore mass and stiffness) of the membrane 28, thereby tuning how the sound amplitude vs. frequency spectrum in cavity 38B may intentionally deviate from the sound amplitude vs. frequency spectrum in cavity 38A in advantageous and desirable ways. Additionally the acoustic flexure properties of the membrane 28 may be modified by using different membrane materials having different properties, a few examples include elasticity, mass, and stiffness.
Located to the left of Tf is (for an illustratory example herein) an undesired transmitted frequency Tu of 140 Hz (as an example for discussion herein) with a relatively low loss (on the graph). It is desirable to remove certain transmitted sound frequency components which detract from the clean engine rumble sound desired by the driver, such as those relatively prominent components about or near frequency Tu. Therefore, a solution is desirable to remove or at least significantly attenuate the transmission of sound components around Tu (specific frequency selected here only to provide an illustratory example for discussion).
According to the present invention, countermeasure ribs may be advantageously configured and incorporated with, formed onto or secured onto the membrane to create a ribbed membrane 128 (see
Advantageously, the present invention enables the transmitted sound of a sound transmission device 10 to be tailored to produce a cleaner engine or engine rumble sound to the driver by intelligent addition of reinforcement countermeasures to the membrane.
The membrane countermeasures are not limited to the ribbing pattern disclosed herein. Any form and pattern of selective ribbing and reinforcement may be applied to attenuate the membrane mode shapes at specific undesired frequencies without deviating from the inventive principles of the present invention. Selective ribbing and reinforcement countermeasures may be determined directly by simulation (such as FEA or CFD) or through experimentation (trial and error).
Advantageously, specific frequencies may be selectively attenuated without the addition of a side branch resonator (SBR) as is typically applied in the prior art. With a side branch resonator a resonator volume of up to 1 liter is typically required, thereby increasing material requirement, requiring additional under-the-hood mounting space, and increasing total sound transmission device cost. Therefore, significant cost and material savings occur through the use of the membrane countermeasures as taught in the sound transmission device of the present invention.
In the foregoing specification, specific embodiments of the present invention have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the present invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present invention. The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.
