Patent Application
20070072688
The present invention relates to a sound and vibration dampening system for use in transportation vehicles.
Torque transmitting shafts are widely used for transferring rotational power between a source of rotational power and a rotatably driven mechanism. An example of a torque transmitting shaft is a driveshaft tube used in a vehicle driveshaft assembly. The driveshaft assembly transmits rotational power from a source, such as an engine, to a driven component, such as a pair of wheels.
A typical vehicle driveline assembly includes a hollow cylindrical driveshaft tube having an end fitting secured to each end thereof. Usually, the end fittings are embodied as end yokes which are adapted to cooperate with respective universal joints. For example, a driveshaft assembly of this general type is often used to provide a rotatable driving connection between the output shaft of a vehicle transmission and an input shaft of an axle assembly for rotatably driving the vehicle wheels. Traditionally, driveshaft tubes were made from steel. More recently, aluminum driveshafts have been developed because of their lighter weight, reduced system cost, and ability to be more readily balanced when used in larger diameters for the purpose of increasing the resident frequency or critical rotational speed of the respective driveshaft assembly.
One problem encountered by all types of driveline assemblies is their tendency to produce and transmit sound while transferring the power of the engine to the axle assembly. It is known that any mechanical body has a natural resonant frequency. This natural resonant frequency is an inherent characteristic of the mechanical body and is based upon many factors, including its composition, size and shape. The natural resonant frequency is made up of many sub-frequencies, often referred to as harmonics. As the vehicle is operated through its normal speed range (i.e. from 0 mph to about 80 mph), the rotational velocity of the driveshaft assembly changes (i.e. from 0 rpm to about 5000 rpm). As the rotational velocity of the driveshaft changes, it passes through the harmonic frequencies of the body's resonant frequency. When the rotational velocity of the driveshaft passes through these harmonic frequencies, vibration and noise may be amplified since the two frequencies are synchronized and the rotational energy of the driveshaft is converted into vibration and noise. This noise can be undesirable to passengers riding in the vehicle. Thus, it would be advantageous to deaden or reduce the sound produced by a vehicle driveshaft assembly in order to provide the passengers with a more quiet and comfortable ride.
Various attempts have been made to deaden the sound produced by vehicle driveshaft tubes. One general direction that many of these attempts have followed is to place a vibration/noise absorbing/deadening structure within the driveshaft. For example, one attempt involves disposing a hollow cylindrical cardboard insert inside an aluminum or steel driveshaft tube to deaden the sound. Another cardboard insert required external rubber ribs to prevent it from sliding inside the aluminum driveshaft tube and dissipate vibration within the molecular structure of the rubber. As a result, the cardboard insert is relatively complicated and expensive to employ. Other attempts at deadening the sound and attenuating frequencies involve completely or partially filling the driveshaft tube with relatively non-resonant material such as steel wool, cotton, elastic foams, and even plaster. The use of external and internal dampening devices of steel and rubber construction so known as ITD's and, plugs of compressible and slightly resilient material such as cork or rubber.
As exemplified by the number of proposed solutions to the sound problem in driveshafts, the particular solution for a specific type of driveshaft is not always straightforward. For instance, there are questions concerning what types of materials are most effective and suitable for the type of driveshaft employed. In addition, there are questions concerning the added weight, cost and performance of the material chosen for the noise reduction structure.
Therefore, a need exists for a noise reduction structure to be utilized in an aluminum-based driveshaft tube which is lightweight, inexpensive, and long-lasting. In addition, it would particularly be desirable to provide this lighter, less expensive, noise reduction structure for an aluminum-based driveshaft tube which is as or more effective in reducing the sound levels of such a driveshaft tube than the known noise reduction structures and mechanisms.
The above needs and more are provided by the present driveshaft including one or more attenuators strategically positioned at the harmonic frequency nodes of the driveshaft, in which the attenuator includes a dampening material about the perimeter of a rigid. carrier, wherein the rigid carrier (also referred to as a rigid carrier) uniformly distributes the dampening material about the interior of the driveshaft to provide a balanced distribution of dampening material. Each attenuator is slideably inserted into the driveshaft and then bonded to strategic locations of the interior surface of the driveshaft. In one embodiment, the dampening material is expanded during an actuation step and engaged to the driveshafts interior. Broadly, the inventive driveshaft assembly includes:
The attenuator includes a dampening material that may be expandable upon activation and provides engagement to the interior surface of the tubular driveshaft. In some embodiments, the dampening material is selected to dampen sound frequencies or vibrations that are typically produced by mechanical movement and interaction of the driveline components, such as differentials, transmissions, transaxles, half-shafts, universal joints, and velocity joints. The rigid carrier provides a means for uniformly distributing the dampening material about the interior surface of the tubular driveshaft, to ensure that the driveshaft may be balanced. The rigid carrier also provides structural rigidity to the tubular driveshaft. Specifically, the rigid carrier substantially reduces dimensional changes in the diameter of tubular driveshaft during operation.
In one embodiment of the present invention, in addition to dampening the frequencies or vibrations produced by the mechanical movement and interaction of the driveline components, the rigid carrier dampens a second range of sound frequencies or vibrations that are produced by dimensional changes in the driveshaft's diameter by increasing the structural rigidity of the driveshaft.
Another aspect of the present invention is a method of forming a dampening driveshaft. Broadly, the inventive method includes:
Another aspect of the present invention is a method of distributing an expandable material in balanced distribution about the interior of a driveshaft. Broadly, the inventive method includes:
A full understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which:
a (side cross-sectional view) depicts another embodiment of the tubular driveshaft having a swaged cross-section.
b (side sectional view) depicts one embodiment of the swaged portions of the tubular driveshaft having a swaged cross section.
The present invention is now discussed in more detail referring to the drawings that accompany the present application. In the accompanying drawings, like and/or corresponding elements are referred to by like reference numbers.
Referring to
The tubular driveshaft 5 of the present invention may have a constant diameter D1, as depicted in
Preferably, the tubular driveshaft 5 is formed from a single piece of metal, but multiple piece driveshaft tubes can alternatively be used. The tubular driveshaft 5 can be formed from any suitable material. Typically, the tubular driveshaft 5 is formed from steel or an aluminum alloy. Preferably, the tubular driveshaft 5 is formed from an aluminum alloy. Suitable methods for forming the tubular driveshaft 5 are well known to persons skilled in the art and may include, but are not limited to: hot extrusion via seamless or bridge die processes, cold drawing, or continuous seam welding of a tube made from roll formed flat sheet.
In one embodiment, a method for forming a tubular driveshaft having a swaged configuration includes at least the steps of providing an 6000 series type alloy hollow elongate tube; and reducing the diameter of at least one portion of the hollow elongate tube to form a reduced diameter section and transition section between the reduced diameter section and the tube; the transition section having at least three subsections: i. a first subsection having a first slope; ii. a second subsection having a second slope; and iii. a third subsection located between the first and second subsections having a third slope which is less than the first and second slopes, the third section forming a circumferential step to stiffen the transition section.
Referring to
The swaged portions 2l, 22 of the driveshaft 5 having a smaller diameter tube portion than the central portion of the driveshaft may be swaged using rotary swaging or push pointing. Rotary swaging is a technique wherein opposing dies are rapidly hammered against the outside diameter of the tube to swage down the diameter to a smaller diameter. Push pointing is a technique wherein a tube or pipe of given diameter is pushed through a tapered reducing die to neck down or reduce the initial tube diameter.
In one preferred embodiment, the aluminum alloy for the tubular driveshaft contains about 0.5 to 1.3% Mg, about 0.4 to 1.2% Si, about 0.6 to 1.2% Cu, about 0.1 to 1% Mn, the balance substantially aluminum and incidental elements and impurities. In another preferred embodiment, the invention drive shafts includes AA alloy 6013, in which Aluminum Association composition limits for alloy 6013 are 0.6 to 1% Si, 0.8 to 1.2% Mg, 0.6 to 1.1% Cu, 0.2 to 0.8% Mn, 0.5% max. Fe, 0.1% max. Cr, 0.25% max. Zn, 0.1% max. Ti, other elements 0.05% each, 0.15% total, the balance substantially aluminum.
In one embodiment, providing the 6000 series type alloy hollow elongate tube may include the process steps of extrusion, cold drawing, solution heat, quench, and artificial aging. In one embodiment, extrusion of the hollow elongate tube may be conducted at temperatures at or above 400° F., typically from about 500° F. to about 700° F., to provide a more uniform or relatively fine recrystallization grain size.
A more detailed description of a method for forming a swaged driveshaft is disclosed in U.S. Pat. No. 6,247,346, to Dickson, titled “Method of Forming a Drive Shaft”, filed Jun. 19, 2001, and incorporated herein by reference for all purposes.
Referring to
The dimensions of the driveshaft are typically dependent on application. As an example, a tubular driveshaft 5 may have an inner diameter of about 54 millimeters to about 146 millimeters and an outer diameter of about 60 millimeters to about 150 millimeters. The length L1 of the tubular driveshaft 5 may range from about 375 millimeters to about 2100 millimeters. The wall thickness of the tubular driveshaft 5 may range from about 2 millimeters to about 4 millimeters. Typically, when aluminum is employed as the tubular driveshaft 5 material, the ratio of diameter to wall thickness is on the order of 18 (60 OD×3 mm wall) to 70 (150 OD×2.3 mm wall).
Referring now to
In one embodiment of the present invention, the dampening material 15 expands upon activation and exerts pressure between the rigid carrier 20 and the interior surface of the tubular driveshaft 5, wherein the compressive force exerted on the rigid carrier 20 secures the attenuator 6 within the tubular driveshaft 5. In one embodiment of the present invention, the dampening material 15 expands upon activation in adhesive engagement with the interior surface of the tubular driveshaft 5.
Preferably, the dampening material 15 is an expandable material that may be heat activated at a temperature consistent with existing automotive and transportation manufacturing processes, even more preferably activating in a temperature range consistent with aluminum driveshaft tube manufacturing processes (i.e., artificial aging or precipitation hardening). The heat activated material may flow, cure (e.g. thermosettable), foam, expand (e.g. foam) or a combination thereof upon exposure to heat. One example of a temperature range consistent with driveshaft manufacturing processes ranges from 300° F. to 400° F. If needed, blowing agent activators can be incorporated into the composition to cause expansion at different temperatures outside the above ranges. Generally, suitable expandable foams have volumetric range of expansion ranging from approximately 100% to 400%. Although heat activated materials are preferred, the dampening material 15 may be activated into expansion and engagement with the interior surface of the tubular driveshaft 5 by alternative means.
In a preferred embodiment, the dampening material 15 displays a high degree of crosslinking upon curing to achieve its final shape. The higher the degree of crosslinking the greater the resistance to shape change or flow once the dampening material 15 has cured. Any material that is heat-activated and expands and cures in a predictable and reliable manner under conditions consistent with driveshaft manufacturing, while meeting structural and acoustical requirements for the selected application, can be used.
The vibration attenuation requirements of the dampening material 15 may be selected to meet the requirement of each application. In one embodiment of the present invention, it is preferred that the dampening material 15 be selected to attenuate sound waves and vibrations in a range of frequencies produced by driveline components, including, but not limited to: differentials, transmissions, transaxles, half-shafts, universal joints, and velocity joints. Typically, this frequency range includes higher frequencies ranging from about 300 Htz to about 700 Htz. It is noted that the dampening material is not limited to materials that dampen the above frequency range since the dampening material may be selected for any frequency range required for different applications.
In some embodiments of the present invention, the dampening material 15 is a foamable or adhesive material, which includes or is based upon an epoxy resin, polyethylene, polyester, ethylene vinyl acetate, ethylene propylene diene rubber (EPDM), styrene-butadiene-styrene block copolymers, polyamide, or mixtures and combinations thereof. For example, without limitation the foam may be an epoxy-based material, including an ethylene copolymer or terpolymer that may posses an alpha-olefin. As a copolymer or terpolymer, the polymer is composed of two or three different monomers, i.e., small molecules with high chemical reactivity that are capable of linking up with similar molecules.
A number of epoxy-based or otherwise based sealing, baffling or acoustic foams are known in the art and may be employed in the present invention. A typical foam includes a polymeric based material, such as an epoxy resin, an EVA or ethylene-based polymer which, when compounded with appropriate ingredients, (blowing and curing agent), expands and cures in a reliable and predicable manner upon the application of heat or the occurrence of a particular ambient condition. Examples of blowing agents include azodicarbonamide and P, P′-oxybis (benzene sulfonyl hydrazide). Examples of curing agents include dicyandiamide and cyanoguanidine. Id. From a chemical standpoint, for a thermally-activated material, the foam is usually initially processed as a flowable thermoplastic and/or thermosettable material before curing. In a preferred embodiment, the dampening material 15 will cross-link (e.g. thermoset) upon curing, resulting in a cured material incapable of further flow.
Some other possible materials include, but are not limited to, polyolefin materials, copolymers and terpolymers with at least one monomer type of alpha-olefin, phenol/formaldehyde materials, phenoxy materials, and polyurethane materials with high glass transition temperatures. In other embodiments of the present invention, the dampening material 15 may include polyamide or include thermosets such as vinyl ester resins, thermoset polyester resins and urethane resins. In general, the desired material will have good adhesion durability properties.
Other exemplary expandable materials can include combinations of two or more of the following: polystyrenes, styrene-butadiene rubber, nitrile-butadiene rubber (NBR), butadiene acrylo-nitrile rubber, styrene butyl styrene (SBS) block co-polymers, epoxy resin, azodicarbonamides, urea-based catalysts such as N,N dimethylphenyl urea, sulfur, dicyandiamide, amorphous silica, and glass microspheres. Other examples of expandable materials are sold under the tradename SIKAELASTOMER®, SIKADAMP®, SIKAREINFORCER®, SIKAFOAM®, SIKASEAL®, and SIKABAFFLE® and are commercially available from the Sika Corporation, Madison Heights, Mich.
In some embodiments of the present invention, the dampening material 15 may be at least partially coated with an active polymer having damping characteristics or an other heat activated polymer, (e.g., a formable hot melt adhesive based polymer or an expandable structural foam, examples of which include olefinic polymers, vinyl polymers, thermoplastic rubber-containing polymers, epoxies, urethanes or the like).
In a preferred embodiment, the dampening material 15 can be processed by injection molding, extrusion, compression molding or with a mini-applicator.
Still referring to
Referring to
Referring to
The rigid carrier 20 may also include cross bracing 17 extending to opposing portions of the rigid carrier's perimeter through a central portion of the attenuator 6. The cross bracing 17 can provide both structural stiffness to the rigid carrier 20, and an insertion contact to facilitate insertion of the attenuator 6 within the tubular driveshaft 5 prior to activation of the dampening material 15. As an added advantage, the cross bracing 17 divides the air-space across the diameter of the tubular driveshaft 5 into smaller constituents. By dividing the air space across the diameter into smaller constituents, the cross bracing 17 may increase the frequencies of noise and/or vibrations produced, conducted, or transmitted by the tubular driveshaft 5. By increasing the frequencies of the noise and/or vibrations, the likelihood that such frequencies will travel through solid structures of the driveline is substantially reduced.
In some embodiments of the present invention, the rigid carrier 20 dampens a range of frequencies for noise and/or vibration that is outside of the range of frequencies that may be dampened by the dampening material 15. The frequency range dampened by the rigid carrier 20 may overlap with the frequency range dampened by the dampening material 15 or the frequency ranges may be distinct. In one embodiment, the rigid carrier 20 substantially reduces dimensional changes in the diameter of the tubular driveshaft 5 and therefore reduces noise and vibration frequencies resulting from those dimensional changes in the driveshaft diameter. These dimensional changes can be so described as changes in the tube's circularity, particularly for the case of such tubes with diameter to wall ratios greater than 65, caused by torque pulses created by driveline architecture. Without wishing to be bound, it is believed that changes in the tubular driveshaft's diameter (tube periphery elastically moving from round to oval) compress and decompress adjacent air in much the same manner as an audio speaker, thus creating low frequency sound in the range of 50 Htz to 100 Htz. Typically, noise and vibration frequencies resulting from dimensional changes in the driveshaft diameter are low frequencies ranging from about 50 Htz to 100 Htz. In a preferred embodiment, in which the dampening material 15 dampens frequencies ranging from 100 Htz to 700 Htz, the rigid carrier 20 is effective in dampening frequencies to a frequency of about 100 Htz or less.
The rigid carrier 20 may be produced from any high temperature resistant performance plastic which can withstand process environment conditions and automotive assembly plant oven temperatures without showing significant degradation in performance. That is, the rigid carrier 20 will retain its' size and shape at such temperatures experienced in the automotive assembly process without any detrimental deformation. Typical plastic materials include, but are not limited to, semi-crystalline or amorphous materials including, polyamides such as nylon 6, nylon 6/6, nylon 6/6/6, polyolefins such as polyethylene or polypropylene, syndiotactic vinyl aromatic polymers such as syndiotactic polystyrene (SPS) and any blends thereof. Other potential polymers include polyesters, polyesteramides, polyarylates, polyurethanes, polyureas, polyphenylene sulfides, and polyetherimides. It is noted that additional materials may be utilized for the rigid carrier 20, and are within the scope of the present disclosure, so long as the materials maintain structural and/or chemical stability through a temperature range suitable for manufacturing of components for using in transportation vehicles.
The rigid carrier 20 can be produced by any molding technique which will produce a cylinder having a set shape and size. Typical molding techniques include, but are not limited to, well known processes such as blow molding, injection molding, rotational molding, pressure forming, linear coextrusion of the rigid carrier's ring and subsequent rolling and bonding with the web material, and the like.
As discussed above, the tubular driveshaft 5 contains one or more attenuators 6 for dampening sound waves and vibrations that may be generated or amplified by the driveline. The location of each attenuator within the tubular driveshaft may be dependent on application and the location of each attenuator 6 may be selected to dampen specific frequency ranges. Preferably, the attenuators 6 may be positioned within the driveshaft 5 on harmonic frequency nodes. Referring to
While the present invention has been particularly shown and described with respect to the preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in forms of details may be made without departing form the spirit and scope of the present invention. It is therefore intended that the present invention not be limited to the exact forms and details described and illustrated, but fall within the scope of the appended claims.
Having described the presently preferred embodiments, it is to be understood that the invention may be otherwise embodied within the scope of the appended claims.
The present invention claims the benefit of U.S. provisional patent application 60/698,747, filed Jul. 13, 2005, and U.S. provisional patent application 60/698,740, filed Jul. 13, 2005, the whole contents and disclosure of which are incorporated by reference as is fully set forth herein.
| Number | Date | Country | |
|---|---|---|---|
| 60698747 | Jul 2005 | US | |
| 60698740 | Jul 2005 | US |
