Patent Application
20190009620
The disclosed inventive concept relates to vehicle tires that demonstrate reduced structure borne and airborne noise. More particularly, the disclosed inventive concept relates to vehicle tires having a bead core formed from wires encased in an impermeable rubber or rubber-like sheath that separates the wires from the molded rubber of the tire. The rubber sheath is preferably impermeable to the in-flow of rubber material from the tire during the molding process. The bundle of wires and the impermeable sheath defines a vibration-damping rope in which the outermost layer of wires of the bundle of wires is bonded to the inner surface of the impermeable sheath by being partially embedded therein. A coulomb friction thus results between the unbonded internal wires of the sheathed wire bundle.
Pneumatic tires have been utilized on motorized vehicles since the very earliest days of motoring. Early wheel rims were of the clincher variety in which a pair of opposed turned-in rim edges provided a seat for the tire beads which were snapped into place. Later wheel rims adopted outwardly-flared bead seats. This later style rim is the type normally fitted to the modern automotive vehicle.
Even the earliest types of tires included a pair of opposed beads with each bead forming a ring at each opening of the tire. Such beads have conventionally included bead cores formed from windings of at least one bead wire, typically a steel monofilament. The beads are virtually inelastic compared with the rest of the tire and prevent the tire from unintentionally being loosened from the wheel rim.
Today's tire relies on a bead construction that has changed little since its initial design. Functioning adequately for its purpose, tire designers had little incentive to improve over the conventional bead design. However, automobile manufacturers are increasingly reviewing all features of the vehicle in terms of reducing noise, vibration and harshness (NVH) during operation. The vehicle tire is one such feature being reexamined as a possible area for NVH reduction.
Many vehicle components are subjected to vibration which is a significant component of undesired NVH. Mechanical and structural components such as vehicle suspensions, engine blocks, and turbine blades and discs as well as support structures for motors, pumps, centrifugal machines and the like are commonly subjected to vibration. When this occurs, these components experience a periodic motion in alternately opposing directions from the position of equilibrium which induces loads that can lead to reduced component life.
Structure borne noise and airborne noise are mainly the byproduct of tires produced according to conventional techniques. Current optimization methods for reducing structure borne noise in tires rely on influencing the first radial mode and depend mainly on either adding damping mass or reducing vertical stiffness. The disadvantages of these methods are that they significantly reduce rolling resistance of the tire or reduce the handling (steering) performance of the vehicle, possibly both. Structure borne noise in a vehicle refers to any noise noticed within a vehicle. The structure borne noises in the vehicle are generally divided into three categories. Structure borne noise having a frequency range of between 60-300 Hz is referred to as “low rumble” noise, noise having a frequency range of between 125-200 Hz is referred to as “high rumble” noise, while noise having a frequency range of between 200-300 Hz is referred to as “cavity” noise. Conversely, airborne noise is defined as any noise noticed within a vehicle having a frequency range of 630-3150 Hz.
Both vehicle and tire manufacturers are devoting an increasing amount of attention to structure borne noise normally generated by the vehicle tire as one of the major quality and competitive areas of reducing vehicle NVH. In the instance of plastics, elastomers, or other polymerized materials such as vehicle tires, these materials inherently have a relatively high damping capacity where the vibrational energy associated with their periodic motion is gradually converted to heat or sound as a result of the internal material damping. However, vehicle tires, while have a generally high damping capacity, are still sources of considerable undesirable NVH, particularly in the instance of airborne noise. Tire manufacturers have found that airborne noise could be mainly minimized by changing the tread pattern design. Another option is to close the lateral grooves in the tire shoulders area to block the sound. However, this measure has a negative effect on vehicle handling on wet roadway surfaces.
In view of the state of the art, it may be advantageous to provide a tire construction offering reduced NVH by including a construction that aids in damping. As in so many areas of tire manufacturing technology, there is always room for improvement related to friction damping relative to interacting mechanical and structural components.
The disclosed inventive concept provides a method and system for increasing damping capacity in a pneumatic tire by utilizing a vibration-damping rope comprising a bundle of individual wires encased by a polymerized outer sheath. The vibration-damping rope is embedded in the tire during the tire molding process. The individual wires allow inter-wire friction to occur during part vibration. The disclosed inventive concept thus runs contrary to the accepted technique of directly connecting wires in the bead core by the tire rubber. Instead, only the outer wires of the bundle of wires are bonded to an encasing rubber sheath, thereby allowing coulomb friction to be generated between the un-bonded wires of the wire bundle. This friction provides a significant increase in the damping capacity of the tire bead core, which reduces the noise emission of the tire.
The tire bead core of the disclosed inventive concept for embedding in a pneumatic tire comprises a bundle of wires having an outermost layer and a polymerized sheath formed over the bundle of wires. The sheath has an inner layer. At least some of the wires of the outermost layer of wires are embedded in the inner layer and are thus bonded thereto, whereby sliding movement of the surfaces of the un-bonded wires relative to one another dampens resonant tire vibration.
The wires are composed of a metal. The wires may be composed of the same metal or may be composed of different metals. The wires may be arranged linearly or helically. The sheath is composed of a polymerized material that is preferably a layer that is impermeable to the in-flow of rubber during the tire molding process.
The vibration-damping rope is preferably formed by extrusion in which at least a portion of the bundle of wires is placed into an extruder. A polymerizable material is added to the extruder to form an outer layer over the wire bundle. By controlling certain parameters surrounding the extrusion process such as temperature of the polymerizable material and extrusion speed, at least a portion of the outermost array of wires is embedded in the inner layer of the outer sheath.
The damping frequencies may be adjusted with different friction combinations by changing the material individual for every wire or for the total for all wires. Additionally the wire shape, thickness, structure and any pretention are factors that can be manipulated to adjust the friction and thus adjust the damping frequencies. The disclosed inventive concept provides a new way of improving the noise behavior of a pneumatic tire with potentially no deterioration in handling, rolling resistance and wet road surface performance. The disclosed inventive concept also allows for the adjustment of damped frequencies.
The above advantages and other advantages and features will be readily apparent from the following detailed description of the preferred embodiments when taken in connection with the accompanying drawings.
For a more complete understanding of this invention, reference should now be made to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention wherein:
In the following figures, the same reference numerals will be used to refer to the same components. In the following description, various operating parameters and components are described for different constructed embodiments. These specific parameters and components are included as examples and are not meant to be limiting.
The accompanying figures and the associated description illustrate the construction and use of vibration-damping wires encased in a sheath which is embedded in the bead of a pneumatic tire. The prior art pneumatic tire is illustrated in
Referring to
Between the peripheral crown 12 and the tire bead 16 is formed a sidewall 20. An inner liner 22 is formed on the entire surface of the inside of the pneumatic tire 10. An internal breaker 24 is continuously formed between the peripheral crown 12 and the bead 14. Between the internal breaker 24 and the inner liner 22 is formed a tire carcass 26. The tire carcass 26 comprises one or more plies of cords as is known in the art. The individual cords are composed of steel or another resilient material, such as a polymerized material.
The pneumatic tire 10 is mounted on a wheel rim 28. As illustrated in both
Formed at the heart of the tire bead 16 is a tire bead core 32. The internal breaker 24 defines a pocket 34 which envelopes the tire bead core 32 and a bead filler 36. The tire bead core 32 conventionally comprises a bundle of individual wires 38.
The disclosed inventive concept is provided to overcome the known NVH challenges faced by today's tire design. With reference to
Referring to
The pneumatic tire 42 is conventionally mounted on a wheel rim 52. As illustrated in both
Formed at the approximate center of the tire bead portion 40 is a tire bead core 56. The internal breaker 48 defines a pocket 58 which envelopes the tire bead core 56 and a bead filler 60. The tire bead core 56 conventionally comprises a bundle of individual wires 62 that are surrounded, wrapped or otherwise encased by a sheath 64 that is impermeable to the in-flow of rubber material. The individual wires 62 are preferably though not exclusively steel monofilament wire. The individual wires 62 may be of the same diameter (as illustrated
Each wire of the bundle of individual wires 62 is preferably made of steel although other metals may be selected for this use. The individual wires within a single vibration-damping rope 66 may be made of the same metal or of different metals. The impermeable sheathing is preferably although not absolutely formed from any one of several elastomeric materials such as the same rubber as that of the pneumatic tire 42 or may be formed from natural or synthetic rubber or rubber-like materials, though the vibration-damping rope 66 is preferably formed as a separate component prior to being molded into the pneumatic tire 42 as discussed below. While a single vibration-damping rope 66 is illustrated as being positioned within the pneumatic tire 42, it is to be understood that more than one vibration-damping rope 66 may be so positioned.
A feature of the disclosed inventive concept is the interface between some of the individual wires of the bundle of individual wires and the impermeable sheath that is illustrated in
A variation of the disclosed inventive concept is illustrated in
The vibration-damping rope 66, 80 is preferably though not absolutely formed by first forming the individual wires then bundling them to form the bundle of individual wires 62, 86. The formed bundle of individual wires 62, 86 is then run through an extruder together with material that will ultimately form the impermeable sheath 64, 82 in a process in which the temperature of the encasing rubber or rubber-like material is regulated to soften said inner surface 68, 84 so that the outermost array of wires 70, 88 become partially embedded within the inner surface 68, 84 of the impermeable sheath 64, 82 as discussed above. One formed vibration-damping rope 66, 80 is then positioned in each of the two tire openings of the tire mold (not shown). Other elements of the pneumatic tire 42, including the internal breaker 48, are placed in the mold as well. Thereafter the mold is filled with tire-forming rubber or rubber-like material to form the pneumatic tire 42. The molded tire having the vibration-damping rope 66, 80 of the disclosed inventive concept embedded therein is then allowed to cool before being released from the tire mold as is known in the art.
The vibration-damping rope 66, 80 of the disclosed inventive concept has virtually unlimited applications when molded into virtually any rubber or other polymerized component. Because of the many conceivable variations of length and diameter of the vibration-damping rope 66, 80, it may be adapted for a virtually unlimited number of uses without compromising its dampening effectiveness. Thus the vibration-damping rope 66 may find applications beyond the applications illustrated herein in
One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims.
