TIRE HAVING A GROOVE WALL LINING FOR REDUCING FORMATION OF ANOMALIES CAUSING SUBJECTIVE USER DISSATISFACTION

Abstract: A tire having a pair of beads; a carcass ply having ends, each of the ends anchored to a respective one of the beads; at least one belt ply extending circumferentially around the tire and disposed axially outward of the carcass ply; and a tread layer disposed axially outward of the at least one belt ply and formed from a first tread compound. The tread layer has a plurality of tread ribs; at least one groove disposed between adjacent tread ribs or blocks; and a groove wall lining extending from the at least one groove. The groove wall lining is made from a second tread compound different than the first tread compound. A tread layer of a tire formed from a first tread compound and having a plurality of tread ribs or blocks; at least one groove disposed between adjacent tread ribs, or blocks; and a groove wall lining extending from the at least one groove. The groove wall lining is made from a second tread compound different than the first tread compound.

Description: TITLE OF THE INVENTION Tire Having A Groove Wall Lining For Reducing Formation of Anomalies Causing Subjective User Dissatisfaction BACKGROUND OF THE INVENTION The present invention relates to a vehicle tire. Specifically, the invention relates to a pneumatic vehicle tire having a groove wall lining that reduces the formation of anomalies causing subjective user dissatisfaction. Tires, especially commercial vehicle tires, may be removed from service due to anomalies on the tread region. These anomalies are depressions in the tread rib or tread block. The anomalies can be caused by unequal normal stress distribution laterally across the rib or block. The stress concentration occurs at the edges of the tread rib or block. The stress concentration at the edges of the tread rib or block is known as the edge effect. The central portion of the tread rib or block experiences a lower stress than the edges of the tread rib or block. The stress at the edge of the tread rib or block may be approximately twice as large as the stress at the central portion of the tread rib or block. The stress concentration at the edges of the tread rib or block typically causes anomalies to form at the edges of the tread rib or block. Once an anomaly forms at the edge of the rib or block, the anomaly will propagate to the remainder of the rib or block; and often to adjacent ribs or blocks . The propagation of the anomaly occurs quickly as the tire continues to roll. The decision to remove a tire is subjective and may depend on the location of the tire on the truck/trailer combination. Generally, a driver can feel an anomaly on a steering tire by the ride of the vehicle. In that case, the driver pulls the tire when uncomfortable with the ride of the vehicle. However, if a tire having an anomaly is a drive tire or is located on the trailer, the driver may not sense any discomfort. The driver may, however, hear an increase in tire noise. If the driver does not sense discomfort or an increase in noise, the driver will pull the tire during a subsequent visual inspection of the vehicle. The removal of a tire due to anomalies causing subjective user dissatisfaction is premature when considering the portions of the tire without the anomaly. The portions of the tire without the anomaly are capable of substantial additional service on the vehicle. Extending the time until the onset of an anomaly or decreasing the severity of the anomaly once found may extend the life of the tire. The extended life of the tire reduces the cost of purchase and installation of new tires. In the commercial traclting field, these potential cost savings are significant. There is much room for improvement in the art. SUMMARY OF THE INVENTION Thus, it is an object of the present invention to provide a tire with an improved tread portion that reduces the formation of anomalies causing subjective user dissatisfaction. It is a further object of the present invention to provide an improved tread portion that reduces the formation of anomalies causing subjective user dissatisfaction. It is a further object of the present invention to provide a tread portion that eliminates the edge effect or ejdiibits a reduced edge effect, defined as the high normal stress value at the edges of a tread rib or block as compared to the center portion of a tread rib or block. It is a further object of the present invention to provide a tread portion that more uniformly distributes normal stress laterally across a tread rib or block. These and other objects of the present invention are accomplished in a first embodiment of the present invention by a tire having a pair of beads; a carcass ply having ends, each of the ends anchored to a respective one of the beads; at least one belt ply extending circumferentially around the tire and disposed axially outward of the carcass ply; and a tread layer disposed axially outward of the at least one belt ply and formed from a first tread compound. The tread layer has a plurality of tread ribs each having a defining circumferential groove on each side thereof; and a groove lining covering the groove walls and bottom. The groove lining is made from a second tread compound different than the first tread compound. The tread layer has a thickness laterally beneath the base of each groove which is covered with the wall lining . The wall lining in the area of the groove base has a thickness which is between about 25 and 50 percent of the tread layer thickness in this area. The tread ribs are formed with a lateral width of which the groove wall lining comprises between 15 and 30 percent The tread compound forming the groove lining has a modulus of elasticity which is 40 to 80 percent less than the modulus of elasticity of the tread compound forming the tread portion. The tread ribs may include sipes and the groove wall lining may include sipes. BRIEF DESCRIPTION OF THE DRAWINGS Other objects of the present invention will become apparent from the following description with reference to the accompanying drawings, wherein: Figure 1 is a perspective view of a tire having a tread portion of the present invention; Figure 2 is a perspective, cross-sectional view of a tire having a tread portion of the present invention; and Figure 3 is a partial cross-sectional view of a tread portion of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS This application uses numerous phrases and terms of art. The phrase "mid-circumferential plane" refers to the plane passing through the center of the tread and being perpendicular to the axis of rotation of the tire. The term "radial" refers to the direction perpendicular to the axis of rotation of the tire. The term "axial" refers to the direction parallel to the axis of rotation of the tire. The term "lateral" refers to the direction along the tread of the tire going from one sidewall of the tire to the other sidewall. The term "groove" refers to an elongated void area in the tread that may extend circumferentially or laterally in a straight, curved of zig-zag manner. The phrase "tread width" refers to the greatest axial distance across the portion of the tread in contact with a road surface, as measured from a footprint of the tire, when the tire is mounted on a rim, subjected to a load, and inflated to a pressure corresponding to the load. All of the other tire dimensions are measured when the tire is mounted on a rim and inflated to a given pressure, but not subjected to a load. The phrase "tread depth" refers to the radial extent, or height, of a tread block or rib on a tread portion of a tire. The phrase "modulus of elasticity" refers to the modulus of elasticity measured at ten percent (10%) elongation. A tire having a tread portion capable of reducing the formation of anomalies causing subjective user dissatisfaction will now be described with reference to Figures 1-3. Although described with reference to a groove between adjacent main ribs or blocks, Applicant recognizes that the present invention is not so limited. For example, the present invention can be used on any groove between adjacent ribs or blocks on a tread portion of a tire. Thus, the present invention is also capable of use between a decoupling rib and an adjacent main tread rib or block. Figure 1 is a perspective view of a tire 10 mounted on a rim R. The exterior features of tire 10 include sidewalls S and a tread portion TP having a tread width TW. Tread portion TP of tire 10 uses a unique design for the groove between adjacent tread ribs/blocks. The specific groove design is described in greater detail below. Figure 2 is a perspective, cross-sectional view of the exterior and interior features of tire 10 having tread portion TP. Tire 10 includes a pair of annular beads 11 on axially opposite sides of a midcircumferential plane M . Beads 11 securely mount tire 10 to rim R for use on a vehicle (not shown). Opposite ends of at least one carcass ply 13 anchor to beads 11. The middle portion of carcass ply 13 forms part of sidewalls S and a crown portion C. At least one belt ply 15 is positioned radially outward of carcass ply 13. Belt ply 15 includes reinforcing cords 17. In commercial vehicle tires, reinforcing cords 17 are typically manufactured from steel. Sidewalls S include shoulder regions 19. Crown portion C extends between sidewalls S. Tread portion TP occupies the radially outermost extent of crown portion C, is situated between shoulder regions 19, and joins sidewalls S. Tread portion TP contacts the ground during rolling movement of tire 10. Tread portion TP may include conventional tire tread sculpture features, such as circumferential grooves 27, lateral grooves (not shown), and sipes 29 in a central portion of tread ribs 21 and at an edge of tread ribs 21 (see Figures 1 and 2). Circumferential grooves 27 can be straight grooves, or grooves having an undulating, or zig-zag, pattern. Tread portion TP also includes tread ribs or tread blocks 21. The use of either tread ribs or tread blocks is or their number is irrelevant to the present invention. The remainder of the application will refer to the tread ribs or tread blocks as tread ribs 21 with the understanding that a tread block could be used instead . Circumferential grooves 27 separates adjacent tread ribs 21. In shoulder region 19, tire 10 can include a shoulder rib 23 and a decoupling, or sacrificial, rib 25. The desirability of a decoupling rib on a shoulder portion of a tire is discussed in U.S. Patent number 4,480,671 to Giron. Figure 3 is a partial cross-sectional view of tread portion TP of tire 10. Tread portion TP includes at least one tread rib 21. Tread rib 21 has a lateral width W. Grooves 27 are located between adjacent tread ribs 21. In the area of each groove 27, tread portion TP has a radial thickness T. In typical long haul commercial vehicle tires, each tread rib 21 can have a lateral width W of between approximately ten and fifty percent (10-50%) of tread width TW; and tread portion TP can have a radial thickness T of between approximately 4 and 8 mm in the area beneath groove 27. Tread portion TP has two components, a main component 31 and a groove wall lining 33. Main component 31 encompasses the majority of tread portion TP and is formed from a first tread compound. Groove wall lining 33 occupies the remaining volume of tread portion TP and is formed from a second tread compound. As seen in Figure 3 , groove wall lining 33 completely lines grooves 27, both in the lateral and in the radially subjacent positions. Groove wall lining 33 includes radial portions 35 that flank groove 27. Radial portions 35 of groove wall lining 33 can mirror the shape of groove 27. Radial portions 35 extend along the lateral outer surface tread rib 21 a lateral extent, or lateral width w. A portion 37 of lining 33 extends across the inner surface groove 27 and connects radial portions 35. Lateral portion 37 has a thickness t in the area across the inner surface of groove 27. It is noted that only tread portion TP grooves 27 are lined with lining 33 including those grooves defining a lateral surface of the shoulder ribs 23. The specific geometric .and physical characteristics of the groove wall lining and the main component 31, and the relationships therebetween will now be discussed. The modulus of elasticity measures, among other characteristics, the hardness of a particular tread compound. The hardness of a particular tread compound can prove to be both beneficial and detrimental to the performance of a tire. For instance, a harder tread compound may be beneficial in terms of tread wear rate and rolling resistance when compared to a softer tread compound. However, the hard tread compound can be more susceptible to the edge effect and have less wet traction than the softer tread compound. On the other hand, a softer tread compound may be less susceptible to the edge effect and have greater wet traction than a harder tread compound. However, the softer tread compound may have a greater tread wear rate and higher rolling resistance than the harder tread compound. The present invention utilizes two tread compounds, one softer than the other . The present invention, by utilizing different tread compounds , can take advantage of the benefits of both softer and harder tread compounds at specific locations on tread portion TP. In a preferred embodiment, a modulus of elasticity (E 33 ) of the second tread compound used in groove wall lining 33 and a modulus of elasticity (E 31 ) of the first tread compound used in main portion or component 31 should satisfy the following approximate ratio: E 33 0.4 to 0.8 In other words, the second tread compound used in groove wall lining 33 is softer than the first tread compound used in main portion 31. Preferably, the ratio between the modulus of elasticity (E 33 ) of the second tread compound used in groove wall lining 33 and the modules of elasticity (E 31 ) of the first tread compound used in main portion 31 should be approximately 0.65. Although Figures 1 and 2 show tire 10 as having a typical array of siping 29 at the edges of tread rib 21 (including groove wall lining 33), the present invention is also capable of use with a fewer number of sipes 29 on tread rib 21 , or with no sipes on tread rib 21. Theoretically, the lower end of the ratio between the moduli of elasticity is more appropriate for a tire with a fewer number of sipes on the tread rib, or no sipes on the tread rib. Also, the upper end of the ratio between the moduli of elasticity is theoretically more appropriate for a tire with a greater number of sipes on the tread rib. Also in the preferred embodiment, lateral width w of radial portion 35 and lateral width W of tread rib 21 should satisfy the following approximate ratio: w 0J5 to 0.3 W Preferably, the ratio between lateral width w of radial portion 35 and lateral width W of tread rib 21 is approximately 0.2. In the preferred ratio, main component 31 encompasses approximately 50 percent of the lateral width W of tread rib 21. As seen in Figure 3, main component or compound 31 is situated in the middle of tread rib 21. In a long haul commercial vehicle tire, lateral width w of radial portion 35 is preferably between approximately 6 and 9 mm. To prevent the formation of cracks propagating from grooves 27, lateral portion 37 of groove wall lining 33 should extend laterally across the bottom of groove 27 at a suitable thickness. In the preferred embodiment, radial thickness t of lateral portion 37 and radial thickness T of tread portion TP should satisfy the followihg approximate ratio: t 0.25 to 0.5 T Preferably, the ratio between the radial thickness t of lateral portion 37 and radial thickness T of tread portion TP is approximately 0.4. In a long haul commercial vehicle tire, radial thickness t of lateral portion 37 is preferably between approximately 2 and 3.5 mm. It has also been found that radial thickness t of lateral portion 37 of groove lining 33 should also always be less than the lateral thickness w of lateral portion 37. The desired ratio is for t to have a thickness which is between 22% to 58% of the thickness w. An experiment was performed to determine the effectiveness of the present invention to reduce the formation of anomalies causing subjective user dissatisfaction. The experiment utilized tires that were identical in all aspects, save the groove wall lining. The tread portion of one set of tires lacked a groove wall lining. The tread portion of the other set of tires had a groove wall lining. The groove wall lining satisfied the parameters of the modulus of elasticity, thickness and lateral width described above. 10 The experiment established that the present invention reduced the formation of anomalies on the tread portion that causes subjective user dissatisfaction. Specifically, the experiment established that the stress concentration across the tread rib was reduced significantly. The normal stress distribution of a tire having the groove wall lining of the present invention was more unifoπn laterally across each rib of the tire. The experiment also established that tires having the groove wall lining of the present invention required a greater amount of use, or mileage, to ediibit an anomaly causing subjective driver discomfort. Applicant also understands that the invention does not merely apply to new tires. For example, Applicant recognizes that the present invention can be applied to tread layers used with retreaded tires and to tire tread layers in strip form which are ultimately cured before or after mounting on a tire casing. Applicant also recognizes that the present invention is not limited to commercial vehicle tires. For example, automobile tires can benefit from the present invention. The above description is given in reference to the preferred embodiment of a tire having a tread portion for reducing the formation of anomalies causing subjective user dissatisfaction. However, it is understood that many variations are apparent to one of ordinary skill in the art from a reading of the disclosure of the invention. Such variations and modifications apparent to those slrilled in the art are within the scope and spirit of the instant invention as defined by the following appended claims. 11

Claims: What is claimed is: 1. A tire comprising: a pair of beads; a carcass ply having ends, each of said ends anchored to respective one of said beads; at least one belt ply extending circumferentially around the tire and disposed axially outward of said carcass ply; and, a tread portion disposed axially outward of said at least one belt ply and formed from a first tread compound having a first modulus of elasticity, said tread portion comprising : a plurality of tread ribs; at least two grooves defining each said tread rib, each groove having a base and a pair of walls; and, a groove lining covering said walls and said base of each said groove, said groove lining being formed from a second tread compound having a second modulus of elasticity less than said first modulus of elasticity of said first tread compound, wherein said second modulus of elasticity is less than approximately 80 percent of said first modulus of elasticity. 2. The tire as recited in claim 1, wherein said tread portion has a thickness radially from the base of each said groove; and, wherein said groove lining has a thickness laterally of each said groove, said thickness of said groove lining being between approximately 25 and 50 percent of said thickness of said tread portion. 12 3. The tire as recited in claim 2, wherein said thickness of said groove lining over said groove base is approximately 40 percent of said thickness of said tread portion beneath said groove base. 4. The tire as recited in claim 2 wherein said groove lining along said groove wall has a lateral width; and, wherein said groove lining along said groove base has a radial thickness, said radial thickness of said base lining being between 22 and 58 percent of said lateral thickness of said wall lining. 5. The tire as recited in claim 1 , wherein said plurality of tread ribs each have a lateral width; and, wherein each said groove wall lining has a lateral width of between approximately 15 and 30 percent of the lateral width of said tread rib. 6. The tire as recited in claim 5 , wherein said lateral width of each said groove wall lining is approximately 20 percent of the lateral width of said tread rib. 7. The tire as recited in claim 1, wherein said second modulus of elasticity is greater than approximately 40 percent of said first modulus of elasticity. 8. The tire as recited in claim 7, wherein said modulus of elasticity of said second tread compound is approximately 65 percent of said modulus of elasticity of said first tread compound. 9. The tire as recited in claim 1, wherein said plurality of tread ribs include sipes. 10. The tire as recited in claim 1, wherein said groove wall linings include sipes. 13 11. A tread layer of a tire, said tire having a pair of beads ; a carcass ply having ends anchored to a respective one of said beads; and at least one belt ply extending circumferentially around said tire and disposed radially outward of said carcass ply, said tread layer including a first tread compound with a first modulus of elasticity and comprising: a plurality of grooves formed in said tread layer each said groove having walls separated by a bottom; at least one tread rib disposed between adjacent of said grooves; a groove lining covering said groove walls and said bottom of each of said grooves, said groove lining being foimed from a second tread compound having a second modulus of elasticity greater than that of said first tread compound; and, said first and second modules of elasticity satisfying a ratio of the second to the first modulus of elasticity between about 0.4 to 0.8. 12. The tread layer of a tire as recited in claim 11 , wherein said at least one tread rib has a lateral width and said groove lining covering said walls has a lateral width, wherein a ratio of said lateral width of said groove wall linings to said lateral width of said tread rib including said linings has a value between about 0J5 to 0.3. 13. The tread layer of a tire as recited in claim 11 , wherein said groove lining covering said bottom of said groove has a first thickness and said thread portion beneath said groove bottom has a second thickness greater than said first thickness, said first and second thickness having a ratio of the first to the second thickness of between about 0.25 to 0.5. 14 14. A tread layer of a tire, said tire having a pair of beads; a carcass ply having ends anchored to a respective one of said beads; and at least one belt ply extending circumferentially around said tire and disposed radially outward of said carcass ply, said tread layer formed from a first tread compound having a first modulus of elasticity and comprising: a plurality of grooves formed in said tread layer each said groove having walls separated by a bottom; at least one tread rib disposed between adjacent of said grooves; a groove lining covering said walls and said bottom of each of said grooves; said groove lining covering said walls having a lateral thickness w and said groove wall lining covering said bottoms having a radial thickness t; wherein, said thickness w is always greater than said thickness t. 15. The tread layer of a tire as recited in claim 11 , wherein said thickness t is between approximately 2 and 3.5 mm. 16. The tire tread layer of a tire as recited in claim 11 wherein said thickness w is between approximately 6 and 9 mm. 15

Inventors: JANAJREH IBRAHIM MUSTAFA, JANAJREH, IBRAHIM, MUSTAFA
Applicants: JANAJREH IBRAHIM MUSTAFA, MICHELIN RECH TECH, JANAJREH, IBRAHIM, MUSTAFA, MICHELIN RECHERCHE ET TECHNIQUE S.A.
Application year: 1999
Main classification: B60C11
IPC codes: B60C11