WO2000076792A1

WO2000076792A1 - Method of mounting tires for vehicle steering prestressing

Info

Publication number: WO2000076792A1
Application number: PCT/US1999/013388
Authority: WO
Inventors: Martin Herewad Cardew
Original assignee: The Goodyear Tire & Rubber Company
Priority date: 1999-06-14
Filing date: 1999-06-14
Publication date: 2000-12-21
Also published as: AU4682299A

Abstract

Pneumatic radial tires (1) are mounted on a vehicle (30) for the reduction of the plysteer effect on the vehicle. The tires (1) mounted on a first side (32) of the vehicle (30) are comprised of two belt reinforcing plies (26o, 26I) wherein the lay-up pattern of the inclined cords (27) of the adjacent belt plies (26o, 26I) are opposite of the lay-up pattern of the inclined cords (27) of the two belt reinforcing plies (26o, 26I) of the tires (1) mounted on a second side (34) of the vehicle (30).

Description

METHOD OF MOUNTING TIRES FOR VEHICLE STEERING PRESTRESSING Technical Field The disclosed invention is directed toward selective mounting of pneumatic radial tires.

Specifically, the pneumatic radial tires are selectively mounted on a vehicle in a manner that reduces the overall plysteer effect of the tires on the vehicle. Background Art

When a pneumatic radial tire with a belt reinforcing structure runs on a road surface a lateral force is generated. This lateral force (LF) is the summation of the plysteer and conicity of the tire, as represented by the following equation:

LF = plysteer + conicity. Values of both the plysteer and the conicity can be positive or negative and are independent of each other. Plysteer changes direction the change of direction of the rotation of the tire. Conicity always acts in the same direction. Lateral force plays an important role in how a car's steering reacts. The force generated pulls a straight running tire in the direction of that force. Lateral force generated by the front tires is countered by a reaction in the steering.

Factors affecting the direction of the plysteer include belt angle lay-up, such as right/left or left/right angle inclinations for the reinforcing cords in the belt plies, and tread pattern design. Asymmetrical tread designs will generate plysteer, whereas symmetrical tread designs will generate negligible plysteer.

Conicity is affected by design parameters such as asymmetric tread patterns or asymmetry in the tire construction.

US. Patent 3,435,874 teaches constructing a tire such that the natural force of the tire and the force of conicity of the tire are in opposition, thereby forming a tire with negligible plysteer. This is done by means of a predetermined eccentricity of the tread and belt structure of the tire. It is taught to alter the configuration of the tread profile curvature or the curvature of the belt structure to achieve the desired negligible plysteer.

U.S. Patents 3,578,054 and 3,630,077 disclose determining the lateral force of each tire and selecting tires with a force value within a defined value. The tires mounted on the front axle of the vehicle have an outward lateral force while the tires mounted on the rear axle have an inward lateral force.

U.S. Patent 4,469,157 discloses a pneumatic radial tire wherein the carcass layers and the belt layers are inclined at defined angles to reduce the plysteer of each tire. U.S. Patent 4,865,101 discloses the combination of a symmetrical V-shaped tread in combination with belt reinforcement plies comprised of cords inclined in a V-shaped configuration.

U.S. Patents 5,229,954 and 5,321,628 disclose reduction of plysteer effect on the vehicle by first determining the steering pull of each tire, and then selecting a set of tires having substantially consecutive pull values. The disclosed method of plysteer reduction is independent of any selective or required tire construction.

In the disclosed invention the lateral force has the effect of prestressing the steering bushings. On one side of the car this will be in one direction, but on the other side of the car will be in the opposite direction.

The present invention proposes to use tires with right/left belt lay-ups on one side of the car and tires with left/right belt lay-ups on the other side of the car. This will have the effect of provoking symmetrical prestressing of the steering bushings, but will leave no net lateral force on the steering, which would be undesirable. This is overcome by designing in controlled levels of conicity so that whereas the prestress on the steering bushings may not be exactly at the same levels, they are however in the same direction. Summary of the Invention

The goal of the disclosed invention is the prestressing of the vehicle steering geometry by mounting a set of tires on the vehicle with opposite plysteer force directions on opposing sides of the vehicle. One advantage of the disclosed invention is a more consistent response of the vehicle steering system.

The disclosed invention is a method of mounting pneumatic radial tires to a first and a second side of a vehicle with respect to the forward direction of travel of the vehicle. Each pneumatic radial tire incorporates a belt package. Each belt package has at least two circumferentially extending reinforcing plies, wherein each ply is comprised of cords inclined at angles between 15° and 35° relative to the equatorial plane of the tire. The cords in adjacent plies are inclined in opposing right and left directions. When the tires are mounted on the vehicle, the inclined cords in the radially outermost reinforcing ply of the at least two belt outermost plies of each tire on the first vehicle side are inclined in the same direction, while the inclined cords in the radially outermost reinforcing ply of the two belt plies of each tire on the second vehicle side are inclined in the opposite direction of the radially outermost belt ply cords of the tires mounted on the first side of the vehicle.

Another aspect of the disclosed invention is the method of mounting pneumatic radial tires where the tires mounted on the first side of the vehicle are characterized by a left/right cord lay-up of the two belt plies in the belt package. The tires mounted on the second side of the vehicle are characterized by a right/left cord lay-up of the two belt plies in the belt package.

Another aspect of the disclosed invention is the method of mounting pneumatic radial tires where the tires mounted on the first side of the vehicle are characterized by a right/left cord lay-up of the two belt plies in the belt package. The tires mounted on the second side of the vehicle are characterized by a left/right cord lay-up of the two belt plies in the belt package. Definitions "Absolute lateral force" means the lateral force generated by the combination of plysteer force and conicity force.

"Apex" means an elastomeric filler located radially above the bead core and between the plies and the turnup ply.

"Aspect ratio" of the tire means the ratio of its section height to its section width. "Aspect ratio of the tire means the ratio of its section height to its section width, multiplied by 100% for expression as a percentage.

"Asymmetric tread" means a tread that has a tread pattern not symmetrical about the centerplane or equatorial plane (EP) of the tire.

"Axial" and "axially" are used herein to refer to lines or directions that are parallel to the axis of rotation of the tire.

"Balance" uniformity of mass distribution of a tire relative to its spin and steer axis.

"Bead" means that part of the tire comprising an annular tensile member wrapped by ply cords and shaped, with or without other reinforcement elements such as flippers, chippers, apexes, toe guards and chafers, to fit the design rim. The radially inner beads are associated with holding the tire to the wheel rim.

"Belt structure" means at least two annular layers or plies of parallel cords, woven or unwoven, underlying the tread, unanchored to the bead, and having both left and right cords angles in the range from 15° to 35° with respect to the equatorial plane of the tire.

"Breakaway" refers to the point at which the lateral force exerted on a tire exceeds the cornering force capability of the tire.

"Breakers", refers to at least two annular layers or plies of parallel reinforcement cords having the same angle with reference to the equatorial plane of the tire as the parallel reinforcing cords in carcass plies.

"Carcass" means the tire structure apart from the belt structure, tread, undertread, and sidewall rubber over the plies, but including the beads.

"Casing" means the carcass, belt structure, beads, sidewalls, and all other components of the tire excepting the tread and undertread. The casing may be new, unvulcanized rubber or previously vulcanized rubber to be fitted with a new tread. "Chafers"; narrow strips of material placed around the outside of bead to protect cord plies from the rim, distribute flexing about the rim and to seal the tire.

"Circumferential" means lines or directions extending along the perimeter of the surface of the annular tire parallel to the Equatorial Plane (EP) and perpendicular to the axial direction. "Compensated tread width" means the tread width multiplied by the aspect ratio.

"Conicity" means the lateral asymmetry of the tire.

"Conicity force" means the lateral force exerted by the tire due its conicity. Directionally remains unchanged with change in direction of rotation.

"Cord" means one of the reinforcement strands of which the plies of the tire are comprised. "Cord" also denotes a plurality of bundles or strands of grouped filaments of a high modulus material.

"Cord angle" means the acute angle, left or right in a plan view of the tire, formed by a cord with respect to the equatorial plane. The "cord angle" is measured in a cured but uninflated tire. "Directional tread" refers to a tread design which has a preferred direction of rotation in the forward direction of travel.

"Equatorial plane (EP)" means the plane perpendicular to the tire's axis of rotation and passing through the center of its tread.

"Force Variation"; the differential response of a rolling tie to radial (parallel to wheel plane-equatorial plane) and lateral (perpendicular to wheel plane-axial) stresses.

"Groove" means an elongated void area in a tread that may extend circumferentially or laterally about the tread in a straight curved, or zigzag manner. Circumferentially and laterally extending grooves sometimes have common portions and may be sub classified as "wide", "narrow", or "slot". The slot typically is formed by steel blades inserted into a cast or machined mold or tread ring therefor. In the appended drawings, slots are illustrated by single lines because they are so narrow. A "slot" is a groove having a width in the range from about 0.2% to 0.8% of the compensated tread width, whereas a "narrow groove" has a width in the range from about 0.8% to 3 % of the compensated tread width and a "wide groove" has a width greater than 3 % thereof. The "groove width" is equal to tread surface area occupied by a groove or groove portion, the width of which is in question, divided by the length of such groove or groove portion; thus, the groove width is its average width over its length. Grooves, as well as other voids, reduce the stiffness of tread regions in which they are located. Slots often are used for this purpose, as are laterally extending narrow or wide grooves. Grooves may be of varying depths in a tire. The depth of a groove may vary around the circumference of the tread, or the depth of one groove may be constant but vary from the depth of another groove in the tire. If such narrow or wide groove are of substantially reduced depth as compared to wide circumferential grooves which they interconnect, they are regarded as forming "tie bars" tending to maintain a rib-like character in the tread region involved.

"High Performance" means tires having a speed capability of 210km/hr and above.

"Inner" means toward the inside of the tire and "outer" means toward its exterior.

"Lateral" means an axial direction.

"Lateral Force Variation" the periodic variation of lateral force of a straight f reerolling tire which repeats each revolution, at a fixed loaded radius, given mean normal force, constant speed, given inflation pressure and test surface curvature.

"Lateral Pull"; the amount of steering pull from direction of travel.

"Outer" means toward the tire's exterior.

"Oversteer"; rear tires having a greater slip angle than the front, thus causing the vehicle to turn more sharply.

"Ply"; unless otherwise specified, means a continuous layer of rubber-coated parallel cords.

"Ply steer": component of "Absolute Lateral Fore" (q.v.) due primarily to the radial asymmetry of a tire's construction and secondarily the distribution of blocks etc in a tire's tread pattern ; changes direction with change of direction of a tire's rotation

"Pneumatic tire": means a laminated mechanical device of generally toroidal shape (usually an open-torus) having beads and a tread and made of rubber, chemicals, fabric and steel or other materials. When mounted on the wheel of a motor vehicle, the tire through its tread provides traction and contains the fluid that sustains the vehicle load. "Radial" and "radially" are used to mean directions radially toward or away from the axis of rotation of the tire.

"Radial-ply tire" means a belted or circumferentially-restricted pneumatic tire in which the ply cords which extend from bead to bead are laid at cord angles between 65° and 90° with respect to the equatorial plane of the tire. "Radial Force Variation" the periodic variation of the normal force of a loaded straight free-rolling tire which repeats each revolution at a fixed loaded radius, given mean normal force, constant speed, given inflation pressure and test surface curvature.

"Response" time lag from instant driver turns the wheel to the instant tire imparts the signal to the road.

"Section height" means the radial distance from the nominal rim diameter to the maximum outer diameter of the tire at the road-contact surface nearest its equatorial plane.

"Shoulder" means the upper portion of sidewall just below the tread edge, effects cornering. Tread shoulder or shoulder rib means that portion of the tread near the shoulder "Sidewall" means that portion of a tire between the tread and the bead.

"Slip"; differential in magnitude or direction between circumferential velocity of tire at the contact surface and velocity of travel.

"Slip Angle"; the direction between the plane of rotation and the direction of travel of tire. "Tread" means a molded rubber component which, when bonded to a tire casing, includes that portion of the tire that comes into contact with the road when the tire is normally inflated and under normal load.

"Turn-up ply" refers to an end of a carcass ply that wraps around one bead only. Brief Description of Drawings The invention will be described by way of example and with reference to the accompanying drawings in which:

FIG. 1 illustrates a pneumatic radial tire in accordance with the disclosed invention; FIG. 2 A is illustrative of a pneumatic radial tire for a first side of a vehicle; FIG. 2B is illustrative of a pneumatic radial tire for a second side of a vehicle; and FIG. 3 is illustrative of a vehicle with tires mounted in accordance with one embodiment of the disclosed invention. Detailed Description of the Invention

FIG. 1 illustrates a pneumatic radial tire in accordance with the disclosed invention. The tire 1 may be either a low or high aspect ratio tire. Low aspect ratio tires, those with an aspect ratio of 70 or less, are conventionally high performance type tires.

The tire 1 has a tread portion 10, two axially bead portions 12 and sidewalls 14. The sidewalls 14 are joined to the bead portions 12 and extend in the radially toward the tread portion 10. The tread portion 10 extends in the circumferential direction of the tire 1.

The tire 1 is provided with a carcass layer 16 comprising at least one ply of reinforcing cords. FIG. 1 illustrates a carcass layer 16 of two plies 16₀, 16j. The carcass layer 16 has a main portion 18 extending from one bead portion 12 to the opposing bead portion 12, the main portion 18 passing below the tread 10. The end portions 20 of the carcass layer 16 are turned about the bead core located in each bead portion 12. The end portions 20 extend a radial distance into the sidewalls 14. Each carcass ply 16₀, 16_! is comprised of elastomeric embedded radial reinforcing cords 17.

Located within each bead portion 12 of the tire 1 is an annular tensile member, otherwise conventionally referred to as a bead core 22. Radially outward of each bead core 22 is a bead filler 24, also known as an apex. Bead cores 22 may be formed in any known conventional configuration, such as circular, hexagonal, or polygonal. The bead filler 24 has a substantially triangular configuration wherein the axial width of the bead filler tapers from the bead core 22 toward the terminal end of the end portion 20 of the carcass layer 16. The filler is typically sandwiched in-between the main carcass portion 18 and the end portion 20 of the carcass layer 16. The bead portion 12 may also be provided with reinforcing members such as toe guards/chafers or chippers. The inclusion such conventional tire elements is within the scope of the disclosed invention, while the election of the use of these elements is within the tire designers purview.

The tread 10 extends circumferentially about the tire 1. The tread may be provided with circumferentially or laterally extending grooves 36, sipes, and slots. The tread features are dependent upon the tire designers desired tire tread characteristics.

Between the carcass layer 16 and the tread 10 is a belt reinforcing package 26. The belt reinforcing package 26 of the disclosed invention is comprised of a plurality of reinforcing plies, with a minimum of at least two plies 26₀, 26,. The reinforcing plies 26 are comprised of elastomeric embedded reinforcing cords 27 arranged inclined with respect to the circumferential direction of the tire 1.

The two reinforcing plies 26₀, 26ι of the tire to be mounted on a first side of the vehicle are illustrated in FIG. 2 A. The cords 27 are inclined at angles in the range from 15° to 35° with respect to the equatorial plane of the tire. In the radially outermost ply 26₀, the cords 27₀ are inclined at a left angle with respect to the equatorial plane of the tire. The cords 27, of the radially inner, adjacent ply 26_j are inclined at a right angle with respect to the equatorial plane. The illustrated cord ply lay-up is referred to as a outer ply left/right lay-up, describing first the cord direction of the radially outer ply, then the cord direction of the adjacent ply.

The two reinforcing plies 26₀, 26_j of the tire to be mounted on the opposing, second side of the vehicle are illustrated in FIG 2B. The belt cords are inclined at angle in the range from 15° to 35° with respect to the equatorial plane of the tire, substantially similar to the belt cords of the tires to be mounted on the first side of the vehicle. Dissimilar to the tires to be mounted on the first side of the vehicle, the cord ply lay-up for the tires on the second side of the vehicle is a right/left lay-up. In the radially outermost ply 26_θ5 the cords 27₀ are inclined at a right angle with respect to the equatorial plane of the tire. The cords 27, of the radially inner, adjacent ply 26, are inclined at a left angle with respect to the equatorial plane.

To assure proper mounting of the tires 1, the tire sidewalls 14 may be marked with indicia 28 that indicate the belt lay-up. Such indicia 28 may be presented as "R/L" or "L/R". When mounting the tires 1, all tires 1 on one side of a vehicle will have the same indicia 28, such as "R/L", and the opposing vehicle side will have tires 1 with the indicia 28 "L/R".

FIG. 3 illustrates mounting of the tires 1 on a vehicle 30 in accordance with the present invention. The forward direction of travel of the vehicle 30 is represented by the arrow F.

Both tires 1 mounted on a first side 32 of the vehicle 30 have a left/right belt lay-up. Both tires 1 mounted on the second side 32 of the vehicle 30 have a right/left belt lay-up. This will have the effect of provoking symmetrical prestressing of the steering bushings, but will leave no net lateral force on the steering, which would be undesirable.

When mounted on the vehicle 30, the determination of the belt cord lay-up direction is made from viewing the tires 1 from the rear of the vehicle 30. However, such a manner of determination is not crucial, as long as the belt cord lay-up directions for all the tires 1 on one side of the vehicle 30 are identical.

In another embodiment of the disclosed invention, all the tires 1 on the first side 32 of the vehicle 30 have a right/left belt cord lay-up. All the tires 1 mounted on the second side 34 of the vehicle 30 have a left/right belt cord lay-up. While the suggested vehicle 30, as illustrated in FIG 3 is a two axle, four tire vehicle

30, the disclosed invention is not limited to such a vehicle. The disclosed method of match mounting tires 1 will provide the disclosed benefit on any type of axle vehicle.

Variations in the present invention are possible in light of the description of it provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the full intended scope of the invention as defined by the following appended claims.

Claims

CLAIMSWhat is claimed is:

1. A method of mounting pneumatic radial tires (1) to a first (32) and a second (34) side of a vehicle (30) with respect to the forward direction of travel F of the vehicle, each pneumatic radial tire (1) comprising a belt package (26), each belt package (26) having at least two circumferentially extending reinforcing plies (26₀, 26,), each ply (26₀, 26,) being comprised of cords (27) inclined at angles between 15° and 35° relative to the equatorial plane EP of the tire (1), the cords (27) in adjacent plies being inclined in opposing right and left directions, said method characterized by mounting tires (1) on the first side (32) of the vehicle (30) wherein the inclined cords (27₀)in the radially outermost reinforcing ply (26₀)of the two belt plies (26₀, 26,)of each tire (1) on the first vehicle side (32) are inclined in the same direction, and mounting tires (1) on the second side (34) of the vehicle (30) wherein the inclined cords (27₀)in the radially outermost reinforcing ply (26₀)of the two belt plies (26₀, 26,)of each tire (1) on the second vehicle side (34) are inclined in the opposite direction of the cords (27₀)in the radially outermost ply (26₀)of the two belt plies of the tires (1) mounted on the first side (32) of the vehicle (30).

2. The method of mounting pneumatic radial tires (1) in accordance with claim 1 wherein the tires mounted on the first side (32) of the vehicle (30) are characterized by a left/right cord (27) lay-up of the two belt phes (26₀, 26,), and the tires mounted on the second side (34) of the vehicle (30) are characterized by a right/left cord (27) lay-up of the two belt plies (26₀, 26,).

3. The method of mounting pneumatic radial tires (1) in accordance with claim 1 wherein the tires mounted on the first side (32) of the vehicle (30) are characterized by a right/left cord (27) lay-up of the two belt phes (26₀, 26,), and the tires mounted on the second side (34) of the vehicle (30) are characterized by a left/right cord (27) lay-up of the two belt plies (26₀, 26τ).

4. The method of mounting pneumatic radial tires (1) in accordance with claim 1 wherein each tire (1) is comprised of means to indicate the belt cord lay-up. The method of mounting pneumatic radial tires (1) in accordance with claim 4 wherein the indicating means are sidewall indicia (28).