AU736829B2

AU736829B2 - Pneumatic tire including belt and circumferential ribs

Info

Publication number: AU736829B2
Application number: AU79717/98A
Authority: AU
Inventors: Robert Ciprian Radulescu
Original assignee: Michelin Recherche et Technique SA Switzerland; Michelin Recherche et Technique SA France
Current assignee: Michelin Recherche et Technique SA France
Priority date: 1997-06-20
Filing date: 1998-06-16
Publication date: 2001-08-02
Anticipated expiration: 2018-06-16
Also published as: JP2002511039A; EP1024967A4; WO1998058810A1; AU7971798A; KR20010014009A; EP1024967A1; BR9810206A; CA2294418A1

Description

PNEUMATIC TIRE INCLUDING BELT AND CIRCUMFERENTIAL RIBS BACKGROUND OF THE INVENTION This invention relates to vehicle tires, and more particularly to heavy duty truck tires specially designed to be used for long haul trucking operations.

An object of the invention is to provide to the driver a more comfortable drive. Another object of the invention is to improve the handling of the tire. More specifically, an object of the invention is to address the problem of deterioration of the comfort and of handling that in certain circumstances has proved to be caused by the tire after the tire has been in use for a number of miles. It may happen that the rolling comfort or the handling becomes unacceptable to the driver at a relatively low mileage such that the tire must be removed well before the end of its normal service life. The problem of bad evolution of comfort is occurring especially in front steer axle tires, in long haul services tires which for most of the time do not pass on the road a torque as significant as the driven 15 wheels -no driving torque, the braking operations do not count for a significant part of the service life-).

SUMMARY OF THE INVENTION According to the present invention, there is provided a pneumatic, radial belted heavy duty long haul truck tire having a tread portion with a selected tread 20 pattern and a delayed onset of unacceptable comfort and handling, said tire characterised by: said tread pattern having a circumferentially extending lateral rib at each outer side of said tread portion, a plurality of circumferentially extending intermediate ribs located between said lateral ribs, said lateral and intermediate ribs defining a circumferentially extending outer surface and a plurality of grooves separating adjacent ones of said ribs; outer limits of at least outer lateral flanges of said lateral ribs forming a juncture with said circumferentially extending outer surface; a carcass and a belt with at least a pair of working plies reinforcing said tread portion, said working piles extending transversely beneath said lateral ribs v\Af A opposed end portions thereof being located outwardly of said tread portion; 2 on each side of a mid-circumferential plane, a protective cover formed axially outward of a respective lateral rib and said end portions and radially outward of each of said end portions of said working plies; a tread reference line extending parallel of the tire axis and in lateral contact with said outer surface, a first limit line extending perpendicular to said tread reference line and through said juncture, a second limit line extending perpendicular to said tread reference line and along said mid circumferential plane; said tread having a thickness measured between a radially innermost part of said carcass and said outer surface along said first and second limit lines, said thickness being constant within 10% between said limit lines; and, said outer surface having a transverse radius of curvature greater than 1500 mm when the tire is mounted on a pre-defined rim and uninflated.

The said working plies preferably include parallel cords and are arranged 15 at an angle to the circumferential direction.

The said transverse radius of curvature may be greater than 5,000 mm.

In a further aspect, there is provided a pneumatic radial belted heavy duty truck tire having a tread portion with a selected tread design pattern and a S:o o delayed onset of unacceptable comfort and handling, said tire characterised by: 20 said tread pattern having a circumferentially extending lateral rib at each outer side of said tread portion, a plurality of circumferentially extending intermediate ribs located between said lateral ribs, said lateral and intermediate ribs defining a circumferentially extending outer surface and a plurality of grooves separating adjacent ones of said ribs; outer limits of at least outer lateral flanges of said lateral ribs forming a juncture with said circumferentially extending outer surface; a carcass and a belt with at least a pair of working plies reinforcing said tread portion, said working plies extending transversely beneath said lateral ribs with opposed end portions thereof being located outwardly of said tread portion; a tread reference line extending parallel to the tire axis a first limit line extending perpendicular to said tread reference line and through said juncture, a

COA/V

PAT C second limit line extending perpendicular to said tread reference line and along a mid circumferential plane; said tread having a thickness of no less than 20 mm measured between a radially innermost part of said carcass and said outer surface along said first and second limit lines, said thickness being constant within between 8% and between said limit lines; and, said outer surface having a transverse radius of curvature of approximately 5,000 mm; wherein, said outer surface is contacted by said tread reference line.

DESCRIPTION OF THE DRAWINGS The invention will be more readily understood from a reading of the following specification and by reference to the accompanying drawings showing two examples of the invention: Figure 1 is a fragmentary plan view of a first variation of a tire featuring this invention; and SFigure 2 is a fragmentary plan view of a second variation of a tire featuring this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE

INVENTION

20 One variation of the preferred embodiment of the tire T of the present invention is shown in Fig. 1 and another variation thereof is shown in Fig. 2.

Turning to common features of the two variations, the tire T has a tread portion having a tread design pattern. The invention is related to a typical tread design pattern having proved being suited for front axle tires used in long haul. That tread design pattern comprises essentially parallel ribs separated by parallel grooves. Those parallel ribs here include, located on each respective side of the tread, a lateral rib 1 that is circumferentially continuous, i.e. not divided into a plurality of blocks. This basic tread pattern unit is repeated laterally, with or without changes of actual shape, so that the tread includes a plurality of other intermediate ribs 2, located between the two lateral ribs 1 and also being C

OAN

oil circumferentially continuous. Each lateral rib 1 and other ribs 2 has a radially external surface Each of the lateral rib 1 and the other ribs 2 are limited laterally by flanges 11, 12 defining at least in part and two by two circumferential continuous grooves 13. In the embodiments illustrating the invention, at least the axially outer lateral flange 11 of the lateral rib 1 is radially outwardly terminated by a junction interconnecting the radially external surface 10 and the axially outer lateral flange 11. In the described embodiment, the junction is an edge 14. In the two variations of the embodiment, all of the lateral ribs 1 and other ribs 2 are bordered laterally by edges forming a sharp angle. The axially outer lateral flange 11 of lateral rib 1 and the radially external surface 10 of the lateral rib 1, as viewed in a radial section like the one of figures 1 and 2, define an angle C ranging between S 900 and 1100. In other words, the axially outer lateral flange 11 of lateral rib 1 and the radially external surface 10 of the lateral rib 1, as viewed in a radial section S 15 like the one of figures 1 and 2, define a sharp angle.

The tire T is reinforced by a carcass comprising at least one carcass ply and by a belt. The belt, as shown in the figures includes two working plies 61, 62 and a protective ply 63. The means to realize the so-called working plies and o**0 protective ply are well known in the art. Thus, further details are not given in the 20 present disclosure. It is enough to recall that the working plies generally are made essentially of inextensible parallel cords arranged at an angle in the range of 150-300, and that a protective ply is generally a ply which can be more extendible. Also it is enough to recall that the belt could also include other reinforcing means like cords arranged at a zero angle with respect to the mid circumferential plane of the tire T, also called "jointless reinforcing ply or plies," having cord or cords substantially parallel to the mid circumferential plane of the tire T (a plane perpendicular to the axis of the tire that latter reinforcement being useful namely to keep unchanged after breaking in the shape and properties of the tire T.

All the lateral and other ribs 1, 2 have a radially external surface 10 for 3b contacting the road. Assuming that the surface of the road is flat (bearing in mind that the tire T of the invention is designed for long haul applications, this assumption is close to reality) the radially external surface 10 will be urged to become flat during rolling. According to an aspect of the invention, the belt and *0 WO 98/58810 PCT/US98/12547 more generally the tread portion as a whole is so designed as to achieve a normal stress perpendicular to radially external surface 10 in the tread as even or uniform as possible in a loaded static condition of the tire T. One could suppose that uniform normal stresses will also be experienced during dynamic rolling of the tire T and that such conditions will enhance the comfort and handling of the tire T. According to a feature of the invention, the belt, more precisely at least the working plies 61, 62 of the belt, extend beneath all the lateral ribs I and other ribs 2 for providing an equal support thereof. In other words, with reference to the drawings, the ends 610, 620 of the working plies 61, 62 is extended beyond a limit line 7 (shown in dotted line). The limit line 7 is defined by a perpendicular to a tread reference line 8. The tread reference line 8, as viewed in a radial section of the tire T like the one shown in figures 1 and 2, is the imaginary line parallel to the axis of the tire T and in contact with the radially outermost point of the radially external surface 10. A second condition that the limit line 7 has to fulfill is to pass through the edge 14 of the lateral rib 1.

It is to be noticed that the tire T tread portion is molded so that the radially external surface 10 of the lateral and other ribs defines a transverse profile which is close to a cylinder when the tire T in mounted on a predefined rim and non inflated. The transverse radius of curvature R is the range of 1,500 mm to an infinite value. Advantageously, the transverse radius of curvature is greater than 5,000 mm. For instance, the two variations show a transverse radius of curvature R reaching 20,000 mm.

With reference to the drawings, one see that the thickness T i of the tread is pointed out at different location: thickness T, at the axially outer border of lateral rib 1, thickness T 2 for respective adjacent other rib 2, and thickness T C in the middle of the tire T (thickness measured at the mid circumferential plane, i.e. the plane perpendicular to the tire's axis of rotation and passing through the center of its tread). The thickness T i is measured between the radially innermost part of the carcass ply 5 and the radially external surface 10. The thickness T i is measured perpendicularly to the tread reference line 8. The portion of the tread measured by the thickness T i includes reinforcing members of the belt, the rubber compounds and the carcass ply. If the carcass includes more than a single carcass ply, the thickness is measured from the radially innermost part of the radially innermost ply. It is thereby established a reference referred to in general by "the radially innermost part of the carcass".

-4- WO 98/58810 PCT/US98/12547 According to another feature of the invention, the thickness Ti, in any point between the middle of the tire tread and the axially outermost part of the lateral rib 1, does not depart from the thickness TC at the middle point by more than 10%, and preferably not more than In any case, the thickness is greater than 20 mm, as it is a tire T for heavy truck. The following table is an example of thickness T i taken on a tire T according to the invention.

Thickness in mm TC 27 T2 27 T, 28.6 (28.6- 27) -59 tu esta In this tire T, the difference of thickness is (28.6-27) thus less than 8%.

27 The onset of unacceptable comfort or unacceptable handling, or the rate of deterioration thereof if any, is thus kept within limits that are by far more compatible with the normal service life of the tire T, thereby avoiding the removal of the tire T well before that the height of the ribs has decreased up to the preset wearing limit.

On each side of the tread, a protective cover is located axially outwardly of the lateral ribs.

The two examples illustrating the invention differ by the embodiment of the cover. The cover on figure 1 is a narrow shoulder rib 3. Standard tread rubber materials can be used for the shoulder rib 3 as for lateral ribs 1 and other ribs 2. The shoulder rib 3 is laterally recessed from the lateral rib 1 by a narrow groove 31. In other words, the surface 30 of the shoulder rib 3 is recessed with respect to the radially external surface 10 of the lateral rib 1. According to the need to protect the extended belt of the invention, a preferred width of the shoulder rib 3 is in a range of about 10 millimeters to about 20 millimeters. The dimensions and geometry of the shoulder rib 3 are selected such that, during normal running of the tire T, experiences different stresses than lateral ribs 1 and other ribs 2. This feature helps to maintain a sharp edge 14 on the lateral ribs 1. In the particular geometry of the shoulder rib 3, the radial height of the shoulder rib 3 is below the radially external surface 10 by a distance in the range of 1 mm to 2 mm.

Figure 2 shows another cover which is not a wearing part of the tread and has no contribution whatsoever to sustain the load. Its function merely is to protect the ends 610, 620 of the working plies 61, 62 and the end 630 of the protective ply 63. The protective cover is a rubber WO 98/58810 PCT/US98/12547 product 4 having an axially inner end joined with the bottom of the axially outer lateral flange 11.

In other words, the radially outer surface 40 of the rubber product 4 is approximately even with the bottom of the grooves 13. This variation may be used to improve cooling of the shoulder part if the help of the shoulder rib appears not being needed.

To be more general, the protective cover could have any radial height between the limits set forth by the above variations illustrating the invention. The protective cover could be made even with the radially external surface 10, and in that case one would use another rubber material than the one of main part of the tread: the rubber material of the protective cover would ideally be less hysteretic than the rubber material of the lateral ribs 1 and the other ribs 2.

In the two variations of the preferred embodiment, the carcass is a radial carcass. The tire T is designed to be mounted on a rim the shape and dimensions of which is defined by well established standards (See e.g. "The Tire and Rim Association, Inc." or "The European Tire Rim Technical Organization"). According to the well known way of designing tires, a tire T of a preselected size is designed to work on one or a couple of desired rim sizes selected among the above mentioned standards. The tire T also is designed to work at a so-called "nominal inflation pressure". In the described embodiment, the carcass is designed to assume, if the tire T is mounted on the specific rim and inflated at the nominal inflation pressure, a natural shape of equilibrium in the sidewalls. In the tread area, the carcass is adhered on the belt and works as a unit with the working plies; the carcass tends to assume a cylindrical shape. In the shoulder portion, beyond the protective cover, the carcass is connected to that part having a cylindrical shape (into the tread portion) and to that part having a natural shape of equilibrium (in the sidewalls) in a manner as progressive and smooth as possible.

Claims

1. A pneumatic, radial belted heavy duty long haul truck tire having a tread portion with a selected tread pattern and a delayed onset of unacceptable comfort and handling, said tire characterised by: said tread pattern having a circumferentially extending lateral rib at each outer side of said tread portion, a plurality of circumferentially extending intermediate ribs located between said lateral ribs, said lateral and intermediate ribs defining a circumferentially extending outer surface and a plurality of grooves separating adjacent ones of said ribs; outer limits of at least outer lateral flanges of said lateral ribs forming a juncture with said circumferentially extending outer surface; S: a carcass and a belt with at least a pair of working plies reinforcing said tread portion, said working piles extending transversely beneath said lateral ribs with opposed end portions thereof being located outwardly of said tread portion; on each side of a mid-circumferential plane, a protective cover formed axially outward of a respective lateral rib and said end portions and radially outward of each of said end portions of said working plies; a tread reference line extending parallel of the tire axis and in lateral contact with said outer surface, a first limit line extending perpendicular to said tread reference line and through said juncture, a second limit line extending perpendicular to said tread reference line and along said mid circumferential plane; said tread having a thickness measured between a radially innermost part of said carcass and said outer surface along said first and second limit lines, said thickness being constant within 10% between said limit lines; and, said outer surface having a transverse radius of curvature greater than 1500 mm when the tire is mounted on a pre-defined rim and uninflated.

2. The tire according to claim 1 wherein each of said working plies includes cords and said cords are parallel and are arranged at an angle to the circumferential direction of between 100 and 300

3. The tire according to claim 1 wherein said radius of curvature is greater than 5000 mm.

4. The tire accordingly to claim 1 wherein said thickness is greater than mm.

The tire according to claim 1 wherein each said protective cover includes a shoulder rib having a radial height below said tread reference line by between about 1 mm to 2 mm.

6. The tire according to claim 1 wherein each said protective cover extends axially outward from said outer lateral surface of said lateral ribs beyond said end portions of said working plies.

7. The tire of claim 1 wherein said outer lateral flanges of said lateral ribs and said outer surface define an angle between 900 and 1100 at said juncture.

8. The tire of claim 1 wherein said juncture is angular.

9. The tire of claim 1 wherein rubber material forming each said protective cover is less hysteretic than rubber material forming the remainder of said tread portion.

The tire of claim 1 wherein each said protective cover includes a radially outer surface, said radially outer surface of said protective cover being aligned with the bottoms of said grooves. 9

11. A pneumatic radial belted heavy duty truck tire having a tread portion with a selected tread design pattern and a delayed onset of unacceptable comfort and handling, said tire characterised by: said tread pattern having a circumferentially extending lateral rib at each outer side of said tread portion, a plurality of circumferentially extending intermediate ribs located between said lateral ribs, said lateral and intermediate ribs defining a circumferentially extending outer surface and a plurality of grooves separating adjacent ones of said ribs; outer limits of at least outer lateral flanges of said lateral ribs forming a juncture with said circumferentially extending outer surface; a carcass and a belt with at least a pair of working plies reinforcing said tread portion, said working plies extending transversely beneath said lateral ribs with opposed end portions thereof being located outwardly of said tread portion; a tread reference line extending parallel to the tire axis a first limit line S extending perpendicular to said tread reference line and through said juncture, a second limit line extending perpendicular to said tread reference line and along a mid circumferential plane; said tread having a thickness of no less than 20 mm measured between a radially innermost part of said carcass and said outer surface along said first and second limit lines, said thickness being constant within between 8% and .':".between said limit lines; and, S:.said outer surface having a transverse radius of curvature of approximately 5,000 mm; wherein, said outer surface is contacted by said tread reference line.

12. The tire according to claim 11 including on each side of a mid circumferential plane a protective cover formed axially outward of a respective lateral rib and said end portions of said working plies, and formed radially outward of each of said end portions of said working plies.

13. The tire according to claim 12 wherein each said protective cover includes a shoulder rib having a radial height below said outer surface by between about 1 mm to 2 mm.

14. The tire according to claim 12 wherein each said protective cover extends axially outward from said outer lateral flanges of said lateral ribs beyond said end portions of said working plies.

The tire of claim 12 wherein rubber material forming each said protective cover is less hysteretic than rubber material forming the remainder of said tread portion.

16. The tire of claim 12 wherein each said protective cover includes a radially outer surface, said radially outer surface of said protective cover being generally aligned with the bottoms of said grooves.

17. The tire of claim 11 wherein said outer lateral flanges of said lateral ribs and said outer surface define an angle between 900 and 1100 at said juncture. 4 DATED this 15 th day of June 2001 .ATM A MICHELIN RECHERCHE ET TECHNIQUE S.A. WATERMARK PATENT TRADEMARK ATTORNEYS 290 BURWOOD ROAD HAWTHORN VICTORIA 3122 AUSTRALIA SKP/DHS/MEH P16815AU00.DOC