FR2564385A1 - LAMELLIZED PNEUMATIC FOR SILENT DRIVING - Google Patents

Abstract

THE INVENTION RELATES TO TIRES CREATING LOW ROLLING NOISE. ACCORDING TO THE INVENTION, THE TIRE IS OF THE LAMELLIZED TYPE, THAT IS TO SAY THAT IT INCLUDES SLOTS 9 CUT OVER THE ENTIRE WIDTH OF THE TREAD. ACCORDING TO THE INVENTION, IN EACH SG SEGMENT OF THE CIRCUMFERENCE OF THE TIRE, THE SLOTS HAVE SEVERAL PITCHES, PREFERABLY THREE, SO THAT THE ROLLING SOUND IS NOTABLY REDUCED. APPLICATION TO TRUCK VEHICLES.

Description

The present invention relates to a tire with a tread

  laminated low noise, that is to say, to reduce the noise created during the rolling of the tire, thanks to the arrangement of the slots with an irregular pitch on a laminated tread, several cutting lines being arranged on any the width of the tread at the place

  o It is in contact with the road.

  Given the very strict criteria applied

  recently for the reduction of noise created by

  biles, from the environmental point of view, it is neces-

  to reduce the level of noise created by all parts of an automobile, including tire rolling. On the other hand, there is an increasing number of vehicles with rubber tires given the considerable improvement in

  roads, such as the construction of very important motorways

  bearing. As a result, automobile transportation is

  expanding in more and more regions.

  A vehicle may encounter various types of weather conditions during travel, and tires must make possible the use of

  vehicle in all weather conditions.

  Heretofore, the ribbed tires have comprised at least two sinuous grooves circumferentially disposed at the surface of the tread. These tires are widely used for paved road courses, such as motorways, and in general, these tires give very good steering stability on dry roads and are desirable from the point of view of noise and fuel consumption. However, tires with such a ribbed pattern are considered worse from the point of view of traction and braking characteristics and when wet driving performance comes into play. This is one of the problems to be solved. Thus, tires with segmented designs, effectively allowing the expulsion

  of water between the surface of the tread

  and the road, and tires with a rolling belt

  laminated (ribbed designs with cracks)

  have recently had some success in reso-

  the problems posed by tires to

  veins. These latter types of tires are

  often called "all weather" tires.

  However, segmented tires and laminated tires can create a lot of noise, and segmented tires tend to wear out quickly, so these tires have

significant disadvantages.

  The invention relates to a tire which enables

  the effective elimination of the disadvantages of pneumatic

  known laminates, that is to say effectively reducing

  noise by using irregularly arranged slots, without reducing wet steering stability and wet grip, wet-road stability, wear resistance, the low consumption of

  fuel and resistance to irregular wear.

  In a preferred embodiment, after manufacture of a non-vulcanized tread belt (i.e., unvulcanized or partially

  vulcanized), it is vulcanized so that the pneumatic

  formed have a tread that does not

  does not have drawings or has a ribbed design

  or-which has a segmented design.

  Then, many very close slots are cut with a certain inclination with respect to the equatorial direction of the tire, these slots completely intersecting the width of the tread and being arranged in a combination comprising more than two step lengths, it is to say that the slots

  form an irregular pitch arrangement.

  Other features and advantages of the invention will be better understood when reading the

  description which will follow of embodiments

  and with reference to the annexed drawings on

  which: Figure 1 is a plan view of a laminated tread pattern of known type;

  Figures 2, 3 and 4 are sections

  the lines A-A, B-B and C-C respectively of Figure 1; Fig. 5 is a plan view of a laminated tread pattern for low noise according to the invention; Fig. 6 is a plan view of the known type laminated tread pattern; Fig. 7 is a plan view of a ribbed tread pattern prior to vulcanization and prior to slit formation; and

  Figures 8 and 9 are graphs

  the results of tests carried out for the comparison

  because of three sculpture drawings, as

  5 to 7, depending on the frequency

this from the noise level.

  As shown in Figure 1 which is a developed plan view of the right half of the drawing

  2 of the tread structure of a tire

  1, and in FIG. 2, which is a section along the line AA of FIG. 1, the tire 1 has a tread surface 3 which has a continuous main longitudinal groove 4 having sinuous ribs in the circumferential direction of the tire. pneumatic, in the central region. The two regions of the shoulders have a central portion 5 and a pair of shoulder portions 6 separating the tread 2 by a main groove 4, a carcass ply 7 being formed of a layer of fiber-based cord or cabled steel in radial or semi-radial direction, with an inclination of 60 to 90 relative to the equatorial axis C of the tire. The belt layer 8 is formed of steel cord placed in the tread 2. A plurality of slots 9, circumferentially spaced and having a certain inclination with respect to the axis C of the tire, are arranged so that 'they completely cut the width of the tread 2. The rolling grooves

  4 can be formed during vulcanization

  by the mold, or in such a way that the

  continuous rolling band is then carved for

  of a suitable tool, after vulcanization

  tion. An unvulcanized toroidal envelope (that is,

  uncured or partially vulcanized)

  carries two axially distant regions, forming

  heels intended to be in contact with the rim (not

  shown in the drawings), a carcass layer reinforced by a reinforcement ply extending from one heel region to another, a belt layer 8 parallel to the ground contact surface and a carcass layer and a tread region 2 which are all

  formed so that the assembly constitutes a toroidal carcass.

  This caracasse is then vulcanized in a mold in a conventional manner, slots 9 are formed in the vulcanized tread as indicated

  previously using a tool with a suitable edge

  ble, for example a knife, a sawtooth or a

  piercer having a thin blade. These slots having a thick

  less than 3 mm, are made transversely over the entire width of the protruding portion between the main grooves 4 of the tread 2 of the tire 1 with an inclination, relative to

  to the equatorial axis C of the tire, without significant width.

  In known manner, the slots are formed under pressure in a mold having thin internal metal plates, and the cuts can not be made with a

  narrow width but become relatively larvae.

  However, according to the invention, the width

  slots 9 formed on the surface of the web

  1 of the tire 1 is such that its dimension is negligible, so that the edges, on either side of each slot 9, are pushed so firmly against each other by the compression forces created in the contact with the ground, that the tread behaves as if it formed a continuous layer of rubber. As a result, rigidity is increased at the tread, and the

  wear resistance property of the roll strip

  is increased. In addition, the stress of flexing

  produced in and around the area of contact with the soil can be distributed and compensated for

  sufficiently effective so that longitudinal wear

  dinal and wear of the shoulders in the tread edge regions can be prevented

  enough in practice and so that the tracing forces

  on wet roads may be increased.

  The two edges of the slots 9 are sufficiently open during the rotation of the tire so that the layer of water carried by the road is dispersed and that the water can pass freely to the main grooves

  4, the hydroplaning phenomenon is thus avoided.

  The slots 9 are cut all over the

  tread portion 2 of the tread, in a straight line, and make an angle of 30 to 90 and preferably 50 to 80 with the equatorial axis C of the tire, so that the aforementioned effect is effectively promoted. When

  the inclination of the slits 9 is too small, the increase

  tion-properties of attachment on wet road and

  resistance to irregular wear becomes lower.

  In addition, as shown in FIGS. 3 and 4 which are sections along lines BB and CC respectively of FIG. 1, the depth d of slots varies in the direction of the width of the tread as shown in FIG. , the depth d of slots 9 progressively increasing from the edge of the tread towards the central portion C or conversely, as shown in FIG. 4, the depth d of slots 9 decreasing from the edge of the tread towards the center C , and bands regularly spaced in

  circumferential correction are arranged with modifications

  fications of the two types of slot 9, with increasing depth d towards the center of the tread

  and reducing the depth to this center. By the-

  the rubber parts of the slots are reinforced by

  slits as indicated, so that the deterioration

  rubber 2 of the tread can be effectively

  avoided. According to the invention, the slots which have a constant depth in the direction of the width and change in depth as indicated, can be used in combination, the depth d of slots 9 being included

  between 50 and 110% of the depth of the circumferential throat

main conference 4.

  The realization of the slots has been described previously

  as a result of various research on the

  steps of the slots on the tread. A perfecti

  tioning obtained according to the invention is the realization of a tire for heavy loads, having a tread pattern which does not have the disadvantages of known tires and increases the characteristics of traction and wet braking and the properties resistance to wear, while reducing rolling noise thanks to the slots which have an irregular pitch, without the other properties being reduced. The arrangement of steps according to the invention appears

  in the following description, which is purely illustrative

  of an embodiment, in cooperation with an accompanying drawing which is a partial plan view of the

  drawing of tire sculptures.

Example 1

  In a tire of size 10.00 R 20 14 PR, the circumference of the surface of the tread is divided into twelve equal parts of which one segment (SG) is composed of three pitch arrangements as shown in the following and on the figure 5:

SSSSMLMSMMSLMLLLLLSM

  The pattern of the tread, for a circumference, is constituted by repetition twelve times of

the aforementioned arrangement.

  The lengths, for each step, are given in the following: Not No, _mm Raportdespas

S (small) 11.0 -

  M (average) 13.7 M / S = 1.25 L (large) 16.4 L / M = 1.20 The ratio of the S, M, L steps, that is, M / S and L / M, is given in the following range: 1.05 <M / S or L / M <1.35 When the ratio is less than 1.05, the mechanical strength of the tread rubber, between these steps, becomes too weak, and as a result, the rubber of the tread tends to deteriorate early; on the other hand, when the ratio exceeds 1.35, the wet suspension tends to decrease because of the

step length.

  Therefore, it is preferable that the M / S or L / M ratio be between 1.15 and 1.25, and that the length L of the slots be between 5 and 50 mm and preferably between 10 and 30 mm. When the slots 9 are too numerous, the rigidity of the part forming the tread becomes so low that the driving stability and the resistance to wear can be

  too small. In addition, the slots 9 must be

  driven by special machines

  good productivity and good manufacturing precision

  and employing automatic slit-handling machines for adjusting the position and inclination of the slits. For example, this machine

  is comparable to a tire mounting device

  axle-forming and slot-forming throughout the width of the tread, the position being able to change in a direction transverse to the surface of the tread. As indicated above, the method of manufacturing the tire according to the invention comprises

  the formation of slits on the tread prior to

  vulcanized, and it becomes possible to

  to form these slits so that their width is practically

  zero; as a result, the two edges of each slot are strongly repelled so that they are in contact under the action of compression stresses, in the area of contact with the ground, and the tread moves as if it had only a continuous layer of rubber, giving an increase in driving stability and wear resistance. In addition, the wet grip properties are increased because the road-formed layer of water can be effectively dispersed using the slots that open when the tread rubber is flexed and simultaneously , efficiency

  and evacuation to the main grooves is increased.

  The mold intended to form the design of the structures

  The tread does not have thin metal blades that form the transverse groove. Other complex treatments are not required in the mold cavity, so the cost of the molds can be reduced. In addition, the slots can have a

  size and configuration of all types, depending on

  criteria imposed by users.

  The invention applies to any new tire

  with a ribbed, rib and tongue-and-groove structure for passenger vehicles and trucks or the like, but is advantageously used in steel-formed radial tires for heavy goods vehicles, having a structural design of

  tread comprising two to five main grooves

  sinuous circumferential blades on the surface of the

tread.

Example 2

  Pneumatic tires with radial steel carcass

  of size 10,00 R 20, having the characteristics

  listed in the following table, were made for testing and compared to tires known for

  the evaluation of the noise level, the resistance to

  re and hanging on wet road. The results of the experiments appear in the same tables, the

  values of known tires being arbitrarily

  to the value 100, and the values of the tires

  the invention being identified with respect to this value 100. As indicated by the results of the table, the

  pneumatic tires according to the invention have better properties.

  than the known tires, in the case of

  previously indicated.

  In FIGS. 8 and 9, the curves in solid line correspond to the tires according to the invention, the curves in dashed lines to the tires having no

  no cracks and curves in phantom lines to pneumatic

  slotted but of known type. The tests cor-

  corresponding to Figure 8 were carried out at a speed of 60 km / h, at a pressure of 7.25 bar, under a load of 2425 kg, the measuring position being 7.5 m from the axle, at a height of 1.2 m. In the case of Figure 9, the speed was 100 km / h, all other parameters being identical. In the figures, the noise level is plotted on the ordinate, in decibels, and the frequency on the abscissa,

in Hz.

  In the following table, the different notes

have the following meaning.

  Note 1: Wet trailer test, properties being better when the index is

most important.

  Note 2: Relative distance index traveled per mm

  wear of the tread rubber.

  Note 3: Test carried out by a rolling resistance tester. Note 4: Measured by a microphone constituting an acoustic sensor placed on one side of a vehicle at a distance of 7.5 m from the center line of the vehicle used, at a height of 1.2 m above the ground

in a deaf room.

  According to the invention Known - 1 Known - 2 Size 10,00R20 14 PR 10,00R20 14 PR 10,00R20 14 PR Sculpture drawing FIG. Fig. 6 Fig. 7 slots yes yes no

Depth (mm) 10_5 'm -

  Width (knife) (mm) 2 mm (250 mm diameter blade) -

Angle (relative to the equiva-

torial) 15 '150 -

Not (mm) 11.0, 13.7, 16.4 13.7 -

  (3 steps) (one step) On-road hook-lock 103 103 Wet 100 (note 1) r - 10 sever 106 106 100 Irregular wear good good normal Wear resistance (note 2) 110 112 100 Rolling resistance (note 3) 100 100 100 Noise level (note 4) See Fig. 8, FIG. 9 iu oo ol

Claims (15)

  1. Laminated tire for a vehicle,   characterized in that it comprises: two sidewalls and a tread area, the tread having a plurality of slots (9) spaced from each other at the circumference of the tread,   the slots (9) being cut with a certain   some inclinason with respect to the equatorial plane (C) of the   pneumatic and completely intersecting the roll   throughout its width, and the circumferential spacing of the slots (9)   such that the adjacent slots have spacings at least two different steps.   2. A tire according to claim 1, characterized   in that the slots (9) are formed after vulcanisation   the tread. -   3. Tire according to claim 1,   characterized in that the slots (9) are spaced circumferentially   conferring distances of between 5 and mm. 4. Pneumatic tire according to claim 1, characterized in that the ratio of the two neighboring steps is between 1.05 and 1.35.   5. A tire according to claim 1, characterized in that at least some of the slots (9) have a variable depth over the width of the strip. rolling.   A tire according to claim 1, characterized in that some of the slots (9) have a greater depth at the outer axial ends than at the center of the tread and other slots have a greater depth in the center of the tread. Band   bearing only at the outer axial end.   7. A tire according to claim 5, characterized in that the other slots have a plus   great depth at the external axial end   be. 8. A tire according to claim 1, characterized in that the tread is molded with circumferentially main grooves (4) only and the slits (9) are cut laterally. in a separate operation.   9. A tire according to claim 8, characterized in that the depth of the slots (9) is between 50 and 110% of the depth of the main grooves. Tire according to claim 1, characterized in that the circumference of the tire is divided into several segments (SG) and each segment is   circumferentially divided into at least two steps.   Tire according to claim 10, characterized in that the surface of the tread is divided into twelve equal circumferential segments (SG), and all the segments are divided into the same number. to not.   Pneumatic tire according to claim 11, characterized in that each segment is divided into less three steps.   Pneumatic tire according to claim 1, characterized in that each segment (SG) is divided into   at least three steps S (short), M (medium) and L (long).   Tire according to claim 9, characterized in that the steps are arranged in each segment in the form of SSSSMLMSMMSLMLLLLLSM.   15. A tire according to claim 1, characterized in that the slots (9) have no significant width, so that when in contact with the ground, the edges of a slot are pushed into intimate contact l against each other, and the tread behaves as if it comprised a continuous layer in the area of contact with the ground, the edges of the slots separating   leaving the area of contact with the ground.