CN1128069C - Pair of high-transverse-curvature tyres, in particular for two-wheeled vehicles, method of controlling behaviour of such vehicles on bend and front tyre of said pair - Google Patents

Abstract

Pairs of tires of high transverse curvature, especially for two-wheeled motor vehicles, the belt structure of the rear tires consists of a layer of non-woven fabric disposed at an angle of substantially zero degrees relative to the equatorial plane of the tires, preferably wrapped around a sheet of elastic material reinforced with aramid pulp stretched cords, and the belt structure of the rear tire comprises at least one radially outer layer of inextensible cords disposed at substantially zero degrees relative to the equatorial plane of the tire and distributed in an axially varying density, preferably also There is another reinforcement layer at a radially inner position. The zero degree cord is preferably a high elongation metal cord made of high carbon steel wire.

Description

Pairs of tires with high transverse curvature, especially for two-wheeled motor vehicles

technical field

The present invention relates to two-wheeled motor vehicles, and more particularly to a pair of tires of high transverse curvature, in particular for two-wheeled motor vehicles, to one of said tires, in particular the front tire, and to a method by which said pair of tires A method of controlling vehicle performance.

The invention relates in particular to a pair of tires for a two-wheeled motor vehicle in which the transverse curvature of the front tires is in no case lower than 0.15 than the transverse curvature of the corresponding rear tires.

More specifically, the invention relates to the structure of said tire centering, in other words, the invention relates to a pair of tires provided with a radial structure of plies, preferably having a shape ratio (H/C) ≤ 80 % and/or on the mounting rim, the rim width is greater than or equal to 60% of the nominal cord of the tire.

Background technique

As we all know, when a two-wheeled motor vehicle travels along a curved track, it tilts on the outside of the curve, forming an angle called "camber", which can reach a value of 65° with respect to the vertical plane of the road surface; , the tires induce a camber thrust that counteracts the centrifugal force acting on the vehicle.

The tire originally has a ply structure, which consists of two layers of rubber compound, reinforced with cords, symmetrically inclined to the equatorial plane of the tire, usually called a cross-ply structure, and also has a belt structure, which is also made of pairs of rubber Composed of chemical fabric strips, the cords of which are inclined to the equatorial plane of the tire.

The ply structure described above is capable of developing significant camber thrusts; moreover, the pair of tires has a well-balanced performance in corners, and although the two tires are of different dimensions, they exert camber thrusts of a similar nature, which are generally sufficient Balance the centrifugal thrust acting on the vehicle.

As a result, driving the vehicle on curves is not particularly difficult, and the vehicle has a balanced driving character, so that the driver can almost instinctively follow a curved trajectory simply by tilting the vehicle, without having to adjust its attitude, especially the steering angle of the handlebars.

To verify the above description, motorcyclists can certainly imagine that they can drive around a bend without holding onto the handlebars with their hands, but simply by shifting their center of gravity.

However, there are also problems in the following directions: riding comfort, directional stability of the vehicle and driving fatigue; these are all related to the excessive stiffness of the tire, the tire structure accumulates elastic energy under the action of the applied deformation, when the stress ceases , it rebounds instantaneously, thus amplifying the interference from the road surface, which makes the vehicle lose stability. Especially when driving on a straight road, the above-mentioned excessive stiffness causes high-frequency (8-10 Hz) oscillations on the front tires at low speeds (front wheel shimmy effect), and low-frequency (3-10 Hz) oscillations on the vehicle at high speeds. 4Hz) oscillations, making driving unstable.

In order to overcome the above-mentioned problems, radial ply tires have recently been used, which have a belt structure of textile or metal cords, especially the rear tires are provided with a belt structure, which includes (sometimes in a unique way) a circumferential The directional, preferably metallic, cords are wound, while the front tire has a belt structure provided with radially overlapping strips of oblique cords.

This tire pair has definitely improved in terms of riding comfort and driving stability: the vehicle vibrations at high speeds in straight driving have practically disappeared, the rear tires have an important damping effect, however, the front wheel shimmy effect is basically not Change.

However, the improved performance on straight roads has given rise to a new problem. The radial structure of the tire, together with the cord belt structure arranged in the circumferential direction (0°), cannot produce the desired camber thrust, which is also related to the increasing use of vehicles. Increased performance requirements.

More specifically, the thrust provided by the rear tires is lower and of a different nature (it is straight) than the thrust of the front tires (curvilinear). Therefore, the vehicle equipped in this way loses its neutral behavior and gains over-steering behavior; on a curve, the rear wheels cannot counteract the increased centrifugal force acting on the axis, and slip at a certain point tends to shift its trajectory toward the outside of the turn, while the front tires move closer to the inside of the turn.

In other words, when the speed increases and the radius of curvature of the trajectory decreases, the tilting of the vehicle alone no longer acts to compensate for the centrifugal force and therefore no longer guarantees the stability of the ride: it is necessary to increase the thrust exerted by the tires, which is achieved by The driver changes the posture of the vehicle through the operation of the handle, which is called "push steering" by those skilled in the art, that is to say, the rolling plane of the front tire is inclined by one degree relative to the tangential direction of the curved track. The angle called the "deflection angle", which is in the direction opposite to the curvature of the trajectory.

In this way, a sufficient thrust is obtained, which is the sum of camber thrust and sliding camber. .

The value assigned to the slip angle depends on the structural and performance characteristics of the front tire, which is related to the point that the tire can transfer between the value of the slip angle and the value of the sliding thrust, plus its external Tilt thrust and thrust exerted by the rear tires.

When moving out of a curve, the opposite operation is required, which is called "pull steering" by those skilled in the art, that is, tilting the handle towards the inside of the curve to lift the vehicle so that it can drive along the curved trajectory again . Therefore, the vehicle performance can be significantly controlled by the tire pair equipped with the vehicle, so the tire pair must be selected and verified.

Someone has proposed a technical solution for this work. The patent document EP0280889 proposes a method for performing the above selection without the need for experimental control. According to the technical solution of this patent, if the slip response (slip response) is defined as S ₁ and S ₂ , that is, for the front and rear tires respectively, the function of contacting the deflection angle and the sliding thrust, then the tire pair whose function S ₂ -S ₁ behaves as a monotonically increasing function will be acceptable.

In fact, the above method does not solve the problem, because the sliding response also depends on the inflation pressure of the tires, in any case, the result does not have an absolute value: in fact, although some tire pairs comply with the above law, they do not Acceptable, there is also the opposite.

EP 565339 A1 discloses a motorcycle tire comprising a ply with at least one radially arranged layer of organic fiber cords and a belt structure with at least one belt cord layer, At least one belt cord is helically wound substantially parallel to the equatorial plane of the tire. The belt cords have a tensile elastic modulus of not less than 600 kgf/mm ² and are arranged to have a lower cord density at the central portion than at the shoulders. The belt structure described above can improve the high-speed durability and steering stability of the tire. However, the technical problem of pairing a front tire with such characteristics with a rear tire with a zero-degree belt structure is not addressed in this document.

JP Kokai Hei 5-319019 discloses a radial tire for motorcycles in which a belt layer is formed of cords having an elliptical cross-section. Said cords are wound helically, with the long axis of the narrow line perpendicular to the outer surface of the ply in the central portion of the tread and almost parallel to the outer surface of the ply in the shoulder region of the tread.

Contents of the invention

In accordance with the present invention, the Applicant has now become convinced that there is a different approach to the problems posed by the new tires described above; this approach does not consist in accepting the existence of the problem and trying to choose among a large number of front and rear tires in the most efficient manner Tires, in order to form an acceptable pair or combination of tires, the present invention consists in designing the structure of the above-mentioned pair of tires to avoid the above-mentioned problems, so that the vehicle equipped with the pair of tires of the present invention can regain its balance performance on curves and absorb shocks and shock-absorbing performance.

A first aspect of the present invention relates to a method of controlling the overall sliding thrust of a pair of tires mounted on a motor vehicle, and more particularly to a method of controlling the performance of a motor vehicle through the structure of the tires, preferably a A method of controlling the sliding thrust exerted by a vehicle along a curved trajectory by varying the density of reinforcing cords of a layer of cords disposed in the circumferential direction at least in a belt structure of a front tire.

A second aspect of the invention relates to a tire for two-wheeled motor vehicles comprising a toric radial ply of high transverse curvature having a central crown and two lateral walls terminating in a pair of beads , a bead for anchoring the tire on the corresponding mounting rim; a tread band applied on said ply along the crown, and a circumferential direction sandwiched between said ply and tread band A non-stretchable belt structure characterized by:

the belt structure of the rear tire comprises at least one radially outer layer consisting of a plurality of axially juxtaposed circumferential turns of cords wound at an angle of substantially zero degrees relative to the equatorial plane of the tire,

The belt structure of the front tire comprises at least one radially outer layer provided with a plurality of cord turns arranged at an angle of substantially zero degrees with respect to the tire track plane at varying densities from one end of said belt structure to the other. axial distribution, and preferably includes an additional reinforcement layer arranged at a radially inner position.

The tires of said pair of tires preferably have a curvature ratio of not less than 0.3, the rear tires having a lower curvature ratio than the front tires.

The radially outer layer in the belt structure of the rear tire consists of a single cord or narrow strip of rubberized fabric comprising 2 to 5 high-elongation metal cords at an angle of substantially zero degrees relative to the equatorial plane of the tire, from The crown is screw-wound on the ply from one end to the other.

With respect to the front tyres, the radially outer cord turns of the belt structure consist of high-elongation metal cords whose distribution increases in density from the equatorial plane to the ends of the belt structure, with a predetermined width on either side of the equatorial plane In one area, the above density does not exceed 8 cords per centimeter.

The cord turns of at least one of said layers are preferably wound on a further reinforcing layer at a radially inner position, which in a first embodiment is a sheet of elastic material positioned at the Between the cord turns and the carcass ply, a padded adhesive means is dispersed in the elastic material.

Alternatively, according to another embodiment, said radially inner layer, preferably in the belt structure of the front tire, may comprise two strips arranged in axial side-by-side relation, wherein reinforcements are provided, relative to the equatorial plane of the tire, the reinforcements Oriented obliquely in each strip and oppositely oriented in both strips.

The reinforcements in said radially inner layer may be selected from the group consisting of textile cords and metal cords; in addition, the material of the reinforcements in one of said strips may be different from that in radially adjacent strips The material of the reinforcement.

With regard to the radially inner layer formed by a sheet of elastic material, the adhesive means dispersed in said elastic material is preferably fibers of short aramid fibril structure uniformly distributed in said elastic material, the density per unit volume of which is 0.5% to 5% of the total volume is preferably oriented in a circumferential direction or in a preferred direction inclined to the aforementioned equatorial plane.

In any embodiment, said radially inner layer may be relayed at the equatorial plane of the tyre, over a portion having a width preferably between 10% and 30% of the axial extension of said belt structure.

Description of drawings

The invention will now be described in detail, by way of example and not limitation, with reference to the following figures.

Figure 1 is a cross-sectional view of a tire centered rear tire according to the present invention.

Figure 2 is a cross-sectional view of a tire centered front wheel according to the present invention.

Figure 3 shows in schematic plan view different alternative embodiments of the belt structure of the front wheel tire.

Figure 4 is a qualitative graph of the combination of sliding thrust and camber thrust in both tires of the aforementioned tire pair and a known front tire.

Detailed ways

Referring now to FIG. 1, a tire of high transverse curvature, especially for the rear wheels, of a motor vehicle according to the invention is designated 1 .

As we all know, the lateral curvature of the tire is defined as the ratio between the distance ht measured on the equatorial plane X-X from the center of the tread to the line b-b between the two ends of the tread and the distance wt between the two ends of the tread. In motor car tires it is a very high value, usually higher than 0.15, while in car tires the ratio is usually lower than 0.05.

If the ends of the tread are not easily identifiable, for example due to lack of precise references, such as the corners indicated by C in FIG. 1 , it is quite possible to take the measurement of the maximum chord length in the tire as the distance wt.

The value of the above-mentioned transverse curvature is called "curvature ratio", and is also commonly called "tread curvature".

In the tires of the invention, this value is preferably between 0.15 and 0.45.

The tire 1 comprises a ply structure 2 comprising at least one ply 3 , the two opposite side edges 3 a of which are bent back over respective bead cores 4 . An elastic filling 5 is applied on the outer periphery of the bead core 4, occupying the space between the ply 3 and the correspondingly bent back side edge 3a of the ply.

It is known that the region of the tire including the bead core and filler constitutes the bead, which is structured to anchor the tire to a corresponding mounting rim (not shown).

Cooperating with the ply is a belt structure 6 consisting of one or more cords 7 arranged in parallel and side-by-side relationship from one end to the other on the crown of the ply, constituting a number of cords substantially in the rolling direction of the tyre. The cord turns 7a in the circumferential direction are generally said to be arranged "at zero degrees" with respect to the equatorial plane of the tyre. Said belt structure preferably consists of a single cord or a narrow strip of rubberized fibers (comprising up to 5 cords arranged side by side) wound helically from one end to the other on said ply crown.

The aforementioned cords are preferably high elongation (HE) known metal cords, the use and characteristics of which are described in detail in the applicant's European Patent No. EP 0461646, to which reference is made for details.

In short, the above-mentioned cords are composed of several cords, the number of which is 1 to 5, preferably 3 to 4, and each cord is composed of a certain number of single wires, the number of which is 2 to 10, preferably 4 to 7. The diameter is greater than 0.10mm, preferably in the range of 0.12-0.35nm. The wires in the strips and the strips in the cords are helically wound in the same direction, and the winding pitch may be the same or different for the wires and the strips.

The aforementioned cords are preferably composed of high-carbon steel wires (HT wires), ie, contain 0.9% or more of carbon. Specifically, in a particular sample prepared by the applicant, the helically wound layer 9 consists of a single cord 7, referred to as a 3 x 4 x 0.20 HE HT cord, extending from one end of the belt structure to The other end is helically wound. The above designation defines a metallic cord wound in one direction and consisting of three strands each consisting of four individual wires with a diameter of 0.20 mm, the abbreviation HE means "high elongation" and the abbreviation HT means "High tensile" steel, ie, high carbon steel.

The above cords have an ultimate elongation of between 4% and 8%, which is a typical well-known pulling behavior, called "spring behavior (spring behavior)", is the construction and molding of the above-mentioned high transverse curvature. required for tires.

The use of metal cords is particularly recommended and does not exclude the use of other cords. Specifically, if necessary, appropriate measures can be taken to use known aramid textile fibers. For example, a layer of zero-degree cords can be laid. Textile (aramid) cords and metallic (HE) cords in adjacent lateral positions, or vice versa. Different helical winding techniques of cords on plies are known and will not be described in detail here.

A tread band 8 is applied to the belt structure 6 in a known manner, by means of which the tire comes into contact with the ground.

As shown in FIG. 1, the cord turns 7a formed by the cords 7 are preferably wound on an auxiliary support 9 substantially consisting of a piece of elastic material sandwiched between the cord layer 7 and the carcass layer 3 .

The aforementioned auxiliary supports 9 perform different functions. First of all, during the step of preparing the belt structure, it is convenient to keep the cord turns 7a connected together due to its attachment and structural resistance, so that the belt structure 6 during its manufacture and in the connection between the belt structure and the ply structure 2 Sufficient structural stability during handling steps prior to assembly. When vulcanization is completed, in the tire in use, the auxiliary support 9 can bring further benefits to the performance characteristics of the tire, in particular it can increase the thrust performance in sliding. Therefore, the auxiliary support 9 should be as thin as possible; in order to limit its weight, since it is placed in the area of the tire with the largest radius, it plays a significant role in generating the centrifugal force.

In order to be able to manufacture and use an auxiliary support 9 with a suitably reduced thickness, it has been proposed according to the invention that the batch (preferably a natural rubber-based batch containing 30 to 70 phr of carbon black) constituting the auxiliary support is provided with a bonding device A homogeneously dispersed reinforcing filler is formed to increase the mechanical resistance and stretchability of the elastic material in its raw state without substantially changing its adhesion properties. The use of aramid pulp (fibers of short fibril structure of poly-para-phenylene-terephthalamide) is recommended in this respect, its trade name is "Kevlar pulp" or "Twaron pulp" (Kevlar and Twaron are registered trademarks of DuPond and Akzo, respectively).

The elastic material reinforced by the aramid mentioned above has an ultimate tensile strength under ecological conditions of 3 to 7 MPa and an elongation of 50% under a tensile stress of 0.6 to 3 MPa.

It has been found that by dispersing aramid fibers in the composition of elastomeric material constituting the secondary support 9, it is possible to form such a support in very thin sheets, but to prevent the plasticity which develops therein during the manufacture of green tires. deformation and stress.

In more detail, it has been found that by placing 1 to 10 phr (parts per 100 parts by weight of rubber) of aramid pulp in the elastomeric raw compound and using fibers of 0.1 to 2.5 mm in length, the best good effect. In practice, in tire manufacture, it is possible to produce and use auxiliary support members 9 having a thickness of 0.075 to 0.5 mm, preferably about 0.25 mm or less.

Calendering the auxiliary support 9 further increases the resistance to different stresses, allowing the aramid fibers to be pre-oriented in a preferred direction in the sheet of elastic material constituting the auxiliary support itself, at least in the tire pairs of the present invention. The preferred direction of use would be the transverse direction of the tire, but good results can also be achieved if the image is taken in the longitudinal direction.

In FIG. 2 , a tire with a high transverse curvature, which is particularly suitable for mounting on the front wheel when used for a tire of a two-wheeled motor vehicle, is designated 2 .

It is known that in order for a vehicle to have good steering and stability, the front tires must have a reduced cross-sectional width, and it is due to this that the high transverse curvature of the tread arises.

In the front tires of the pair of tires according to the invention, the aforementioned curvature has a value greater than 0.30, preferably greater than that of the corresponding rear wheel.

In its most general construction, and with respect to features not explicitly described here, the tire identified in Figure 2 does not differ from the tire shown in Figure 1, and the same reference numerals are therefore used in both figures.

The front tire also comprises a belt structure 6 applied on the ply crown, which comprises at least one radially outer layer 7 of reinforcements in the circumferential direction, said belt structure preferably also comprising at least one reinforced Radially inner layer 9. This radially inner layer essentially corresponds to the auxiliary support 9 in the rear tyre, except that it is more redundant in the front tyre.

The reinforcements in the radially outer layer are preferably cords of the same kind as in the above-mentioned rear tire, wound on the ply in the circumferential direction, ie at zero degrees.

In this case, the above-mentioned radially outer layer also consists of a number of cord turns, preferably a narrow strip of at least one cord or several (preferably 2 to 5) cords wound helically on Formed on the crown of the ply, however, the winding is preferably carried out with varying pitch, in each case of varying density increasing from the center towards the ends of the belt structure.

Although both the helical winding itself and the variability of the pitch lead to a non-zero winding angle, the value of this angle remains small and can always be considered to be a zero degree angle. Specifically, in the present invention, an angle not exceeding 5°, preferably not exceeding 3° can be regarded as "substantially equal to zero degree". It should also be noted that the constant winding pitch along the circumference of the belt structure always induces a variable density in the axial direction due to the curvature of the ply.

According to the invention, the density of the distribution of the 7 turns of the cord varies preferably according to a predetermined relationship along the layer from the equatorial plane to the ends. According to the applicant's test, the above relationship can be conveniently expressed as: $N_x=K\frac{R^2}{{\mathrm{<figure-callout\; id="2"\; label="r"\; filenames="C9711580900201.png,C9711580900211.png"\; state="\{\{state\}\}">r</figure-callout>}}^2}\mathrm{no}$

in,

No is the number of cord turns set in the central length of the unit value (eg 1cm) on either side of the equatorial plane;

R is the distance between the center of said central length in the radially outermost layer and the axis of rotation of the tire;

r is the distance between the center of one of said unit lengths and the axis of rotation of the tire in the region between the center of the radially outermost layer and the two ends;

k is a parameter that takes into account the constituent material and structure of the cord, and the amount of rubber on the cord, and the weight of the radially outermost portion per unit length of the nearest said unit length, which varies in the type of material and the structure of the strip Structural features change as they vary along the crown profile, diverging from baseline values.

In the case where the cords have the same structure over the extension of the entire layer and all the connecting materials are the same, this parameter takes a value substantially equal to 1, while extending along the perimeter of the belt structure, the material and the structure of the reinforcements vary, this parameter then take a different value.

Although the axial density of the cords at 0° varies, the cord distribution according to the above relationship can ensure the uniformity of the stress on the belt structure due to the centrifugal force during the use of the tire. Variations in stiffness are required, as will be detailed below.

Those skilled in the art will obviously be able to find other relationships, depending on the design variables mentioned above, which can achieve both different stiffnesses in the axial direction and different stiffnesses in the axial direction by varying the density of the cords in a controlled and predictable Uniformity of stresses in the tire belt structure in use.

Those skilled in the art can also use the method described above to manufacture rear tire belt structures as well as belt structures for two tires, combining the different characteristics of the two tires in order to achieve a neutral behavior of the motor vehicle in sliding.

With regard to the density of zero-degree cords in the region either side of the equatorial plane where maximum thinning occurs, it should not exceed 8 cords per centimeter, preferably 3 to 6 cords per centimeter.

The aforementioned area is preferably 10% to 30% of the axial extension of the belt structure.

The number of cords in the above-mentioned central region is equal to a value of 60% to 80% of the number of cords near the shoulder of the tire, the density of the cords near the shoulder of the tire should not exceed 10 cords per cm, preferably 6 to 8 cords per centimeter.

Considering now the aforementioned radially inner layer, different alternative embodiments are possible for its manufacture, from which the person skilled in the art can choose the most suitable one according to the specific requirements.

The reinforcing elements of the radially inner layer may be either individual threads or cords in any case in a direction crossing the equatorial plane, or reinforcing fillers such as fibrous fillers, which may be placed arbitrarily, but preferably in accordance with Placement in preferred orientation parallel to or crossing the equatorial plane.

The reinforcements of the above-mentioned layers may be monofilament and/or twisted or non-twisted yarns, they may be of various textile materials such as natural fibers or synthetic materials such as amides, nylons and aramids, or metallic materials.

It should be noted that in the following description the term "cord" will always be used, which term always refers to a single thread or a non-knot skeined yarn when the context permits.

Firstly, said layer may consist of two radially superposed strips 9a, 9b of rubberized fabric constituted by reinforcements in an elastic matrix, in which the reinforcements are intersecting and preferably symmetrically inclined Oriented in two preferred directions in the equatorial plane X-X in a manner substantially similar to prior art belt structures.

The basic difference between the new belt structure and the prior art belt structure is that the new belt structure has a lower stiffness over a large area (10% to 30% of the axial extension of the belt structure) on either side of the equatorial plane; this This lower stiffness is conveniently obtained by manipulation of the density of the reinforcement, or of the material of construction, or of the orientation of the reinforcement relative to the equatorial plane, or of the abovementioned measures The combination. The aforementioned stiffness values can be expressed in different ways, for example by the density of the reinforcement (all other things being equal), but more generally by the modulus of elasticity or by the radially inner layer measured in the circumferential direction. Expressed in terms of tensile stress; the stiffness of the layers preferably does not exceed 65% of that of comparable belt structures of the prior art.

Specifically, when the material, structure and laying angle are the same, on either side of the equatorial plane, in the direction inclined to the equatorial plane, the overall density of reinforcements intersecting the right section (right section) per unit width does not exceed, A reinforcement density lower than that of prior art tape structures (approximately 14 cords per centimeter) is preferred.

The included angle of the cords relative to the equatorial plane is 18° to 50°, preferably 22° to 45°.

According to a proposed alternative embodiment, said strips are interrupted at the equatorial plane so as to form a region a ( FIG. 3 ) having a width of 10% to 30% of the axial extension of said band structure, in which Only circumferential reinforcing cords 7 are present.

The above-described solution has the advantage that an appropriate density value of the strips can be selected for the lateral portions of the fringe without correspondingly densifying the central crown of the fringe.

Specifically, the nylon cord designation 940/2, a density value of 4 to 8 cords per centimeter, has been found suitable for use with an orientation angle of 30° to 50° relative to the radial direction.

In a particularly preferred embodiment, the two strips are constructed of cords of the same material, while in another embodiment the cord material of one strip is different from the cord material of the other, for example nylon/ Aramid or an aramid/metal combination; in this case, the angles of said cords within the range specified above are preferably different from each other and asymmetric.

In an alternative technical solution, the radially inner layer consists only of two strips arranged in side-by-side relationship axially along the peripheral profile, each strip being provided with a reinforcement oblique to the crossing direction of the equatorial plane, so that the two The strips form a substantially herringbone-shaped reinforcement structure. In this case, the adjacent two pieces can also remain close to each other, or can also be joined along the facing longitudinal edges, or can be completely separated from each other. As noted in the case of overlapping strips, it appears to be beneficial to maintain the same axial width between said facing longitudinal edges.

What has been said above regarding the constituent materials, orientation and density of the reinforcements of the two strips also applies to the strips just described.

In another advantageous embodiment of the invention, said radially inner layer is constituted by a sheet 9e of elastic material, as in the case of the strips 9c, 9d already described, in the It may be continuous or interrupted at the equatorial plane X-X; the sheet is preferably filled with a reinforcement filler composed of broken short fibers dispersed randomly in the elastic material, but preferably in a predetermined direction in the circumferential direction, axial direction orientation, or, when the sheet 9e is composed of two distinct and axially adjacent sheets, oriented obliquely to the equatorial plane of the tire.

In this case, it is impossible to speak of the linear density of the fibers, but the distribution density per unit volume must be taken into account: this density is preferably 0.5% to 5% of the total volume. The thickness of the sheet does not exceed 1 mm, preferably between 0.3 and 0.8 mm.

The filler is the same as described above for the rear tire belt structural support 9 .

Figure 4 shows in a qualitative manner, for some tires, the combination of sliding and camber thrusts exerted by the tire. This combination is represented in the coordinate diagram in kilograms (y-coordinate axis) when the inclination of the vehicle changes, and in degrees (x-coordinate axis) under the conditions of standard working pressure, rated load and rims usually used by the vehicle Expressed. Lines a and p represent the above functions for the front and rear tires of the tire pair according to the invention, respectively.

Line c, on the other hand, represents the combination of sliding thrust and camber thrust exerted by a prior art front tire having a belt structure of cross cords.

It can be seen that this combination is a curvilinear function which is still a curvilinear function in combination with the substantially rectilinear function of the rear tire.

This basically means that a vehicle equipped with front and rear tires with the properties shown by lines a and c has a cornering behavior that varies with the inclination relative to the road surface due to the combined thrust in the two tires Rather than being linear, it is a combination of linear thrust (rear tyres) and non-linear thrust (front tyres), thus requiring continuous adjustment of vehicle attitude.

It can be seen that, qualitatively speaking, the thrust a and p are ideal functions, specifically, they are basically straight-line functions, so their combination is also basically a straight-line function, and their values change in a continuous and uniform manner with the vehicle inclination angle , Therefore, the vehicle has the balance performance of cornering steering, which means that there is no need to adjust the handlebar, but only gradually increase the inclination angle with the increase of centrifugal force.

In order to evaluate the qualitative results obtained with the pair of tires according to the invention, a series of road and track tests were carried out and the pair of tires according to the invention was compared with a comparable pair of tires of the best commercially available brand for the same car model .

These tires were those normally produced by the applicant and tires from two different manufacturers of competitors judged to be the best under normal and extreme driving conditions.

The vehicles used are characterized as follows:

Motorcycle HONDA CBR 1000F

Front tire Specification 120/70 ZR17

Inflation pressure 2.5bars

Wheel rim 3.50-17

Rear tire Specification 170/60 ZR17

Inflation pressure 2.9bars

Wheels 5.50-17

The road test is intended to assess the qualitative level of the most important performance characteristics while driving, depending in particular on the belt structure, the subjective judgment being converted into a score from 1 to 7, the highest score being given to the pair of tires showing the best performance of each evaluated characteristic. The tires are marked as follows:

A: The tire pair of the present invention

B: PIRELLI tire pair (currently produced MTR01; MEZ2)

C: Competitor's first tire pair

D: Competitor's second tire pair

It should be noted that the individual structural and performance characteristics of different comparative tire pairs with more than one characteristic differing from each other are not evaluated separately, but only the overall performance of the tire equipment, which is characterized by the finished product and is mainly affected by the belt of the two tires. Influenced by structure type. On the other hand, the specific purpose of the test was to evaluate the overall results of the inventive pair of tires compared to the best tire setup currently available on the market.

In all cases, the tires constituting the pair of tires according to the invention were manufactured as follows:

The front tire has a radial double ply with rayon (designation 1220/2) cords and a belt structure consisting of a radially outer layer of metal cords 3×4×0.20 HE HT with a corresponding final elongation At 6%, the density of the distribution increases from a minimum of 4 cords per centimeter at the equatorial plane to a maximum of 8 cords per centimeter at the shoulder, as previously described, by a narrow band of two cords spiraling Type winding, the thickness of the radial inner layer is 0.5mm, mixed with aramid pulp, its orientation is the circumferential direction,

The rear tire has a radial double ply with nylon (designation 1400/2) cords and a belt structure consisting of a narrow belt of three steel cords of type 3×4×0.20 HE HT with an elongation corresponding to 6% , is helically wound on the ply with an axial winding pitch of 5 mm under a tension of approximately 400 grams.

In contrast, the competitor's two tires are basically the same, the front tire has a radial double ply of nylon, and a pair of radially stacked strips of belt construction, which are provided with aramid cords, in two Symmetrically intersecting in the strips, the distribution density is 9 cords per centimeter, the inclination angle relative to the equatorial plane is 23°, all the above values are measured in the direction of the crown of the tire according to the prior art. The rear tire is provided with a double ply of nylon and a belt structure consisting of circumferentially oriented aramid cords wound helically at different densities depending on the tire, respectively 130 threads per decimeter and 130 threads per minute. m 160 lines.

The following table shows the comparison results between different tire pairs:

surface

Test/Tires A B C D

Sensitivity to front wheel runout 7 5 5 4.5

Drivability 7 6 6 6

Shock Absorption Capacity 7 6 6 5

Steering Stability 7 7 6 5

Braking performance 7 5.5 4 4.5

Comfort 7 6 6 5.5

It can be seen that the performance of the tire pair according to the invention is generally better than that of the competitor's tire pair, especially in terms of sensitivity to runout of the front wheel, as well as damping performance and braking performance on uneven road surfaces, i.e. directional stability and Braking distance.

The invention achieves all of the objectives, in particular the elimination of the front wheel heave action and the poor damping ability of the front tires to uneven road surfaces, as well as the tendency to oversteer and the vehicle to lift in bends when braking.

The pair of tires of the invention has completely restored the balanced performance on the curves, which is achieved by means of the belt structure of the new front tire, which is provided with zero-degree winding cords that are thinned out in the central area, in fact, this structure makes the tire With a straight-line response on bends, that is, qualitatively identical to the response of the rear tires, thus the combination of the responses of the two tires, the vehicle response on bends is still a straight-line response, resulting in a balanced performance when driving .

In addition, due to the general decrease in stiffness of the belt structure of the front tires, the above reaction is balanced between the two tires and can be further adjusted by simultaneously increasing the lateral stiffness of the rear tires by adding auxiliary supports It is realized by means of pieces, and the auxiliary support is made of elastic material reinforced with aramid pulp.

Surprisingly and contrary to all expectations, the reduced stiffness of the front tire belt structure, combined with the performance characteristics of the rear tires, has resulted in a belt structure with high lateral stiffness in its lateral parts by restoring the vehicle's balanced performance on bends The need for this is no longer essential, whereas previously this stiffness was necessary in order to support the sliding thrust caused by the deflection angle exerted on the front tires when cornering.

Therefore, the use of a single or double reinforcing inner layer in the front tire has become an optional and appropriate measure for a particular vehicle or specific tire construction, preferably in the center tread Partially interrupted in order to meet the following dual, conflicting requirements, namely, a high degree of flexibility of the belt structure in straight driving conditions and a high stiffness in curves. In fact, in the two lateral parts of the belt structure, the stiffeners oriented in the cross direction with respect to the equatorial plane compensate for the reduction in stiffness due to the replacement of the strips of the ordinary belt structure.

Specifically, by controlling the overall density value of the reinforcement, and by controlling the angle at which the underlying reinforcement is laid, it is possible to achieve different values of stiffness of the belt structure from one area to another, increasing towards the end of the belt structure In order to absorb and reduce the vibration caused by uneven road surface, at the same time, the important lateral thrust increases with the inclination angle of the vehicle, so that the tire has good directional stability and great insensitivity to front wheel vibration, and High driving comfort.

It has also been unexpectedly found that the provision of a layer with zero degree stiffeners and the density of the stiffeners in the axial direction is variable, thus giving the belt structure a greater deformability which improves the straightness. And the stability of the vehicle when braking on a curve, the force acting on the two tires does not change qualitatively when the vehicle speed and the load on the vehicle are changed in different driving conditions. Specifically, during the braking action, the load distribution between the front and rear tires undergoes a change, but when driving in a curve, this situation does not produce a thrust interruption on the front tires with a zero-degree belt structure, whereas in the prior art However, it occurs on the tires because of its non-linear thrust function with respect to the vehicle's inclination angle.

In addition to the above, the belt structure is equipped with zero-degree reinforcement, which has greater flexibility, so that it can increase the contact area of the tire with the ground during braking, thus reducing the braking distance of the vehicle, which is beneficial Drive safely.

Once a person skilled in the art understands the aforementioned invention, he will be able to realize all the options, changes and modifications of the variables related to the invention, which help him to solve the specific technical problems he has to deal with.

Claims (16)

1. Pair of tires for two-wheeled motor vehicles, said tires comprising a toric radial ply having a central crown and two sidewalls terminating in a pair of beads for anchoring the tire On the corresponding mounting rim; a tread band applied in the crown direction on said ply; and a belt structure inextensible in the circumferential direction provided between said ply and the tread band, characterized in in: the belt structure of the rear tire comprises at least one radially outer layer consisting of a plurality of axially juxtaposed circumferential cord turns (7a), the cords (7) being wound at an angle of substantially zero degrees relative to the equatorial plane of the tire, The belt structure of the front tire comprises at least one radially outer layer provided with a plurality of cord turns arranged at an angle of substantially zero degrees with respect to the equatorial plane of the tire at varying density axes from one end of said belt structure to the other. to the distribution. 2. The pair of tires for two-wheeled vehicles according to claim 1, characterized in that: the curvature ratio of the tires is not lower than 0.3, and the curvature ratio of the rear tires is lower than that of the front tires. 3. The pair of tires for a two-wheeled motor vehicle according to claim 1, characterized in that said cord layer of the belt structure in the rear tire is a rubberized cord comprising 1 to 5 high elongation metal cords A narrow strip of fabric is formed which is wound helically over said ply from one end of said crown to the other at an angle of substantially zero degrees relative to the equatorial plane of the tire. 4. The pair of tires for a two-wheeled motor vehicle according to claim 1, characterized in that said cord turns of the radially outer layer in the belt structure of the front tire comprise high elongation made of high carbon steel wires Metal cord. 5. The pair of tires for two-wheeled motor vehicles according to claim 4, characterized in that: the density of the cord turns gradually increases from both ends of the belt structure, and the value of the unit width area on either side of the equatorial plane is Not to exceed 8 cords per cm. 6. The pair of tires for a two-wheeled motor vehicle according to claim 1, characterized in that the cord turns of said radially outer layer in the belt structure of at least one of said tires are wound on at least one other of said radially on the reinforcing layer at the inner position. 7. Tire pair according to claim 6, characterized in that said radially inner layer in the belt structure of at least one of said tires is at the equatorial plane of the tire at a width of said belt structure 10% to 30% of the axial extension is interrupted. 8. The pair of tires for two-wheeled motor vehicles according to claim 6, characterized in that said radially inner layer is formed by a piece of elastic material (9) sandwiched between the belt structure (2) and the ply ( 3) In between, comprising coupling means dispersed in the elastic material of the sheet. 9. The pair of tires for a two-wheeled motor vehicle according to claim 8, characterized in that said coupling means are reinforcing fiber fillers, the material of which is selected from the group consisting of textile, metal or fiberglass. 10. Pair of tires according to claim 9, characterized in that said reinforcing fibrous fillers are aramid fibers of short fibril structure. 11. The tire pair according to claim 10, characterized in that the reinforcing fiber filler is uniformly dispersed in the elastic material with a density per unit volume of 0.5% to 5% of the total volume. 12. The tire pair according to claim 9, characterized in that said reinforcing fiber filling is oriented in a preferred direction inclined to said equatorial plane. 13. The pair of tires for a two-wheeled motor vehicle according to claim 6, characterized in that, in the belt structure of the front tires, said radially inner layer is formed by axially facing strips, inside which are provided reinforcements , with respect to the equatorial plane of the tire, the reinforcements are obliquely oriented in each strip and oppositely oriented in the strip. 14. The pair of tires for a two-wheeled motor vehicle according to claim 13, characterized in that the reinforcing members of the radially inner layer are selected from the group consisting of textile cords and metal cords. 15. The pair of tires for a two-wheeled motor vehicle according to claim 13, characterized in that said radially inner layer comprises two radially overlapping strips on both sides of the equatorial plane, which are provided with reinforcements, relative to the tire In the equatorial plane, the stiffeners are oriented obliquely in each strip and oppositely oriented in both strips. 16. Pair of tires for two-wheeled motor vehicles according to claim 15, characterized in that the reinforcement in one of said strips is of a different material than the radially adjacent reinforcement.

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