Patent Application
20240375455
The present application claims priority to European Patent Application No. 23172084.8 filed on May 8, 2023, which application is incorporated herein by reference in its entirety.
The invention relates to studded tyres. The invention relates to studded pneumatic tyres. The invention relates to studded pneumatic tyres for passenger car vehicles.
Functions of a tyre on an automotive vehicle include providing sufficient traction for accelerating, driving, and braking; and providing adequate steering control particularly at high speeds. Traction is commonly referred to as grip and steering control as handling. Grip is affected also by the ground on which the tyre is commonly used. Winter tyres, which are intended for icy and snowy (wintry) roads, are commonly equipped with studs to improve grip on ice. However, studded tyres cause more road wear and noise than tyres without studs.
Reduced noise is beneficial from environmental and well-being points of view. Reduced noise would make driving and travelling in a vehicle less annoying and might improve comfort for the driver and passengers. Reduced noise would not only improve comfort of people in the vehicle but also people outside the vehicle. For example, in cities where traffic is large and where a lot of people live, reduced noise would improve the quality of life. Reduced noise induced by a studded tyre is therefore an important issue of a studded tyre. Naturally, also grip and handling are important characteristics of a studded tyre. A good studded tyre may be an optimal compromise between these features.
An aim of the present invention is to provide a studded tyre which produces less noise than prior art tyres and still provides for good grip.
According to a first aspect of the invention, a studded tyre is presented, comprising a tread having a plurality of tread blocks, a plurality of studs installed in at least some of the tread blocks, wherein a constellation of the studs is such that less than two studs are in a line perpendicular to a rolling direction of the tyre, that within an area of a footprint less than two studs are in the same line parallel to the rolling direction, and that a distance between two adjacent studs is more than 20 mm.
The tread blocks may be arranged in a periodic fashion called as a pitch. In other words, similar sequence of such a group of tread blocks of one pitch may be repeated over the whole circumference of the tyre. In other words, each pitch includes a predetermined geometry of whole and/or partial tread blocks. The number of tread blocks in each pitch may vary in width across the tire. There may be several different pitches, with variable dimensions or geometry.
In accordance with an embodiment, the configuration of the studs is such that the location of studs on one side from a centre line of the tyre differ at least 5 mm and less than or equal to 100 mm from the location of studs on another side of the centre line in the direction of rotation.
Such a tyre can be manufactured by vulcanizing a green tyre to form the tyre and forming stud holes to the tread of the tyre 200 during the vulcanizing the green tyre so that all the studs can be installed in a different radial location.
Within this description the term tyre refers to a tyre configured to be used on a wheel of a car, especially a passenger car. In line with this, within this description, a road wear of the studded tyre is defined as the road wear in the test specified in the standard SFS7503: 2022:en, which concerns primarily tyres designed for vehicles in categories M1 and N1, as defined in the Consolidated Resolution on the Construction of Vehicles (R.E.3), document ECE/TRANS/WP.29/78/Rev.4, para. 2. These categories are:
The standard SFS7503: 2022:en specifies the test procedure in detail. On the general level, in the test, a vehicle equipped with the tyres to be tested is driven over test specimens (i.e. test stones) with specified speed for a specific number of times. The test requires that two identical tyres are tested simultaneously; they are used on one side of the vehicle in the test. According to the standard, a properly loaded vehicle is driven two-hundred times over the test stones at the speed of 100 km/h. As both the front and rear wheel pass the test stones, there are a total of four hundred passes of the test tyres over the test stones; and these passes cause the test stones to wear. Road wear according to the standard SFS7503: 2022:en is the average weight loss of three test stone rows compensated by the weight loss of reference stones, if applicable. For further details refence is made to the standard. The average wear of test specimens is expressed in units of mass (i.e. in grams). The less the tyres wear the specimens, the less is the result (grams, g) of the test, and thus the less the tyres wear a regular road, too.
In the following the invention will be explained in more detail with reference to the appended drawings, in which
Referring to
Some measures of a tyre 200 are depicted in
In practice, the tyre width W200 is related to the size marking shown on the tyre 200. In general, the size marking is shown on a tyre as w/hRr, wherein w denotes a width, h an aspect ratio and r a radius. According to the ETRTO standards manual, typical size markings refer to Design Width (i.e. the width W200 of the tyre 200) and an overall diameter as shown in the Table 1 below:
It is noted that Table 1 shows only some examples. A tyre may have a different size, in particular another aspect ratio than 55, such as 40, 45, 60 or 65.
According to a first aspect of the invention, there is provided a studded tyre 200, which produces less noise than prior art studded tyres.
The direction Sz of
Referring to
To provide a good grip, the pin 110 should protrude from second part 130 sufficiently. A first height H110 is the height that the pin 110 protrudes from the second part 130 (e.g. from an upper flange 134 of the second part 130). The second part 130 extends in the longitudinal direction Sz of the stud 100 from the bottom flange 140 to an interfacial point 112 between the second part 130 and the pin 110 and does not extend further in this direction. In
The pin 110 and the second part 130 define the first height H110, which is the length the pin 110 protrudes from the interfacial point 112 in the longitudinal direction Sz to the extremal point 114 of the pin 110 in the longitudinal direction Sz of the stud. Thus, the pin 110 protrudes the first height H110 from the second part 130 of the stud; particularly from the interfacial point 112.
For good grip, the first height H110 should be sufficient. However, if the first height H110 is excessive, the road wear caused by the stud may increase. Moreover, not only the tip 110 affects grip and road wear. Particularly, a size of the bottom flange 140 affects grip and road wear, too. A large bottom flange 140 oftentimes implies that the stud 100 is arranged in the stud hole 250 in a stiff manner, i.e. the bottom flange 140 resists movement of the studs in the negative radial direction-Sr when the stud is pressed in this direction. A reason is that the large bottom flange 140 supports the stud 100 to the rubber material of the tyre beneath the bottom flange in a sturdy manner. This typically results in a high piercing force of the stud on the road; and a high piercing force implies high road wear. This applies also vice versa. A small bottom flange will, in general, reduce the piercing force and in this way the road wear.
The piercing force herein refers to the piercing force as defined in the regulation “Ajoneuvon nastarenkaiden tekniset vaatimukset ja tyyppihyväksyntä” TRAFICOM/220809/03.04.03.00/2019 of the Ministry of Transport and Communications on studs of tyres for vehicles (dated Oct. 2, 2021). This Ministry is the Ministry of Transport and Communications of Finland.
According to an aspect of the invention, a studded tyre has such properties that the tyre, in use, causes only low noise. Such properties include e.g. the constellation of the studs, a dynamic impact of the studs to the road, a number of the studs and the rubber material to which the studs are installed. The term constellation refers to the mutual positioning of studs in the tread 210. Also the terms arrangement configuration of the studs and configuration of the studs may be used to describe how the studs 100 are positioned in the tread 210 with respect to each other.
According to an embodiment, a tyre 200 comprises a tread 210 and multiple studs 100 in the tread 210. The studs 100 comprise pins 110 of hard metal or ceramic. What has been said above about the hardness of the pin applies. The studs 100 are arranged to the tread 210 such that at least the pins 110 of the studs 100 are exposed on the tread 210. The tyre 200, in particular the constellation of the studs 100 thereof, are configured such that noise induced by the tyre 200 during driving is particularly low compared to prior art tyres.
The low value of noise may be achieved e.g. by having only one stud impacting the road at the same time. Another feature which may affect the noise is that the studs have sufficiently low dynamic impact to the road. Features affecting the dynamic impact of the studs to the road include:
When a vehicle having studded tyres is running on a road, studs become in contact with a surface of the road i.e. the studs hit the surface of the road. This causes deformation to the surface structure of the tyre to occur which then is further propagating in the structure of the tyre having a wave form. As this propagating deformation wave meets the interface between the tyre and the structure of the vehicle, it from there on travels in the structure of the vehicle finally reaching the driving compartment of the vehicle and can be audibly sensed, by the operator of the vehicle, as noise. According to the present invention the purpose of the relative positioning of individual studs is to have deformation waves from different studs to not amplify each other but rather compensate each other at least partially. This may be achieved by positioning the studs so that only one stud hits the surface of the road at a time and that when a next stud hits the surface of the road the deformation wave generated by that stud has a different phase compared to the deformation wave generated by the previous stud. Studs which are not within the footprint area do not typically produce any noise so it is sufficient to concentrate the area of the footprint.
In accordance with an embodiment the configuration of the studs is such that studs on one side from the centre line CL of the tyre 200 differ at least 5 mm in the direction of rotation from studs on the other side of the centre line CL and is less than or equal to 100 mm. Advantageously, this difference (803 in
In accordance with an embodiment the configuration of the studs on one side (a first side, e.g. the left side) from the centre line CL is a mirror image of the configuration of the studs on the other side (a second side, e.g. the right side), but so that no stud on the first side is in the same line 801 perpendicular to the direction of rotation R than any of the studs on the second side. In accordance with an embodiment, the arrangement of the studs is such that the orientation of the studs on the left side is a mirror image from the orientation of the studs on the right side but slightly in offset in the direction of rotation. The centre line CL is one example of the mirroring plane but there may also be another mirroring plane or planes.
Moreover, a distance between any two adjacent studs is not less than 20 mm.
As for the material of the tyre 200, also the rubber material of the tread 210 may affect noise induced by the studs 100 of the tyre 200. Thus, in an embodiment, the tread 210 comprises rubber material having a Shore hardness in the range 48 to 59 Sh (A) as measured with durometer type A, at the temperature 23° C. In an embodiment, the tread 210, in particular the part of the tyre that is configured to contact a road in use, is formed of rubber material having a Shore hardness in the range 48 to 59 Sh (A) as measured with durometer type A, at the temperature 23° C.
The stiffness of the tread blocks 220 can also be reduced by providing sipes 240 to the tread 210. Thus, in an embodiment, at least some of the tread blocks 220 are provided with sipes 240. As is well known, sipes 240 are narrow openings in tread blocks 220. Sipes 240 are shown in
The tread blocks 220 of the tread 210 also limit grooves 230. Thus, the tread 210 comprises tread blocks 220 such that grooves 230 are arranged between the tread blocks 220. As an example,
When the tyre 200 comprises sipes, preferably, no sipe 240 is provided close to a stud hole 250, in which a stud 100 has been installed. Referring to
In an embodiment, at least some of the grooves 230 are inclined such that they define a V-shape or a half of a V-shape, the V-shape or the half thereof defining a direction of rotation R of the tyre 200 when used driving forwards, the direction of rotation R being reverse to the direction to which the V-shape or the half thereof opens. As an example, the grooves of
Such a tyre can be manufactured by vulcanizing a green tyre to form the tyre 200 and forming stud holes to the tread 210 of the tyre 200 during the vulcanizing the green tyre. After vulcanization, the studs 100 are installed to the stud holes 250 of the tread 210.
When the tyre comprises sipes 240, in an embodiment, the sipes are formed to the tread 210 of the tyre 200 during the vulcanizing the green tyre by using lamella blades.
As detailed above both (i) the area of the cross section of the pin 110 and (ii) a sturdiness of the support of the bottom flange 140 affect the dynamic impact. Thus, as an example, the tyre according to the invention may comprise a stud 100 comprising the bottom flange 140, the second part 130, and the pin 110 such that the greatest diameter of the bottom flange 140 is in the range from 7.5 mm to 10.5 mm and the smallest diameter of the bottom flange 140 is in the range from 5.0 mm to 9.5 mm.
The cross-section of the bottom flange 140 is preferably greater than a cross-section of the second part 130. Thus, the bottom flange 140 anchors the stud 100 well to the stud hole 250. Therefore, in an embodiment, the second part 130 has a third cross-section on a plane that has a normal in the longitudinal direction Sz of the stud 100, the third cross-section having a third area (A130, A132, A134), and the first area A140 is greater than the third area (A130, A132, A134). The third area A130 may correspond to a (sole) third area of the second part; or the third area A130 may correspond to an area A132 of a cross-section of a waist 132 or an area A134 of a cross-section of the upper flange 134.
As detailed above, the protrusion P100 of a stud 100 affects the dynamic impact. Preferably, the protrusion P100 is between 0.6 mm and 2.0 mm, more preferably between 0.7 mm and 1.6 mm, and most preferably between 0.8 mm and 1.4 mm measured from an inflated unused tyre. The protrusion of stud P100 is shown in
In an embodiment the tyre 200 comprises multiple studs 100a of a first stud type only. Thus, in an embodiment, all the studs of the tyre 200 are identical in shape.
To this end, in an embodiment the tyre 200 comprises multiple studs 100a of a first stud type and multiple studs 100b of a second stud type.
In
In accordance with an embodiment, the central region CR has a width which is in a range from 33% to 49% of the total width of the tread 210, but may be different from that, such as from 35% to 40% or from 44% to 48%.
The tread blocks 220 of the tyre 200 define a land portion LP of the tread 210. A part of the land portion LP of the tread is shown by black colour in
An area of the tread 210 which is simultaneously contacting a surface may be called as a footprint. The area of the footprint may slightly vary due to certain conditions. For example, the load affected to each tyre and the pressure within the tyres may affect the area of the footprint. The more load the larger may be the area of the footprint. On the other hand, the higher the pressure the smaller the footprint may be.
The tread blocks 220 of the tyre 200 define an envelope surface. The envelope surface consists of the land portion LP of the tread 210 and the regions defined by the openings of the grooves 230.
The openings of the grooves 230 may be commonly referred to as a sea portion SP of the envelope surface, as shown in black colour in
Thus, the total envelope area A210 is the sum of the land area A220 and the sea area A230, i.e. A210=A220+A230. Referring to
In this description, an average land ratio refers to the ratio of the total land area A220 to the total envelope area A210. In other words, by the land ratio is meant the ratio of the ground contacting surface area of tread blocks to the imaginary ground contacting area of the tread, the imaginary ground contacting area of the tread including spaces (i.e. grooves) between adjacent blocks and the blocks themselves. In other words, by the land ratio is meant the ratio of the ground contacting surface area of tread blocks to a ground contacting area of an imaginary tread, the imaginary tread having been formed from the tread by filling the grooves with tread material.
In the art, one sometimes uses the term sea area ratio to mean the ratio of the sea area to the imaginary ground contacting area of the tread. In line with these definitions the sum of the land ratio and the sea area ratio equals one.
In the art, the term “land-to-sea ratio” may, occasionally, be used interchangeably with the land ratio as defined above. However, the term land-to-sea ratio or land/sea ratio may relate to a ratio of the land area (ground contacting area) to the sea area (non-contacting area) of the tread. To avoid possible confusion, the term land area is used throughout this description and in the meaning defined above.
According to an embodiment, the land ratio of the tread is greater in a central area than in a shoulder area.
In an embodiment, at least two thirds of the studs 100 that are arranged in the central region CR are of the second stud type (they are studs 100b), and at least two thirds of the studs that are arranged in the first and second shoulder regions SR1, SR2 are of the first stud type (they are studs 100a).
In an embodiment, the studs 100a of the first stud type comprise substantially identical first pins. A cross-section of a first pin, the plane of the cross-section having a normal to the longitudinal direction Sz of the stud, has a first shape. Moreover, the studs 100b of the second stud type comprise substantially identical second pins. A cross-section of a second pin, the plane of the cross-section having a normal to the longitudinal direction Sz of the stud, has a second shape. The second shape is different from the first shape. For example, the pin 110 of the stud 100a of the first type is shown in
In an embodiment, not only the stud pins 110 of the first stud type are different from the stud pins of the second type, but also at least some parts of the body 130 of the studs 100a of the first stud type are different from corresponding parts of the body 130 of the studs 100b of the second stud type.
By using at least two different types of studs, the grip properties of the tyre can be optimized. This is particularly true, when studs of the second type are used in the central region CR, and studs of the first type are used in the shoulder regions SR1, SR2.
The grip of the tyre can be improved by using sufficiently many studs. The grip of the tyre can be improved by using sufficiently many studs on both sides of the circumferential central line CL.
Concerning the former, in an embodiment, the tread 210 has the first width W210 and the first circumference C210, as defined above. Moreover, the tread 210 is provided with a total number N100 of studs 100. A ratio (N100/(W210×CL)) of the total number of the studs N100 to the width of the tread W210 and the circumference C210 of the tread can be equal to or more than 5.6 pieces per square-decimetre (pcs/dm2). In an embodiment, the ratio (N100/(W210×C210)) of the total number N100 of the studs to the product W210×C210 of the first width W210 and the first circumference C210 is more than 6.8 pieces per square-decimetre (pcs/dm2). In another embodiment, the ratio (N100/(W210×C210)) of the total number N100 of the studs to the product W210×C210 of the first width W210 and the first circumference C210 is more than 7.2 pieces per square-decimetre (pcs/dm2). The first circumference C210 may be measured along the circumferential central line CL, e.g. along a circumferential central line of the envelope surface of the tread 210.
Thus, in an embodiment, N100/(W210×C210CL)≥5.6 pcs/dm2, wherein N100 is a total number of studs in the tire, W210 is the width of the tread (dm), and C210 is the circumference of the tyre 200 in dm, measured along the circumferential central line CL.
In the other embodiment mentioned above, N100/(W210×C210CL)>6.8 pcs/dm2.
In the third embodiment mentioned above, N100/(W210×C210CL)>7.2 pcs/dm2. Concerning the latter (the number of studs on each half of the tread), in an embodiment, the circumferential central line CL of the tread 210 (as well as the equatorial plane EP) defines a first half of the tread 210 and a second half of the tread 210 (see
The width W210 of the tread 210 may be somewhat smaller than a width W200 of the tyre. Within this description, the width W200 of the tyre 200, as shown in
The first width W210 (i.e. that of the tread) may be equal to the reference tread width as defined in the ETRTO standards manual 2023 (see Design Guide, Page PC.7). In accordance with the definitions therein, the reference tread width C is calculatable as
C=(1.075−0.005ar)s1.001
Herein s is the Section Width (defined above), i.e. the width W200 of the tyre, and ar is the nominal aspect ratio, which is readable from the size marking w/hRr (see above), the “h” indicating the aspect ratio. Thus, the first width W210 of the tread 210 may equal the value C as calculatable with the equation given above, wherein s equals W200.
The following Table 2 shows some examples of measures of tyres. The size indicates the diameter and width of the tyre, the aspect ratio indicates the height of the tyre as a percentage of the width of the tyre, ETRTO design width is the width of the tyre according to ETRTO, the reference tread width is the actual width of the tread.
Referring to
Referring to
Preferably, the circumferential central line CL of the tread 210 defines the first half of the tread 210 and the second half of the tread 210, and the studs are arranged such that at least three different circumferential rows (r11, r12, r13, r14, r15, r16, r17, r18, r19) of the at least six different circumferential rows (r11, r12, r13, r14, r15, r16, r17, r18, r19, r21, r22, r23, r24, 25, r26, r27, r28, r29) are arranged on the first half, and at least three different circumferential rows (r21, r22, r23, r24, r25, r26, r27, r28, r29) of the at least six different circumferential rows (r11, r12, r13, r14, r15, r16, r17, r18, r19, r21, r22, r23, r24, r25, r26, r27, r28, r29) are arranged on the second half.
Having such many rows rij effective spreads the studs to the tread 210 reasonably evenly, thereby improving the grip.
In addition to the tread 210 of the tyre 200, the structure of the tyre 200 provides for sufficient stiffness of the tyre 200 and thereby also affect the grip and road wear properties of the tyre 200. The tread 210 is provided as an outermost layer of a carcass of the studded tyre 200. A quarter of a cross-section of a tyre 200 is shown in
As detailed above, the tyre comprises the tread blocks 220 that define the grooves 230 and the tread 210, which is an outermost layer of the carcass. Preferably, the carcass of the studded tyre 200 comprises one or more layers of reinforcing textile or textiles and one of more reinforcing metal layers.
In general, a tyre 200 has side surfaces on opposite sides of the tread 210. The side surfaces connect the bead area of the tyre to the tread 210. The side surfaces may have various markings indicating the tire size, tire speed class, tire purpose (winter/summer), tire manufacturer and/or tire name. The bead area of a tyre has a cable. The function of the cable and the bead area is to fit the tire 200 to the rim.
The tyre 200, in particular the carcass thereof, comprises a first ply 288. The ply/plies 288 may comprise fibrous material, e.g. Kevlar, polyamide, carbon fibres, polyester or glass fibres. In an embodiment, the tire further comprises a second ply. In this embodiment, the second ply may also comprise fibrous material.
The carcass further comprises a first metal belt 287. Preferably, the carcass further comprises a textile belt 284, such as a textile belt 284 comprising fibrous polyamide (e.g. Nylon, aramid, or Cordura). Preferably, the carcass further comprises the second ply and a second metal belt 286. The metal belt(s) 287, 286 is/are resilient metal belts, such as steel belts comprising wires.
The tread blocks 220 are formed in a cap layer 291 of the tyre 200. The cap layer 291 may further comprise material connecting the tread blocks 220 to the cap layer 291 and layers beneath the cap layer 291. Under the tread blocks 220 of the tread 210, i.e. under the cap layer 291, the tyre preferably comprises an underlayer 293 made of suitable rubber material. A purpose of the underlayer 293 is to adaptively affect the impact of the studs to the road according to temperature. Thus, at higher temperatures (e.g. above 0° C.) the impact of the studs may be lower than at lower temperatures, e.g. below 0° C. Hence, road wear due to the studs 100 of the tyre 200 may be lower when roads are not covered by show and/or ice. Thus, in an embodiment, the bottom flange 140 of at least a part of the studs 100 of the tyre 200 are arranged partly in the underlayer 293.
The underlayer 293 may have a hardness which may vary substantially with the ambient temperature, wherein the wear of the road surface may be reduced. The underlayer 293 is preferably arranged at least partly below the anti-skid stud. Thus, the bottom of the anti-skid stud can be in contact with the underlayer 293, and the anti-skid stud can be pressed against and/or retract into the underlayer 293.
The anti-skid stud 100, preferably the bottom flange 140 of the anti-skid stud, can be in direct contact with the underlayer 293. Thus, in this embodiment, there is no other material layer between the anti-skid stud 100 and the underlayer 293. Alternatively, for example, a separate stud pad 199 may be arranged between the anti-skid stud 100 and the underlayer 293.
Further, the studded tyre 200 may comprise a separate bottom rubber ply (also called as an undertread) arranged below the underlayer 293. Thus, the properties of the studded tyre 200 can be improved. Moreover, the process of manufacture of the tyre 200 can be easier to control. In an example, the studded tyre 200 is not provided with a bottom rubber ply below the underlayer 293. Thus, the manufacturing costs of the tyre 200 can be reduced.
As depicted in
For these reasons, in an embodiment, at an ambient temperature of −30° C. a Shore (A) hardness of the underlayer 293 is not less than a Shore (A) hardness of the material of the tread blocks 220. The mechanical properties of the underlayer 293 need not depend on temperature; whereby this difference in the Shore hardnesses may apply also at higher temperatures.
However, preferably, the material of the underlayer 293, which supports the bottom flange 140, is selected such that it softens at higher temperatures. In other words, the hardness of the material of the underlayer 293 under each stud 100 decreases when temperature of the material increases (i.e. the hardness has a negative temperature coefficient). This has the effect that even if the studs are highly supported at low temperatures (because of the shore hardness, see above), at higher temperatures the studs do not wear the road as much, because of the reduced support provided by the softer underlayer 293.
Therefore, in an embodiment, the underlayer 293 comprises adaptive material. The adaptive material is adaptive to the temperature in the sense that it hardens at low temperatures and softens at high temperatures. Thus, the underlayer according to this specification can also be called as an adaptive underlayer. The underlayer may consist primarily or entirely of the adaptive material layer. The adaptive material layer comprises a material having a hardness substantially depending on ambient temperature.
The adaptive material layer can be made of a material compound having a hardness substantially depending on ambient temperature. Preferably, the underlayer is made of an elastomer material having a hardness depending on the temperature of the elastomer material.
The materials for the underlayer and the intermediate layer can be selected so that a dynamic stiffness of the underlayer differs from a dynamic stiffness of the intermediate layer at most temperatures.
The dynamic stiffness of the underlayer, determined at a temperature of 20° C., can be configured to be less than 25 MPa, preferably from 5 to 20 MPa. Further, the dynamic stiffness of the intermediate layer, determined at a temperature of 20° C., can be configured to be at least 25 MPa, preferably at least 27 MPa, and more preferably from 30 to 100 MPa. Technical effect is to decrease road wear while the intermediate layer supports the whole tire and the studs of the tire at the warmer temperature.
The dynamic stiffness of the underlayer, determined at a temperature of 0° C., can be configured to be at least two times the dynamic stiffness of the underlayer at a temperature of 20° C. Further, the dynamic stiffness of the intermediate layer, determined at a temperature of 0° C., can be configured to be from 1 to 1.5 times, preferably from 1.1 to 1.4 times, the dynamic stiffness of the intermediate layer at a temperature of 20° C. Technical effect is that the winter grip properties of the winter tire can be substantially improved while the intermediate layer supports the whole tire and the studs of the tire at warmer temperatures.
The dynamic stiffness of the underlayer can be at least 100% higher, preferably at least 150% higher than the dynamic stiffness of the intermediate layer at a temperature of 0° C. Technical effect is that the ice grip properties of the winter tire can be substantially improved at 0° C. The dynamic stiffness of the underlayer may further be equal to or less than 1000% higher, such as equal to or less than 900% higher, preferably equal to or less than 580% higher than the dynamic stiffness of the intermediate layer at a temperature of 0° C.
Furthermore, the dynamic stiffness of the intermediate layer can be higher than the dynamic stiffness of the underlayer at a temperature of at least 5° C., such as at a temperature of at least 7° C. In a particularly advantageous embodiments, the dynamic stiffness of the intermediate layer is higher than the dynamic stiffness of the underlayer at temperatures from 10° C. to 20° C. Technical effect is to reduce road wear while improving handling properties of the tire. Further technical effect is that the intermediate layer effectively supports the stud.
The dynamic stiffness of the underlayer at −25° C. can be at least 20 times the dynamic stiffness of the underlayer at +20° C. Thus, the grip properties of the winter tire can be substantially improved, and, for example, the braking distance needed by the winter tire under certain conditions can be substantially reduced.
The dynamic stiffness E* of the underlayer 293 can be
The change in the dynamic stiffness of the underlayer upon a decrease in the temperature can have a greater impact on the grip of the tire in winter than the change in the hardness of the material upon a decrease in the temperature. For the above-mentioned dynamic stiffness values, the adjustment of the stud's dynamic impact of the tire at different temperatures can be more controllable, and the grip properties of the winter tire can be better optimized for different temperatures. Thanks to the above-mentioned dynamic stiffness, for example the braking distance on an icy road can be substantially reduced.
In a preferred example, for optimizing the grip properties of the tire in winter,
In general, the higher the dynamic stiffness E*, the harder the material. These values have been found suitable for providing sufficient grip at low temperatures, yet low road wear at high temperatures. In this specification, the term dynamic stiffness E* refers to the stiffness of the material as determined according to the standard ASTM D5992-96 (reapproved 2018).
The temperature dependence of dynamic stiffness E* can be affected by selecting the tan delta peak temperature of the material in a suitable manner. The underlayer 293 can comprise, primarily comprise, or consist of a material whose tan delta peak temperature can be at least −20° C., for example at least −15° C., preferably at least −12° C., more preferably at least −10° C., or at least −8° C., and most preferably at least −5° C. Furthermore, the tan delta peak temperature of said material may not be higher than 20° C., for example not higher than 15° C., preferably not higher than 12° C., more preferably not higher than 10° C., or not higher than 8° C., and most preferably not higher than 5° C. Thus, the hardening of the underlayer can be suitable in view of road wear and winter grip. The closer to 0° C. the tan delta peak temperature of the material is arranged, the more accurately the hardening of the underlayer can take place at a point optimal in view of road wear and winter grip, and the easier the impact of the stud can be to control at different temperatures.
Therefore, in an embodiment, the underlayer 293 is made of a material having a tan delta peak temperature that is between −20° C. and +12° C., and more preferably between −5° C. and +5° C.
The term “tan delta” refers to tan δ and the term “tan delta peak” refers to the temperature associated to the turning point of tan delta curve and tan delta maximum value.
The dynamic stiffness E* also affects the hardness of the material. In an embodiment, a Shore A hardness of the underlayer 293 can be configured to be in a range between 45 ShA and 65 ShA at an ambient temperature of +22° C., more preferably at least 65 ShA, at 0° C., and at least 75 ShA at an ambient temperature of −30° C. More preferably, a Shore A hardness of the underlayer 293 is between 45 ShA and 60 ShA, most preferably in a range between 45 ShA and 55 ShA at an ambient temperature of +22° C., and higher than 75 ShA at an ambient temperature of −30° C.
Furthermore, the dynamic stiffness of the underlayer can be lower than 20 MPa at an ambient temperature of 20° C., between 40 and 400 MPa at an ambient temperature of 0° C., and at least 500 MPa at an ambient temperature of −30° C.
In this specification, the term Dynamic stiffness (E*) refers to the stiffness of the material which can be determined according to the standard ASTM D5992-96 (reapproved 2018).
The mechanical properties as well as their temperature dependence can be adapted by material selections.
The underlayer can comprise one or more polymer materials having a hardness depending on the temperature of the respective polymer material. The underlayer can comprise elastomer material.
In addition to the material of the underlayer 293 as such, also the thickness thereof affects the support of the stud 100.
Advantageously, the thermally adaptive underlayer has a thickness in a direction Sz substantially perpendicular to the direction of rotation of the tyre, wherein the thickness dl is in the range of 0.5 mm to 8 mm, preferably in the range of 1 mm to 7.5 mm, most preferably in the range of 1.5 mm to 7 mm. Thus, the properties of the underlayer can be easier to control so that the underlayer can yield to a particularly suitable extent when the ambient temperature rises, which can further reduce wear of the road surface. In this application, the thickness of the underlayer refers to the thickness of the underlayer when the anti-skid stud is in a rest position, that is, when the anti-skid stud is not subjected to external forces, such as pressure caused by the driving surface.
Referring to
Other features of the stud 100 that are particularly related to the amount of noise include the following, each one separately or in combination:
Preferably, a total length of the stud 100 is more than 9.5 mm, advantageously in the range from 10.0 mm to 11.0 mm.
In accordance with an embodiment, the density of the studs 100 in the tread 210 is more than or equal to 5.6 studs/dm2, preferably more than 6.8 studs/dm2, and more preferably 7.2 studs/dm2.
In accordance with an embodiment, the studs are arranged in three or more rows in the direction of rotation at both sides of the centre line CL. In other words, there are at least six rows of studs.
In accordance with an embodiment, the number of studs 100 on each side of the tyre 200 is the same or a difference of the number of studs 100 on each side of the tyre 200 is not higher than 10%.
In accordance with an embodiment, there is a lamella-free area around each stud 100 so that the radius of the lamella-free area is more than 6 mm, preferably about 8 mm. In accordance with an embodiment, the radius is about 10 mm.
In accordance with an embodiment, the studs 100 of the tyre 200 have one, two or three axes of symmetry.
In addition to the above mentioned properties related to the studs, properties of the tyre 200 may also affect the noise generated by the tyre 200 during driving. In the following, some examples are provided, wherein any of these properties or any combination of these properties may be implemented in a studded tyre 200 according to the invention.
In accordance with an embodiment, there is a base layer beneath the studs 100. The base layer may also be called as an underlayer 293.
In accordance with an embodiment, there is a layer of material under each stud 100 which is softer than the intermediate layer at least when the temperature of the tyre is higher than 10° C.
In accordance with an embodiment, there is an intermediate layer 292 around each stud 100.
In accordance with an embodiment, there is a stud pad 199 under each stud 100.
In accordance with an embodiment, the tyre 200 comprises one kind of studs 100.
In accordance with an embodiment, the tyre 200 comprises at least two different kinds of studs 100.
In accordance with an embodiment, the tread blocks 220 are arranged to groups of over 50 pitch on both sides of the tread 210.
In accordance with an embodiment, stud holes 250 have been formed to the tread during vulcanization of the tyre 200.
In accordance with an embodiment, the tread 210 of the tyre 200 comprises a mixture of two or more layers.
In accordance with an embodiment, the properties of the tyre 200 are such that a result of a road wear as measured according to SFS7503: 2022:en is less than 1.0 g for a tyre of the size 215/60R16 having load capacity of 775 kg (99), speed class 190 km/h (T) and extra load (XL).
In accordance with an embodiment, the properties of the tyre 200 are such that a result of a road wear test as measured according to SFS7503: 2022:en is less than 1.00 g and the load index (LI) of the tyre (200) is 99 or more.
In accordance with an embodiment, the properties of the tyre 200 are such that a result of the road wear of the tyre 200 as measured according to the standard SFS7503: 2022:en is less than 0.91 g and the load index (LI) of the tyre (200) is 93 or more.
In accordance with an embodiment. the properties of the tyre 200 are such that a result of the road wear of the tyre (200) as measured according to the standard SFS7503: 2022:en is less than 1.09 g and the load index (LI) of the tyre (200) is 105 or more.
| Number | Date | Country | Kind |
|---|---|---|---|
| 23172084.8 | May 2023 | EP | regional |
