Process for producing tyres capable of reducing cavity noise and set of tyres obtained thereby

Abstract

The process for producing tyres comprises arranging no more than four sets of noise-reducing elements, each set being associated with a respective dimension L.sub.x different from each other; feeding in succession a set of tyres for vehicle wheels, having different values C of the inner circumferential extension; for each inner circumferential extension value, determining a respective number n.sub.x of noise-reducing elements for each set of noise-reducing elements, with x ranging from 1 to N, wherein for at least one value of the inner circumferential extension at least two respective numbers n.sub.x differ from 0; for each tyre, collecting from each set of noise-reducing elements the respective number n.sub.x of noise-reducing elements and applying the collected noise-reducing elements in circumferential sequence along an inner surface of the tyre, with dimension L.sub.x oriented circumferentially.

Claims

1. A process for producing tyres, comprising: arranging a plurality N of sets of noise-reducing elements, wherein all the noise-reducing elements belonging to each set have a respective substantially equal dimension L.sub.x, with x ranging from 1 to N, the respective dimension L.sub.x of the noise-reducing elements of each set differs from the respective dimension L.sub.x of the noise-reducing elements of the other N−1 sets, and the plurality N of sets comprises no more than four sets; feeding in succession a set of tyres for wheels of vehicles, wherein each tyre has a respective inner circumferential extension, and the set of tyres has different values of the inner circumferential extension; for each one of the inner circumferential extension values, determining a respective number n.sub.x of noise-reducing elements for each set of noise-reducing elements, with x ranging from 1 to N, as a function of the value of the inner circumferential extension, wherein for at least one value of the inner circumferential extension of the set of tyres, at least two respective numbers n.sub.x differ from 0; and for each tyre of the set of tyres, collecting from each set of noise-reducing elements the respective number n.sub.x of noise-reducing elements determined for the value of the inner circumferential extension of each tyre and applying the collected noise-reducing elements in a circumferential sequence along an inner surface of each tyre, with the respective dimension L.sub.x oriented circumferentially.

2. The process according to claim 1, wherein the plurality N of sets of noise-reducing elements comprises no more than three sets.

3. The process according to claim 1, wherein the plurality N of sets of noise-reducing elements consists of two sets.

4. The process according to claim 1, wherein the respective numbers n.sub.x determined for each value of the inner circumferential extension of the set of tyres are determined further as a function of a free arc, wherein the free arc is a circumferential length of an overall portion of the inner circumferential extension left free of the noise-reducing elements of the circumferential sequence applied.

5. The process according to claim 1, wherein the respective numbers n.sub.x determined for each value of the inner circumferential extension of the set of tyres are determined further as a function of a mean interval between the noise-reducing elements, wherein the mean interval is a mean distance between the noise-reducing elements of the circumferential sequence applied.

6. The process according to claim 1, wherein the respective numbers n.sub.x are determined, for each value of the inner circumferential extension of the set of tyres, using the formula: ${.Math.}_{x = 1}^{N} n_{x} * L_{x} + Δ * {.Math.}_{x = 1}^{N} n_{x} = C$ wherein C is the value of the inner circumferential extension and Δ is a mean distance between the noise-reducing elements.

7. The process according to claim 1, further comprising: for a plurality of n-tuples of numbers n.sub.x, with each n.sub.x ranging from zero to a given maximum value, calculating a respective free arc, wherein the free arc is a circumferential length of an overall portion of the inner circumferential extension left free of the noise-reducing elements of the circumferential sequence applied; and selecting from among all the n-tuples of numbers n.sub.x considered, at least one n-tuple of numbers n.sub.x as a function of the calculated free arcs.

8. The process according to claim 7, wherein the respective numbers n.sub.x are determined by selecting, among all the n-tuples of numbers n.sub.x, with n.sub.x ranging from 0 to the given maximum value, an n-tuple of numbers to which a minimum of the calculated free arc corresponds.

9. The process according to claim 8, further comprising selecting, among all the n-tuples of numbers n.sub.x to which a minimum of the calculated free arc corresponds, an n-tuple of numbers having the minimum sum of the numbers n.sub.x.

10. The process according to claim 1, further comprising: for a plurality of n-tuples of numbers n.sub.x, with each n.sub.x ranging from zero to a given maximum value, calculating a respective mean interval, wherein the mean interval is a mean distance between the noise-reducing elements of the circumferential sequence applied; and selecting from among all the n-tuples of numbers n.sub.x considered, at least one n-tuple of numbers n.sub.x as a function of the calculated mean intervals.

11. The process according to claim 10, wherein the respective numbers n.sub.x are determined by selecting, among all the n-tuples of numbers n.sub.x, with each n.sub.x ranging from zero to the given maximum value, an n-tuple of numbers for which at least one of: the mean interval is less than or equal to a given maximum threshold value, and the mean interval is greater than or equal to a given minimum threshold value differing from zero.

12. The process according to claim 11, wherein the given maximum threshold value of the mean interval is 20 mm and the given minimum threshold value of the mean interval is 3 mm.

13. The process according to claim 11, further comprising selecting, among all the n-tuples of numbers for which at least one of: the mean interval is less than or equal to the given maximum threshold value and the mean interval is greater than or equal to the given minimum threshold value, an n-tuple of numbers having the minimum sum of the numbers n.sub.x.

14. The process according to claim 1, wherein the respective dimension L.sub.x of all the noise-reducing elements is greater than or equal to 100 mm and wherein, sorting the sets of noise-reducing elements in ascending order of the respective dimension L.sub.x, a difference between the respective dimension L.sub.x of the noise-reducing elements of each set and the respective dimension L.sub.x of the noise-reducing elements of at least one of a respective preceding and subsequent set is greater than or equal to 10 mm.

15. A set of tyres for wheels of vehicles, wherein each tyre has a respective value of the inner circumferential extension and at least some tyres of the set of tyres have different values of the inner circumferential extension, wherein a respective sequence of noise-reducing elements is applied circumferentially along an inner surface of each tyre of the set of tyres, wherein the noise-reducing elements applied to the set of tyres belong to a plurality N of sets of noise-reducing elements, wherein all the noise-reducing elements belonging to each set of noise-reducing elements have a respective substantially equal circumferential dimension L.sub.x, with x ranging from 1 to N, wherein the respective circumferential dimension L.sub.x of the noise-reducing elements of each set of noise-reducing elements differs from the respective circumferential dimension L.sub.x of the noise-reducing elements of the other N−1 sets of noise-reducing elements, and the plurality N of sets comprises no more than four sets, wherein for each set of noise-reducing elements, the respective sequence of noise-reducing elements comprises a respective number n.sub.x of noise-reducing elements, with x ranging from 1 to N, the n-tuple of the respective numbers n.sub.x being a function of the respective value of the inner circumferential extension, and wherein for at least one sequence of noise-reducing elements, at least two respective numbers n.sub.x differ from zero.

16. The set according to claim 15, wherein the plurality N of sets of noise-reducing elements comprises no more than three sets.

17. The set according to claim 15, wherein the plurality of N sets of noise-reducing elements consists of two sets.

18. The set according to claim 15, wherein a mean interval is a mean distance between the noise-reducing elements of the sequence circumferentially applied, the mean interval being less than or equal to a given maximum threshold value equal to 20 mm.

19. The set according to claim 15, wherein a mean interval is a mean distance between the noise-reducing elements of the sequence circumferentially applied, the mean interval being greater than or equal to a given minimum threshold value differing from zero.

20. The set according to claim 15, wherein the respective dimension L.sub.x of all the noise-reducing elements is greater than or equal to 100 mm.

21. The set according to claim 20, wherein the respective dimension L.sub.x of all the noise-reducing elements is less than or equal to 300 mm.

22. The set according to claim 15, wherein, sorting the sets of noise-reducing elements in ascending order of the respective dimension L.sub.x, a difference between the respective dimension L.sub.x of the noise-reducing elements of each set and the respective dimension L.sub.x of the noise-reducing elements of at least one of a respective preceding and subsequent set is greater than or equal to 10 mm.

23. The set according to claim 22, wherein, sorting the sets of noise-reducing elements in ascending order of the respective dimension L.sub.x, a difference between the respective dimension L.sub.x of the noise-reducing elements of each set and the respective dimension L.sub.x of the noise-reducing elements of at least one of a respective preceding and subsequent set is less than or equal to 80 mm.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The description will be set out below with reference to the accompanying figures, provided for indicative purposes only and, therefore, not for limiting purposes, in which:

(2) FIG. 1 shows in a purely schematic way and for descriptive purposes only, a section, not to scale, along the middle plane of a tyre produced with the process of the present invention;

(3) FIG. 1a shows a possible deformation profile of a noise-reducing element when applied to the inner surface of a tyre;

(4) FIG. 2 schematically shows a flow chart of the process of the present invention;

(5) FIGS. 3a, 3b; 5; 6; 7a and 7b show graphically the numerical results for some embodiments of the present invention;

(6) FIGS. 4a, 4b, 8a and 8b show graphically the numerical results of some comparative examples.

DETAILED DESCRIPTION OF SOME EMBODIMENTS OF THE INVENTION

(7) With reference to FIG. 1, the tyre 1 has a rotation axis 10 and an inner circumferential extension of the internal surface 3 on the middle plane.

(8) A sequence of noise-reducing elements 2 having two different dimensions (circumferential lengths) L.sub.1, L.sub.2 is applied circumferentially on the inner surface portion 3 of the tyre, preferably placed at the tread band 4.

(9) FIG. 1a shows a possible deformation profile of a noise-reducing element 2, which is exemplarily in the form of a straight parallelepiped in its undeformed configuration (although other shapes, such as prisms, non-straight parallelepipeds, etc. are contemplated).

(10) Each noise-reducing element, when undeformed (continuous line), has a dimension L, a further dimension (perpendicular to the plane of FIG. 1a) and a thickness T.

(11) When applied to the tyre (dashed line), the element 2 is subjected to a deformation to adapt its shape to the curved inner surface of the tyre. The nature and the extent of the deformation depends on one or more of some factors, such as the material and the shape of the undeformed element 2, the curvature profile of the tyre and the deformation modality of the element.

(12) It is noted that due to the aforesaid deformation, it may happen that the distance between two adjacent elements varies along the direction of the thickness of the elements (i.e. along the radial direction). For example, the side faces of the elements 2 applied to the tyre can converge towards each other approaching the axis 10 (as shown in FIG. 1), so that the distance between two adjacent elements taken at the radially internal faces 5 is less than the respective distance taken on the liner 3.

(13) In the present description, any reference to the sizes and thickness of an element 2 will be understood with respect to the undeformed element. This approach is particularly practical and simple. However, it is also possible, without departing from the present invention, to refer to the deformed element. For example, it is possible to take the aforesaid dimension of an element such as the circumferential length L′ of its face in contact with the inner surface 3 of the tyre, or its circumferential length L″ at any height along the thickness, for example at half-height (as shown in the figure) or on the radially inner face 5. Each of the lengths L, L′, L″ can be associated with the aforementioned dimension L.sub.x.

(14) Similarly, in the following it will be used the inner circumferential extension C as measured on the inner surface 3 (typically the inner surface of the liner) on the middle plane. However, it is possible, without departing from the present invention, to use other linear circumferential extensions depending on the aforesaid inner circumferential extensions C. For example, with reference to FIG. 1, it is possible to use the circumference of the rim which envelopes the radially internal surfaces 5 of the elements 2.

(15) FIG. 2 shows a flowchart of the process 100 for producing tyres 1 for wheels of vehicles according to the present invention.

(16) It is provided the operation 20 of arranging a plurality N, wherein N is a number which goes from two to four, of sets of noise-reducing elements, wherein all the noise-reducing elements belonging to each set have substantially equal dimension L.sub.x (with x ranging from 1 to N), and wherein the dimension L.sub.x of the noise-reducing elements of each set differs from the dimension L.sub.x of the noise-reducing elements of the other sets.

(17) It is provided the operation 30 of feeding in succession a set of tyres for wheels of vehicles, typically to a noise-reducing elements application station, each tyre having a respective inner circumferential extension C, wherein the set of tyres has different values of the inner circumferential extension, for example, the set includes tyres different in model and/or sizes.

(18) Typically, said feeding occurs randomly as regards models and/or sizes of tyres fed, and consequently as regards the value of the inner circumferential extension. Typically, the number of different models and/or sizes can reach several tens in an industrial tyre production.

(19) Preferably, for each tyre, the respective value of the inner circumferential extension C is determined, for example by identifying the size and/or the model of the tyre contained in a tyre identifier, such as a barcode or a QR code.

(20) It is provided the operation 40 of determining, for each set of noise-reducing elements, a respective number n.sub.x of noise-reducing elements, with x ranging from 1 to N, as a function of said value of the inner circumferential extension C. This determination is made for each of the values of the inner circumferential extension of the different tyres to which the noise-reducing elements have to be applied. For at least one of said inner circumferential extension values, at least two respective numbers n.sub.x are different from zero. Typically, operation 40 is performed off-line. In particular, the N-tuples of numbers n.sub.x can be predetermined for each inner circumferential extension value and loaded into the treatment recipe of the tyres arriving at the noise-reducing elements application station. Once the inner circumferential extension of the tyre arriving at the station has been identified, the relative N-tuple of numbers n.sub.x is selected.

(21) It is provided the operation 50 of, for each tyre of said set of tyres, collecting from each set of noise-reducing elements the respective number n.sub.x of noise-reducing elements and applying the collected noise-reducing elements in a circumferential sequence along the inner surface of said each tyre, with the dimension L.sub.x oriented circumferentially. The order of application along the sequence can be any. Preferably the noise-reducing elements are applied circumferentially equidistant from each other. In an embodiment the noise-reducing elements of different sizes are intercalated in the most possible homogeneous way (for example as shown in FIG. 1).

(22) In the tyre exemplarily shown in FIG. 1, the sequence of noise-reducing elements consists of eleven elements belonging to two sets homogeneous in circumferential dimension (i.e. N=2), where five noise reducing elements 6 have dimension L1 greater than the dimension L2 of the remaining four noise reducing elements 7.

(23) In the following, there will be described some exemplifying embodiments, with different values of N and L.sub.x and with different N-tuples selection methods for a set of tyres of different models and/or sizes, having different values of inner circumferential extension, according to what described above.

(24) For all the examples and embodiments, the thickness of the elements is equal to 30 mm.

(25) In all the graphs shown in the figures, the horizontal axis represents the inner circumferential extension C in mm and the considered values of inner circumferential extension C range from 1760 to 2600 mm.

First Embodiment

(26) N=2

(27) L.sub.1=220 mm

(28) L.sub.2=176 mm

(29) For each value of the inner circumferential extension C, for all the pairs of numbers n.sub.1 and n.sub.2, for example with n.sub.1 and n.sub.2 each going from zero to fifteen, the relative free arc A is calculated using the aforesaid formula:

(30) ${.Math.}_{x = 1}^{N} n_{x} * L_{x} + Δ * {.Math.}_{x = 1}^{N} n_{x} = C$
and the minimum value of free arc A is identified, namely the minimum of the term A=Δ*Σ.sub.x=1.sup.N n.sub.x.

(31) In the case where the minimum value corresponds to several pairs of numbers n.sub.1 and n.sub.2, it is selected the pair having the minimum of the sum n.sub.1+n.sub.2 of the two numbers.

(32) FIGS. 3a and 3b show the graphs of the numerical values calculated in this way. FIG. 3a shows, as a function of the extension C, the trend of the free arc A in mm, continuous line and left axis, and the trend of the mean interval Δ in mm, dashed line and right axis. The mean value and the standard deviation of the mean interval Δ over the whole considered range of values of the extension C are equal to 2.1 mm and 1.3 mm respectively.

(33) FIG. 3b shows, as a function of the extension C, the corresponding total number of elements (n.sub.1+n.sub.2, solid line), the number n.sub.1 of elements with dimension L.sub.1, dashed line, and the number n.sub.2 of elements with dimension L.sub.2, dashed line.

(34) As it can be seen, in this example the inner circumferential extension has been covered with a total number of elements that does not exceed twelve elements, as the extension C varies over a wide range and with a mean interval that always remains about between 0 and 5 mm.

(35) It is observed that for C=1900 mm, the free arc assumes its minimum value (among all the possible pairs of numbers n.sub.1 and n.sub.2), equal to 8 mm, in correspondence with two pairs of numbers: n.sub.1=7 and n.sub.2=2 (mean interval=8/9=0.9 mm); n.sub.1=3 and n.sub.2=7 (mean interval=0.8 mm). In this case it may be advantageous to select the first pair consisting of one element less than the second pair (nine against ten elements).

(36) Similarly, for C=2400 mm, the free arc assumes its minimum value, equal to 24 mm, in correspondence with three pairs of numbers: n.sub.1=10 and n.sub.2=1; n.sub.1=6 and n.sub.2=6; n.sub.1=2 and n.sub.2=11. In this case it may be advantageous to select the first pair consisting of only eleven elements.

(37) It is also noted that for some values of C (for example C=2000 mm) the optimal solution provides elements having a single length L.sub.1 or L.sub.2 (that is, belonging to a single set).

Comparative Examples

(38) FIGS. 4a and 4b show the results calculated for two comparative examples, respectively, in which it is used only one set of elements (N=1) having dimension L=130 mm and L=200 mm respectively, searching for the minimum value of the free arc. In particular, each of the FIGS. 4a and 4b shows, on the same vertical axis on the left, as a function of the extension C (variable in the same range of values of the previous example), the trend of the mean interval Δ in mm (dashed line) and trend of the number of elements n (continuous line).

(39) In the example of FIG. 4a, the mean value and the standard deviation of the mean interval Δ, over the range of values of the extension C, are respectively equal to 4.2 mm and 2.5 mm.

(40) In the example of FIG. 4b, the mean value and the standard deviation of the mean interval Δ, over the range of values of the extension C, are respectively equal to 4.2 mm and 2.5 mm.

(41) As can be seen, in the example of FIG. 4a the number of elements is considerably greater than the present invention (for example with respect to the example of FIG. 3b), in addition to a mean interval Δ which in any case assumes higher peak values and/or has a larger excursion.

(42) In the example of FIG. 4b, against a number of elements comparable with that of the present invention (for example with respect to the example of FIG. 3b), the mean interval Δ however assumes much higher peak values and has an excursion greater than that of the example of FIG. 3b.

(43) Therefore, the use of only one type of elements does not allow, among other things, an effective control of the mean interval and/or a limitation of the total number of elements composing the sequence.

Second Embodiment

(44) N=3

(45) L.sub.1=220 mm

(46) L.sub.2=199 mm

(47) L.sub.3=174 mm

(48) The minimum of the free arc A is identified as in the aforesaid first embodiment. FIG. 5 shows, as a function of the extension C, the total number of elements (n.sub.1+n.sub.2+n.sub.3), solid line and left axis, and the mean interval Δ in mm, dashed line and right axis. The mean value and the standard deviation of the mean interval over the range of values of the extension C are 0.11 mm and 0.13 mm, respectively.

(49) For example, for C=1900 mm, the free arc assumes its minimum value, equal to 4.0 mm, in correspondence with the optimal triad of numbers: n.sub.1=5, n.sub.2=4 and n.sub.3=0 for a total of nine elements (mean interval=4/9=0.44 mm); while for C=2400 mm, the free arc assumes its minimum value, equal to 0.0 mm, in correspondence with the optimal triad of numbers: n.sub.1=3, n.sub.2=0 and n.sub.3=10 for a total of thirteen elements (mean interval=0.0 mm).

Third Embodiment

(50) N=4

(51) L.sub.1=220 mm

(52) L.sub.2=203 mm

(53) L.sub.3=188 mm

(54) L.sub.4=175 mm

(55) The minimum of the free arc is identified similarly to the aforesaid first embodiment. FIG. 6 shows, as a function of the extension C, the trend of the total number of elements (n.sub.1+n.sub.2+n.sub.3+n.sub.4), solid line and left axis, and the trend of the mean interval Δ in mm, dashed line and right axis. The mean value and the standard deviation of the mean interval, over the range of values of the extension C, are 0.01 mm and 0.04 mm, respectively.

(56) For example, for C=1900 mm, the free arc assumes its minimum value, equal to 0.0 mm, in correspondence with the optimal quadruplet of numbers: n.sub.1=1, n.sub.2=2, n.sub.3=3 and n.sub.4=4 for a total of ten elements (mean interval=0.0 mm) while for C=2400 mm, the free arc assumes its minimum value, equal to 0.0 mm, in correspondence with the optimal quadruplet of numbers: n.sub.1=4, n.sub.2=1, n.sub.3=4 and n.sub.4=3 for a total of twelve elements (mean interval=0.0 mm).

(57) As it can be seen, as the number N of sets of noise-reducing elements increases, the excursion of the mean interval drastically decreases (in other words, a greater control of the mean interval and/or of the free arc is possible), against a greater complexity in the management of a greater number N of sets of elements.

Fourth Embodiment

(58) N=2

(59) L.sub.1=220 mm

(60) L.sub.2=176 mm

(61) In this example, a minimum and a maximum threshold value of the mean interval are set, for example, equal to 3 mm and 8 mm, respectively.

(62) For each value of the inner circumferential extension C in the aforesaid interval, for all the pairs of numbers n.sub.1 and n.sub.2, for example with n.sub.1 and n.sub.2 each one going from zero to fifteen, the respective mean interval Δ is calculated by means of the aforesaid formula

(63) ${.Math.}_{x = 1}^{N} n_{x} * L_{x} + Δ * {.Math.}_{x = 1}^{N} n_{x} = C$
and there are identified all the pairs for which the mean interval Δ satisfies the predetermined minimum and maximum values. Among all the pairs of numbers thus identified for each value C, it is (possibly) selected the pair of numbers n.sub.1 and n.sub.2 having the minimum of the sum n.sub.1+n.sub.2 of the two numbers. FIGS. 7a and 7b show two graphs of the numerical values thus calculated. FIG. 7a shows, as a function of the extension C, the trend of the free arc A in mm, solid line and left axis, and the trend of the mean interval Δ in mm, dashed line and right axis. In the figure there are also shown the predetermined lower and upper limits of the mean interval Δ. FIG. 7b shows, as a function of the extension C, the total number of elements (n.sub.1+n.sub.2, solid line), the number n.sub.1 of elements with dimension L.sub.1, dashed line, and the number n.sub.2 of elements with dimension L.sub.2, point-like dashed line.

(64) It is observed that the present solution guarantees, among other things, a remarkable uniformity of characteristics for the whole range of values C considered, in terms of mean interval, against a limited total number of elements (in the example from eight to twelve elements), comparable with the solution of FIGS. 3a and 3b.

Comparative Example

(65) FIGS. 8a and 8b show the results calculated for a comparative example in which it is used only one set of elements (N=1) having dimension L=130 mm, looking for, as a function of the inner circumferential extension C in the aforesaid interval, the solutions for which the mean interval Δ satisfies the minimum and the maximum values predetermined to 3 mm and 8 mm, respectively. In particular, FIG. 8a shows, as a function of the extension C in mm, the trend of the free arc A in mm, broken solid line and left axis, and the trend of the mean interval Δ in mm, broken dashed line and right axis. In the figure there are also shown the predetermined lower and upper limits of the mean interval Δ. FIG. 8b shows the number n of elements as a function of the extension C. In FIGS. 8a and 8b all the lines of the trends are interrupted at the regions of values of the extension C in which there are no solutions that satisfy the conditions imposed on the mean interval Δ. In other words, in these regions it is not possible to make a sequence, with the available noise-reducing elements, that leaves a mean interval Δ between 3 and 8 mm.

(66) Therefore, in the comparative example of FIGS. 8a and 8b, not only the number of elements (which varies between thirteen and nineteen elements) and the variation of the free arc (up to 144 mm) are considerably greater than the respective ones of the present invention (for example with respect to the example of FIGS. 7a and 7b), but also, for some values of the extension C, it is not possible to find the desired solution.

Process for producing tyres capable of reducing cavity noise and set of tyres obtained thereby

Assignee

Inventors

Cpc classification

Classification Explorer

B60C19/002

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

B29D30/0016

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

B29D30/0061

PERFORMING OPERATIONS; TRANSPORTING

International classification

Classification Explorer

B60C19/00

PERFORMING OPERATIONS; TRANSPORTING

Classification Explorer

B29D30/00

PERFORMING OPERATIONS; TRANSPORTING

Abstract

Claims

Description