Elastomeric tire having magnetized sidewall and method of manufacturing same

Abstract: The present invention provides a tire with a sidewall having a magnetized outer layer. The sidewall outer layer is peripherally divided into sections with radially extending ribs between each adjacent pair of sections. The ribs protrude above the sections. In the peripheral direction, the ribs are significantly narrower than the sections. The sections are magnetized in a peripheral direction, but with alternating polarity. The ribs close the circles of magnetic flux by allowing lines of magnetic flux to enter and exit the sidewall outer layer after moving through the surrounding air and the magnetized sections, respectively. The ribs focus the location of the entry and exit of the lines of magnetic flux into and out of the sidewall outer layer. This focused entry and exit is achieved by the accumulation of magnetized material in the ribs which causes the lines of magnetic flux moving through the ribs to point in a direction perpendicular to the plane of the tire sidewall. As a result of this focused entry and exit, sharp edges between the areas of opposite polarization are achieved which enables the precise measurement of the peripheral locations of the lines of magnetic flux. By enabling such a precise measurement, the present invention provides for a more accurate determination of information relating to the dynamic behavior of the tire.

Description: The present invention relates generally to an elastomeric tire and a method of manufacturing the same and, more particularly, to a tire with a sidewall having a magnetized outer layer, the sidewall outer layer being peripherally divided into sections of alternating polarity with radially extending ribs between each adjacent pair of sections, and a method of manufacturing the same. Published European Patent Application 849 597 describes a tire comprising at least one magnetized area which can be used for instance for providing information about the rotary speed of the tire when mounted an a vehicle and to measure other physical quantities. The subject of this published patent application is a tire that, at least at one predetermined location, contains a rubber mixture that is permeated with magnetizable particles. These magnetizable locations, in general an annular band in the, sidewall of the tire, have successive sections of alternating magnetization, either equidistant or in a pattern. Thus, with the aid of a sensor that is secured to the chassis, not only the rotational speed of the respective wheel can be provided, but also, by measuring the tire distortion through deflection of the applied magnetized sections, forces acting on the tires can be determined. This known tire is manufactured by mixing ferromagnetic particles into the rubber mixture which is applied to the area where the magnetization is carried out. The magnetization is then achieved by applying magnetic fields with lines of flux that extend in the peripheral direction of the tire in alternating polarizations. This magnetization is effected after installation of the magnetizable rubber mixture and after vulcanization thereof. There is also described an apparatus to carry out the magnetization. Unfortunately on the tire described, the desired magnetization is very hard to achieve. Depending on the method applied, either there is no identifiable signal at all, or the magnetized areas or sections of opposite polarizations are separated by wide lines bluring and distorting the signals detected by a respective sensor. Thus the measurements obtained are imprecise. It is an object of this invention to enhance the precision and liability of the measurements of the dynamic behavior of the tire and especially the measurements of the longitudinal and lateral forces acting on the tire. For this purpose it is desired that the lines separating different magnetized sections are narrow. This object is achieved and the problem is resolved by a tire according to claim 1 and by a method of manufacturing the same according to claim 8. Starting at a tire with a sidewall having a magnetized outer layer, this sidewall outer layer being peripherally divided into sections, the present invention is characterized by arranging radially extending ribs between each adjacent pair of sections. These ribs protrude above the sections and are, in the peripheral direction, significantly narrower than the sections. The sections are magnetized in a peripheral direction, but with alternating polarity. The ribs close the circles of magnetic flux by allowing lines of magnetic flux to enter and exit the sidewall outer layer after moving through the surrounding air and the magnetized sections, respectively. The ribs focus the location of the entry and exit of the lines of magnetic flux into and out of the sidewall outer layer. This focused entry and exit is achieved by the accumulation of magnetized material in the ribs which causes the lines of magnetic flux moving through the ribs to point in a direction perpendicular to the plane of the tire sidewall. As a result of this focused entry and exit, sharp edges between the areas of opposite polarization are achieved which enables the precise measurement of the peripheral locations of the lines of magnetic flux. By enabling such a precise measurement, the present invention provides a more, accurate determination of information relating to the dynamic behavior of the tire. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 shows a side view of a tire constructed according to the principles of the present invention in which an outer layer of a sidewall of the tire is peripherally divided into sections of alternating polarity with radially extending ribs between each adjacent pair of sections; Fig. 2 shows a cross-sectional view of the sidewall outer layer shown in Figure 1 taken along arcuate line 2-2; Fig. 3 shows an alternate embodiment for the arrangement of radially extending ribs an a sidewall outer layer; and Fig. 4 shows another embodiment for the arrangement of radially extending ribs an a sidewall outer layer. DETAILED DESCRIPTION OF THE INVENTION In Figure 1, a tire 1 is depicted with a sidewall 2 having a magnetized outer layer 3. Throughout the following description, the term "peripheral" is used for the direction along a rotary movement of the tire sidewall, while "radial" is used for directions perpendicularly crossing an imaginary rotary axis of the tire, i.e., from hub to tread. The sidewall outer layer 3 is peripherally divided into sections 4 and 5 with radially extending protrusions or ribs 6 between each adjacent pair of sections 4 and 5. The ribs 6 protrude above the sections 4 and 5 (see Figure 2). In the embodiment of the invention shown in Figures 1 and 2, the ribs 6 are equidistant from one another in the peripheral direction. However, depending on the purpose to be served, the peripheral distance between the ribs 6 could vary. By varying the peripheral distance between the ribs 6, a unique pattern can be established. In the peripheral direction, the ribs 6 are significantly narrower than the sections 4 and 5. Generally, the sidewall outer layer 3 includes as many ribs as feasible to enable the precise measurement of the lines of magnetic flux, even at low speeds. For a standard passenger tire, the sidewall outer layer 3 includes approximately 96 ribs where the height x of the ribs 6 is less than or equal to 1/16 of an inch (1 inch = 2,54 cm), the width y of the ribs 6 is less than or equal to 1/16 of an inch (1 inch = 2,54 cm), and and the width z of the sections 4 and 5 is approximately 2 inches (1 inch = 2,54 cm). For a larger truck tire, however, the sidewall outer layer could include 200 or more ribs. In the embodiment of the invention shown in Figure 2, the ribs 6 have a generally semicircular shape in cross-section. However, the ribs 6 could have other shapes, e.g., triangular, square. Figure 2 shows the lines of magnetic flux in the sidewall outer layer 3, including the sections 4 and 5 and the ribs 6. Generally, the sections 4 are magnetized in a clockwise Orientation with respect to the tire as shown by lines of magnetic flux 7 and the sections 5 are magnetized in a counterclockwise orientation as shown by lines of magnetic flux 8. Thus, the magnetization of the sections 4 and 5 is always applied in a peripheral direction, but with alternating polarity. Outside of the sidewall outer layer 3 in the surrounding air, lines of magnetic flux 9 correspond to lines 7 and lines of magnetic flux 10 correspond to lines 8. The ribs 6 close the circles of magnetic flux by allowing lines of magnetic flux 11 to enter the sidewall outer layer 3 after moving through the surrounding air and lines of magnetic flux 12 to exit the sidewall outer layer 3 after moving through either magnetized section 4 or 5. Thus, one circle of magnetic flux is formed by the lines of magnetic flux 7, 12, 9, 11, in this order. A circle of magnetic flux in the opposite direction is formed by the lines of magnetic flux 8, 12, 10, 11. As can be seen from Figure 2,the present invention utilizes the principle of a horseshoe magnet in the magnetized sidewall outer layer 3. The ribs 6 form alternating North and South poles N and S, where each of the poles is shared by two adjacent imaginary horseshoe magnets. The sidewall outer layer 3, including the sections 4 and 5 and the ribs 6, can be magnetized using any known method of magnetization. Such methods are well-known in the art and will not be discussed herein. As can be seen from Figures 1 and 2, the ribs 6 focus the location of the entry and exit of the lines of magnetic flux into and out of the sidewall outer layer 3. This focused entry and exit is achieved by the accumulation of magnetized material in the ribs 6 which causes the lines of magnetic flux 11 and 12 to point in a direction perpendicular to the plane of the tire sidewall z. As a result of this focused entry and exit, sharp edges between the areas of opposite polarization are achieved which enables the precise measurement of the peripheral locations of the lines of magnetic flux. By enabling such a precise measurement, the.present invention provides a more accurate determination of information relating to the dynarnic behavior of the tire (as will be discussed in greater detail below). The ribs 6 separating the sectiöns 4 and 5 of opposite polarization of magnetization do not have to radially extend over the entire sidewall outer layer 3. Figure 3 shows an alternate embodiment of the invention where ribs 16 only extend over the radially outer half of sidewall outer layer 13. Similarly, Figure 4 shows another alternate embodiment where ribs 26 only extend over the radially central area of sidewall outer layer 23. Generally, however, the ribs preferably extend over at least part of the radially outer area of the sidewall outer layer. The ribs 16 and 26 in Figures 3 and 4 serve the same purpose as the ribs 6 in Figures 1 and 2. Typically, the present invention is applied to a pneumatic vehicle tire and the magnetization is carried out from the outside of the inner sidewall of the tire. For a suitable rubber mixture, European Patent Application 849 597 discloses a mixture that contains particles of neodymium iron boride or of another ferromagnetic substance. Tests have shown that iron Oxide, Fe 2 O 3 , and strontium ferrite, SrFe, are also suitable for this purpose. The ferromagnetic substance will be mixed into the soft rubber in powder form. Due to the fact that the applied magnetization is reduced at the vulcanization temperature, the magnetization is applied after vulcanization. The sidewall 2, including the sidewall outer layer 3, is extruded from the rubber mixture. The tire 1, including the sidewall 2 and all other components of the tire, will be put into its final form using a tire mold, as is well-known in the art. Only afterwards, the peripherally alternating magnetic fields are applied to the sidewall outer layer 3 which results in the magnetization shown in Figures 1 and 2. A tire constructed according to the principles of the present invention can be used to generate signals which can be detected by sensors and used to identify the tire or to determine information relating to the dynamic behavior of the tire. Some of the information which can be determined using the present invention include the rotational speed of the tire, the angular position of the tire, the lateral or cornering forces on the tire, the radial forces on the tire, and the longitudinal forces on the tire (e.g., sidewall torsion, torques, and fore-aft forces). For example, in order to determine the sidewall torsion, a tone wheel can be attached to a vehicle chassis and used to compare the location of the radially inner and outer portions of the ribs. The results of such a comparison are used to determine the sidewall torsion of the tire. The determination of accurate information relating to the dynamic 7 behavior of the tire depends an the precise measurement of the lines of magnetic flux. By enabling such a precise measurement, the present invention provides for a more accurate determination of the information.

Claims: Elastomeric vehicle tire with sidewalls, at least one of said sidewalls including at least one magnetized annular band said magnetized annular band being subdivided in a number of sections, said sections being magnetized differently each of said magnetized sections being seperated from each adjacent magnetized section by a separating line, the tire being characterized by said sidewall with said magnetized annular band comprising protrusions and said protrusions being situated at said separating lines with the effect of focussing the entering and exiting lines of magnetic flux at said protrusions. A tire according to claim 1, wherein said protrusions of the sidewall consist of accumulations of magnetizable material. A tire according to claim 1, wherein the protrusions form one piece with the respective magnetized annular band. A tire according to claim 1, wherein the protrusions are aligned in the radial direction. A tire according to claim 4, wherein the lines of magnetic flux inside all the magnetized sections are essentially aligned in the peripheral direction whereby the lines of magnetic flux change their orientation alternating from section to section. A tire according to claim 4, wherein said protrusions are equidistant from one another. A tire according to claim 4, wherein the protrusions are significantly narrower than the sections are in the peripheral direction. A method of manufacturing an elastomeric tire with at least one magnetized annular band, the method comprising the steps of: applying a layer of magnetizable material on said tire sidewall, forming a plurality of protrusions on said layer of magnetizable material and vulcanizing the tire magnetizing said magnetizable layer in a pattern of differently magnetized sections, said magnetized sections being seperated from each other by separating lines wherein said protrusions are situated at said separating lines between adjacent magnetized sections. A method according to claim 7, including the step of producing the magnetizable material by adding ferromagnetic particles to an elastomeric material. A method according to claim 8, wherein the ferromagnetic particles comprise strontium ferrite.

Inventors: CETIN A YUECEL, GIUSTINO JAMES M, CETIN, A. YUECEL, GIUSTINO, JAMES M.
Applicants: CONTINENTAL AG, CONTINENTAL AKTIENGESELLSCHAFT
Application year: 2000
Main classification: G01P3
IPC codes: B60C13, G01P3