Tire comprising sensor unit

Abstract

To provide a tire comprising a sensor unit that can determine a deflection of the tire with high accuracy.SOLUTION: A sensor unit (10) includes a flexible sheet (16), one permanent magnet (12) formed on the flexible sheet and at least two magnetic sensor elements (14a and 14b), where at least one magnet sensor element is arranged on each of a region at one side and a region at the other side respectively of a sheet surface reference line (L1) in a concave circle (C), and the permanent magnet is single-pole magnetized, and poles of the permanent magnet are oriented to the one side and the other side respectively of the sheet surface reference line, of the flexible sheet.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a tire equipped with a sensor unit that allows the deflection to be determined with high precision. [Background technology]

[0002] Conventionally, tire sensor units have been disclosed that include a substrate formed into a generally sheet-like shape from a flexibly deformable material and to be placed on a tire, and a sensor that is attached to the substrate and detects strain (deflection) of the tire (for example, Patent Document 1, Figure 2).The tire sensor unit of Patent Document 1 can be installed on a tire through the simple process of installing the substrate with the sensor on the tire, which makes it easy to install the tire sensor unit on the tire and maintains good tire productivity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-64565 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the tire sensor unit of Patent Document 1, the sensor is composed of one magnet and one magnetic sensor element. Therefore, tire deflection must be determined based on one signal output from the magnetic sensor element, and there is a risk that tire deflection cannot be determined with high accuracy, particularly when the tire exhibits complex deformation behavior, such as when stress is applied to the tire from multiple directions.

[0005] The present invention has been made in consideration of the above circumstances, and its object is to provide a tire equipped with a sensor unit that can determine the deflection of the tire with high precision even when the tire exhibits complex deformation behavior, such as when stress is applied to the tire from multiple directions. [Means for solving the problem]

[0006] The tire of the present invention is a tire having a sensor unit on a tire cavity surface that determines the deflection of the tire during bending deformation of the tire, the sensor unit includes a non-magnetic, non-stretchable flexible sheet, one permanent magnet and at least two magnetic sensor elements formed on the flexible sheet, a signal from each of the at least two magnetic sensor elements is used to calculate a deflection of the tire; determining a concave circle formed by projecting onto the tire surface a circle that is centered on the center of gravity of the permanent magnet, is included in a plane perpendicular to a straight line that includes a perpendicular line extending from the center of gravity to the tire surface, and has a radius that is the longest distance between this straight line and the magnetic sensor element; Next, when a line including the diameter of the concave circle with the largest radius of curvature is defined as a seat surface reference line, at least one magnetic sensor element is disposed in each of regions on one side and the other side of the seat surface reference line within the concave circle, The permanent magnet is unipolarly magnetized, and each pole of the permanent magnet is oriented on one side and the other side of the sheet surface reference line of the flexible sheet. [Effects of the Invention]

[0007] In the tire according to the present invention, not only are two or more magnetic sensor elements included in one sensor unit, but each pole of the unipolar permanent magnet is oriented toward one side and the other side of the sheet surface reference line of the flexible sheet, respectively. This makes it possible to efficiently compare the signal values ​​output from each magnetic sensor element over time, and to compare the differences in the signal values ​​output from multiple magnetic sensor elements over time. In addition, by combining the signal values ​​output from multiple magnetic sensor elements, it is possible to determine the deflection of the tire with high accuracy, even if the tire exhibits complex deformation behavior. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a meridian cross-sectional view of a tire according to the present embodiment. [Figure 2] FIG. 2 is a diagram showing the three-dimensional positional relationship between the permanent magnet and the magnetic sensor element when the sensor unit is placed on the tire cavity surface. [Figure 3] Figure 3 is a plan view showing the positions of magnetic sensor elements in a sensor unit, where (A) shows an example in which two magnetic sensor elements are arranged in a predetermined area, (B) shows an example in which two more magnetic sensor elements are arranged in an area other than the predetermined area in the example shown in (A), (C) shows an example in which three magnetic sensor elements are arranged in a predetermined area, and (D) shows an example in which four magnetic sensor elements are arranged in a predetermined area. [Figure 4] FIG. 4 is a diagram showing the relationship between the sheet surface reference line and the three directions of the permanent magnet. [Figure 5] FIG. 5 is a meridian cross section of a tire showing the relationship between the dimensions of the permanent magnet and the tire thickness. [Figure 6] FIG. 6 is a diagram showing the state of adhesion of the flexible sheet on the tire cavity surface. [Figure 7] FIG. 7 is a diagram showing the positional relationship between the permanent magnet and the magnetic sensor element before and after placing a flexible sheet (sensor unit) on the tire cavity surface, and shows an example in which the magnetization direction is parallel to the flexible sheet before placement. [Figure 8] FIG. 8 is a diagram showing suitable examples (A) and (B) of the position of the magnetic sensor element and an inappropriate example (C) of the position of the magnetic sensor element when the sensor unit is disposed on the surface of the tire. [Figure 9] FIG. 9 is a tire meridian cross-sectional view showing a part of the tire of this embodiment. [Figure 10] FIG. 10 is a diagram showing a circle passing through the centers of gravity of the permanent magnet and the two magnetic sensor elements that constitute the sensor unit. [Figure 11] Figure 11 is a meridian cross section of a tire showing the position of a reference line on the tire cavity surface, and (A) shows an example in which not only the reference line but also the magnetic sensor element on the inner side in the tire width direction is located within a predetermined range on the tire cavity surface, while (B) shows an example in which the magnetic sensor element on the inner side in the tire width direction is not located within the predetermined range on the tire cavity surface. [Figure 12] FIG. 12 is a meridian cross section of a tire showing the position of a reference line on the tire cavity surface and the position of an end of a flexible sheet on the tread surface and closer to a point on the tire equatorial plane. [Figure 13] Figure 13 is a diagram showing the positional relationship between a permanent magnet, a magnetic sensor element, and a belt, where (A) shows the positional relationship between the magnetic sensor element and the belt, and (B) shows the positional relationship between the permanent magnet and the magnetic sensor element. [Figure 14] Figure 14 is a meridian cross section of a tire showing suitable positions for placing a circuit board connected to a sensor unit, where (A) shows an example in which the circuit board is placed closer to the center of the tread than an area where it is undesirable to place it, and (B) shows an example in which the circuit board is placed closer to the bead than an area where it is undesirable to place it. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the tire according to the present invention (Basic Embodiment 1 and Additional Embodiments 2 to 15 shown below) will be described in detail with reference to the drawings. Note that these embodiments do not limit the present invention. Furthermore, the components of each embodiment include those that are easily replaceable by a person skilled in the art, or those that are substantially identical. Furthermore, each embodiment can be arbitrarily combined within the scope of what is obvious to a person skilled in the art.

[0010] In the following description, the tire radial direction refers to the direction perpendicular to the tire rotational axis, the tire radial inner side refers to the side toward the tire rotational axis in the tire radial direction, and the tire radial outer side refers to the side away from the tire rotational axis in the tire radial direction. The tire circumferential direction refers to the direction around the tire rotational axis as the central axis. Furthermore, the tire width direction refers to the direction parallel to the tire rotational axis, the tire width inner side refers to the side toward the tire equatorial plane (tire equator line) in the tire width direction, and the tire width outer side refers to the side away from the tire equatorial plane in the tire width direction. The tire equatorial plane refers to the plane that is perpendicular to the tire rotational axis and passes through the center of the tire width.

[0011] Similarly, in the following description, a regular rim refers to an "applicable rim" as defined by JATMA, a "design rim" as defined by TRA, or a "measuring rim" as defined by ETRTO.

[0012] Similarly, in the following explanation, "normal internal pressure" refers to the "maximum air pressure" specified by JATMA, the maximum value specified in "Tire Load Limits at Various Cold Inflation Pressures" specified by TRA, or the "Inflation Pressures" specified by ETRTO. Also, "normal load" refers to the "maximum load capacity" specified by JATMA, the maximum value specified in "Tire Load Limits at Various Cold Inflation Pressures" specified by TRA, or the "Load Capacity" specified by ETRTO.

[0013] Although not shown in detail, the tire described below has, in a tire meridian cross section, a bead portion, a sidewall portion, a shoulder portion, and a tread portion from the inner side to the outer side in the tire radial direction, and similar to a normal tire, has, for example, a carcass extending from the tread portion to the bead portions on both sides and wound around a pair of bead cores, and a belt and a belt reinforcing layer formed sequentially on the outer side in the tire radial direction of the carcass.

[0014] The tire of this embodiment is obtained through the usual manufacturing steps, namely, a tire material mixing step, a tire material processing step, a green tire molding step, a vulcanization step, and a post-vulcanization inspection step.

[0015] [Basic form 1] FIG. 1 is a meridian cross-sectional view of a tire according to this embodiment. The tire 20 shown in FIG. 1 is mounted on a standard rim R and is in a normal internal pressure state (non-contact state) with no load. The tire 20 shown in FIG. 1 includes a sensor unit 10 on the tire cavity surface that determines the tire's deflection during bending deformation. The sensor unit 10 is a unit that includes one permanent magnet 12, at least two magnetic sensor elements 14 (two magnetic sensor elements 14a and 14b in the figure), and a flexible sheet 16 disposed on the tire cavity surface. The two magnetic sensor elements 14a and 14b detect changes in magnetic flux density before and after bending deformation of the tire 20. Based on this change in magnetic flux density, signals output from the magnetic sensor elements 14a and 14b are calculated by a calculation circuit, for example, via an amplifier circuit (not shown), to determine the tire's deflection. The magnetic sensor element 14 may be a Hall element, a magnetoresistive element, or the like.

[0016] When a tire 20 equipped with the sensor unit 10 shown in FIG. 1 undergoes bending deformation, the deformation behavior of the tire 20 is determined, for example, by performing appropriate arithmetic processing using the values ​​of the signals output from each of the magnetic sensor elements 14a and 14b.

[0017] FIG. 2 illustrates the three-dimensional positional relationship between the permanent magnet and the magnetic sensor element when the sensor unit is placed on the tire cavity surface. As shown in the figure, a circle is projected onto the concave curved surface of the flexible sheet 16. The circle is centered at the center of gravity G of the permanent magnet 12 and is included in a plane perpendicular to a line including a perpendicular line from the center of gravity G to the tire surface. The circle has a radius equal to the longest distance between this line and the magnetic sensor element 14a (or 14b). The concave circle C is determined by projecting the circle C onto the concave curved surface. The sheet surface reference line L1 is then determined as the line including the diameter with the largest radius of curvature among the diameters of the concave circle C. In this specification, "projection" refers to the projection of a circle, line, contour, or other figure as a shadow onto the projection surface when parallel light is irradiated from the opposite side of the projection surface. The light is irradiated in a direction perpendicular to the tangent plane including the center of gravity on the projection surface (specific region). The orientation of the sheet surface reference line L1 is independent of the longitudinal direction or shape of the flexible sheet 16.

[0018] Here, when determining the longest distance from the center of gravity G of the permanent magnet 12 to the magnetic sensor element 14a (or 14b) that is farthest from the permanent magnet 12, the entire magnetic sensor element 14a (or 14b) is included within the concave circle C. In other words, this distance is the distance between the center of gravity G of the permanent magnet 12 and the point farthest from the center of gravity G on the magnetic sensor element 14a (or 14b) that is farthest from the center of gravity G.

[0019] In addition, in this embodiment, the concave curved surface (tire cavity surface) of the tire 20 on which the sensor unit 10 is arranged means the tire cavity surface when the tire 20 is not deformed, more specifically, the tire cavity surface when the tire is mounted on a regular rim and pressurized to the regular internal pressure, in an unloaded state (non-contact state).

[0020] 2, in the tire of this embodiment, at least one magnetic sensor element 14a, 14b is arranged in each of regions on one side and the other side of the sheet surface reference line L1 within the concave circle C of the flexible sheet 16. Furthermore, although not shown, the permanent magnet 12 is unipolarly magnetized, and each pole of the permanent magnet 12 is oriented toward one side and the other side of the sheet surface reference line L1 of the flexible sheet 16, respectively.

[0021] (effect, etc.) A conventional sensor unit such as that described in Patent Document 1 includes only one magnetic sensor element that detects changes in magnetic flux density when a tire deforms, and therefore can only realize a very simple mode for determining tire deformation behavior. However, in reality, the way in which stress, which is a prerequisite for tire deformation behavior, is applied to a tire can be from multiple directions, not just one direction, and in such cases, there is a risk that the conventional sensor unit will not be able to determine tire deflection with high accuracy.

[0022] Under such circumstances, the inventor has discovered that by including two or more magnetic sensor elements 14 that detect changes in magnetic flux density within the sensor unit 10, it is possible to implement a more complex determination method for determining the deformation behavior of the tire 20.

[0023] The sensor unit 10 based on the inventor's knowledge can determine the deflection of the tire 20 with high accuracy even when the tire 20 exhibits complex deformation behavior, such as when stress is applied to the tire 20 from multiple directions rather than just one direction.

[0024] The number of magnetic sensor elements 14 in the sensor unit 10 and the locations of the magnetic sensor elements 14 relative to the permanent magnet 12 can be changed as appropriate depending on the direction and magnitude of bending deformation to be determined. However, even if five or more magnetic sensor elements 14 are arranged in the sensor unit 10, the results of determining the deflection of the tire 20 do not differ significantly from when four magnetic sensor elements 14 are arranged. Therefore, taking into consideration manufacturing costs, etc., it is preferable that the number of magnetic sensor elements 14 in the sensor unit 10 be four or less.

[0025] Next, as described above, the sheet surface reference line L1 is a line that includes the diameter with the largest radius of curvature among the diameters of the concave circle C of the flexible sheet 16. Among the regions of the flexible sheet 16, the region near the sheet surface reference line L1 is the region that is least susceptible to bending deformation in the length direction of the sheet surface reference line L1 when the tire 20 is bent, but is the region that is most susceptible to bending deformation in the direction perpendicular to the sheet surface reference line L1 and where the change in the radius of curvature is greatest.

[0026] Considering that the sensor unit 10 is disposed on the concave curved surface of the tire 20 (see FIG. 1), the seat surface reference line L1 is usually assumed to be a curve, but the seat surface reference line L1 may also be a straight line.

[0027] By arranging at least one magnetic sensor element 14a, 14b in each of the areas on one side and the other side of the sheet surface reference line L1, bending deformation of the tire 20 can be detected over a wider range than when the magnetic sensor element is arranged in an area only on one side, which results in increased sensitivity in sensing bending deformation of the tire 20 and ultimately enables the deflection of the tire 20 to be determined with high accuracy.

[0028] In the example shown in Figure 2, one magnetic sensor element 14a is arranged on one side of the seat surface reference line L1 and one magnetic sensor element 14b is arranged on the other side, but this embodiment is not limited to this case, and (two, one), (two, two), ..., (m, n (m is a natural number greater than or equal to 2, n is a natural number greater than or equal to 1)) magnetic sensor elements 14 may be arranged on (one side, the other side) of the seat surface reference line L1.

[0029] Next, when the sensor unit 10 including the permanent magnet 12 and the magnetic sensor element 14 is arranged so as to follow the bending deformation of the tire 20 (for example, when the permanent magnet 12 and the magnetic sensor element 14 are embedded in the tire cavity surface, or when the permanent magnet 12 and the magnetic sensor element 14 are arranged in the tire 20 via an elastic sheet), the change in magnetic flux density detected by each magnetic sensor element 14 is affected by both the expansion / contraction deformation and the bending deformation of the deformation behavior of the sensor unit 10, that is, the detection is based on all of the deformation behavior of the actual tire 20.

[0030] In contrast, when the permanent magnet 12 and at least two magnetic sensor elements 14 (14a to 14d) are arranged on the tire 20 via a non-magnetic, non-stretchable flexible sheet 16, the change in magnetic flux density detected by each magnetic sensor element 14 is affected almost exclusively by bending deformation, which is one of the deformation behaviors of the sensor unit 10; that is, the change in magnetic flux density detected by each magnetic sensor element 14 is detected in a manner that focuses almost exclusively on bending deformation, which is one of the deformation behaviors of the actual tire 20. Therefore, according to this embodiment, bending deformation of the tire 20 can be extracted more easily, and as a result, the sensitivity of sensing bending deformation of the tire 20 can be increased, and ultimately the deflection of the tire 20 can be determined with high accuracy.

[0031] The flexible sheet 16 may be a resin film with a high elastic modulus.

[0032] The tensile modulus of flexible sheet 16 is preferably 20 times or more the tensile modulus of the placement surface material of tire 20 on which flexible sheet 16 is placed, from the viewpoint that deformation of flexible sheet 16 can be ignored compared to deformation of tire 20, and is most preferably 50 times or more. It is more preferable that the tensile modulus of flexible sheet 16 is 1 GPa or more (measured by a tensile test specified in ASTM D882).

[0033] In addition, because the permanent magnet 12 is unipolarly magnetized and each pole of the permanent magnet 12 is oriented toward one side and the other side of the sheet surface reference line L1 of the flexible sheet 16, the distance from the magnetic pole along the magnetic field lines is short, and the magnetic flux density detected by the magnetic sensor elements 14a, 14b can be increased. As a result, the sensitivity for sensing the bending deformation of the tire 20 can be further increased, and the deflection of the tire 20 can be determined with high accuracy.

[0034] [Additional Form 2] 3A and 3B are plan views showing the positions of magnetic sensor elements in a sensor unit, with (A) showing an example in which two magnetic sensor elements are arranged in a predetermined area, (B) showing an example in which two magnetic sensor elements are arranged in an area other than the predetermined area in the example shown in (A), (C) showing an example in which three magnetic sensor elements are arranged in a predetermined area, and (D) showing an example in which four magnetic sensor elements are arranged in a predetermined area. Note that while the north and south poles of permanent magnet 12 are tentatively depicted in FIG. 3, a type in which these poles are reversed is also included in the scope of this embodiment. The same applies to the other drawings.

[0035] In the basic form 1, as shown in FIG. 3, in a plan view of the sensor unit 10, it is preferable that the magnetic sensor element 14 is formed in a region (predetermined region) at 45° on both sides of a line L that passes through the midpoint of the permanent magnet 12 in the direction of the sheet surface reference line L1 and extends in the magnetization direction Dm on either side of the sheet surface reference line L1 (additional form 2).

[0036] Such a predetermined region has a higher magnetic flux density than other regions, and by placing the magnetic sensor elements 14 (14a to 14d) in that region, the sensitivity in sensing the bending deformation of the tire 20 can be further increased, and ultimately the deflection of the tire 20 can be determined with even higher accuracy.

[0037] In FIG. 3, it is more preferable that the magnetic sensor element 14 is formed in an area of ​​40 degrees on either side of the sheet surface reference line L1, and it is extremely preferable that it is formed in an area of ​​35 degrees on both sides of a line L that passes through the midpoint of the permanent magnet 12 in the direction of the sheet surface reference line L1 and extends in the magnetization direction Dm.

[0038] In Fig. 3, the magnetization direction Dm preferably forms an angle of 80° to 100° with respect to the sheet surface reference line L1 (in other words, an angle of 10° or less on either side of the line L). When the shape of the tire cavity surface and the bending deformation behavior of the tire are taken into consideration, the flexible sheet 16 is usually arranged in the tire 20 so that the sheet surface reference line L1 shown in Fig. 3 is aligned along the tire circumferential direction and so that the vertical direction shown in the same figure is aligned roughly along the tire radial direction. In such a case, by setting the magnetization direction Dm to a direction extending at an angle of 80° to 100° with respect to the sheet surface reference line L1, the above-mentioned predetermined area can be secured relatively widely, and the selection area for the positions of the magnetic sensor elements 14a, 14b can be further expanded.

[0039] The reason why the magnetization direction Dm is set to form an angle of 80° to 100° with respect to the sheet surface reference line L1 is as follows.

[0040] That is, it is assumed that arranging the magnetic sensor elements 14 (14a to 14d) so that they face each other across the seat surface reference line L1 will improve sensing sensitivity, but in addition, if an attempt is made to increase the magnetic flux density detected by the magnetic sensor elements 14, it is essential that the magnetization direction be directed toward the magnetic sensor elements 14. For this reason, it is preferable to arrange the magnetic sensor elements 14 so that the magnetization direction Dm and the seat surface reference line L1 form a right angle or an angle close to a right angle.

[0041] Furthermore, when the flexible sheet 16 flexes when the tire touches the ground, particularly if the permanent magnet 12 is a rectangular parallelepiped, the adhesive durability of the permanent magnet 12 will decrease if the permanent magnet 12 is arranged at an angle to the direction in which the tire flexes significantly (i.e., the direction of line L) in Figures 3(A) to 3(D). For this reason, it is preferable to arrange the magnetic sensor element 14 so that the magnetization direction Dm and the sheet surface reference line L1 form a right angle or an angle close to a right angle. Generally, when the permanent magnet 12 is a rectangular parallelepiped, the magnetization direction is parallel to one axis of the rectangular parallelepiped.

[0042] The magnetization direction Dm is more preferably set to a direction extending at an angle of 82° to 98° with respect to the sheet surface reference line L1, and most preferably set to a direction extending at an angle of 85° to 95°.

[0043] [Additional Form 3] Fig. 4 is a diagram showing the relationship between the sheet surface reference line and three directions of the permanent magnet. In Basic Mode 1 or a mode in which Additional Mode 2 is added to Basic Mode 1, as shown in Fig. 4, for the permanent magnet 12, it is preferable that the dimension T is the smallest among the dimension T in the magnetization direction Dm, the dimension H in the height direction which is the direction of the perpendicular line from the center of gravity G to the tire cavity surface, and the dimension W in the direction perpendicular to both the magnetization direction Dm and the height direction (Additional Mode 3).

[0044] By making the dimension T as small as possible, the permanent magnet 12 can suitably follow the deformation behavior of the tire 20 when the tire 20 undergoes bending deformation, and the adhesion state of the sensor unit 10, including the permanent magnet 12, to the tire 20 can be maintained well over the long term, resulting in excellent durability of the tire 20.

[0045] For example, when the permanent magnet 12 is magnetized in the direction shown in Fig. 4, the larger the product of the dimension W and the dimension H and / or the larger the dimension T, the wider the magnetic field formed around the permanent magnet 12. For this reason, it is preferable to increase the dimension W and / or the dimension H by the amount that the dimension T is reduced. However, with regard to which of the dimension W and the dimension H should be increased first, it is preferable to increase the dimension H first over the dimension W from the viewpoint of maintaining the adhesion state of the sensor unit 10, including the permanent magnet 12, to the tire 20 for a long period of time.

[0046] The preferable relationship between the above dimensions T, W, and H can be summarized as dimension T≦dimension W≦dimension H, and the effect of these relationships is particularly pronounced when the permanent magnet 12 is a rectangular parallelepiped.

[0047] Furthermore, the dimension T is more preferably 1.0 mm or more and 5.0 mm or less, even more preferably 1.2 mm or more and 4.8 mm or less, and extremely preferably 1.5 mm or more and 4.5 mm or less. The dimension W is more preferably 1.5 mm or more and 10.0 mm or less, even more preferably 1.7 mm or more and 9.8 mm or less, and extremely preferably 2.0 mm or more and 9.5 mm or less. The dimension H is more preferably 2.0 mm or more and 15.0 mm or less, even more preferably 2.5 mm or more and 14.0 mm or less, and extremely preferably 3.0 mm or more and 13.0 mm or less.

[0048] [Additional Form 4] In Basic Form 1 or a form in which Basic Form 1 is combined with at least one of Additional Form 2 and Additional Form 3, it is preferable that the maximum value of the surface magnetic flux density of permanent magnet 12 is 50 mT or more and 900 mT or less (Additional Form 4).

[0049] By setting the maximum value of the surface magnetic flux density of the permanent magnet 12 to 50 mT or more, the distance between the two magnetic sensor elements 14a, 14b will not become too close, even if the magnetization direction Dm of the permanent magnet 12 is the direction shown in Fig. 4, and a wide bending deformation range and, therefore, sufficient sensing sensitivity can be obtained. On the other hand, by setting this maximum value to 900 mT or less, the magnetic force of the permanent magnet 12 will not be excessive, and there will be no risk of metal foreign objects such as nails being attracted to the surface of the tire 20 on which the sensor unit 10 including the permanent magnet 12 is disposed, thereby preventing accidental damage to the tire 20. It is more preferable that this maximum value be 60 mT to 890 mT, and extremely preferably 100 mT to 850 mT.

[0050] As the permanent magnet 12 as a component of the sensor unit 10 of the present invention, a unipolar magnetized sintered magnet can be used, such as a ferrite magnet or a neodymium magnet.

[0051] [Additional Form 5] Fig. 5 is a meridian cross-sectional view of a tire showing the relationship between the dimensions of a permanent magnet and tire thickness. Note that, like the tire 20 shown in Fig. 1, the tire 20 shown in Fig. 5 is in an unloaded state (non-ground-contacting state) where it is mounted on a regular rim and given a regular internal pressure. In Basic Mode 1 or a mode in which Basic Mode 1 is combined with at least one of Additional Modes 2 to 4, as shown in Fig. 5, it is preferable that the dimension T of the permanent magnet 12 in a direction perpendicular to both the sheet surface reference line L1 (a line extending substantially in the tire circumferential direction, i.e., a line extending in a direction penetrating the page) and the perpendicular line from the center of gravity G of the permanent magnet 12 to the tire cavity surface be 0.10 to 0.75 times the tire thickness Ga on the perpendicular line from the center of gravity G of the permanent magnet 12 to the tire cavity surface (Additional Mode 5).

[0052] By making the dimension T 0.10 times or more the tire thickness Ga, the magnetic force of the permanent magnet 12 can be further increased, thereby further increasing the sensitivity for sensing the bending deformation of the tire 20 and enabling the deflection of the tire 20 to be determined with even higher accuracy.

[0053] In contrast, by setting the dimension T to 0.75 times the tire thickness Ga or less, the adhesion state between the permanent magnets 12 and the flexible sheet 16 is maintained well during bending deformation of the tire, and the permanent magnets 12 are prevented from falling off the flexible sheet 16, thereby further improving the durability of the tire 20.

[0054] From this viewpoint, it is more preferable that the dimension T be 0.12 times or more and 0.73 times or less, and it is extremely preferable that the dimension T be 0.15 times or more and 0.70 times or less, of the tire thickness Ga.

[0055] [Additional Form 6] 6 is a diagram showing the state of adhesion of the flexible sheet on the tire cavity surface. Note that in this figure, only the area of ​​the tire 20 corresponding to the sensing area Rs (described later) is shown, but the surface of the tire 20 is usually larger than the surface on which the flexible sheet 16 is placed.

[0056] In Basic Form 1 or a form in which Basic Form 1 is combined with at least one of Additional Forms 2 to 5, when two lines that are parallel to the sheet surface reference line L1 in a plan view, include the magnetic sensor elements 14a, 14b, and 14c on the side of the sheet surface reference line L1, and pass through the ends of the magnetic sensor elements 14a, 14b, and 14c, and are respectively defined as sheet surface outer lines L2 and L3, and the area of ​​the flexible sheet that exists between the two sheet surface outer lines L2 and L3 is defined as sensing area Rs, it is preferable that 60% or more of the back surface of sensing area Rs be adhered to the tire 20 (Additional Form 6). In the example shown in Figure 6, the magnetic sensor elements 14a and 14b are at the same distance from the seat surface reference line L1, so both ends are on the seat surface outer line L2. However, if the distances from the seat surface reference line L1 to the magnetic sensor elements 14a and 14b are different, the magnetic sensor element that is farthest from the seat surface reference line L1 (for example, 14a) will be the magnetic sensor element that serves as the basis for determining the seat surface outer line L2.

[0057] Here, the sheet surface outer lines L2, L3 are set so that all the magnetic sensor elements (magnetic sensor elements 14a to 14c in FIG. 6) are included in the sensing region Rs on each side of the sheet reference line L1. In addition, in view of the excellent adhesion of the flexible sheet 16 to the tire 20, it is more preferable that the dimension of the flexible sheet 16 in the direction of the sheet surface reference line L1 be smaller than the dimension of the tire 20 in the direction of the sheet surface reference line L1.

[0058] Since 60% or more of the back surface of the sensing area Rs is adhered to the tire 20, when the tire 20 deforms, the flexible sheet 16 deforms in response to the deformation of the tire 20, allowing changes in magnetic flux density to be detected more accurately, and ultimately allowing the deflection of the tire 20 to be determined with even greater precision.

[0059] In this embodiment, it is more preferable that 80% or more of the back surface of the sensing region Rs is adhered to the tire 20, and it is extremely preferable that 100% of the back surface is adhered to the tire 20.

[0060] Furthermore, if another elastic body (e.g., a rubber layer) exists between the tire 20 and the flexible sheet 16 as a buffer material, the deformation behavior of the flexible sheet 16 may not accurately follow the deformation behavior of the tire 20. For this reason, it is preferable to place the flexible sheet 16 directly on the tire cavity surface. Specifically, it is preferable to place the flexible sheet directly on the inner liner that constitutes the tire cavity surface.

[0061] Furthermore, when the manufacturing process of the tire 20 includes a vulcanization process, the flexible sheet 16 may be disposed on the tire 20 before or after vulcanization. However, when the flexible sheet 16 is disposed on the tire 20 before vulcanization, the vulcanization is performed without disposing the permanent magnet 12 or the magnetic sensor element 14 on the flexible sheet 16.

[0062] [Additional Form 7] FIG. 7 is a diagram showing the positional relationship between the permanent magnet and the magnetic sensor element before and after placing a flexible sheet (sensor unit) on the tire cavity surface, and shows an example in which the magnetization direction is parallel to the flexible sheet before placement.

[0063] In Basic Form 1 or a form in which Basic Form 1 is combined with at least one of Additional Forms 2 to 6, as shown in FIG. 7, when the flexible sheet 16 is not placed on the tire 20 (the diagram to the left of the arrow), it is preferable that the dimension Hc (mm) from the flexible sheet 16 to the highest point of the magnetic sensor element 14 and the distance d (mm) between the permanent magnet 12 and the magnetic sensor element 14 satisfy the following relationship (Additional Form 7). Hc≦30-120{cos(d / 50)―0.5)} 2 The distance d between the permanent magnet 12 and the magnetic sensor element 14 refers to the dimension between the center line of the permanent magnet 12 in the width direction and the center line of the magnetic sensor element 14 in the width direction, as shown in FIG.

[0064] In FIG. 7, when moving from the left diagram to the right diagram, the tire 20 bends, causing the position of the magnetic sensor element 14 to change in the magnetic field generated by the permanent magnet 12, thereby changing the value of the sensed magnetic field strength. Furthermore, if the size of the magnetic sensor element 14 (for example, the above-mentioned dimension Hc) is too large, the sensitivity of the signal to bending decreases, and the sensing accuracy deteriorates. In this situation, the inventors have found that even if the elastic body E bends in the same way, the position of the magnetic sensor element 14 in the magnetic field changes, so they have introduced a function of d, and have discovered that if this function satisfies the above range, good sensing sensitivity can be ensured.

[0065] [Additional Form 8] 8A and 8B show suitable examples (A) and (B) of the position of the magnetic sensor element when the sensor unit is disposed on the tire surface, and an inappropriate example (C) of the position of the magnetic sensor element. In Additional Example 2, as shown in FIGS. 8A and 8B, in a state before bending deformation of the tire 20 in which the sensor unit 10 is disposed on the tire cavity surface, the magnetic sensor element 14 (the center of gravity of the magnetic sensor element 14) is preferably disposed on the center line Lc of the arrangement height of the permanent magnet 12 on the concave curved surface of the tire 20 (FIG. 4A) or on the opposite side of the arrangement surface of the permanent magnet 12 with respect to the center line Lc (FIG. 4B) (Additional Example 3). Here, the center line of the arrangement height refers to a line that passes through the center of gravity of the permanent magnet 12, determines a perpendicular line to the tire cavity surface, and passes through the midpoint on this perpendicular line from the surface of the permanent magnet 12 facing the tire 20 (the lower surface in FIG. 8) to the opposite surface (the upper surface in FIG. 8), and is perpendicular to the perpendicular line.

[0066] 8, the magnetic field lines generated by the permanent magnet 12 are generally symmetrical with respect to the center line Lc because the tire 20 is made up of a high proportion of non-magnetic materials. When sensing the bending deformation behavior of the tire 20 based on changes in magnetic flux density, it is important to position the magnetic sensor element 14 so that it detects only the magnetic field on the same side of the center line Lc before and after the bending deformation of the tire 20, in order to accurately detect changes in magnetic flux density.

[0067] The sensor unit 10 of the present application determines the behavior of bending deformation, i.e., deflection, based on, for example, the difference (amount of change) in magnetic flux density detected by the magnetic sensor element 14 before and after bending deformation of the tire 20. In the example shown in FIG. 8(A) (an example in which the magnetic sensor element 14 is disposed on the center line Lc before deformation of the tire 20) and the example shown in FIG. 8(B) (an example in which the magnetic sensor element 14 is disposed on the opposite side of the center line Lc from the arrangement surface of the permanent magnet 12 before deformation of the tire 20), when bending deformation occurs from the state before bending deformation shown in the figure, the magnetic sensor element 14 moves above the center line Lc. Therefore, because the magnetic sensor element 14 is located on only one side of the center line Lc before and after bending deformation, changes in magnetic flux density can be accurately detected, and ultimately, deflection of the tire 20 can be determined with even higher accuracy.

[0068] 8(c) (an example in which the magnetic sensor element 14 is disposed on the same side of the center line Lc as the arrangement surface of the permanent magnet 12 before deformation of the tire 20), when bending deformation occurs from the state before bending deformation shown in the figure, the magnetic sensor element 14 may move beyond the center line Lc. For this reason, it is conceivable that the magnetic sensor element 14 may be located on both sides of the center line Lc before and after bending deformation, and it may not be possible to accurately detect changes in magnetic flux density.

[0069] [Additional Form 9] In basic form 1 or a form in which basic form 1 is combined with at least one of additional forms 2 to 8, it is preferable that the above-mentioned flexible sheet 16 is a flexible substrate, the sensor unit 10 is provided with electrical wiring made of a conductor, and the magnetic sensor element 14 is mounted so as to be connected to the electrical wiring (additional form 9).

[0070] By using a flexible substrate for the flexible sheet 16, the flexible sheet 16 can better follow the deformation of the tire 20, thereby further increasing the durability of the tire 20. Although a flexible film can be interposed between the tire 20 and the flexible sheet 16, using the flexible sheet 16 itself as a flexible substrate can suppress a decrease in sensing sensitivity due to differences in deformation behavior between the layers, and ultimately enables the deflection of the tire 20 to be determined with even higher accuracy.

[0071] In this embodiment, the electrical wiring refers to wiring that supplies power to the magnetic sensor element 14 and wiring that transmits signals by connecting to the output side of the magnetic sensor element 14. In this embodiment, the flexible substrate preferably includes at least one layer of highly inelastic polyimide, and copper, which has low resistance, is preferably used as the conductor.

[0072] [Additional Form 10] 9 is a meridian cross-sectional view of a part of the tire of this embodiment. The tire 20 shown in the drawing is mounted on a regular rim R and is in a no-load state (non-contact state) with a regular internal pressure.

[0073] In Basic Form 1 or a form in which Basic Form 1 is combined with at least one of Additional Forms 2 to 9, it is preferable that the sheet surface reference line L1 extends along the tire circumferential direction (the direction penetrating the paper surface) as shown in FIG. 9 (Additional Form 10).

[0074] Here, the sheet surface reference line L1 being along the tire circumferential direction means that the extension direction of the sheet surface reference line L1 is allowed to be shifted by 10° on each side along the surface of the flexible sheet 16 relative to the tire circumferential direction.

[0075] Considering that when the tire rolls on the ground, the tire exhibits substantially the same bending deformation behavior at any circumferential position, by extending the sheet surface reference line L1 (the line that is most likely to become the axis of bending deformation) along the tire circumferential direction in this manner, it is possible to achieve a high level of sensitivity in sensing the bending deformation of the tire 20, and ultimately to determine the deflection of the tire 20 with even greater accuracy.

[0076] As shown in FIG. 9, by forming a sensor unit 10, which has a permanent magnet 12 and two magnetic sensor elements 14a, 14b formed on a flexible sheet 16, on the tire cavity surface of a tire 20, there is no need to embed the permanent magnet 12 or the magnetic sensor elements 14a, 14b in the tire cavity surface, and a tire with a sensor unit can be easily manufactured.

[0077] [Additional Form 11] 10 is a diagram showing a circle passing through the centers of gravity of the permanent magnet and two magnetic sensor elements that constitute the sensor unit. In Basic Configuration 1 or a configuration in which at least one of Additional Configurations 2 to 10 is added to Basic Configuration 1, it is preferable that the radius r of a circle passing through three points: the center of gravity of one magnetic sensor element 14a among the magnetic sensor elements arranged on one side of the seat surface reference line L1 in the concave circle C, the center of gravity of one magnetic sensor element 14b among the magnetic sensor elements arranged on the other side of the seat surface reference line L1 in the concave circle C, and the center of gravity G of the permanent magnet 12 (Additional Configuration 11).

[0078] Here, the circle passing through the three points refers to a circle in an unloaded state (non-contact state) when the tire 20 is mounted on a regular rim and given a regular internal pressure.

[0079] By making the radius r of the circle 20 mm or more, bending deformation can be detected over a wider area with respect to the region between the two magnetic sensor elements 14a, 14b of the tire 20 in the tire meridian cross section, thereby further increasing the sensitivity for sensing bending deformation of the tire 20 and ultimately enabling the deflection of the tire 20 to be determined with even higher accuracy.

[0080] Furthermore, when the strength of the magnetic field (i.e., magnetic flux density) at positions equidistant from each pole of the permanent magnet 12 is taken into consideration, the magnetic flux density is highest on an extension of the magnetization direction, and decreases as the distance from the magnetization direction increases. Therefore, if the radius r of the circle is less than 20 mm, the position of the magnetic sensor element 14 may approach a direction perpendicular to the magnetization direction when the tire 20 flexes, which may weaken the detected magnetic field.

[0081] Furthermore, by setting the radius r of the circle to 120 mm or less, it is possible to ensure sufficient change in the radius of curvature of the concave curved surface of the tire 20 before and after bending deformation of the tire 20, and it is possible to prevent the dynamic range (the ratio between the minimum and maximum values ​​of the identifiable signal) of the signal output from the magnetic sensor element 14 from becoming too small.As a result, it is possible to further increase the sensitivity in sensing the bending deformation of the tire 20, and ultimately to determine the deflection of the tire 20 with even higher accuracy.

[0082] The radius r (see FIG. 10) is more preferably 22 mm or more and 118 mm or less, and most preferably 25 mm or more and 115 mm or less.

[0083] The two magnetic sensor elements 14a and 14b used to define the radius in this embodiment are one of the magnetic sensor elements 14a arranged on one side of the sheet surface reference line L1 and one of the magnetic sensor elements 14b arranged on the other side within the concave circle C in Fig. 2. In this embodiment, in addition to these magnetic sensor elements 14a and 14b, magnetic sensor elements that are not used to define the radius r in this embodiment may be arranged.

[0084] [Additional Form 12] 11A and 11B are meridian cross-sectional views of a tire showing the position of a reference line on the tire cavity surface, and (A) shows an example in which not only the reference line but also the magnetic sensor element on the inner side in the tire width direction is located within a predetermined range, while (B) shows an example in which the magnetic sensor element on the inner side in the tire width direction is not located within the predetermined range. In both (A) and (B), the tire 20 shown in the figure is mounted on a regular rim R and pressurized to the regular internal pressure, in an unloaded state (non-contact state).

[0085] In a configuration in which Basic Configuration 1 or Basic Configuration 1 is combined with at least one of Additional Configurations 2 to 11, as shown in FIG. 11, a belt 22 consisting of at least one belt layer 22a, 22b (two belt layers in the configuration shown in the figure) is provided on the tire radially outer side of a carcass (not shown), and when the foot of a perpendicular line drawn from the tire width direction end of the belt layer 22a of the belt layers 22a, 22b that has the largest dimension in the tire width direction to the tire cavity surface is defined as a first point P1, and the outermost point in the tire radial direction among the feet of perpendicular lines drawn from each outer peripheral point of the bead core 24 to the tire cavity surface is defined as a second point P2, it is preferable that a reference line L0 obtained by projecting the sheet surface reference line L1 onto the tire cavity surface exists between the first point P1 and the second point P2 along the tire cavity surface (Additional Configuration 12).

[0086] By locating the reference line L0, which is the projection of the sheet surface reference line L1 onto the tire cavity surface, between the first point P1 and the second point P2 along the tire cavity surface, the portion of the tire close to the magnetic sensor elements 14a, 14b that straddles the sheet surface reference line L1 becomes a portion that is subject to very large deformation, thereby further increasing the sensitivity in sensing the bending deformation of the tire 20, and ultimately enabling the deflection of the tire 20 to be determined with even higher accuracy.

[0087] If the permanent magnet 12 is placed too close to the belt layers 22a, 22b containing steel cords, the steel cords may bias the distribution of magnetic field lines generated by the permanent magnet 12 in a specific direction, which may weaken the magnetic field received by the magnetic sensor elements 14a, 14b. Also, if the permanent magnet 12 is placed too close to the tire equatorial plane, the permanent magnet 12 may be deteriorated and demagnetized due to the influence of heat generated in the tread. In consideration of such undesirable situations, the position of the reference line L0 based on the sheet surface reference line L1 defined in this embodiment is set within the predetermined range as described above.

[0088] In addition, in Figure 11, (A) is an example in which not only the reference line L0 but also the magnetic sensor element 14a on the inner side in the tire width direction is located within the above-mentioned specified range of the tire cavity surface (between the first point P1 and the second point P2), while (B) is an example in which the magnetic sensor element 14a on the inner side in the tire width direction is not located within the above-mentioned specified range of the tire cavity surface, but the present embodiment is intended to include both the cases of Figure 11 (A) and (B) within the scope of the invention.

[0089] [Additional Form 13] 12 is a meridian cross-sectional view of a tire showing the position of a reference line on the tire cavity surface and the position of an end portion of a flexible sheet on the tread surface and closer to a point on the tire equatorial plane. The tire 20 shown in the figure is mounted on a regular rim R and is in a no-load state (non-contact state) with a regular internal pressure applied.

[0090] In a configuration in which Basic Configuration 1 or Basic Configuration 1 is combined with at least one of Additional Configurations 2 to 12, as shown in FIG. 12, a belt 22 consisting of at least one belt layer 22a, 22b (two belt layers in the configuration shown in the figure) is provided on the tire radially outer side of a carcass (not shown), and when the foot of a perpendicular line drawn from the tire width direction end of the belt layer 22a of the belt layers 22a, 22b that has the largest dimension in the tire width direction to the tire cavity surface is defined as a first point P1 and the maximum width position of the tire cavity surface is defined as a third point P3, it is preferable that a reference line L0 obtained by projecting the sheet surface reference line L1 onto the tire cavity surface is located between the first point P1 and the third point P3 along the tire cavity surface, and an end of the flexible sheet 16 that is on the tread surface and closer to a point on the tire equatorial plane is located more inward in the tire width direction than the first point P1 (Additional Configuration 13).

[0091] By locating the reference line L0, which is the projection of the sheet surface reference line L1 onto the tire cavity surface, between the first point P1 and the third point P3 along the tire cavity surface, the portion of the tire close to the magnetic sensor elements 14a, 14b that straddles the sheet surface reference line L1 becomes a portion that is subject to very large deformation, thereby further increasing the sensitivity in sensing the bending deformation of the tire 20, and ultimately enabling the deflection of the tire 20 to be determined with even higher accuracy.

[0092] Furthermore, by positioning the end of the flexible sheet 16 on the tread surface and closer to a point on the tire equatorial plane more inward in the tire width direction than the first point P1, this end can be placed on the tire cavity surface of the tread portion, which has a significantly higher hardness than the sidewall portion. This makes it possible to maintain a stronger bond between the tire 20 and the inner portion (the end) of the sensor unit 10 in the tire width direction in particular. As a result, the end can be stably formed as a connection portion for electrical wiring and a connector connected to the sensor unit 10, and ultimately the durability of the tire 20 can be improved.

[0093] [Additional Form 14] 13A and 13B are diagrams showing the positional relationship between the permanent magnet, the magnetic sensor element, and the belt, where (A) shows the positional relationship between the magnetic sensor element and the belt, and (B) shows the positional relationship between the permanent magnet and the magnetic sensor element. The tire 20 shown in Fig. 13A is mounted on a regular rim R and is in a no-load state (non-ground-contact state) with the regular internal pressure applied.

[0094] In Basic Configuration 1 or a configuration in which Basic Configuration 1 is combined with at least one of Additional Configurations 2 to 13, as shown in FIG. 13, a belt 22 consisting of at least one belt layer 22a, 22b is provided on the tire radial outside of a carcass (not shown), and it is preferable that the distance t from the tire widthwise end of the belt layer 22a, 22b, which has the largest dimension in the tire widthwise direction, to the innermost magnetic sensor element 14a arranged on the innermost side in the tire widthwise direction, and the distance d along the flexible sheet 16 from the magnetic sensor element 14a to the permanent magnet 12, satisfy d / t≦1.8 (Additional Configuration 14).

[0095] In this embodiment, the distance t and the distance d satisfy d / t≦1.8, thereby preventing the distance t between the magnetic sensor element 14a and the belt (specifically, the belt cord) from being excessively small relative to the distance dD between the permanent magnet 12 and the magnetic sensor element 14a. This prevents magnetic field disturbance (deflection in a specific direction) around the magnetic sensor element 14a, which is relatively close to the belt cord, and allows the magnetic sensor element 14a to accurately measure the original magnetic flux density. Therefore, according to this embodiment, the sensitivity for sensing bending deformation of the tire 20 can be further improved, and ultimately the deflection of the tire 20 can be determined with even higher accuracy.

[0096] In this embodiment, the distance t between the magnetic sensor element 14a located at the innermost side in the tire width direction and the belt cord is set to 3.5% or more of the tire cross-sectional height, thereby enabling the original magnetic flux density to be measured at an extremely high level.

[0097] In addition, in this embodiment, by setting the distance d along the flexible sheet 16 from the magnetic sensor element 14a located at the innermost side in the tire width direction to the permanent magnet 12 to be 4% or more and 20% or less of the tire cross-sectional height, the sensitivity for sensing the bending deformation of the tire 20 can be further increased when the actual radius of curvature of the tire inner cavity surface and the actual position of the sensor unit 10 are taken into consideration, and ultimately the deflection of the tire 20 can be determined with even higher accuracy.

[0098] [Additional Form 15] In basic form 1 or a form in which basic form 1 is combined with at least one of additional forms 2 to 14, when the contour of flexible sheet 16 is projected onto the carcass layer, it is preferable that the number of carcass cords that intersect with the projected sheet surface reference line L1 across the projected width of flexible sheet 16 (hereinafter referred to as the "number of intersecting cords") is 2 or more and 15 or less (additional form 15).

[0099] Here, the projected width of the flexible sheet 16 refers to the maximum dimension of the flexible sheet 16 projected onto the carcass layer in the direction of the sheet surface reference line L1. Furthermore, if the carcass is composed of multiple carcass layers, the number of cross cords refers to the number of carcass cords in the carcass layer that is the innermost layer of the tire (closest to the tire cavity surface).

[0100] 13(A), all or most of the flexible sheet 16 is disposed in the tire width direction region where no belt layer is present. Therefore, how the flexible sheet 16 deforms due to deformation caused by the tire contacting the ground depends greatly on the deformation of the carcass cords. This is because the tensile modulus of elasticity of the carcass cords is much greater than that of rubber.

[0101] If the circumferential width of the flexible sheet 16 is less than two carcass cords (i.e., if the number of cross cords is less than two), the adhesive surface of the flexible sheet 16 to the inner liner is strongly affected by the movement of the carcass cords included in the projection range of the flexible sheet 16 onto the carcass layer.

[0102] Specifically, due to the symmetry of the tire, the normal vector of the flexible sheet 16 passing through the center of gravity of the permanent magnet 12 should be contained within the meridian section of the tire that includes the center of gravity of the permanent magnet 12 at the tire circumferential center position of the tire. However, at the tire circumferential end portions, the normal vector of the flexible sheet 16 may deviate from the meridian section. This is because the face width (dimension in the tire circumferential direction) of the flexible sheet 16 is so small that it cannot absorb the movement of the carcass cords averaged in the tire circumferential direction.

[0103] This phenomenon can cause the permanent magnet 12, which stands vertically toward the tire cavity, to tilt in the circumferential direction of the tire when the tire is rolling, resulting in a so-called rocking motion, which can ultimately cause a decrease in sensing accuracy.

[0104] On the other hand, when the surface width of the flexible sheet 16 exceeds 15 carcass cords (i.e., when the number of cross cords exceeds 15), there is no problem in that the adhesive surface of the flexible sheet 16 to the inner liner can absorb the movement of the carcass cords evenly in the circumferential direction of the tire.

[0105] However, in this case, the width of the flexible sheet 16, which exceeds the width of 15 carcass cords, is too large in the circumferential direction of the tire, and therefore, as the flexible sheet 16 moves from the non-ground contact area to the ground contact area during tire rolling, the distance between the carcass cords increases in the ground contact area and its vicinity, while the distance between the carcass cords has not yet increased in areas far from the ground contact area, resulting in a situation in which the deformation behavior of the carcass varies locally in the circumferential direction of the tire.

[0106] As a result, the in-plane stress acting on the flexible sheet 16 becomes non-uniform in the tire circumferential direction. Here, since the flexible sheet 16 is less stretchable (has a higher elastic modulus) than the tire constituent members (carcass, inner liner, etc.), it cannot follow the expansion between the carcass cords (i.e., the expansion of the carcass rubber following the expansion of the carcass cords). As a result, the adhesive surface between the tire cavity surface and the flexible sheet 16 is subjected to the aforementioned local stress changes in the tire circumferential direction, resulting in a decrease in the durability of the adhesive of the flexible sheet 16.

[0107] From this viewpoint, the number of crossing cords is more preferably 3 or more and 14 or less, and most preferably 4 or more and 12 or less.

[0108] [Other tire types] Further preferred examples of the tire 20 equipped with the sensor unit 10 described above will be described below.

[0109] (Suitable example 1) It is preferable that two to ten of the above-described sensor units 10 are arranged in the tire circumferential direction on the tire cavity surface. When determining the state of tire deformation for the purpose of vehicle attitude control while the tire is rolling, obtaining data for determining the state of deformation at different points in the tire circumferential direction is advantageous for comprehensively determining the deformation of the entire tire. However, even if eleven or more sensor units 10 are arranged in the tire circumferential direction, the effect of determining the state of tire deformation more accurately in proportion to the number of sensor units 10 arranged is not sufficiently obtained, so the preferred number of sensor units 10 to be arranged is ten or less.

[0110] In addition, when multiple sensor units 10 are arranged in the tire circumferential direction, it is highly preferable to arrange the multiple sensor units 10 at equal intervals in the tire circumferential direction, since detecting the deformation state of the tire 20 evenly in the tire circumferential direction is effective in efficiently determining the deformation state of the entire tire.

[0111] (Preferable example 2) Figure 14 is a meridian cross section of a tire showing suitable positions for placing a circuit board connected to a sensor unit, where (A) shows an example in which the circuit board is placed closer to the center of the tread than an area where it is undesirable to place it, and (B) shows an example in which the circuit board is placed closer to the bead than an area where it is undesirable to place it.

[0112] The circuit board 30a shown in FIG. 14(A) and the circuit board 30b shown in FIG. 14(B) include an amplifier circuit, a power supply circuit, a signal processing circuit, a communication circuit, and the like.

[0113] In the example shown in Figures 14(A) and 14(B), if the foot of a perpendicular line drawn from the tire width direction end of the belt layer 22a having the maximum dimension in the tire width direction to the tire cavity surface is defined as a first point P1 and the maximum width position of the tire cavity surface is defined as a third point P3, both of the circuit boards 30a and 30b are arranged in areas along the tire cavity surface where bending deformation is relatively small other than the area between the first point P1 and the third point P3.

[0114] In this way, by arranging the circuit board 30 (30a, 30b) in an area that experiences relatively little bending deformation during tire deformation, it is possible to suppress the circuit board 30 from falling off from the tire cavity surface during bending deformation of the tire 20, thereby further increasing the durability of the tire 20. [Example]

[0115] Below, we will compare the effects of the tire inventions defined in claims 1 to 15 of the present application (hereinafter referred to as "Invention Examples 1 to 15") with an invention similar to the invention described in Patent Document 1 (hereinafter referred to as "Prior Art Example").

[0116] The tire size was 245 / 40R19 (specified by JATMA), and each of the tires in Examples 1 to 15 of the invention was mounted on a rim as shown in Figure 1. The tires were subjected to bending deformation from a no-load state (before deformation) with normal internal pressure applied to a state (after deformation) with 80% of the normal load applied. The rate of change in the difference between the outputs of the two magnetic sensor elements 14a and 14b before and after tire deformation was calculated. The rim width of the wheel was 8.5 inches (215.9 mm).

[0117] In contrast, in the conventional example, since there was one magnetic sensor element, the rate of change in the output value of that one magnetic sensor element before and after tire deformation was calculated, and the other conditions were the same as those of each of the invention examples.

[0118] Then, for the tires of the conventional example and each of the invention examples, this rate of change was converted to a value with the conventional example being set at 100, and used as an evaluation value (expressed as an index) indicating the tire deflection sensing sensitivity. A larger evaluation value indicates that the tire deflection can be determined with higher sensitivity. The tire conditions for the conventional example and invention examples 1 to 15 are as shown in Table 1 below. In each example, a unipolar magnetized permanent magnet was used. The magnetization direction was parallel to the flexible sheet and perpendicular to the sheet surface reference line L1 when the sensor unit was not placed on the tire.

[0119] [Table 1]

[0120] In Table 1, the sheet surface reference line L1, straight line L, dimension T, dimension H, dimension W, tire thickness Ga, sensing area Rs, dimension Hc, radius r, d / t, T / Ga, number of intersecting cords, etc. conform to the definitions described in this specification.

[0121] Table 1 shows that all tires within the technical scope of the present invention have high sensitivity in sensing tire flexure. [Explanation of symbols]

[0122] 10 Sensor Unit 12 Permanent magnets 14 (14a, 14b, 14c, 14d) Magnetic sensor element 16 Flexible sheet 20 tires 22 Belt 22a, 22b belt layers 24 bead core 30a, 30b Circuit board C concave circle d Distance from the magnetic sensor element to the permanent magnet along the flexible sheet Dm Magnetization direction G Center of gravity of permanent magnet Ga Tire Thickness H: The height dimension of the permanent magnet, which is the direction of the perpendicular line from the center of gravity to the tire cavity surface Hc: Dimension from the flexible sheet to the highest point of the magnetic sensor element L straight line L0 reference line L1 Sheet surface reference line L2, L3 Sheet surface outer line Lc Center line of permanent magnet placement height P1 First point P2 Second point P3 Third Point R rim Rs sensing area r radius of the circle T: Dimension of a permanent magnet in the direction perpendicular to both the height direction and the direction of the reference line t is the distance from the end of the belt layer with the largest dimension in the tire width direction to the innermost magnetic sensor element W Dimension of the permanent magnet in the direction of the reference line

Claims

1. A tire comprising a sensor unit on a tire cavity surface for determining the deflection of the tire during bending deformation of the tire, the sensor unit includes a non-magnetic, non-stretchable flexible sheet, one permanent magnet and at least two magnetic sensor elements formed on the flexible sheet, The deflection of the tire is determined by performing a calculation using signals output from each of the at least two magnetic sensor elements; determining a concave circle formed by projecting onto the tire surface a circle that is centered on the center of gravity of the permanent magnet, is included in a plane perpendicular to a straight line that includes a perpendicular line extending from the center of gravity to the tire surface, and has a radius that is the longest distance between this straight line and the magnetic sensor element; Next, when a line including the diameter of the concave circle with the largest radius of curvature is defined as a seat surface reference line, at least one magnetic sensor element is disposed in each of regions on one side and the other side of the seat surface reference line within the concave circle, The permanent magnet is unipolarly magnetized, and each pole of the permanent magnet is oriented on one side and the other side of the flexible sheet with respect to a reference line on the surface of the sheet.

2. 2. The tire according to claim 1, wherein, in a plan view of the sensor unit, the magnetic sensor elements are formed in regions at 45° on both sides of a line L that passes through a midpoint of the permanent magnet in a direction of the sheet surface reference line and extends in a magnetization direction, on either side of the sheet surface reference line.

3. Regarding the permanent magnet, A dimension T in the magnetization direction; A height dimension H, which is a direction of a perpendicular line from the center of gravity to the tire cavity surface; a dimension W in a direction perpendicular to both the magnetization direction and the height direction; The tire according to claim 1 or 2, wherein the dimension T is the smallest among the above.

4. 3. The tire according to claim 1, wherein the maximum value of the surface magnetic flux density of the permanent magnet is 50 mT or more and 900 mT or less.

5. 3. The tire according to claim 1, wherein a dimension of the permanent magnet in a direction perpendicular to both the sheet surface reference line and a perpendicular line from the center of gravity of the permanent magnet to the tire cavity surface is 0.10 to 0.75 times the tire thickness on the perpendicular line from the center of gravity of the permanent magnet to the tire cavity surface.

6. In a plan view, when two lines that are parallel to the sheet surface reference line, include the magnetic sensor element on the sheet surface reference line side, and pass through an end of the magnetic sensor element are defined as sheet surface outer lines, and the area of ​​the flexible sheet that exists between the two sheet surface outer lines is defined as a sensing area, The tire according to claim 1 or 2, wherein 60% or more of the back surface of the sensing area is adhered to the tire.

7. 3. The sensor unit of claim 1, wherein when the flexible sheet is not placed on the elastic body, the dimension Hc from the flexible sheet to the highest point of the magnetic sensor element and the distance d (mm) between the permanent magnet and the magnetic sensor element satisfy the following relationship: Hc≦30-120{cos(d / 50)―0.5)} ２

8. In a state before the tire is bent and deformed, in which the sensor unit is disposed on the tire cavity surface, the magnetic sensor element is located on the concave curved surface of the flexible sheet. The permanent magnet is disposed on the center line of the height of the concave curved surface, or The permanent magnet is disposed on the opposite side of the center line from the surface on which the permanent magnet is disposed.

3. The tire according to claim 1 or 2.

9. the flexible sheet is a flexible substrate, The tire according to claim 1 or 2, further comprising an electric wiring made of a conductor, and the magnetic sensor element is mounted so as to be connected to the electric wiring.

10. The tire according to claim 1 or 2, wherein the sheet surface reference line extends along the tire circumferential direction.

11. 3. The tire according to claim 1, wherein a radius r of a circle passing through three points, namely, the center of gravity of one of the magnetic sensor elements arranged on one side of the sheet surface reference line within the concave circle, the center of gravity of one of the magnetic sensor elements arranged on the other side of the sheet surface reference line within the concave circle, and the center of gravity of the permanent magnet, is 20 mm or more and 120 mm or less.

12. In a tire meridian cross section, a belt having at least one belt layer is provided on an outer side of the carcass in the tire radial direction, When a foot of a perpendicular line extending from an end portion in the tire width direction of the belt layer having the largest dimension in the tire width direction among the belt layers to the tire cavity surface is defined as a first point, and a point on the outermost side in the tire radial direction among the feet of perpendicular lines extending from each outer peripheral point of the bead core to the tire cavity surface is defined as a second point, The tire according to claim 1 or 2, wherein a reference line obtained by projecting the sheet surface reference line onto a tire cavity surface exists between the first point and the second point along the tire cavity surface.

13. In a tire meridian cross section, a belt having at least one belt layer is provided on an outer side of the carcass in the tire radial direction, when a first point is a foot of a perpendicular line extending from an end portion in the tire width direction of the belt layer having the largest dimension in the tire width direction among the belt layers to a tire cavity surface and a third point is a maximum width position on the tire cavity surface, a reference line obtained by projecting the sheet surface reference line onto the tire cavity surface exists along the tire cavity surface between the first point and the third point, The tire according to claim 1 or 2, wherein an end of the flexible sheet on the tread surface and closer to a point on the tire equatorial plane is located more inward in the tire width direction than the first point.

14. a belt having at least one belt layer on the tire radial direction outer side of the carcass; 3. The tire according to claim 1, wherein a distance t from an end in the tire width direction of a belt layer that has a maximum dimension in the tire width direction among the belt layers to an innermost magnetic sensor element that is arranged on the innermost side in the tire width direction, and a distance d from the innermost magnetic sensor element to the permanent magnet along the flexible sheet satisfy d / t≦1.

8.

15. 3. The tire according to claim 1, wherein, when the contour of the flexible sheet is projected onto the carcass layer, the number of carcass cords that intersect with the projected sheet surface reference line across the projected width of the flexible sheet is 2 or more and 15 or less.

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