Sensor unit and tire with sensor unit

Abstract

To provide a sensor unit capable of determining deflection of an elastic body with high accuracy even when the elastic body exhibits complicated deformation behavior such as when stress from the other direction is complicatedly applied to the elastic body.SOLUTION: A sensor unit (10) is disposed on a surface of an elastic body (E) to determine deflection of the elastic body when the elastic body is bent and deformed, and includes one permanent magnet (12) and at least two magnetic sensor elements (14a and 14b), and the deflection of the elastic body is determined by calculation using signals output from each of the at least two magnetic sensor elements.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a sensor unit that can determine the deflection of an elastic body with high precision, and to a tire equipped with a sensor unit. [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 purpose is to provide a sensor unit that can determine the deflection of an elastic body with high precision even when the elastic body exhibits complex deformation behavior, such as when stress is applied to the elastic body from multiple directions, and is not limited to tires. [Means for solving the problem]

[0006] The sensor unit of the present invention is a sensor unit that is placed on the surface of an elastic body and determines the deflection of the elastic body when the elastic body is bent and deformed, and is characterized in that the sensor unit includes one permanent magnet and at least two magnetic sensor elements, and the deflection of the elastic body is determined by calculation using signals output from each of the at least two magnetic sensor elements. [Effects of the Invention]

[0007] The sensor unit according to the present invention includes two or more magnetic sensor elements, which makes it possible to compare the signal values ​​output from each magnetic sensor element over time, to compare the differences in the signal values ​​output from multiple magnetic sensor elements over time, and to combine the signal values ​​output from multiple magnetic sensor elements to determine the deflection of the elastic body with high accuracy even when the elastic body exhibits complex deformation behavior. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a diagram showing a sensor unit according to this embodiment. [Figure 2] FIG. 2 is a diagram showing the deformation behavior of the sensor unit shown in FIG. 1 when the sensor unit is placed on an elastic body and the elastic body undergoes bending deformation. [Figure 3] FIG. 3 is a diagram showing the three-dimensional positional relationship between the permanent magnet and the magnetic sensor element in a state in which the sensor unit shown in FIG. 2 is placed on an elastic body with a concave curved surface. [Figure 4]FIG. 4 shows suitable examples (A) and (B) of the position of the magnetic sensor element and an unsuitable example (C) of the position of the magnetic sensor element when the sensor unit is disposed on the concave curved surface of the elastic body. [Figure 5] FIG. 5 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. [Figure 6] FIG. 6 is a diagram showing the relationship between the reference line and three directions of the permanent magnet. [Figure 7] Figure 7 shows a sensor unit in which permanent magnets and magnetic sensor elements are formed on a flexible sheet, where (A) shows the case where there are two magnetic sensor elements, (B) and (C) show the case where there are three magnetic sensor elements, and (D) shows the case where there are four magnetic sensor elements. [Figure 8] FIG. 8 is a diagram showing the state of adhesion of the flexible sheet on the elastic body. [Figure 9] Figure 9 shows the positional relationship between the permanent magnet and the magnetic sensor element before and after placing a flexible sheet (sensor unit) on an elastic body, where (A) shows the case where the magnetization direction is perpendicular to the flexible sheet before placement, and (B) shows the case where the magnetization direction is parallel to the flexible sheet before placement. [Figure 10] FIG. 10 is a tire meridian cross section showing a part of the tire of this embodiment. [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 14a 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 14a 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-sectional view of a tire showing the positions of the reference lines on the tire cavity surface and the positions of the end portions of the flexible sheets on the side closer to 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] FIG. 14 is a meridian cross section of a tire showing the relationship between the dimensions of the permanent magnet and the tire thickness. [Figure 15] Figure 15 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] Below, embodiments of the sensor unit according to the present invention (Basic Form 1 and Additional Forms 2 to 10 shown below) and embodiments of the tire according to the present invention (Basic Form 11 and Additional Forms 12 to 16 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 combined in any way within the scope that 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] <Sensor unit> [Basic form 1] 1 is a diagram showing a sensor unit of this embodiment. As shown in the figure, the sensor unit 10 of this embodiment is a unit including one permanent magnet 12 and at least two magnetic sensor elements 14 (two magnetic sensor elements 14a and 14b in the figure).

[0014] The two magnetic sensor elements 14a, 14b detect the change in magnetic flux density before and after bending deformation of the elastic body, and the signals output from the magnetic sensor elements 14a, 14b based on this change in magnetic flux density are calculated by an arithmetic circuit Ar via, for example, an amplifier circuit Am, to determine the deflection of the elastic body. The magnetic sensor elements 14 can be Hall elements, magnetoresistive elements, or the like.

[0015] Fig. 2 is a diagram showing the deformation behavior of the sensor unit shown in Fig. 1 when the elastic body undergoes bending deformation with the sensor unit placed on the elastic body. As shown in Fig. 2, when the elastic body E deforms from one of states (A) and (B) to the other state, the deformation behavior of the elastic body E is determined by, for example, performing appropriate arithmetic processing using the values ​​of the signals output from the magnetic sensor elements 14a and 14b.

[0016] (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 the elastic body deforms, and therefore can only realize a very simple mode for determining the deformation behavior of the elastic body. However, in reality, the way in which stress, which is a prerequisite for the deformation behavior of the elastic body, is applied to the elastic body can be such that stress is applied to the elastic body not only in one direction but also in multiple directions, and in such cases, there is a risk that the conventional sensor unit will not be able to determine the deflection of the tire with high accuracy.

[0017] 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 manner in which the deformation behavior of the elastic body E is determined.

[0018] According to the sensor unit 10 based on the inventor's knowledge, the deflection of the elastic body E can be determined with high accuracy even when the elastic body E exhibits complex deformation behavior, such as when stress is applied to the elastic body E from multiple directions rather than just one direction.

[0019] 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 determination result of the deflection of the elastic body E does not change much 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.

[0020] [Additional Form 2] 3 is a diagram showing the three-dimensional positional relationship between the permanent magnet and the magnetic sensor element when the sensor unit shown in FIG. 2 is placed on an elastic body with a concave curved surface. In Basic Form 1, as shown in FIG. 3, the surface of the elastic body (not shown) is a concave curved surface, and a concave circle C is determined by projecting a circle centered on the center of gravity G of the permanent magnet 12 onto the elastic body, the circle being included in a plane perpendicular to a line including a perpendicular line from the center of gravity G to the surface of the elastic body, and the circle having a radius equal to the longest distance between this line and the magnetic sensor elements 14 a and 14 b. Next, a reference line L0 is defined as a line including the diameter of the concave circle C with the largest radius of curvature. In this specification, projection refers to the projection of a figure such as a circle, line, or contour as a projection source onto a surface as a shadow when parallel light is irradiated from the opposite side of the surface to which the figure is to be projected. The light is projected in a direction perpendicular to the tangent plane that includes the center of gravity of the plane (specific area) onto which the light is projected.

[0021] 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.

[0022] In this embodiment, the concave curved surface of the elastic body E on which the sensor unit 10 is arranged refers to the concave curved surface of the elastic body in an undeformed state. For example, if the elastic body E is a tire, the concave curved surface refers to the inner cavity surface of the tire in an unloaded state (non-contact state) when the tire is mounted on a regular rim and given a regular internal pressure.

[0023] As described above, the reference line L0 is a line that includes the diameter with the largest radius of curvature among the diameters of the concave circle C. For this reason, within the curved surface of the concave circle C, the region near the reference line L0 is the region that is least susceptible to bending deformation in the length direction of the reference line L0 when the elastic body E is bent, but is the region that is most susceptible to bending deformation in the direction perpendicular to the reference line L0, and where the change in curvature is greatest.

[0024] Considering that the reference line L0 is a line on the concave curved surface of the elastic body E (see FIG. 2), the reference line L0 is generally assumed to be a curved line, but the reference line L0 may also be a straight line.

[0025] In this way, by arranging at least one magnetic sensor element 14a, 14b in each of the areas on one side and the other side of the reference line L0, bending deformation of the elastic body E can be detected over a wider range than when the magnetic sensor element is arranged in an area only on one side, thereby increasing the sensitivity in sensing the bending deformation of the elastic body E and ultimately enabling the deflection of the elastic body E to be determined with even greater accuracy.

[0026] In the example shown in FIG. 3, one magnetic sensor element 14a is arranged on one side of the reference line L0 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 of 2 or more, n is a natural number of 1 or more)) magnetic sensor elements 14 may be arranged on (one side, the other side) of the reference line L0.

[0027] [Additional Form 3] Figure 4 shows suitable examples (A) and (B) of the position of the magnetic sensor element and an unsuitable example (C) of the position of the magnetic sensor element when the sensor unit is placed on the concave curved surface of an elastic body. The poles (N pole, S pole) of the permanent magnet 12 in Figure 4 are provisionally indicated, but these poles may be reversed. The same applies to the other figures.

[0028] In Additional Form 2, in a state in which a sensor unit is disposed on an elastic body before bending deformation of the elastic body, as shown in Figures 4(A) and (B), it is preferable that the magnetic sensor elements 14 (14a, 14b) are disposed on the center line Lc of the arrangement height of the permanent magnet 12 on the concave curved surface, or on the opposite side of the arrangement surface of the permanent magnet 12 with respect to the center line Lc (Additional Form 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 concave curved surface of the elastic body E, and passes through the midpoint of a line segment on this perpendicular line from the surface of the permanent magnet 12 on the elastic body E side (the lower surface in Figure 4) to the opposite surface (the upper surface in Figure 4), and is perpendicular to the perpendicular line.

[0029] 4, the magnetic field lines generated by the permanent magnet 12 are generally symmetrical with respect to the center line Lc when the elastic body E is non-magnetic. When sensing the bending deformation behavior of the elastic body E 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 elastic body E, in order to accurately detect changes in magnetic flux density.

[0030] 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 elastic body E. In the example shown in FIG. 4(A) (an example in which the magnetic sensor element 14 is disposed on the center line Lc before deformation of the elastic body E) and the example shown in FIG. 4(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 elastic body E), 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 only on one side of the center line Lc (the upper side in the figure) before and after bending deformation, changes in magnetic flux density can be accurately detected, and ultimately, the deflection of the elastic body E can be determined with even higher accuracy.

[0031] 4(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 elastic body E), 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. Therefore, 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.

[0032] [Additional Form 4] Fig. 5 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 Additional Mode 2 or an embodiment in which Additional Mode 3 is added to Additional Mode 2, it is preferable that the radius r (see Fig. 5) of a circle passing through three points: the center of gravity of one magnetic sensor element 14a among the magnetic sensor elements arranged directly or indirectly (i.e., via other members such as various sheet members) on one side of the reference line L0 within the concave circle C in Fig. 3; the center of gravity of one magnetic sensor element 14b among the magnetic sensor elements arranged directly or indirectly on the other side of the reference line L0 within the concave circle C; and the center of gravity of the permanent magnet 12 (Additional Mode 4).

[0033] Here, the circle passing through the three points refers to the circle when the elastic body E is in an undeformed state. For example, if the elastic body E is a tire, the radius r refers to the radius when the tire is mounted on a regular rim and pressurized to the regular internal pressure, in an unloaded state (non-contact state).

[0034] By setting the radius r of the circle to 20 mm or more, the bending deformation of the elastic body E can be detected over a sufficiently wide area, in the region between the two magnetic sensor elements 14a and 14b in Figure 5, thereby further increasing the sensitivity for sensing the bending deformation of the elastic body E, and ultimately enabling the deflection of the elastic body E to be determined with even greater accuracy.

[0035] Furthermore, by setting the radius r of the circle to 120 mm or less, it is possible to ensure sufficient change in the curvature of the concave curved surface of the elastic body E before and after bending deformation of the elastic body E, and it is possible to prevent the dynamic range of the signal output from the magnetic sensor element 14 (the ratio between the minimum and maximum values ​​of the identifiable signal) from becoming too small.As a result, the sensitivity for sensing the bending deformation of the elastic body E can be further increased, and ultimately the deflection of the elastic body E can be determined with even greater accuracy.

[0036] The radius r (see FIG. 5) is more preferably 22 mm or more and 118 mm or less, and most preferably 25 mm or more and 115 mm or less.

[0037] The two magnetic sensor elements 14a and 14b used to define the radius r in this embodiment are the magnetic sensor element 14a, which is one of the magnetic sensor elements arranged on one side of the reference line L0, and the magnetic sensor element 14b, which is one of the magnetic sensor elements arranged on the other side within the concave circle in Fig. 3. 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.

[0038] [Additional Form 5] In Additional Form 2 or a form in which Additional Form 2 is combined with at least Additional Form 3 or Additional Form 4, it is preferable that the angle θ formed by an arc connecting the centers of gravity of the two magnetic sensor elements on a circle passing through three points: the center of gravity of one magnetic sensor element 14a among the magnetic sensor elements arranged directly or indirectly on one side of the reference line L0 within the concave circle C in Figure 3, the center of gravity of one magnetic sensor element 14b among the magnetic sensor elements arranged directly or indirectly on the other side of the reference line L0 within the concave circle C, and the center of gravity of the permanent magnet 12, is 5.5° or more and 60° or less (Additional Form 5).

[0039] Here, the arc is set so that the entire two magnetic sensor elements 14a, 14b are included in the area of ​​the angle θ shown in Fig. 5. Furthermore, the circle passing through the above three points refers to the circle when the elastic body E is in an undeformed state. For example, if the elastic body E is a tire, the above angle θ refers to the angle when the tire is mounted on a regular rim and pressurized to the regular internal pressure, in an unloaded state (non-contact state).

[0040] By making the angle θ 5.5° or more, bending deformation can be detected over a sufficiently wide area of ​​the region between the two magnetic sensor elements 14a, 14b of the elastic body E, thereby further increasing the sensitivity for sensing the bending deformation of the elastic body E, and ultimately enabling the deflection of the elastic body E to be determined with even greater accuracy.

[0041] Furthermore, by making the angle 60° or less, the distance between the two magnetic sensor elements 14a, 14b and the permanent magnet 12 can be prevented from becoming excessive, there is no need to make the dimensions of the permanent magnet 12 excessively large, and the adhesion state between the sensor unit 10 including the permanent magnet 12 and the elastic body E can be maintained well for a long period of time, resulting in excellent durability of the elastic body E.

[0042] The angle θ (see FIG. 5) is more preferably 6.0° or more and 58° or less, and most preferably 6.5° or more and 55° or less.

[0043] The two magnetic sensor elements used to define the angle θ in this embodiment are magnetic sensor element 14a, which is one of the magnetic sensor elements arranged on one side of the reference line L0 within the concave circle in Fig. 3, and magnetic sensor element 14b, which is one of the magnetic sensor elements arranged on the other side. In this embodiment, in addition to these magnetic sensor elements 14a and 14b, magnetic sensor elements that are not used to define the angle θ in this embodiment may also be arranged.

[0044] [Additional Form 6] Fig. 6 is a diagram showing the relationship between the reference line and three directions of the permanent magnet. In Additional Mode 2 or a mode in which Additional Mode 2 is combined with at least one of Additional Modes 3 to 5, as shown in Fig. 6, it is preferable that the dimension T of the permanent magnet 12 is the smallest among the dimension H in the height direction, which is the direction of the perpendicular line from the center of gravity G to the concave curved surface of the elastic body, the dimension W in the direction of the reference line L0, and the dimension T in the direction perpendicular to both the height direction and the direction of the reference line L0 (Additional Mode 6).

[0045] By making the dimension T as small as possible, the permanent magnet 12 can suitably follow the deformation behavior of the elastic body E when the elastic body E is bent and deformed, and the adhesion state of the sensor unit 10, including the permanent magnet 12, with the elastic body E can be maintained even better for a long period of time, resulting in even greater durability of the elastic body E.

[0046] For example, as shown in Fig. 6, when the permanent magnet 12 is magnetized in the height direction, the larger the product of the dimension W and the dimension T and / or the dimension H, 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 rather than the dimension W from the viewpoint of maintaining a good adhesion state between the sensor unit 10 including the permanent magnet 12 and the elastic body E for a long period of time.

[0047] The preferable relationship between the dimensions T, W, and H is summarized as follows: dimension T≦dimension W≦dimension H, and the effect of these relationships is particularly pronounced when the permanent magnet 12 is a rectangular parallelepiped.

[0048] 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.

[0049] Furthermore, with regard to the permanent magnet 12, the maximum value of the magnetic flux density on the surface is preferably 50 mT or more and 900 mT or less. By setting this maximum value to 50 mT or more, the distance between the two magnetic sensor elements 14a, 14b is not too close, even when the magnetization direction of the permanent magnet 12 is the direction shown in FIG. 6, thereby achieving a wider bending deformation range and, ultimately, sufficient sensing sensitivity. On the other hand, by setting this maximum value to 900 mT or less, the magnetic force of the permanent magnet 12 is not excessively large, and there is no risk of metal foreign objects such as nails being attracted to the surface of the elastic body E on which the sensor unit 10 including the permanent magnet 12 is disposed, thereby preventing accidental damage to the elastic body E. It is more preferable that this maximum value be 60 mT or more and 890 mT, and extremely preferably 100 mT or more and 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 7] 7A to 7D show sensor units in which permanent magnets and magnetic sensor elements are formed on a flexible sheet. (A) shows a sensor unit with two magnetic sensor elements, (B) and (C) show a sensor unit with three magnetic sensor elements, and (D) shows a sensor unit with four magnetic sensor elements. In Additional Configuration 2 or a configuration in which Additional Configuration 2 is combined with at least one of Additional Configurations 3 to 6, as shown in FIGS. 7A to 7D, a permanent magnet 12 and at least two magnetic sensor elements 14 (14a to 14d) are preferably disposed on an elastic body via a non-magnetic, non-stretchable flexible sheet 16. In other words, the permanent magnet 12 and the magnetic sensor elements 14 are preferably formed on the flexible sheet 16 (Additional Configuration 7). The magnetic sensor elements 14 may be located on the reference line L0 in a plan view, as shown in example 14b in FIG. 7B.

[0052] When a sensor unit 10 including a permanent magnet 12 and a magnetic sensor element 14 (14a, 14b) is arranged so as to follow deformations in all directions of the elastic body E (for example, when the permanent magnet 12 and the magnetic sensor element 14 are embedded in the elastic body E, or when the permanent magnet 12 and the magnetic sensor element 14 are arranged on the elastic body E via an elastic sheet), the change in magnetic flux density detected by each magnetic sensor element 14 is affected by both the stretching deformation and bending deformation of the deformation behavior of the sensor unit 10, i.e., the detection is based on all of the deformation behavior of the actual elastic body E.

[0053] 7, when a permanent magnet 12 and at least two magnetic sensor elements 14 (14a to 14d) are arranged on an elastic body 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 among 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 among the deformation behaviors of the actual elastic body E. Therefore, according to this embodiment, the bending deformation of the elastic body E can be extracted more easily, and as a result, the sensitivity for sensing the bending deformation of the elastic body E can be increased, and ultimately the deflection of the elastic body E can be determined with even higher accuracy.

[0054] The flexible sheet 16 may be a resin film with a high elastic modulus.

[0055] It is more preferable that the tensile modulus of flexible sheet 16 is 20 times or more the tensile modulus of the surface material of elastic body E on which flexible sheet 16 is placed, from the viewpoint that deformation of flexible sheet 16 can be ignored compared to deformation of elastic body E, and it is extremely preferable that it is 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).

[0056] [Additional Form 8] 8 is a diagram showing the state of adhesion of the flexible sheet on the elastic body. In this figure, the elastic body E is shown only in the area corresponding to the sensing area Rs described later, but normally the surface of the elastic body E is larger than the surface on which the flexible sheet 16 is placed.

[0057] In Additional Form 2 or a form in which Additional Form 2 is combined with at least one of Additional Forms 3 to 7, when the line obtained by projecting the reference line L0 passing through the center of gravity of the permanent magnet 12 (not shown in Figure 8) onto the concave curved surface of the flexible sheet 16 in the direction of the normal to the concave curved surface of the elastic body E is defined as the sheet surface reference line L1 (Figure 8), and when two lines that are parallel to the sheet surface reference line L1 in a planar 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 are defined as sheet surface outer lines L2 and L3, respectively, and when the area of ​​the flexible sheet existing between the two sheet surface outer lines L2 and L3 is defined as the sensing area Rs, it is preferable that 60% or more of the back surface of the sensing area Rs is adhered to the elastic body E (Additional Form 8). In the example shown in Figure 8, the magnetic sensor elements 14a and 14b are equidistant 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 (for example, 14a) that is farthest from the seat surface reference line L1 will be the magnetic sensor element that serves as the basis for determining the seat surface outer line L2.

[0058] Here, the sheet surface outer lines L2 and L3 are set so that all the magnetic sensor elements (magnetic sensor elements 14a to 14c in FIG. 8) are included in the sensing region Rs on each side of the sheet reference line L1. Furthermore, in view of the excellent adhesion of the flexible sheet 16 to the elastic body E, 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 elastic body E in the direction of the sheet surface reference line L1.

[0059] Since more than 60% of the back surface of the sensing area Rs is adhered to the elastic body E, when the elastic body E is deformed, the flexible sheet 16 deforms in a manner that closely follows the deformation of the elastic body E, allowing changes in magnetic flux density to be detected more accurately, and ultimately allowing the deflection of the elastic body E to be determined with even greater precision.

[0060] In this embodiment, it is more preferable that 80% or more of the rear surface of the sensing region Rs is adhered to the elastic body E, and it is extremely preferable that 100% of the rear surface is adhered to the elastic body E.

[0061] Furthermore, if another elastic body (e.g., a rubber layer) exists between the elastic body E 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 elastic body E. For this reason, it is preferable to place the flexible sheet 16 directly on the concave curved surface of the elastic body E. For example, if the elastic body E is a tire, it is preferable to place the flexible sheet directly on the inner liner that forms the tire cavity surface (concave curved surface).

[0062] Furthermore, when the manufacturing process of the elastic body E includes a vulcanization process, the flexible sheet 16 may be placed on the elastic body E before or after vulcanization. However, when the flexible sheet 16 is placed on the elastic body E before vulcanization, the vulcanization is performed without placing the permanent magnet 12 or the magnetic sensor element 14 on the flexible sheet 16.

[0063] [Additional Form 9] Figure 9 shows the positional relationship between the permanent magnet and the magnetic sensor element before and after placing a flexible sheet (sensor unit) on an elastic body, where (A) shows the case where the magnetization direction is perpendicular to the flexible sheet before placement, and (B) shows the case where the magnetization direction is parallel to the flexible sheet before placement.

[0064] In Additional Form 2 or a form in which Additional Form 2 is combined with at least one of Additional Forms 3 to 8, as shown in Figure 9, in a state in which the flexible sheet 16 is not placed on the elastic body E (the view to the left of the arrow in both (A) and (B)), 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 9). 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.

[0065] 9(A) and 9(B), when moving from the left side to the right side, the elastic body E 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, the inventors discovered that if the size of the magnetic sensor element 14 (e.g., the aforementioned dimension Hc) is too large, the sensitivity of the signal to bending decreases, resulting in a deterioration in sensing accuracy. Under these circumstances, the inventors introduced a function of d, because the position of the magnetic sensor element 14 in the magnetic field changes even when the elastic body E bends in the same way. They discovered that if the function satisfies the above range, good sensing sensitivity can be ensured.

[0066] [Additional Form 10] In Additional Form 2 or Additional Form 2 plus at least one of Additional Forms 3 to 9, it is preferable that the above-mentioned flexible sheet 16 is a flexible substrate, the sensor unit 10 has 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 10).

[0067] By using a flexible substrate for the flexible sheet 16, the flexible sheet 16 can better follow the deformation of the elastic body E, thereby further increasing the durability of the elastic body E. Although a flexible film can be interposed between the elastic body E 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 allows the deflection of the elastic body E to be determined with even higher accuracy.

[0068] 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.

[0069] <Tires> [Basic form 11] 10 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.

[0070] Although not shown in detail, the tire 20 of this embodiment 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.

[0071] 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.

[0072] 10, a tire 20 is provided with a sensor unit 10 on the tire cavity surface. In the example shown in the figure, the sensor unit 10 is formed by forming one permanent magnet 12 and two magnetic sensor elements 14a, 14b on a flexible sheet 16, and the reference line L0 (a point on the tire cavity surface) described in the section on elastic bodies extends along the tire circumferential direction (a direction penetrating the page).

[0073] Here, the reference line L0 extending along the tire circumferential direction means that the extension direction of the reference line L0 is allowed to be shifted by 10° on either side along the tire cavity surface relative to the tire circumferential direction.

[0074] Considering that when the tire rolls on the ground, the tire exhibits approximately the same bending deformation behavior at any circumferential position, by extending the reference line L0 (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.

[0075] As shown in FIG. 10, 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.

[0076] [Additional Form 12] 11A and 11B are meridian cross sections 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 14a 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 14a on the inner side in the tire width direction is not located within the predetermined range on the tire cavity surface. Note that the tire 20 shown in both (A) and (B) is in an unloaded state (non-contact state) where the tire is mounted on a regular rim R and pressurized to the normal internal pressure.

[0077] In basic form 11, as shown in FIG. 11, a belt 22 consisting of at least one belt layer 22a, 22b (two belt layers 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, 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 the reference line L0 exists between the first point P1 and the second point P2 along the tire cavity surface (additional form 12).

[0078] By locating the reference line L0 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 straddle the reference line L0 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.

[0079] If the permanent magnet 12 is placed too close to the belt layers 22a, 22b containing the steel cords, the steel cords may bias the distribution of the 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 portion. In consideration of such undesirable situations, the position of the reference line L0 defined in this embodiment is set within the predetermined range as described above.

[0080] As mentioned above, 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 (the range between point P1 and 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 this embodiment is intended to include both the cases of Figure 11 (A) and (B) within the scope of the invention.

[0081] [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 the end of a flexible sheet closer to 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.

[0082] In the basic configuration 11 or the configuration obtained by adding additional configuration 12 to the basic configuration 11, as shown in FIG. 12, a belt 22 consisting of at least one belt layer 22a, 22b (two belt layers 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, 22b that has the largest dimension in the tire width direction among the belt layers 22a, 22b, 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 the reference line L0 exists between the first point P1 and the third point P3 along the tire cavity surface, the permanent magnet 12 and at least two magnetic sensor elements 14a, 14b are arranged on the tire cavity surface via a non-magnetic, non-stretchable flexible sheet, and the end of the flexible sheet 16 closer to the tire equatorial plane is located more inward in the tire width direction than the first point P1 (additional configuration 13).

[0083] By locating the reference line L0 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 straddle the reference line L0 becomes a portion that is subject to extremely large deformation, thereby further increasing the sensitivity for sensing the bending deformation of the tire 20, and ultimately enabling the deflection of the tire 20 to be determined with even higher accuracy.

[0084] Furthermore, by positioning the end of the flexible sheet 16 closer to the tire equatorial plane on the inner side 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 significantly higher rigidity than the sidewall portion. This makes it possible to maintain a stronger adhesion state with the tire, particularly at the inner portion in the tire width direction of the sensor unit 10 (the end). As a result, the end can be stably formed as a connection portion with electrical wiring and a connector connected to the sensor unit 10, and ultimately the durability of the tire 20 can be further improved.

[0085] [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.

[0086] In the basic form 11 or a form in which at least one of additional forms 12 and 13 is added to the basic form 11, as shown in FIG. 13, a belt 22 consisting of at least one belt layer 22a, 22b (two in the figure) is provided on the tire radial outer side of a carcass (not shown), a permanent magnet 12 and at least two magnetic sensor elements 14a, 14b are arranged on the tire cavity surface via a non-magnetic, non-stretchable flexible sheet 16, and it is preferable that the distance t 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 innermost magnetic sensor element 14a that is arranged on the innermost side in the tire width direction, and the distance d along the flexible sheet 16 from the innermost magnetic sensor element 14a to the permanent magnet 12 satisfy d / t≦1.8 (additional form 14).

[0087] 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 d 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.

[0088] 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.

[0089] Furthermore, in this embodiment, by setting the distance d along the flexible sheet 16 from the magnetic sensor element 14a located at the innermost position 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, it is possible to further increase the sensitivity for sensing the bending deformation of the tire 20 when the actual curvature of the tire cavity surface and the actual position of the sensor unit 10 are taken into consideration, and therefore it is possible to determine the deflection of the tire 20 with even higher accuracy.

[0090] [Additional Form 15] Fig. 14 is a meridian cross-sectional view of a tire showing the relationship between the dimension of a permanent magnet and tire thickness. Note that, like the tire 20 shown in Fig. 10, the tire 20 shown in Fig. 14 is in an unloaded state (non-ground-contacting state) mounted on a normal rim R and given a normal internal pressure. In basic mode 11 or a mode in which basic mode 11 is combined with at least one of additional modes 12 to 14, as shown in Fig. 14, the dimension T of the permanent magnet 12 in a direction perpendicular to both the reference line L0 (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 is preferably 0.10 to 0.75 times the tire thickness Ga on the perpendicular line from the center of gravity G of the permanent magnet to the tire cavity surface (additional mode 15).

[0091] 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.

[0092] 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 even better during bending deformation of the tire, and the permanent magnets 12 are further prevented from falling off the flexible sheet 16, thereby further improving the durability of the tire 20.

[0093] 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.

[0094] [Additional Form 16] In basic form 11 or a form in which basic form 11 is combined with at least one of additional forms 12 to 15, when the outline of flexible sheet 16 shown in FIG. 14 is projected onto a carcass layer (not shown), 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 16).

[0095] 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 in the tire radial direction.

[0096] 14, 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, because the tensile modulus of elasticity of the carcass cords is much greater than that of rubber.

[0097] 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.

[0098] 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.

[0099] 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.

[0100] 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] [Other tire types] Further preferred examples of the tire 20 equipped with the sensor unit 10 described above will be described below.

[0105] (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.

[0106] 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.

[0107] (Preferable example 2) Figure 15 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.

[0108] The circuit board 30a shown in FIG. 15(A) and the circuit board 30b shown in FIG. 15(B) include an amplifier circuit, a power supply circuit, a signal processing circuit, a communication circuit, and the like.

[0109] In the examples shown in Figures 15(A) and 15(B), if the foot of a perpendicular line drawn from the tire width direction end of the belt layer 22a having 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, 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.

[0110] 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]

[0111] Below, we will compare the effects of the tire inventions defined in claims 11 to 16 of the present application (hereinafter referred to as "Invention Examples 11 to 16") with those of an invention similar to the invention described in Patent Document 1 (hereinafter referred to as "Prior Art Example").

[0112] The tire size was 245 / 40R19 (specified by JATMA), and each of the tires of Examples 11 to 16 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).

[0113] In contrast, in the conventional example, since there was only 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.

[0114] 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 11 to 16 are as shown in Table 1 below. In all examples, a unipolar magnetized permanent magnet was used. The magnetization direction was perpendicular to the flexible sheet when the sensor unit was not placed on the tire.

[0115] [Table 1]

[0116] In Table 1, the reference line L0, point P1, point P2, point P3, d / t, T / Ga, number of crossing cords, etc. conform to the definitions set forth in this specification.

[0117] Table 1 shows that all tires within the technical scope of the present invention have high sensitivity in sensing tire flexure. [Explanation of symbols]

[0118] 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 Amplifier circuit Ar arithmetic circuit C concave circle d distance between the permanent magnet and the magnetic sensor element E Elastic body G Center of gravity of permanent magnet Ga Tire Thickness H is the height dimension of the permanent magnet, which is the direction of the perpendicular line from the center of gravity to the concave curved surface of the elastic body. Hc: Dimension from the flexible sheet to the highest point of the magnetic sensor element 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 θ angle

Claims

1. a sensor unit arranged on a surface of an elastic body to determine a deflection of said elastic body when said elastic body is bent, the sensor unit includes one permanent magnet and at least two magnetic sensor elements; A sensor unit, characterized in that the deflection of the elastic body is determined by performing a calculation using signals output from each of the at least two magnetic sensor elements.

2. the surface of the elastic body is a concave curved surface, 2. The sensor unit of claim 1, wherein a concave circle is determined by projecting onto the elastic body 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 from the center of gravity to the surface of the elastic body, and has a radius that is the shortest distance between the straight line and the magnetic sensor, and then a line that includes the diameter of the concave circle with the largest radius of curvature is used as a reference line, and at least one magnetic sensor element is arranged in each region on one side and the other side of the reference line within the concave circle.

3. In a state where the sensor unit is disposed on the elastic body and the elastic body is not yet bent, the magnetic sensor element 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. The sensor unit according to claim 2 .

4. 4. The sensor unit according to claim 2, wherein a radius r of a circle passing through three points, namely, the center of gravity of one of the magnetic sensor elements arranged directly or indirectly on one side of the reference line within the concave circle, the center of gravity of one of the magnetic sensor elements arranged directly or indirectly on the other side of the 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.

5. 4. The sensor unit according to claim 2, wherein an angle θ formed by an arc connecting the centers of gravity of the two magnetic sensor elements on a circle passing through three points: the center of gravity of one of the magnetic sensor elements arranged directly or indirectly on one side of the reference line within the concave circle; the center of gravity of one of the magnetic sensor elements arranged directly or indirectly on the other side of the reference line within the concave circle; and the center of gravity of the permanent magnet is 5.5° or more and 60° or less.

6. Regarding the permanent magnet, A height dimension H, which is a direction of a perpendicular line from the center of gravity to the concave curved surface of the elastic body; A dimension W in the direction of the reference line; A dimension T in a direction perpendicular to both the height direction and the direction of the reference line; 4. The sensor unit according to claim 2, wherein the dimension T is the smallest among the above.

7. 4. The sensor unit according to claim 2, wherein the permanent magnet and the at least two magnetic sensor elements are arranged on the elastic body via a non-magnetic, non-stretchable flexible sheet.

8. a line obtained by projecting the reference line onto the concave curved surface of the flexible sheet in a direction perpendicular to the concave curved surface is defined as a sheet surface reference line; 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 sensor unit according to claim 7 , wherein 60% or more of the rear surface of the sensing area is adhered to the elastic body.

9. A sensor unit as described in claim 7 or 8, 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

10. the flexible sheet is a flexible substrate, The sensor unit according to claim 7 or 8, 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.

11. A tire comprising the sensor unit according to claim 2 on a tire cavity surface, A tire characterized in that the reference line extends along the tire circumferential direction.

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, 12. The tire of claim 11, wherein the reference line lies along the tire cavity surface between the first point and the second point.

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 drawn from an end portion in the tire width direction of a belt layer having a maximum 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, the reference line exists along the tire cavity surface between the first point and the third point, the permanent magnet and the at least two magnetic sensor elements are disposed on a tire cavity surface via a non-magnetic, non-stretchable flexible sheet; The tire according to claim 11 , wherein an end of the flexible sheet closer to 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; the permanent magnet and the at least two magnetic sensor elements are disposed on the elastic body via a non-magnetic, non-stretchable flexible sheet; 13. The tire according to claim 11 or 12, 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. 13. The tire according to claim 11 or 12, wherein a dimension of the permanent magnet in a direction perpendicular to both the 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.

16. 13. The tire according to claim 11 or 12, wherein, when the outline 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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