Method for estimating tire condition, and system for estimating tire condition

Abstract

This tire state estimation method includes the following. (1) Disposing, on the inner side of a tire, at least one power generator that generates voltage in response to deformation of the tire. (2) Acquiring measurement data in a time series obtained by measuring, while the tire is rotating, the voltage and / or a physical quantity corresponding to the voltage. (3) Identifying a peak that repeatedly appears in the measurement data. (4) Identifying a value of the peak and / or an interval of the peak. (5) Estimating the state of the tire on the basis of the identified value and / or the identified interval. The power generator is provided with a first member and a second member. The first member and the second member are configured such that one is positively charged and the other is negatively charged in accordance with pressure applied to the first member and the second member.

Description

Technical Field

[0001] The present disclosure relates to a method for estimating the state of a tire and a system for estimating the state of a tire.

Background Art

[0002] Japanese Patent Application Laid-Open No. 2016-190615 (Patent Document 1) discloses a method for estimating the wear amount of a tire using the output signal of an acceleration sensor disposed on the inner surface of a tire tread. In this method, a tire radial acceleration waveform is extracted from the tire radial acceleration continuously detected by the acceleration sensor, and this is differentiated with respect to time to obtain a differential acceleration waveform. From the obtained differential acceleration waveform, among the peaks that appear at the grounding end, those that satisfy the conditions are extracted and used as differential peak values for wear estimation. Based on the reference differential peak value calculated from the differential peak value for wear estimation and a map showing the relationship between the wear amount and the reference differential peak value stored in a storage means in advance, the wear amount of the tire is estimated.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The method of Patent Document 1 focuses on the fact that as the tread portion of the tire wears, the deformation speed of the tread portion at the time of tire grounding changes. However, in this method, when the vehicle on which the tire is mounted is mainly traveling at a low speed (for example, about 40 km / h), the radial acceleration of the tire decreases and the signal-to-noise ratio deteriorates, so there is a possibility that the estimation accuracy of the wear amount decreases. Therefore, an estimation method that can accurately estimate the wear state of the tire even when the vehicle is traveling at a low speed has been desired.

[0005] Incidentally, the inventors have discovered that when the tread portion of a tire wears down, a change occurs in the shape of the tire's contact surface. This is thought to be because the wear of the tire's tread portion causes a change in the tire's rigidity. According to this finding, detecting changes in the shape of the tire's contact surface is useful for obtaining information about the tire's wear state. Information about the tire's wear state includes, for example, whether or not the tire is worn down, and whether or not uneven wear has occurred, which is a state where wear is concentrated in a particular area.

[0006] Furthermore, when a vehicle is moving straight, changes in the shape of the contact patch can also occur due to changes in tire pressure, mounting condition, and wheel load applied to the tire. For this reason, estimating the tire's contact condition, including changes in the shape of the tire's contact patch, is useful not only for obtaining information about wear conditions, but also for obtaining information about the tire's mounting condition to the wheel, tire pressure, and wheel load applied to the tire. Information about the tire's mounting condition includes, for example, whether the tire is mounted in the correct position relative to the wheel. Information about tire pressure includes, for example, whether the tire pressure is low or low, or whether the tire pressure is excessively high. Information about wheel load includes, for example, whether uneven loading is occurring, where the load is concentrated on a specific part of the vehicle. Based on the above, estimating the tire's contact condition, including its relationship to tire wear conditions, can be useful for vehicle control.

[0007] This disclosure aims to provide a method and system for estimating tire wear, which accurately estimates the tire wear state even when the vehicle is traveling at low speeds, as well as a method and system for estimating the tire contact state. [Means for solving the problem]

[0008] The method for estimating the condition of a tire relating to the first aspect of this disclosure includes the following: (1) At least one power generator that generates voltage in accordance with the deformation of the tire is placed inside the tire. (2) While the tire is rotating, acquire time-series measurement data of the voltage and at least one physical quantity equivalent to the voltage. (3) Identifying the peaks that repeatedly appear in the measurement data. (4) Specify at least one of the peak value and the interval between the peaks. (5) Estimate at least one of the tire wear condition and contact condition based on at least one of the specified values ​​and intervals. The power generation unit comprises a first member and a second member. The first member has a first insulating film that forms a first surface. The second member has a second insulating film that faces and contacts the first surface and forms a second surface. The first member and the second member are configured such that the true contact area between the first surface and the second surface changes in response to the pressure applied to the first member and the second member. The first insulating film and the second insulating film are configured such that one becomes positively charged and the other becomes negatively charged as the true contact area changes.

[0009] According to the estimation method relating to the first aspect, at least one of the tire wear state and contact state is estimated based on at least one of the peak values ​​and intervals that repeatedly appear in the measurement data of at least one of the voltage of a generator that generates voltage in response to tire deformation and the corresponding physical quantity. The peak appears when the impact from the road surface is most strongly transmitted to the generator at a specific rotational position of the tire, so it can be easily identified even when the vehicle's travel speed, i.e., the tire's rotational speed, is low. This makes it possible to avoid a decrease in the accuracy of the wear state estimation even when the vehicle is traveling at low speeds.

[0010] A method for estimating the state of a tire relating to a second perspective is a method for estimating the state of a tire relating to a first perspective, wherein identifying the peaks includes identifying a first peak and a second peak that appears in conjunction with the first peak. Furthermore, identifying at least one of the peak values ​​and the intervals between the peaks includes identifying at least one of the following: a first peak value which is the value of the first peak, a second peak value which is the value of the second peak, a first interval which is the interval between the first peaks, a second interval which is the interval between the second peaks, and the time interval between the paired first and second peaks.

[0011] A method for estimating the tire condition relating to a third perspective is a method for estimating the tire condition relating to a second perspective, wherein identifying at least one of the peak value and the interval between peaks includes identifying the first peak value, the second peak value, the time interval, and the first interval or the second interval. Furthermore, estimating at least one of the tire wear condition and contact condition includes calculating at least one of a peak comparison value comparing the first peak value and the second peak value, and a time comparison value comparing the time interval with the first interval or the second interval, and estimating the tire wear condition based on at least one of the calculated peak comparison value and time comparison value.

[0012] The method for estimating the tire condition relating to the fourth perspective is a method for estimating the tire condition relating to the third perspective, wherein the peak comparison value is the ratio of the first peak value to the second peak value, and the time comparison value is the ratio of the time interval to the first interval or the second interval. Estimating the tire wear condition includes estimating the tire wear condition based on the peak comparison value and the time comparison value.

[0013] A method for estimating the tire condition relating to the fifth viewpoint is a method for estimating the tire condition relating to any of the first to fourth viewpoints, wherein placing at least one power generator inside the tire includes placing at least one power generator at a position outside the width of the contact surface when the tire is new. Furthermore, specifying at least one of the peak value and the interval between the peaks includes specifying the peak value of the power generator placed at the outer position. In addition, estimating at least one of the tire wear state and the contact state includes estimating at least one of the tire wear state and the contact state based on the change in the specified value.

[0014] Depending on the tire, as the tread wears down, the width of the contact patch (contact width) increases compared to when it is not worn, and parts that were previously not in contact with the ground begin to make contact. As a result, the shock from the road surface is more easily transmitted to the power generator located in that area, causing a significant change in the measurement data. This allows for the detection of a change in the contact patch shape, and consequently, the estimation that tire wear is occurring. Note that the "width direction" of the tire refers to the direction parallel to the axis of rotation of the tire mounted on the vehicle.

[0015] Furthermore, wear on the tire tread, changes in tire wheel load, changes in mounting conditions, and changes in air pressure can increase the width of the contact patch, causing previously uncontacted areas to come into contact with the ground. This makes the power generator positioned in that area more sensitive to road shocks, resulting in significant changes in the measurement data. This allows us to estimate the state in which a change has occurred in the tire's contact patch shape.

[0016] A method for estimating the condition of a tire relating to the sixth viewpoint is a method for estimating the condition of a tire relating to either the first viewpoint or the fifth viewpoint, wherein placing at least one power generator inside the tire includes placing at least one power generator at the widthwise edge of the contact surface when the tire is new. Furthermore, specifying at least one of the peak value and the interval between the peaks includes specifying the peak value of the power generator placed at the edge. In addition, estimating at least one of the tire wear state and contact state includes estimating at least one of the tire wear state and contact state based on the change in the specified value.

[0017] Depending on the tire, as the tread wears down, the width of the contact patch becomes shorter compared to when it was not worn, and the portion that was previously in contact with the ground no longer makes contact. As a result, the impact from the road surface is less easily transmitted to the power generator located in that area, causing a significant change in the measurement data. This allows for the detection of a change in the contact patch shape, and consequently, the estimation that tire wear is occurring.

[0018] Furthermore, wear on the tire tread, changes in wheel load, changes in mounting conditions, and changes in air pressure can shorten the widthwise length of the contact patch, causing previously contacting areas to cease contact. As a result, the impact from the road surface is less effectively transmitted to the power generator positioned in that area, leading to a significant change in the measurement data. This allows for the estimation of conditions in which the tire's contact patch shape has changed.

[0019] A method for estimating the tire condition relating to the seventh viewpoint is a method for estimating the tire condition relating to the second viewpoint, wherein specifying at least one of the peak value and the interval between peaks includes specifying the time interval and the first interval or the second interval. Furthermore, estimating at least one of the tire wear state and the contact state includes calculating a time comparison value comparing the time interval and the first interval or the second interval, and estimating the tire contact state based on the calculated time comparison value.

[0020] The method for estimating the tire condition relating to the eighth viewpoint is a method for estimating the tire condition relating to the seventh viewpoint, further comprising obtaining the circumference of the tire. Estimating the contact condition of the tire includes estimating the circumferential length of the tire's contact surface based on the calculated time comparison value and the obtained circumference.

[0021] The paired first and second peaks correspond to the point in time when a specific part of the tire's circumferential direction begins contact with the ground and the point in time when contact ends, respectively. In other words, the time interval between the paired first and second peaks corresponds to the circumferential length of the tire's contact patch. Furthermore, the first and second intervals represent the time it takes for the tire to complete one rotation and correspond to the tire's circumference. This allows us to estimate the circumferential length of the tire's contact patch based on the time comparison value and the tire's circumference. Note that the "circumferential direction" of the tire corresponds to the direction of the tire's movement.

[0022] The tire condition estimation system according to the ninth aspect includes at least one power generator, a measurement device, and an estimation unit. The at least one power generator is disposed inside the tire and generates a voltage in response to deformation of the tire. The measurement device is disposed inside the tire and measures at least one of the voltage and a physical quantity corresponding to the voltage while the tire rotates, and outputs time-series measurement data. The estimation unit identifies peaks repeatedly appearing in the measurement data, identifies at least one of the peak values and the intervals between the peaks, and estimates at least one of the wear condition and the grounding condition of the tire based on at least one of the identified values and intervals. The power generator includes a first member and a second member. The first member has a first insulating film forming a first surface. The second member has a second insulating film forming a second surface facing and contacting the first surface. The first member and the second member are configured such that the true contact area between the first surface and the second surface changes in response to the pressure applied to the first member and the second member. The first insulating film and the second insulating film are configured such that one becomes positively charged and the other becomes negatively charged as the true contact area changes.

[0023] The tire condition estimation system according to the tenth aspect is the tire condition estimation system according to the ninth aspect, and further includes at least two or more of the power generators and a power storage device. The power storage device is configured to store the charges of some of the at least two or more power generators.

[0024] According to the estimation system according to the tenth aspect, a part of at least two or more power generators can be used as an energy source. Therefore, the power for driving the mechanism inside the tire of the estimation system can be provided inside the tire.

[0025] The tire condition estimation method according to the eleventh aspect includes the following. (1) At least one piezoelectric element that generates a voltage in response to the deformation of the tire is placed on the inside of the tire, at a position outside the width of the contact surface when the tire is new, and at the widthwise edge of the contact surface when the tire is new. (2) While the tire is rotating, acquire time-series measurement data of the voltage and at least one physical quantity equivalent to the voltage. (3) Estimate at least one of the tire wear condition and contact condition based on the acquired measurement data.

[0026] The method for estimating the tire condition related to the 12th perspective includes the following: (1) Inside the tire, elements that generate voltage in response to the deformation of the tire are arranged two-dimensionally along the circumferential and width directions of the tire. (2) While the tire is rotating, acquire time-series measurement data of the voltage and at least one physical quantity equivalent to the voltage. (3) Estimate at least one of the tire wear condition and contact condition based on the acquired measurement data.

[0027] The tire condition estimation system relating to the 13th aspect comprises at least two elements, a measuring device, and an estimation unit. The at least two elements are arranged two-dimensionally inside the tire, along the circumferential and width directions of the tire, and generate a voltage in accordance with the deformation of the tire. The measuring device is located inside the tire and measures the voltage and at least one of a physical quantity equivalent to the voltage while the tire is rotating, and outputs time-series measurement data. The estimation unit estimates at least one of the tire's wear state and contact state based on the measurement data. [Effects of the Invention]

[0028] This disclosure provides a method and system for estimating tire wear, which can accurately estimate the tire wear state even when the vehicle is traveling at low speed. Furthermore, this disclosure provides a method and system for estimating the tire contact state. Estimating the tire contact state is useful for obtaining information such as the tire wear state, the tire mounting state to the wheel, the tire pressure, and the tire wheel load. [Brief explanation of the drawing]

[0029] [Figure 1] A diagram showing the overall configuration of an estimation system according to one embodiment. [Figure 2] A block diagram showing the electrical configuration of the estimation system. [Figure 3] Cross-sectional view of a power generator according to one embodiment. [Figure 4] A diagram explaining the principle of charge generation in a power generator. [Figure 5] A schematic diagram showing the configuration of the module. [Figure 6] Cross-sectional view of a tire assembly. [Figure 7] Another cross-sectional view of the tire assembly. [Figure 8] A diagram showing an example of the arrangement of power generators. [Figure 9] A diagram explaining the estimation principle. [Figure 10] A diagram showing the configuration of the experimental apparatus. [Figure 11] A diagram comparing the contact surface shape in a new condition and a worn condition. [Figure 12] A graph plotting the dimensions of the contact surface under various conditions. [Figure 13A] A graph of time-comparison values. [Figure 13B] A graph comparing peak values. [Figure 13C] A graph of time-comparison values. [Figure 13D] A graph comparing peak values. [Figure 13E] A graph of time-comparison values. [Figure 13F]A graph comparing peak values. [Figure 14] A graph plotting experimental data on a time-comparison value-peak-comparison plane. [Figure 15] A flowchart illustrating an example of the process for estimating wear status. [Figure 16] A flowchart illustrating an example of the grounding state estimation process. [Figure 17A] Deconstructed diagram of a tire assembly. [Figure 17B] A diagram illustrating the rotational force generated in a tire assembly due to the uneven distribution of mass. [Figure 18A] An unfolded diagram of a tire assembly showing an example of the arrangement of power generators. [Figure 18B] Figure 18A is a cross-sectional view of the tire assembly as seen from the direction of the rotation axis. [Figure 18C] An unfolded diagram of a tire assembly showing an example of a T-shaped arrangement of power generators. [Figure 18D] Figure 18C is a cross-sectional view of the tire assembly as seen from the axis of rotation. [Figure 18E] An unfolded diagram of a tire assembly showing an example of a V-shaped arrangement of power generators. [Figure 18F] Figure 18E is a cross-sectional view of the tire assembly as seen from the axis of rotation. [Figure 18G] An unfolded diagram of a tire assembly showing an example of a W-shaped arrangement of power generators. [Figure 18H] An unfolded diagram of a tire assembly showing an example of a U-shaped arrangement of power generators. [Figure 18I] An unfolded diagram of a tire assembly showing an example of an O-shaped arrangement of power generators. [Figure 18J] An unfolded diagram of a tire assembly, showing an example of a two-dimensional arrangement of components. [Figure 19] Unfolded diagram of a tire assembly created in an experiment. [Figure 20A] A graph overlaying the measured contact surface shape with the estimated circumferential length. [Figure 20B] A graph overlaying the measured contact surface shape with the estimated circumferential length. [Figure 20C] A graph overlaying the measured contact surface shape with the estimated circumferential length. [Figure 20D] A graph overlaying the measured contact surface shape with the estimated circumferential length. [Figure 21] A diagram of a tire assembly created in another experiment. [Figure 22] A diagram comparing the voltage waveforms of each piezoelectric element. [Figure 23A] A graph overlaying the measured contact surface shape with the estimated circumferential length. [Figure 23B] A graph overlaying the measured contact surface shape with the estimated circumferential length. [Figure 23C] A graph overlaying the measured contact surface shape with the estimated circumferential length. [Figure 23D] A graph overlaying the measured contact surface shape with the estimated circumferential length. [Figure 23E] A graph overlaying the measured contact surface shape with the estimated circumferential length. [Figure 24A] A graph plotting the position of the piezoelectric element against its peak comparison value. [Figure 24B] A graph plotting the position of a piezoelectric element against its time-based comparison. [Figure 25] A graph overlaying the contact surface shape measured during wear with the estimated circumferential length. [Figure 26] A graph overlaying the contact surface shape measured when the product was new with the estimated circumferential length. [Modes for carrying out the invention]

[0030] Hereinafter, with reference to the drawings, a method for estimating the wear state and a method for estimating the contact state performed by the tire state estimation system according to the embodiments of this disclosure will be described. As described below, the wear state estimation system and the contact state estimation system have common components, and therefore they can be configured as a tire state estimation system using the same hardware resources. Accordingly, hereafter, the wear state estimation system and the contact state estimation system will be collectively referred to as the "estimation system". Furthermore, as described below, it is sometimes possible to estimate the tire's contact state and the tire's wear state simultaneously based on the same data. Accordingly, hereafter, a method for estimating these will be described, while touching upon the relationship between the tire's wear state and the tire's contact state.

[0031] <1. Overview of the estimation system> Figure 1 is an overall configuration diagram of the estimation system 9 according to one embodiment, and Figure 2 is a block diagram showing the electrical configuration of the estimation system. The estimation system 9 can be implemented in a vehicle 6 on which tire assemblies 7a to 7d are mounted. The type of vehicle 6 is not particularly limited, but for example, it is a four-wheeled vehicle equipped with a left front wheel FL, a right front wheel FR, a left rear wheel RL, and a right rear wheel RR. Tire assemblies 7a to 7d are mounted on the wheels FL, FR, RL, and RR of the vehicle 6, respectively. Although the wheels to which the tire assemblies 7a to 7d are mounted are different, they have the same structure and function. Therefore, in the following, they may be referred to as tire assemblies 7a to 7d without distinction. The vehicle 6 and tire assemblies 7 will be described later.

[0032] The estimation system 9 includes an external computer 60 located outside the tire 70 of the tire assembly 7. The external computer 60 is not particularly limited, but is, for example, an on-board device mounted on a vehicle 6. The external computer 60 is capable of wireless communication with the tire assembly 7 of each wheel and receives data collected by the tire assembly 7 via wireless communication. The external computer 60 is configured to estimate at least one of the tire wear state and the contact state based on the data received from the tire assembly 7. In this embodiment, the external computer 60, together with the internal computer 81 (described later), constitutes an estimation unit that estimates at least one of the tire wear state and the contact state.

[0033] The estimation system 9 further comprises a power generator 1, an internal computer 81, a measuring device 82, and a communication device 83. These elements are arranged inside the tire 70 and constitute the tire assembly 7, which will be described later. As will be described later, the power generator 1 is configured to generate a voltage by utilizing the impact transmitted from the road surface when the tire assembly 7 rotates on the road surface as the vehicle 6 moves. The voltage generated in the power generator 1 is measured by the measuring device 82 and output to the internal computer 81 as time-series measurement data. The internal computer 81 can transmit at least one of the measurement data and the processed measurement data to the external computer 60 via the communication device 83. In this embodiment, the internal computer 81, together with the external computer 60, constitutes an estimation unit. The various components of the estimation system 9 will be described below.

[0034] <2. Vehicles> [External computer 60] Vehicle 6 is further equipped with an external computer 60. The external computer 60 is a general-purpose computer in terms of hardware, and includes a CPU 600, an I / O interface 601, RAM 602, ROM 603, and a non-volatile, rewritable storage device 604. The I / O interface 601 is a communication device for wired or wireless communication with external devices such as a display unit 65 and a tire assembly 7. ROM 603 stores a program 610 for controlling the operation of the estimation system 9. The program 610 is written to ROM 603 from a storage medium 611, such as a CD-ROM or USB memory. The CPU 600 reads the program 610 from ROM 603 and executes it, thereby virtually operating as a data acquisition unit 620, an estimation unit 621, and an alarm output unit 622. Details of the operation of each unit will be described later. Note that the storage location of the program 610 may be the storage device 604 instead of ROM 603. Also, RAM 602 and storage device 604 are used as appropriate for calculations by the CPU 600.

[0035] The storage device 604 is composed of a hard disk, flash memory, or the like. The storage device 604 has pre-stored data for estimating the wear state of the tire 70 and data for estimating the contact state of the tire 70. The estimation unit 621 refers to the data stored in the storage device 604 as needed and estimates at least one of the wear state and contact state of the tire 70.

[0036] [Display] Vehicle 6 is further equipped with a display unit 65. The display unit 65 is not limited in form as long as it can display various types of information and convey them to the user. For example, it can be implemented in any form, such as an LCD monitor, liquid crystal display element, organic EL display, plasma display, etc. The mounting position of the display unit 65 can be selected as appropriate, but it is desirable to install it in a position that is easily visible to the driver, such as on the instrument panel. When an external computer 60 is connected to a car navigation system, it is possible to use a monitor for the car navigation system as the display unit 65, or to use a multi-information display as the display unit 65.

[0037] <3. Power Generator> Figure 3 is a cross-sectional view showing the configuration of the power generator 1. However, the direction in which the power generator 1 is used is not limited to the direction shown in Figure 3. As shown in Figure 3, the power generator 1 comprises a first member 10 and a second member 20, and the members are stacked in this order. The power generator 1 is not limited to this, but for example, it has a square shape in plan view. The length of one side of the square is not limited, but can be about 10 mm to 100 mm. Furthermore, it is preferable that the length of one side of the square is less than or equal to the contact length of the tire 70 on which the power generator 1 is placed. Here, the contact length of the tire 70 is defined by the method described in the previous application of the present applicant, Japanese Patent Application Publication No. 2020-200012.

[0038] [First component] The first member 10 comprises a first base material 130, a first electrode 120, and a first insulating film 110. Each element of the first member 10 has a square shape with substantially the same dimensions in a plan view, and is stacked in this order from the outside to the inside of the power generator 1. These elements 110 to 130 may be fixed to each other. The first base material 130 is made of a flexible or viscoelastic material, such as a resin or elastomer, so that it can be deformed when subjected to external forces. In this embodiment, the first base material 130 is made of silicone rubber. Numerous irregularities are formed on the surface of the first base material 130 that is in contact with the first electrode 120. As a result, the irregularities corresponding to those of the first base material 130 are reproduced on the first surface 100 formed by the first insulating film 110 via the first electrode 120.

[0039] The configuration of the irregularities on the first substrate 130 is not particularly limited. For example, the irregularities may be formed regularly along the surface direction of the first substrate 130, or they may be formed somewhat randomly. The cross-sectional shape of the irregularities is also not particularly limited.

[0040] The first electrode 120 is a part for extracting the charge generated in the first insulating film 110 to the outside of the power generator 1, and is positioned on the back surface of the first surface 100 so as to be in contact with the first insulating film 110. The first electrode 120 can be made of a conductive material, and examples of such materials include conductive films such as Ag and Cu, and conductive fabric. The composition of the conductive fabric is not particularly limited, but it may be an organic fiber fabric made of polymer material with metal plating, or a fabric made of polymer material with metal fibers mixed in. The first electrode 120 is flexible and can deform in accordance with the deformation of the first substrate 130. In addition, the surface of the first electrode 120 that is in contact with the first insulating film 110 reproduces the irregularities corresponding to the irregularities of the first substrate 130.

[0041] The first insulating film 110 is a film made of an insulator and is flexible. In this embodiment, the surface of the first insulating film 110 opposite to the first electrode 120 corresponds to the first surface 100. The first surface 100 has irregularities formed on it by the first substrate 130, corresponding to the irregularities of the first substrate 130. The first surface 100 faces the second surface 200 formed by the second insulating film 210, which will be described later, and is in contact with the second surface 200. When the pressure applied to the power generator 1 changes the true contact area, which is the actual contact area between the first surface 100 and the second surface 200, the first insulating film 110 becomes charged with the opposite polarity to the second insulating film 210. That is, when the second insulating film 210 is positively charged, the first insulating film 110 becomes negatively charged. Conversely, when the second insulating film 210 is negatively charged, the first insulating film 110 becomes positively charged.

[0042] The ten-point average roughness of the first surface (100) is preferably 100 μm or more and 2 mm or less. The method for measuring the ten-point average roughness shall be in accordance with JIS B 0601:2001.

[0043] Furthermore, when we say that the first surface 100 and the second surface 200 are "in contact," it is sufficient if they are only partially in contact, and there may be parts where the first surface 100 and the second surface 200 are not in contact. The power generator 1 is configured such that the first surface 100 and the second surface 200 overlap completely. In other words, in the power generator 1, one side of the first insulating film 110 and one side of the second insulating film 210 are in complete contact.

[0044] [Second component] The second member 20 comprises a second base material 230, a second electrode 220, and a second insulating film 210. Each element of the second member 20 has a square shape in plan view, similar to that of the first member 10, and is stacked in this order from the outside to the inside of the power generator 1. These elements 210 to 230 may be fixed to each other. The second base material 230, like the first base material 130, is made of a flexible or viscoelastic material, such as a resin or elastomer, so that it can be deformed when subjected to external forces. In this embodiment, the second base material 230 is made of silicone rubber. Numerous irregularities are formed on the surface of the second base material 230 that contacts the second electrode 220. As a result, the irregularities corresponding to those of the second base material 230 are reproduced on the second surface 200 formed by the second insulating film 210 via the second electrode 220.

[0045] The configuration of the irregularities on the second substrate 230 is not particularly limited. For example, the irregularities may be formed regularly along the surface direction of the second substrate 230, or they may be formed somewhat randomly. The cross-sectional shape of the irregularities is also not particularly limited.

[0046] The second electrode 220 is a part for extracting the charge generated in the second insulating film 210 to the outside of the power generator 1, and is positioned on the back surface of the second surface 200 so as to be in contact with the second insulating film 210. The second electrode 220 can be made of a conductive material, and examples of such materials include conductive films such as Ag and Cu, and conductive fabric. The composition of the conductive fabric is not particularly limited, but may be an organic fiber fabric made of polymer material with metal plating, or a fabric made of polymer material with metal fibers mixed in. The second electrode 220 is flexible and can deform in accordance with the deformation of the second substrate 230. In addition, the second electrode 220 reproduces the unevenness corresponding to the unevenness of the second substrate 230 on the surface that contacts the second insulating film 210.

[0047] The second insulating film 210 is a film made of a different insulator than the first insulating film 110 and is flexible. In this embodiment, the surface of the second insulating film 210 opposite to the second electrode 220 corresponds to the second surface 200. The second surface 200 has irregularities formed on it by the second substrate 230, corresponding to the irregularities of the second substrate 230. The second surface 200 faces the first surface 100 formed by the first insulating film 110 and is in contact with the first surface 100. When the pressure applied to the power generator 1 changes the true contact area between the first surface 100 and the second surface 200, the second insulating film 210 becomes charged with the opposite polarity to the first insulating film 110. That is, when the first insulating film 110 is positively charged, the second insulating film 210 becomes negatively charged. Conversely, when the first insulating film 110 is negatively charged, the second insulating film 210 becomes positively charged. As a result, a voltage is generated in the power generator 1.

[0048] The ten-point average roughness of the second surface (200) is preferably between 100 μm and 2 mm. The method for measuring the ten-point average roughness shall conform to JIS B 0601:2001.

[0049] [material] The materials constituting the first insulating film 110 and the second insulating film 210 can be selected from the group consisting of, for example, diamond-like carbon (DLC), perfluoropolyether, polymethyl methacrylate, nylon, polyvinyl alcohol, polyester, polyisobutylene, polyurethane (PU), polyethylene terephthalate, polyvinyl butyral, polychloroprene, natural rubber, polyacrylonitrile, polydiphenol carbonate, polychloride polyether, polyvinylidene chloride, polystyrene, polyethylene, polypropylene, polyimide, polyvinyl chloride, polydimethylsiloxane, polytetrafluoroethylene, tetrafluoroethylene and hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and other materials mainly composed of fluorocarbon organic substances.

[0050] From the group described above, from the viewpoint of minimizing wear due to frictional contact, it is preferable to select DLC, which has high hardness and a low coefficient of friction, or a material mainly composed of highly lubricating organic fluorocarbons. Furthermore, from the viewpoint of increasing the voltage of the power generator 1, it is preferable to select a pair of materials from the group described above that are further apart on the triboelectric series. Note that either the first insulating film 110 or the second insulating film 210 may be positively charged and the other negatively charged.

[0051] In this embodiment, the first insulating film 110 is made of polyimide, and the second insulating film 210 is made of nylon. As a result, in this embodiment, the first insulating film 110 becomes the negatively charged insulating film, and the second insulating film 210 becomes the positively charged insulating film.

[0052] [thickness] It is preferable that at least one of the thickness W1 of the first insulating film 110 and the thickness W2 of the second insulating film 210 is 20 μm or less. More preferably, both thicknesses W1 and W2 are 20 μm or less. Note that the figures do not necessarily reflect the dimensions of each element of the actual power generation unit 1.

[0053] [Charging principle of power generator 1] The first insulating film 110 and the second insulating film 210 become charged by the following operation. As shown in Figure 3, both the first surface 100 and the second surface 200 of this embodiment have irregularities, and even when no external pressure is applied to the power generator 1, they do not completely separate, leaving a portion in contact with each other. At this time, the distance between the average surface of the first surface 100 and the average surface of the second surface 200 (average surface spacing) is relatively large, which is equivalent to a relatively small true contact area between the first surface 100 and the second surface 200.

[0054] Next, when pressure is applied to the power generator 1 so that the first insulating film 110 and the second insulating film 210 are closer together, the shapes of the first surface 100 and the second surface 200 change as shown in Figure 4, the unevenness becomes slightly flatter, and the average surface spacing decreases. In other words, the true contact area increases. Furthermore, when the pressure applied to the power generator 1 is removed, the first insulating film 110 and the second insulating film 210 move apart again, and the average surface spacing increases. In other words, the true contact area decreases. As the true contact area changes in this way, the amount of charge on the first insulating film 110 and the second insulating film 210 increases compared to the initial state, and more charge is induced on the first electrode 120 and the second electrode 220. Thus, a voltage is generated in the power generator 1. In the tire assembly 7, the tire 70 rotates on the road surface, and the impact from the road surface is transmitted to the power generator 1, causing an increase or decrease in the true contact area. That is, the power generator 1 is configured to convert the vibration energy of the tire 70 into electrical energy and generate electricity.

[0055] Furthermore, in a configuration in which irregularities are formed on at least one of the first surface 100 and the second surface 200, the true contact area also changes to some extent as the first insulating film 110 and the second insulating film 210 move relative to each other in the planar direction. Therefore, among the forces applied to the power generator 1, not only forces that increase or decrease the average planar spacing, but also forces that cause the first insulating film 110 and the second insulating film 210 to slide relative to each other in the planar direction contribute to the power generation of the power generator 1.

[0056] <4. Modules> The power generator 1 is electrically connected to module 8. Module 8 is located inside the tire 70 and, together with the power generator 1, constitutes the tire assembly 7. Figure 5 is a schematic diagram showing the configuration of module 8. Module 8 includes, but is not limited to, an internal computer 81, a measuring device 82, a communication device 83, and a power storage device 80 mounted on a printed circuit board 84. These elements are integrally encapsulated in epoxy resin 86, except for lead wires 85, 85 extending from the measuring device 82. This suppresses the effects of water vapor inside the tire 70 on each element 80-84 and also protects them from impact. As also shown in Figure 2, the measuring device 82, the communication device 83, and the power storage device 80 are electrically connected to the internal computer 81.

[0057] [Measuring device] The measuring device 82 is a device for measuring the voltage generated in the power generator 1 and is electrically connected to the power generator 1. The first electrode 120 and the second electrode 220 of the power generator 1 and the measuring device 82 are connected by lead wires 85, 85. Here, the tire assembly 7 may include one or more power generators 1, but one measuring device 82 may be connected to multiple power generators 1, or multiple measuring devices 82 may be connected to individual power generators 1. The measuring device 82 is not limited to this, but may include an input impedance adjustment circuit, an input gain bias circuit, an analog / digital converter, etc. The time-series voltage generated in the power generator 1 is measured by the measuring device 82 and converted into a digital signal, and output to the internal computer 81 as time-series measurement data.

[0058] [Energy storage device] The tire assembly 7 may optionally include a power generator 1 for power supply, in addition to the power generator 1 for collecting measurement data. In this case, the tire assembly 7 may include a power storage device 80 connected to the power supply power generator 1. The power storage device 80 is not limited to but may include a rectifier, capacitor, power supply controller, etc. The power storage device 80 is configured to store the charge induced in the power generator 1 and release the stored charge as needed. This allows the voltage generated in the power generator 1 to be used to supply power to the internal computer 81 and communication device 83, so that the power for the operation of the module 8 can be supplied internally by the tire assembly 7. Power allocation control may be performed by the internal computer 81.

[0059] [Internal Computer] The internal computer 81 is a general-purpose microcomputer in terms of hardware, and is equipped with a processor, main memory, and a non-volatile, rewritable storage device. The storage device of the internal computer 81 contains programs for controlling the operation of module 8 and programs for processing measurement data, and these programs are executed by the processor. As described above, the internal computer 81 controls the operation of the energy storage device 80 and uses the charge stored in the energy storage device 80 as needed. The internal computer 81 also processes the measurement data acquired from the measurement device 82 and transmits the results to the external computer 60 at predetermined intervals via the communication device 83. The data processing by the internal computer 81 will be described later.

[0060] [communication equipment] The communication device 83 enables the internal computer 81 to wirelessly transmit and receive data with external devices of the tire assembly 7. The communication device 83 may be a general-purpose communication module equipped with an antenna.

[0061] <5. Tire Assembly> The configuration of the tire assembly 7 will be explained below with reference to the figures. Figures 6 and 7 are schematic partial cross-sectional views of the tire assembly 7. Figure 6 shows a cross-section when the tire assembly 7 is cut by a plane containing the rotation axis of the tire assembly 7. Figure 7 shows a cross-section when the tire assembly 7 is cut by a plane passing through the center of the tread portion 700 of the tire assembly 7 and perpendicular to the rotation axis of the tire assembly 7. In Figure 7, the direction from the back to the front of the paper, or from the front to the back of the paper, is parallel to the rotation axis of the tire assembly 7. Note that the dimensions of each element in the figures may be exaggerated for the sake of explanation and do not necessarily represent the actual dimensions and relative sizes.

[0062] [tire] As shown in Figures 6 and 7, the tire assembly 7 further comprises a tire 70 and a cover 50 in addition to the power generator 1 and module 8 already described. The tire 70 is made of vulcanized rubber or the like and is elastic. As shown in Figure 6, the tire 70 has a tread portion 700, a shoulder portion 701, a sidewall portion 702, and a bead portion 703. The tread portion 700 is the part that defines the side circumference of the tire assembly 7 and moves the vehicle 6 forward by contacting the road surface and generating friction. The shoulder portion 701 is the part adjacent to the tread portion 700 and the sidewall portion 702. The sidewall portion 702 bends and flexes to absorb shocks from the road surface. The bead portion 703 has a bead wire (not shown) built inside and is fixed to the wheel rim 710 formed on the periphery of the wheel 71.

[0063] [Cover body] The power generator 1 is positioned on the inner surface 720 of the tire 70. The cover body 50 is a member positioned on the inner surface 720 so as to cover the entire power generator 1, and its outer circumference is fixed to the inner surface 720 with the power generator 1 sandwiched between the cover body and the inner surface 720. In this way, the power generator 1 is fixed to the inner surface 720. The cover body 50 is preferably made of an elastic material, and more preferably made of a material that has heat resistance, impact resistance and durability. Examples of such materials include elastomers. The cover body 50 is not limited to these, but a tire repair member mainly made of elastomer with a layer of reinforcing cords built in can be used. The method of fixing the cover body 50 to the inner surface 720 is not particularly limited and can be appropriately selected, such as bonding with adhesive or bonding by vulcanization.

[0064] [Placement] The power generator 1 may be arranged such that the first member 10 faces the inner surface 720 of the tire 70 and the second member 20 faces the cover body 50, or the second member 20 faces the inner surface 720 of the tire 70 and the first member 10 faces the cover body 50. Furthermore, there are no particular limitations on the number of power generators 1 to be arranged and their positions on the inner surface 720, but from the viewpoint of accurately estimating tire wear and contact condition, for example, as shown in Figure 8, five power generators 1 can be arranged at different positions on the inner surface 720. For the sake of explanation, in Figure 8, the five power generators 1 are distinguished as power generators 1A to 1E. The configuration of power generators 1A to 1E may be the same, or they may differ in dimensions, for example.

[0065] In Figure 8, the power generators 1A to 1E are arranged in this order along the width direction of the tire 70. The middle power generator 1C is positioned so that its centerline coincides with the centerline of the tread portion 700, and power generators 1B and 1D, and power generators 1A and 1E are each positioned symmetrically in the width direction with respect to the centerline of the tread portion 700 (the centerline representing the center in the width direction of the contact surface). Power generators 1B and 1D are positioned (on the inner surface 720) corresponding to the edges on both sides in the width direction of the contact surface when the tire 70 is new. Power generators 1A and 1E are positioned (on the inner surface 720) corresponding to the width direction outside the width of the contact surface when the tire 70 is new. Note that power generators 1A to 1E may be positioned in the same position or in different positions in the circumferential direction of the tire 70. The reason for arranging power generators 1A to 1E in this way will be explained later.

[0066] Module 8 is located outside the cover body 50 and inside the tire 70. The position of module 8 is not particularly limited as long as it is connected to the generator 1 by lead wires 85, and can be placed at an appropriate position on the inner surface 720 or on the surface of the cover body 50. It is preferable that module 8 be fixed in place so that it does not become disconnected from the generator 1. The fixing method is not particularly limited, and known methods such as using adhesive tape or adhesive can be selected.

[0067] <6. Operation of the tire assembly> The operation of the tire assembly 7 is described below. When the tire assembly 7 is stationary, the average surface spacing and true contact area between the first surface 100 of the first insulating film 110 and the second surface 200 of the second insulating film 210 of the power generator 1 do not change or hardly change. For this reason, no charge is induced or hardly induced at the first electrode 120 and the second electrode 220, and the voltage of the power generator 1 measured by the measuring device 82 is zero or very small.

[0068] As the tire assembly 7 rotates on the road surface, the tire 70 receives an impact at the part that contacts the road surface. When this impact is transmitted to the entire tire 70, the sidewall portion 702 in particular flexes to absorb the impact, and the entire tire 70 deforms. Subsequently, the sidewall portion 702 tries to return to its original shape, but receives another impact from the road surface through another part of the tread portion 700. In this way, the tire 70 as a whole undergoes repeated expansion and contraction deformation. The expansion and contraction deformation of the tire 70 is transmitted to the power generator 1 located on the inner surface 720 of the tire 70. The power generator 1 deforms in response to the expansion and contraction deformation of the tire 70 that is transmitted to it. As a result, the first insulating film 110 and the second insulating film 210 move closer to or further apart from each other, or the relative positions of the first insulating film 110 and the second insulating film 210 shift in the planar direction, changing the average planar spacing and the true contact area. In this way, electric charge is induced in the first electrode 120 and the second electrode 220, and a voltage greater than that when the tire assembly 7 is stationary is measured by the measuring device 82.

[0069] During one rotation of the tire assembly 7, the impact received by the tire 70 is best transmitted to the power generator 1 when the fixed position of the power generator 1 is at the position where the tire 70 begins to make contact with the ground (contact start position) and when the tire 70 ends contact with the ground (contact release position). At the contact start position, the power generator 1 reaches its lowest position, and at the contact release position, the power generator 1 moves away from its lowest position. At these positions, the time change in the average plane spacing of the power generator 1 is greatest. Since the magnitude of the current drawn from the power generator 1 is proportional to the time change in the average plane spacing between the first surface 100 and the second surface 200, the voltage measurement data generated in the power generator 1 reflects the degree of impact transmitted to the power generator 1 and the timing of the tire 70's contact start and contact release.

[0070] Figure 9 is a graph that supports this. This graph shows the time-series voltage of the power generator 1 measured while the tire assembly 7 was rotated at a constant speed using the experimental apparatus. As the power generator 1 is repeatedly subjected to impacts from the road surface as the tire 70 rotates, peaks repeatedly appear in the voltage waveform of the power generator 1, as shown in the graph on the left side of Figure 9. Therefore, the time interval T from the appearance of one peak to the appearance of the next peak indicates the rotational speed of the tire 70. The graph on the right side of Figure 9 is a magnified view of one peak. As shown in this graph, each peak that repeatedly appears in the voltage waveform of the power generator 1 includes a first peak P1 and a second peak P2 with the opposite polarity. The first peak P1 is a positive voltage peak with an absolute value Vp and corresponds to the start of ground contact. The second peak P2 is a negative voltage peak with an absolute value Vn and corresponds to the time of disconnection from ground contact. Therefore, the first peak P1 and the second peak P2 appear as a pair. The absolute value Vp is an example of the first peak value, and the absolute value Vn is an example of the second peak value. Hereafter, Vp will be referred to as the first peak value and Vn as the second peak value, and these will sometimes be collectively referred to as the peak value. Below, we will explain the principle by which the wear state and contact state of the tire 70 can be estimated from the voltage waveform of such a generator 1.

[0071] <7. Estimation principle> When the tread portion 700 of tire 70 wears down, the rigidity of tire 70 decreases. When rigidity decreases, the distribution of load applied to tire 70 changes, and consequently, the shape of the contact surface of tire 70 changes. In other words, the circumferential length and widthwise length of the contact surface change. This causes a change in how the impact from the road surface is transmitted to the power generator 1, and this is reflected in the measurement data. Therefore, based on the changes in the measurement data of power generator 1, the changes in the circumferential length and widthwise length of the contact surface can be estimated, and the contact state of tire 70 can be estimated. If other conditions that cause the contact state of tire 70 to change remain constant, the wear state of tire 70 can be estimated based on the changes in the contact state.

[0072] [Circumferential length of the contact surface] Refer to Figure 9 again. During one rotation of the tire 70, the time interval Tc from the appearance of the first peak P1 to the appearance of the next second peak P2 represents the time it takes for the tire 70 to advance by the circumferential length of the contact surface. In other words, the time interval Tc corresponds to the circumferential length of the contact surface of the tire 70, and the time interval T corresponds to the circumference of the tire 70. From this, the ratio Tc / T of the time interval T to the time interval T can represent the ratio of the circumferential length of the contact surface of the tire 70 to the circumference of the tire 70 at that time, considering the internal pressure, rotational speed, and wheel load of the tire 70. The time interval T can be either the first interval T1, which is the interval between the first peak P1, or the second interval T2, which is the interval between the second peak P2. Therefore, the ratio Tc / T is an example of a time comparison value that compares the time interval Tc with the first interval T1 or the second interval T2.

[0073] By comparing the time comparison value Tc / T with the time comparison value Tc / T of a new or near-new tire 70 in its initial state, it is possible to estimate whether or not the circumferential length of the contact surface has changed. However, changes in the time comparison value Tc / T can occur not only due to tire wear, but also due to changes in tire pressure, rotational speed, and wheel load. Therefore, when estimating the wear state of the tire 70 based on this, it is preferable to separately acquire at least one of the internal pressure, rotational speed, and wheel load of the tire 70 and compare it with the time comparison value Tc / T of a new or relatively similar tire 70 acquired under equivalent or similar conditions. Furthermore, depending on the type of tire 70, it is thought that the circumferential length of the contact surface may increase or decrease as it wears down. Therefore, when estimating the wear state of the tire 70, it is preferable to pre-determine in which direction the circumferential length of the contact surface changes as the tire 70 included in the estimation system 9 wears down.

[0074] The time comparison value Tc / T of the tire 70 in its initial state under various internal pressure, rotational speed, and wheel load conditions may be obtained during actual vehicle operation of the vehicle 6, or may be obtained in advance by experiment or simulation. These obtained values ​​may be stored, for example, in the storage device 604 of the external computer 60. In addition, thresholds for estimating that the circumferential length of the contact surface has changed, thresholds for estimating that the tire 70 is in a worn state, or data defining these thresholds can be predetermined by experiment or simulation. The thresholds or data defining them may be stored in advance in the storage device 604 of the external computer 60, similar to the time comparison value Tc / T of the tire 70 in its initial state.

[0075] Furthermore, assuming that the change in the circumference of the tire 70 is negligibly small compared to the change in the circumferential length of the contact surface of the tire 70, it is possible to estimate the circumferential length of the contact surface of the tire 70 at the given internal pressure, rotational speed, and wheel load by calculating (circumferential length of tire 70) × (Tc / T). The circumference of the tire 70 can be calculated, for example, from the diameter of the tire 70 when it is new. Estimating the circumferential length of the contact surface of the tire 70 is included in estimating the contact condition of the tire 70. In addition, by comparing the estimated circumferential length of the contact surface with the circumferential length of the contact surface of the tire 70 when it is first used, at the same internal pressure, rotational speed, and wheel load, it may be estimated whether the tire 70 is worn or not. In this case, the circumferential length of the contact surface of the tire 70 when it is first used may be determined in advance by experiment or simulation for various internal pressure, rotational speed, and wheel load conditions, and these values ​​may be stored, for example, in the storage device 604 of the external computer 60.

[0076] Thresholds for estimating a change in the circumferential length of the contact surface, thresholds for estimating that the tire 70 is in a worn state, or data defining these thresholds can be predetermined by experiment or simulation for various internal pressure, rotational speed, and wheel load conditions. The thresholds or data defining them, like the circumferential length of the contact surface of the tire 70 in its initial state of use, may be stored in advance in the storage device 604 of the external computer 60.

[0077] As described above, when estimating the wear state of tire 70 based on changes in the contact condition of tire 70, it is preferable that the conditions of the tire's internal pressure, rotational speed, and wheel load are known by some means, and that it is possible to compare it with the time comparison value Tc / T or the circumferential length of the contact surface of a new tire 70 under equivalent or similar conditions. If this is not possible, it is preferable to use an index that is less affected by air pressure and wheel load in conjunction with the time comparison value Tc / T. An example of such an index is the peak comparison value, which will be described later.

[0078] [Width of the contact surface] To detect changes in the widthwise length of the contact surface, it is conceivable to arrange multiple power generators 1A to 1E along the widthwise direction of the tire 70, as shown in Figure 8. For example, when the widthwise length of the contact surface of the tire 70 becomes longer than at the start of use, and parts that were not in contact at the start of use begin to make contact, the first peak value Vp and the second peak value Vn of power generator 1 at that position will increase significantly from the values ​​at the start of use. Power generators 1A and 1E in Figure 8 are arranged using this principle. In other words, the peak values ​​Vp and Vn of power generators 1A and 1E are the magnitude of the noise level compared to the peak values ​​of other power generators 1B to 1D at the start of use of the tire 70, but if these increase significantly, it can be estimated that the widthwise length of the contact surface of the tire 70 has increased. Therefore, it is preferable that the widthwise positions for arranging power generators 1A and 1E are positions that correspond to the increase in the widthwise length of the contact surface of the tire 70, which can be assumed in advance through experiments or simulations.

[0079] Conversely to the example above, if the widthwise length of the contact surface of the tire 70 becomes shorter than when it was first used, and the part that was in contact with the ground in the initial stages of use no longer makes contact, then the first peak value Vp and the second peak value Vn of the power generator 1 at that location will both decrease significantly compared to when it was first used. Power generators 1B and 1D in Figure 8 are positioned at the widthwise edge of the contact surface when the tire 70 is new, taking advantage of this fact. In other words, the peak values ​​Vp and Vn of power generators 1B and 1D fall within a certain range compared to the peak values ​​Vp and Vn of power generator 1C when the tire 70 is first used, but if they decrease significantly compared to the peak values ​​Vp and Vn of power generator 1C, it can be estimated that the widthwise length of the contact surface of the tire 70 has shortened.

[0080] Based on the above, in all of the examples described, the contact condition of the tire 70 can be estimated by comparing the peak values ​​Vp and Vn of the power generator 1 with the values ​​of the tire 70 at the beginning of use. Furthermore, when estimating the wear condition of the tire 70 based on this change in contact condition, it is preferable to determine in advance which direction the widthwise length of the contact surface changes when the tire 70 wears down. If the widthwise length of the tire 70 shortens when it wears down, the peak values ​​Vp and Vn of the power generators positioned at the widthwise edge of the contact surface of the tire 70 when it is new will decrease significantly, indicating that the tire 70 is in a worn state. Conversely, if the widthwise length of the tire 70 lengthens when it wears down, the peak values ​​Vp and Vn of the power generators positioned outside the widthwise direction of the contact surface of the tire 70 when it is new will increase significantly, indicating that the tire 70 is in a worn state.

[0081] The peak values ​​Vp and Vn of the tire 70 at the beginning of use may be obtained, for example, during actual driving of the vehicle 6, or by experimentation or simulation using the same type of tire 70. These values ​​may also be obtained for various conditions of tire 70 internal pressure, rotational speed, and wheel load. Thresholds or data defining them for estimating whether the widthwise length of the contact patch has changed and whether the tire 70 has worn down can be predetermined by experimentation or simulation. By storing the thresholds or data defining them together with the peak values ​​Vp and Vn of the tire 70 at the beginning of use in the storage device 604 of the external computer 60, the wear state and contact state can be estimated.

[0082] Furthermore, by arranging the power generators 1 more densely in the width direction and remembering the width direction position of each power generator 1, it becomes possible to estimate the width direction length of the contact surface of the tire 70 based on the peak values ​​Vp and Vn of each power generator 1. In other words, by observing the changes in the peak values ​​Vp and Vn of each power generator 1, it is possible to estimate whether or not the part where that power generator 1 is located makes contact with the ground. Among the power generators 1 located in the contact area, the distance between the two power generators 1 that are furthest apart in the width direction can be estimated to be the width direction length of the contact surface.

[0083] [Regarding uneven contact with the ground] Incidentally, the power generators 1A to 1E are positioned symmetrically in the width direction with respect to the center line of the tread portion 700. However, even if the power generators 1 are positioned on only one side with respect to the center line of the tread portion 700, it is still possible to estimate the change in the widthwise length of the contact surface. In other words, if at least one power generator 1 is positioned outside the width of the contact surface of the tire 70 when it is new, the change in the widthwise length can be estimated. Also, if at least one power generator 1 is positioned at the widthwise edge of the contact surface of the tire 70 when it is new, the change in the widthwise length can be estimated.

[0084] However, by arranging the power generators 1 so that their positions in the width direction are symmetrical with respect to the center line of the tread portion 700, more information can be obtained regarding the contact state of the tire 70 by comparing the measurement data of a pair of power generators 1 in symmetrical positions, and by comparing these measurement data with the measurement data of the power generator 1 at the center in the width direction. For example, if the peak values ​​Vp and Vn of a pair of power generators 1 in symmetrical positions are compared, and one peak value Vp and Vn is significantly larger than the other peak value Vp and Vn, it can be estimated that the tire 70 is unevenly making contact in the width direction. Also, if the peak values ​​Vp and Vn of the power generator 1 at the center in the width direction are compared with the peak values ​​Vp and Vn of the power generator 1 on the outside in the width direction, and the former is significantly larger than the latter, it can be estimated that the tire 70 is unevenly making contact in the center in the width direction. On the other hand, if the latter is significantly larger than the former, it can be estimated that the tire 70 is unevenly making contact in the outside in the width direction, and the central part in the width direction is relatively not making contact.

[0085] The uneven contact of the tire 70 in the width direction can be caused by factors such as the mounting position of the tire assembly 7 to the wheel axle, pressure reduction of the tire 70, pressure enhancement of the tire 70, and uneven wear of the tire 70. Specifically, if the tire assembly 7 is mounted with its rotation axis tilted relative to the wheel axle of the vehicle 6, the tread portion 700 will be inclined in one direction relative to the road surface, causing the inner or outer portion of the tread portion 700 in the width direction to make concentrated contact. Also, if the tire 70 is under reduced pressure, the area near the center of the tread portion 700 in the width direction will be indented radially inward, and the area near the outer edge of the tread portion 700 in the width direction will make concentrated contact. If the tire 70 is under excessive pressure, the area near the center of the tread portion 700 in the width direction will protrude radially outward compared to other parts, causing concentrated contact in the area near the center of the tread portion 700 in the width direction. These factors can also cause uneven wear of the tire 70, where the tire wears unevenly in the width direction. Furthermore, if there is a bias in the width direction of the tire 70's contact with the ground despite no apparent factors such as mounting position or improper tire pressure, it can be presumed that the tire 70 is experiencing uneven wear. Therefore, estimating the bias in the tire 70's contact with the ground also means estimating the state of uneven wear and the contact conditions that could lead to uneven wear.

[0086] [Peak comparison value] According to the inventors' findings, when the rigidity of the tire 70 decreases due to wear, the second peak value Vn at the time of contact loss tends to be smaller than the first peak value Vp at the start of contact. Therefore, as the tire 70 wears down, the ratio of peak values, Vp / Vn, increases, or Vn / Vp decreases. This allows the wear state of the tire 70 to be estimated based on the change in Vp / Vn or Vn / Vp. Vp / Vn and Vn / Vp are examples of peak comparison values ​​that compare the first peak value and the second peak value. The peak comparison values ​​have been confirmed to be indicators that are less affected by air pressure, rotational speed, and wheel load through the following experiments.

[0087] [experiment] The inventors confirmed through the following experiment that a change occurs in the shape of the contact surface when the tire 70 wears down, and that the wear state of the tire 70 can be estimated based on the measurement data of the power generator 1. First, four types of tires TY1 to TY4 were prepared, all of the same type (size 145 / 80R12) but with different tread wear states. Tire TY1 was new, with an average tread groove depth of 5.63 mm. Tire TY2 was slightly worn, with an average tread groove depth of 4.82 mm. Tire TY3 was quite worn, with an average tread groove depth of 2.29 mm. Tire TY4 was the most worn, with an average tread groove depth of 1.94 mm.

[0088] Tires TY1 to TY4 were each mounted on wheels 71 and assembled into an experimental apparatus as shown in Figure 10. This experimental apparatus comprises a drum 91 that can rotate at a predetermined rotational speed around a rotation axis 90, and a rotation axis 92 on which the wheels 71 can be rotatably mounted. By mounting the wheels 71 of tires TY1 to TY4 on the rotation axis 92 and rotating the drum 91 with the tread portions of tires TY1 to TY4 in contact with the outer surface of the drum 91, tires TY1 to TY4 can be rotated. Furthermore, a predetermined wheel load can be applied to tires TY1 to TY4.

[0089] First, the inventors measured the shape of the contact surface of tires TY1 to TY4 while varying the internal pressure conditions (150kPa, 200kPa, 250kPa) and wheel load conditions (2kN, 2.5kN, 3kN) of tires TY1 to TY4, without rotating the drum 91. This measurement was performed by pressing the tread portion of tires TY1 to TY4, which had been coated with ink, against paper attached to the outer circumference of the stationary drum 91. Figure 11 shows the shape of the contact surface of tire TY1 and tire TY4 measured by this method under the same conditions. The results shown in Figure 11 confirm that the circumferential length of the contact surface of tire TY4 is shorter and the widthwise length of the contact surface is longer than that of tire TY1. Furthermore, when the circumferential length and widthwise length of the contact surface, determined from the shape of the contact surface measured for each condition of tires TY1 to TY4, were plotted, the graph shown in Figure 12 was obtained. As shown in Figure 12, when this type of tire wears down, regardless of tire pressure and wheel load conditions, the circumferential length of the contact patch tends to shorten slightly and the widthwise length tends to increase. Therefore, it is possible to estimate the tire wear state based on the changes in the circumferential and widthwise lengths of the contact patch.

[0090] Next, the inventors incorporated the power generator 1F, described below, into tires TY1 to TY3 to create three types of tire assemblies. The power generator 1F used a polyimide film as the first insulating film 110 and a nylon film as the second insulating film 210. Conductive nonwoven fabric was used as the first electrode 120 and the second electrode 220, and these were connected to the measurement module 93 so that the voltage of the power generator 1F could be measured. The first base material 130 and the second base material 230 were silicone rubber sheets with cylindrical protrusions of 0.5 mm in height and 1.5 mm in diameter formed all over them. The first member 10 and the second member 20 were 50 mm x 50 mm squares. The power generator 1F was positioned so that one side of the power generator 1F was along the circumferential direction of tires TY1 to TY3, and the center line of the power generator 1F was along the center line of the tread portion of tires TY1 to TY3. The cover body 50 was then attached to the inner surface of tires TY1 to TY3 to cover the power generator 1F. The cover body 50 was made primarily of elastomer and incorporated a tire repair component with reinforcing cords.

[0091] Three types of tire assemblies were rotated at the aforementioned internal pressures (150kPa, 200kPa, 250kPa), wheel loads (200kgf, 250kgf, 300kgf), and various rotational speeds, and measurement data for each power generator 1F was acquired via telemetry. From the acquired measurement data, the peak values ​​Vp, Vn and the average values ​​of time intervals T and Tc were calculated. Based on these average values, the peak comparison values ​​Vp / Vn and time comparison values ​​Tc / T for the three types of tire assemblies were calculated for each internal pressure, each wheel load, and each rotational speed, and the plotted graphs are shown in Figures 13A to 13F. According to the graphs shown in Figures 13A to 13F, the time comparison value Tc / T changes relatively depending on the conditions of internal pressure, wheel load, and rotational speed. On the other hand, the peak comparison value Vp / Vn shows a clear difference between tire TY1 and tire TY3, regardless of the conditions of internal pressure, wheel load, and rotational speed. Therefore, by determining a threshold value Vp / Vn for estimating tire 70 wear through experimentation or simulation, and comparing this threshold value with the peak comparison value Vp / Vn identified during vehicle 6 operation, the wear state of tire 70 can be estimated.

[0092] Figure 14 is a graph plotting the same data as in Figures 13A to 13F, with the horizontal axis representing the time comparison value Tc / T and the vertical axis representing the peak comparison value Vp / Vn. As can be seen from Figure 14, tires TY1 and TY2 and tire TY3 are clearly distinguishable on the graph. Therefore, if a boundary curve is predetermined to distinguish between the worn region, which is estimated to be in a worn state, and the non-worn region, on a plotting plane with the time comparison value Tc / T as the first axis and the peak comparison value Vp / Vn as the second axis, it is possible to estimate whether or not tire 70 is in a worn state based on the peak comparison value Vp / Vn and the time comparison value Tc / T.

[0093] The method for identifying the boundary curve described above is not particularly limited. For example, a straight line can be created on a graph plotting numerous points of (Tc / T, Vp / Vn) obtained experimentally, distinguishing between worn and non-worn regions, and the equation of this line can be determined. Alternatively, the wear status of tire 70 can be estimated by creating a machine learning model that takes a dataset of (Tc / T, Vp / Vn) as input and outputs an estimated result of whether tire 70 is worn or not (the probability that the input dataset is in the worn region). The machine learning model can be trained using data that combines numerous datasets of time comparison values ​​Tc / T and peak comparison values ​​Vp / Vn obtained experimentally with the correct answer of whether they are in the worn region or the non-worn region. The machine learning model can be a decision tree, support vector machine, neural network, convolutional neural network, clustering, etc., and is not particularly limited.

[0094] <7. Estimation process for wear state of the estimation system> The following describes the operation of the estimation system 9 when it is configured as a wear state estimation system. Figure 15 is a flowchart showing an example of the estimation process performed by the estimation system 9. The estimation system 9 can be configured to start the following estimation process when, for example, the ignition switch of the vehicle 6 is turned ON, and to stop the estimation process when the vehicle 6 has stopped and a certain amount of time has elapsed. It is assumed that the tire assemblies 7a to 7d have a common configuration, and that it is known in advance that the widthwise length of the contact surface of the tire 70 increases as it wears down. In addition, it is assumed that in each tire assembly 7, power generators 1A to 1E (hereinafter collectively referred to as power generator 1) having a common configuration are arranged as shown in Figure 8.

[0095] In step S1, the measuring device 82 of the tire assembly 7 measures the voltage generated at each power generator 1. The measuring device 82 outputs the time-series measured values ​​at a predetermined measurement time as measurement data to the internal computer 81. The internal computer 81 associates the outputted measurement data with identification information that distinguishes each power generator 1 and stores it in the main memory or storage device.

[0096] In step S2, the internal computer 81 identifies numerous first peaks P1 and second peaks P2 included in the measurement data of each power generator 1. The identification of the first peaks P1 and second peaks P2 can be performed by known sampling methods, so a detailed explanation is omitted here. If the absolute value of the voltage of a power generator 1 is extremely small and determined by the internal computer 81 to be at the noise level, the processing from step S2 onward is not performed on the measurement data of that power generator 1, and it is processed as having no measurement data. Therefore, power generators 1A and 1E are usually processed as having no measurement data.

[0097] In step S3, the internal computer 81 identifies a time interval T. The time interval T can be the average value of the first interval T1, which is the period of the first peak P1; the average value of the second interval T2, which is the period of the second peak P2; or the average value of the first interval T1 and the second interval T2. The internal computer 81 associates the identified time interval T with the identification information of each power generator 1 and stores it in the main memory or storage device.

[0098] In step S4, the internal computer 81 identifies the first peak value Vp and the second peak value Vn, respectively. The first peak value Vp and the second peak value Vn can be the average values ​​of a number of first peaks P1 and second peaks P2 included in the measurement data, respectively. The internal computer 81 associates the identified first peak value Vp and second peak value Vn with the identification information of each power generator 1 and stores them in main memory or storage device.

[0099] In step S5, the internal computer 81 identifies the time interval Tc between a pair of first peaks P1 and second peaks P2. The time interval Tc can be the average value of multiple time intervals Tc between first peaks P1 and second peaks P2 included in the measurement data. The internal computer 81 associates the identified time interval Tc with the identification information of each power generator 1 and stores it in main memory or storage device.

[0100] In step S6, the internal computer 81 transmits the time interval T, first peak value Vp, second peak value Vn, and time interval Tc identified in steps S3 to S5 to the external computer 60, associating them with the identification information of each power generator 1. This transmission is performed, for example, at predetermined intervals. The internal computer 81 also transmits the identification information of any power generator 1 for which no measurement data is available to the external computer 60. Subsequently, if the vehicle 6 has not stopped, the measuring device 82 outputs the measurement data for the next measurement time to the internal computer 81. The internal computer 81 then performs the processing in steps S2 to S6 for the new measurement data. In other words, the tire assembly 7 repeats the processing in steps S1 to S6 until the vehicle 6 stops moving.

[0101] In step S7, the data acquisition unit 620 of the external computer 60 receives data transmitted from the internal computer 81 of each tire assembly 7. The data acquisition unit 620 associates the received data with identification information that distinguishes the tire assemblies 7a to 7d and the identification information of each power generator 1, and stores it in the RAM 602 or storage device 604. For power generators 1 for which there is no measurement data, the RAM 602 or storage device 604 also stores a note indicating that there is no measurement data, associated with the identification information of that power generator 1.

[0102] In step S8, the estimation unit 621 selects a power generator 1 for which to calculate the time comparison value Tc / T and the peak comparison value Vp / Vn. The estimation unit 621 normally selects power generators 1B to 1D for each tire assembly 7, but excludes any of them that are stored as having no measurement data.

[0103] In step S9, the estimation unit 621 calculates the time comparison value Tc / T and the peak comparison value Vp / Vn for each power generator 1 selected in step S8, and creates a dataset of (Tc / T, Vp / Vn). The estimation unit 621 associates the created dataset with the identification information of each power generator 1 and stores it in the RAM 602 or storage device 604.

[0104] In step S10, the estimation unit 621 estimates whether the tires 70 of each tire assembly 7 are worn based on the measurement data of each power generator 1. First, the estimation unit 621 determines whether the first peak value Vp and the second peak value Vn were saved in the most recent step S7 for power generators 1A and 1E. If the first peak value Vp and the second peak value Vn were saved in the most recent step S7 for at least one of the power generators 1A and 1E, the estimation unit 621 estimates that the tires 70 of the tire assembly 7 that includes that power generator 1 are worn.

[0105] Next, the estimation unit 621 determines whether the (Tc / T, Vp / Vn) dataset calculated in step S9 lies in the wear region or the non-wear region defined on the plotting plane of the time comparison value Tc / T and the peak comparison value Vp / Vn. The boundary curves defining the wear region and the non-wear region are assumed to be predetermined and stored in the storage device 604. If at least one (Tc / T, Vp / Vn) dataset is determined to be in the wear region, the estimation unit 621 estimates that the tire 70 of the tire assembly 7 containing the power generator 1 is in a worn state.

[0106] The estimation unit 621 can estimate the wear condition using the estimation method described above. If, in step S10, it is not estimated that the tires 70 of each tire assembly 7 are worn, the estimation unit 621 ultimately estimates that none of the tires on the vehicle 6 are worn (NO). In this case, the external computer 60 then repeats the processing in steps S7 to S10 for the data transmitted from the internal computer 81.

[0107] On the other hand, if there is a tire assembly 7 in step S10 in which tire wear is estimated, the estimation unit 621 estimates that the tire 70 is worn (YES). In this case, in the following step S11, the alarm output unit 622 generates an alarm and outputs it to the display unit 65. The alarm may be, for example, a message or image warning the driver of the vehicle 6 that the tire 70 is worn. Furthermore, the alarm output unit 622 may generate at least one of text information and / or graphics indicating the location of the tire 70 that is estimated to be worn, and display this on the display unit 65. Alternatively, or in addition to the above, the alarm output unit 622 may generate an audio alarm and output it through a speaker (not shown).

[0108] <8. Grounding state estimation process of the estimation system> The following describes the operation of the estimation system 9 when it is configured as a grounding state estimation system. Figure 16 is a flowchart of an example of the grounding state estimation process performed by the estimation system 9, which is similar in many ways to the wear state estimation process shown in Figure 15. Therefore, the following will explain in detail the configurations that differ from the wear state estimation process, and omit the explanation of the common configurations.

[0109] The processes from step S21 to step S26 are the same as steps S1 to S6 in the wear state estimation process.

[0110] In step S27, the data acquisition unit 620 receives data of the first peak value Vp, second peak value Vn, time interval T, and time interval Tc of each power generator 1 contained in each tire assembly 7 from the internal computer 81, along with the identification information of each power generator 1, and stores it in the RAM 602 or storage device 604. The data acquisition unit 620 may also acquire data of at least one of the following: internal pressure of the tire 70, rotational speed, and wheel load, which are acquired by other sensors mounted on the vehicle 6 or tire assembly 7, and store this data in association with the received data in the RAM 602 or storage device 604.

[0111] In step S28, the data acquisition unit 620 determines whether the first peak value Vp, second peak value Vn, time interval T, and time interval Tc of the generators 1B to 1D at the beginning of use of the tire 70 are stored in the storage device 604 as initial data. If it is determined that the initial data is stored (YES), the process proceeds to step S30. Note that the voltages of generators 1A and 1E at the beginning of use should be noise levels, so there is no measurement data in the initial data.

[0112] If it is determined that initial data is not saved (NO), the data acquisition unit 620 saves the data received in the most recent step S27 as initial data in the storage device 604 (step S29). This initial data may be saved in association with at least one of the following data: internal pressure of the tire 70, rotational speed, and wheel load, which are acquired by sensors mounted on the vehicle 6 or tire assembly 7. After a certain amount of data has been saved as initial data, step S30 is executed after step S28 without going through step S29.

[0113] In step S30, the estimation unit 621 calculates the time comparison value Tc / T for the power generators 1B to 1D. The estimation unit 621 stores the calculated time comparison value Tc / T in RAM 602 or storage device 604, associating it with the original data.

[0114] In step S31, the estimation unit 621 compares the time comparison value Tc / T calculated in step S30 with the time comparison value Tc / T at the beginning of use of the tire 70. The estimation unit 621 reads the time interval T and time interval Tc of the initial data stored in the storage device 604, calculates the time comparison value Tc / T at the beginning of use, and compares this with the time comparison value Tc / T calculated in step S30. Alternatively, the estimation unit 621 extracts at least one of the internal pressure, rotational speed, and wheel load associated with the time comparison value Tc / T in step S30, reads the initial data of time interval T and Tc associated with an equivalent or relatively similar condition, calculates the time comparison value Tc / T at the beginning of use, and compares this with the time comparison value Tc / T calculated in step S30.

[0115] Furthermore, the estimation unit 621 compares the data of the first peak value Vp and the second peak value Vn obtained in step S27 for power generators 1A to 1E with the initial data. The estimation unit 621 simply reads the initial data of the first peak value Vp and the second peak value Vn stored in the storage device 604 and compares it with the first peak value Vp and the second peak value Vn obtained in step S27, respectively. Alternatively, the estimation unit 621 reads the initial data of the first peak value Vp and the second peak value Vn that are associated with conditions equivalent to or relatively similar to at least one of the conditions associated with the data to be compared, and compares them. Note that for power generators 1A and 1E, since there is no initial data, it is determined whether or not the first peak value Vp and the second peak value Vn for at least one of power generators 1A and 1E have been newly obtained.

[0116] In step S32, the estimation unit 621 estimates whether the shape of the ground surface has changed based on the comparison results from step S31. First, if it is determined in step S31 that a first peak value Vp and a second peak value Vn of at least one of the power generators 1A and 1E have been newly acquired, the estimation unit 621 estimates that the widthwise length of the ground surface has increased and that the shape of the ground surface has changed (YES). Also, if it is determined that a first peak value Vp and a second peak value Vn of at least one of the power generators 1B to 1D have changed by more than a threshold compared to the first peak value Vp and second peak value Vn of the initial data, the estimation unit 621 estimates that the shape of the ground surface has changed (YES). Furthermore, if it is determined that a time comparison value Tc / T of at least one of the power generators 1B to 1D has changed by more than a threshold compared to the time comparison value Tc / T of the initial data, the estimation unit 621 estimates that the circumferential length of the ground surface has increased or decreased and that the shape of the ground surface has changed (YES).

[0117] If there is no measurement data for either power generators 1A or 1E, and it is determined that the first peak value Vp, second peak value Vn, and time comparison value Tc / T for any of the power generators 1B to 1D have not changed by more than a threshold compared to the first peak value Vp, second peak value Vn, and time comparison value Tc / T of the initial data, then the estimation unit 621 estimates that there is no change in the shape of the ground surface (NO). In this case, the process returns to step S27, and steps S28 to S32 are repeated for newly received data.

[0118] Furthermore, the comparison between the peak values ​​Vp, Vn and time comparison value Tc / T and the initial data's peak values ​​Vp, Vn and time comparison value Tc / T may be performed by calculating the difference between the two, or by calculating the ratio between the two. The grounding state may then be estimated based on whether the calculated difference or ratio exceeds a predetermined threshold.

[0119] If it is estimated in step S32 that the shape of the contact surface has changed, the estimation unit 621 may further estimate the bias of the contact state in step S33. For example, if the estimation unit 621 newly obtains peak values ​​Vp and Vn for only one of the power generators 1A and 1E in the same tire assembly 7, it can estimate that the tire 70 of that tire assembly 7 is making contact with the ground biased to one side in the width direction (YES). Also, for example, if the estimation unit 621 determines that the peak values ​​Vp and Vn of power generator 1C have decreased significantly from the initial data and are smaller than a threshold when compared with the peak values ​​Vp and Vn of other power generators, it can estimate that the tire 70 is making contact with the ground biased to the outside in the width direction (YES). Furthermore, for example, if the estimation unit 621 determines that the peak values ​​Vp and Vn of power generator 1C have increased significantly compared to the initial data, and in addition to or instead, the peak values ​​Vp and Vn of power generators 1B and 1D have decreased significantly compared to the initial data, it can estimate that the tire 70 is unevenly grounded towards the center in the width direction (YES). If neither of these conditions applies, the estimation unit 621 can estimate that there is no unevenness in the ground contact state or that it is within an acceptable range (NO).

[0120] If it is estimated in step S33 that there is no bias in the grounding conditions or that it is within an acceptable range, the process returns to step S27, and steps S28 to S32 are repeated for newly received data.

[0121] If an imbalance in the contact condition is estimated in step S33, the alarm output unit 622 generates an alarm in step S34 and outputs it to the display unit 65. The alarm may be a message or image warning the driver of the vehicle 6 that the contact condition of the tire 70 is uneven and that pressure reduction, pressure increase, improper mounting, or uneven wear of the tire 70 is suspected. Otherwise, it is the same as the alarm generated in the wear condition estimation process.

[0122] <9. Variation> Although several embodiments of the present disclosure have been described above, the present invention is not limited to the above embodiments, and various modifications are possible without departing from the spirit thereof. For example, the following modifications are possible. Furthermore, the gist of the following modifications can be combined as appropriate.

[0123] (1) In the above embodiment, the wear state or grounding state estimation process was performed based on the measured voltage output of the power generator 1, but the estimation process may also be performed based on the measured data of other physical quantities equivalent to voltage, such as current or power supplied by the power generator 1.

[0124] (2) In the above embodiment, both the first surface 100 and the second surface 200 had an uneven shape. However, the power generation body 1 may be configured such that only one of the first surface 100 and the second surface 200 has an uneven shape.

[0125] (3) In addition to the module 8, the tire assembly 7 may also be equipped with an air pressure sensor, a temperature sensor, a rotational speed sensor, etc. The tire assembly 7 may also be equipped with a power generator 1 to supply power to these sensors. The number of power generators 1 equipped in the tire assembly 7 may be one or more. The estimation system 9 as a whole only needs to be equipped with at least one power generator 1.

[0126] (4) The external computer 60 may not be an in-vehicle device but another portable computer. In other words, the external computer 60 may be a smartphone, laptop computer, tablet, etc. Also, in the estimation method of Figures 15 and 16, the external computer 60 performed the calculations for estimation and the estimation of wear state and grounding state, but the internal computer 81 may perform these processes. In other words, the internal computer 81 may be equipped with the estimation unit 621 instead of the external computer 60. Conversely, the internal computer 81 may transmit the measurement data to the external computer 60 without specifying the peaks, etc., and the external computer 60 may specify the peaks that appear in the measurement data, as well as at least one of the peak values ​​and intervals. That is, specifying the peaks that appear in the measurement data, specifying at least one of the peak values ​​and intervals, estimating the wear state, and estimating the grounding state can each be performed by the estimation unit, and there is no particular limit to which element of the estimation unit performs these tasks.

[0127] (5) In the above ground contact state estimation process, changes in the contact surface shape and bias in the ground contact state were estimated for each tire 70. However, in addition to or instead of this, the ground contact state of the entire vehicle 6 may be estimated by considering the position of the wheels of the tire assembly 7, etc. For example, if changes in the contact surface shape are estimated for only one of the right tire assemblies 7b and 7d or the left tire assemblies 7a and 7c, then a state of uneven loading, where the load on the vehicle 6 is biased to either the left or right side, is estimated.

[0128] (6) The time comparison value may be defined as T / Tc, or as (T-Tc). Similarly, the peak comparison value may be defined as Vn / Vp, or as (Vp / Vn). 2 (Vn / Vp) 2 , may be defined as (Vp-Vn) or (Vn-Vp).

[0129] (7) The first peak P1 and the second peak P2 may be reversed. That is, the first peak P1 may be a negative voltage peak and the second peak may be a positive voltage peak. Furthermore, the peak values ​​appearing in the measurement data of the voltage and the physical quantity equivalent to the voltage generated in the power generator 1 and the piezoelectric element PE described later may be either signs or absolute values. Accordingly, the first peak value and the second peak value may be signs, and the peak comparison value may be an index that compares the first peak value and the second peak value, including the sign. Furthermore, the first peak value and the second peak value, which are determined based on the measurement data of the power generator 1 and the piezoelectric element PE located at the widthwise edge of the contact surface when the tire 70 is new, or at a position further out, may also be signs. That is, the widthwise length of the contact surface of the tire 70 may be estimated based on the change in the peak value, including the sign.

[0130] (8) The above-mentioned wear state estimation process and contact state estimation process may be performed when it is determined that the vehicle 6 is moving in a straight line, from the viewpoint of improving estimation accuracy. In addition, in the above-mentioned wear state estimation process, if it is known in advance that the widthwise length of the contact surface shortens when the tire 70 wears down, it may be determined that the tire 70 is worn down when the first peak value Vp and the second peak value Vn of at least one of the generators 1B and 1D fall below a predetermined threshold, or when there is no measurement data. When estimating the wear state and the shape change of the contact surface in steps S10 and S32 above, the peak values ​​obtained for the generators 1A and 1E may be either the first peak value Vp or the second peak value Vn.

[0131] (9) From the viewpoint of more accurately estimating the wear state or contact state of the tire 70, it is preferable to arrange two or more power generators 1 on the inner surface of the tire 70, as shown in Figure 8. Here, the two or more power generators 1 can all be arranged one-dimensionally at the same position in the circumferential direction of the tire, but if the mass of the power generators 1 is concentrated at one point in the circumferential direction of the tire 70, the mass balance of the tire assembly 7 may be disrupted, and the rotation axis of the tire assembly 7 may wobble. Wobble of the rotation axis may adversely affect the ride comfort of the vehicle 6. From the viewpoint of preventing this, it is preferable to distribute the two or more power generators 1 at different positions in the circumferential direction, and it is more preferable to distribute them at positions that are roughly equally spaced in the circumferential direction, and it is even more preferable to arrange them so that the mass balance is even in the circumferential direction, taking into account the mass balance of the tire 70 itself. Also, as shown in Figure 17A, even if the two or more power generators 1 are distributed in the circumferential direction, if the mass of the power generators 1 is unevenly distributed to one side in the width direction, the mass balance of the tire assembly 7 may be disrupted. This generates a force that rotates the tire assembly 7 with respect to an axis passing through the center of the tire 70 in the width direction, which may negatively affect the ride comfort of the vehicle 6 (see Figure 17B). To prevent this, it is preferable to arrange two or more power generators 1 in positions symmetrical with respect to the center line of the tread portion 700 in order to reduce the uneven distribution of mass in the width direction.

[0132] For the reasons described above, it is preferable that two or more power generators 1 be arranged two-dimensionally along the circumferential and width directions of the tire 70, and it is even more preferable that these power generators 1 be distributed at positions that are approximately equally spaced in the circumferential direction of the tire 70, and that they be distributed at positions that are symmetrical with respect to the center line of the tread portion 700. An example of such an arrangement is shown in Figures 18A and 18B, in which a power generator 1 located at one end of the tire 70 in the width direction is used as a reference, and the other power generators 1 are located further away from the reference power generator 1 in the circumferential direction as one moves toward the other end in the width direction (however, "further away in the circumferential direction" refers to the positional relationship on the unfolded view of the tire 70 shown in Figure 18A). Furthermore, as shown in Figures 18C and 18D, there are T-shaped arrangements in which only the power generator 1 located at the center in the width direction is placed at different positions in the circumferential direction; as shown in Figures 18E and 18F, there are V-shaped arrangements in which a pair of power generators 1 located symmetrically with respect to the center line of the tread portion 700 are placed at the same position in the circumferential direction; as shown in Figure 18G, there is a W-shaped arrangement; as shown in Figure 18H, there is a U-shaped arrangement; and as shown in Figure 18I, there is an O-shaped arrangement. In any of the arrangements in Figures 18C to 18I, the pair of power generators 1 located symmetrically with respect to the center line of the tread portion 700 may be placed at different positions in the circumferential direction, rather than at the same position. Note that the outputs from power generators 1 placed at different positions in the circumferential direction will have shifted peak positions on the time axis of the measurement data. Therefore, when using the power generators 1 as a power source, the power supply can be smoothed out over time.

[0133] (10) The power generator 1 constituting the estimation system 9 may be replaced with a piezoelectric element PE that generates a voltage when pressure is applied. That is, the estimation system 9 may be configured as an estimation system comprising a piezoelectric element PE placed on the inner surface 720 of the tire 70, a measuring device 82 that measures the voltage generated in the piezoelectric element PE and at least one of the physical quantities equivalent to the voltage, and outputs time-series measurement data, and an estimation unit (at least one of an internal computer 81 and an external computer 60) that estimates at least one of the tire wear state and ground contact state based on the measurement data. The piezoelectric element PE, like the power generator 1, outputs a voltage with a waveform in which a first peak P1, a second peak P2, time intervals T and Tc are observed as the tire 70 rotates, as shown in Figure 22. Therefore, the estimation of at least one of the tire wear state and ground contact state based on the time comparison value Tc / T, peak values ​​Vp, Vn, and peak comparison value Vp / Vn, etc., as already described for the power generator 1, can be similarly applied to the piezoelectric element PE. Furthermore, the processes of steps S1 to S11 and S21 to S34 of the above embodiment can also be applied to the piezoelectric element PE. Similar to the power generator 1, it is preferable that the piezoelectric element PE be positioned on the inner surface 720 at at least one of the following locations: a position corresponding to the edges on both sides in the width direction of the contact surface when the tire 70 is new, and a position corresponding to a position outside the width direction of the contact surface when the tire 70 is new.

[0134] Furthermore, similar to the power generator 1, it is preferable that two or more piezoelectric elements PE are arranged two-dimensionally along the circumferential and width directions of the tire 70. It is even more preferable that these piezoelectric elements PE are distributed at approximately equal intervals along the circumferential direction of the tire 70, and that they are distributed symmetrically with respect to the center line of the tread portion 700. Therefore, the two-dimensional arrangement examples of the power generator 1 shown in Figures 18A to 18I also apply to the piezoelectric elements PE. In this case as well, it is even more preferable that at least one of the piezoelectric elements PE is positioned on the inner surface 720 at a location corresponding to the edges on both sides in the width direction of the contact surface when the tire 70 is new, and at a location corresponding to a position outside the width direction of the contact surface when the tire 70 is new.

[0135] (11) When the power generator 1 or piezoelectric element PE is arranged in two dimensions, the number of these elements is not particularly limited as long as it is two or more. For example, as shown in Figure 18J, if there are at least two power generators 1 or piezoelectric elements PE arranged in different positions in the circumferential and width directions on the tire assembly 7, it can be said that "two or more elements are arranged in two dimensions along the circumferential and width directions of the tire 70."

[0136] <10. Features> According to the estimation system 9 described above, the impact transmitted to the tire 70 is converted into voltage by the power generator 1, so even when the vehicle 6 is traveling at low speed, the signal-to-noise ratio of the measurement data is less likely to deteriorate, and the estimation accuracy of the wear state and contact state is maintained. In addition, since the measurement data is generated by the power generator 1, a power supply to operate the power generator 1 is not required, and the power consumption of the tire assembly 7 is reduced. If the tire assembly 7 is equipped with a power generator 1 for power supply in addition to the power generator 1 for acquiring measurement data, the power required for the estimation processing can be supplied internally by the tire assembly 7, and the cost of configuring a separate power supply can be reduced. Furthermore, when estimating the wear state of the tire 70 from sensing data such as strain sensors, it is conceivable that the cornering force acting on the tire 70 when the vehicle 6 is cornering may affect the sensing data and reduce the estimation accuracy. However, in the case of the power generator 1, the impact from the road surface is considered to be extremely large compared to the effect of the cornering force, so the possibility of the estimation accuracy being reduced due to the effect of cornering is low.

[0137] According to the estimation system 9 described above, it is possible to estimate the driver's driving tendencies, the characteristics of the vehicle 6 itself, the environment in which the vehicle 6 is likely to be used, evaluate the performance of the tires 70, and propose tires 70 accordingly. For example, other sensors mounted on the vehicle 6 determine the vehicle's turning, acceleration, deceleration, and high-speed driving conditions, and analyze the contact condition estimated by the estimation system 9 under each condition. When the vehicle 6 is turning, if there is a large difference in the circumferential length at both ends in the width direction of the contact surface shape, or if there is a large difference in the contact area between the tire 70 on the outside of the turn and the tire 70 on the inside of the turn, or if the time-series change of the contact surface shape of each tire 70 is rapid, it can be said that the driver has a relatively aggressive driving tendency, or the vehicle 6 is prone to driving with sharp changes in speed. On the other hand, if the opposite is true, it can be said that the driver has a relatively mild driving tendency, or the vehicle 6 is prone to driving with fewer changes in speed. If the driver has an aggressive driving tendency, or if vehicle 6 is expected to be driven with frequent changes in speed, tires with high grip performance can be suggested. On the other hand, if the driver has a mild driving tendency, or if vehicle 6 is expected to be driven with few changes in speed, fuel-efficient tires, highly durable tires, or tires with high quietness can be suggested.

[0138] Furthermore, by estimating the contact state in conjunction with information on the road surface on which the vehicle 6 is traveling, such as dry and wet surfaces, the grip performance of the tire 70 can be evaluated. For example, if there is little change in the contact patch shape between dry and wet surfaces, it can be said that the tire 70 maintains good grip performance even on wet surfaces. On the other hand, if there is a large change in the contact patch shape between dry and wet surfaces, or if the change is large during cornering, it can be said that the grip performance of the tire 70 tends to decrease when driving on wet surfaces. In addition, for example, by determining a lane change using time-series data from at least one of the yaw rate sensor, steering angle sensor, lateral acceleration sensor, and gyro sensor mounted on the vehicle 6, the sway suppression performance of the tire 70 can be evaluated by the change in the contact state of the tire 70 during a lane change. Specifically, when the vehicle 6 starts driving straight after a lane change, if the contact state of the tire 70 returns to the contact state when the vehicle 6 is driving straight quickly, the sway suppression performance can be evaluated as high, and if it takes a long time to return to the contact state when driving straight, the sway suppression performance can be evaluated as low. According to the estimation system 9 described above, based on the performance evaluation of the tire 70 as described above, it is possible to propose a tire with appropriate performance for the driver.

[0139] The estimation of the driver's driving tendencies, the characteristics of the vehicle 6 itself, the environments in which the vehicle 6 is likely to be used, and the performance evaluation of the tire 70, as well as the proposal of a corresponding tire 70, can also be performed based on time-series data from various sensors used to control the vehicle 6, such as wheel speed sensors, acceleration sensors, yaw rate sensors, steering angle sensors, lateral acceleration sensors, and gyro sensors mounted on the vehicle 6. However, by adding the estimation results of the ground contact state by the estimation system 9, it is possible to perform more complex and valid estimations, evaluations, and proposals. [Examples]

[0140] The inventors' experiments and results are described below. However, the present invention is not limited thereto. <Experiment 1> A new tire (size 145 / 80R12) was prepared, and five power generators 1G to 1K, with the same configuration as power generator 1F described above, were placed on the inner surface of the tire to create an experimental tire assembly. However, the size of each power generator was 15mm x 15mm. As shown in Figure 19, each power generator was placed 200mm apart in the circumferential direction of the tire. Power generator 1I was positioned so that its centerline coincided with the centerline in the width direction of the tread, and power generators 1H and 1J, and power generators 1G and 1K were positioned symmetrically in the width direction with respect to the centerline of the tread. The distance from the centerline of the tread was 40mm for power generators 1H and 1J, and 50mm for power generators 1G and 1K, with power generators 1G and 1K positioned at the widthwise edge of the tire's contact surface. The cover body that covers power generators 1G to 1K and fixes it to the inner surface was made from tire repair material, similar to that used in the experiment described above, cut to the size of each power generator. Each electrode of the power generator (1G to 1K) was connected to the measurement module.

[0141] The fabricated tire assemblies were mounted on wheels and incorporated into the experimental apparatus shown in Figure 10 while varying the tire's internal pressure and wheel load. The shape of the contact surface when the tire assembly was stationary was then measured. The measurement method was the same as in the experiment described above, by transferring ink from the tread onto paper. There were four combinations of internal pressure and wheel load: (250kPa, 3kN), (250kPa, 2.5kN), (200kPa, 2kN), and (150kPa, 2kN).

[0142] Next, for each combination of internal pressure and wheel load, the tire assembly was rotated at an equivalent speed of 30 km / h (converted to rotational speed), and measurement data for the power generators from 1G to 1K was acquired via telemetry. From the acquired measurement data, the average time interval T and time interval Tc were identified, and the time comparison value Tc / T was calculated. Based on the calculated time comparison value Tc / T and the circumference calculated from the tire diameter, the circumferential length of the tire's contact surface was estimated for power generators from 1G to 1K.

[0143] <Experimental Result 1> Figures 20A to D show graphs for each combination of internal pressure and wheel load, where the circumferential length of the contact surface is on the horizontal axis and the widthwise length is on the vertical axis. The graphs superimpose the shape of the contact surface measured when the tire assembly is stationary with the circumferential length of the contact surface estimated based on measurement data from the power generator at 1G to 1K. The plotted points representing the estimated circumferential length are shown on the plane with the midpoint being 0 on the horizontal axis, and are also shown at the positions in the widthwise direction of the power generator at 1G to 1K. As can be seen from Figures 20A to D, the estimated circumferential length and the circumferential length of the measured contact surface shape generally coincide in all four conditions. From these results, it was confirmed that the dynamic shape of the contact surface of a rotating tire can be estimated based on the position and output of the power generator.

[0144] <Experiment 2> A tire assembly was fabricated by further incorporating a power generator 1F for power supply and a module 8 similar to that in the above embodiment into the tire assembly prepared in Experiment 1. This tire assembly was mounted on a wheel and incorporated into the experimental apparatus shown in Figure 10, and rotated to confirm whether the module 8 would function correctly without the need for other batteries.

[0145] <Experimental Results 2> Module 8 functioned correctly, and it was confirmed that data for the first peak value Vp, second peak value Vn, time interval T, and time interval Tc of the power generator 1G~1K were transmitted wirelessly at predetermined intervals. From these results, it was confirmed that a tire assembly equipped with a power generator for power supply can operate without a separate power source, thus offering advantages in simplifying the estimated system configuration and reducing costs.

[0146] <Experiment 3> A tire assembly for the experiment was fabricated by placing 13 piezoelectric elements (LDT0 Solid State Switch / Vibration Sensor, manufactured by Measurement Specialties Incorporated), including a piezo film, on the inner surface of a new tire of the same type used in Experiment 1. The piezoelectric elements were covered with a repair material for tire inner liners and attached to the inner surface of the tire. Each piezoelectric element consisted of a 28 μm thick polyvinylidene fluoride (PVDF) film, a 0.125 mm thick polyester substrate, and a connector. Its external dimensions were approximately 25 mm x 13 mm, and its internal impedance was 40 MΩ to 60 MΩ.

[0147] As shown in Figure 21, the piezoelectric elements were placed at 10 mm intervals at positions between -60 mm and 60 mm in the width direction of the tire, with the tread centerline set to 0 mm. This resulted in the formation of two rows of piezoelectric elements with approximately 50 mm of spacing between them in the circumferential direction of the tire. Here, the -40 mm position corresponds to the widthwise edge of the tire's contact surface on the wheel cap side, and the 50 mm position corresponds to the widthwise edge of the tire's contact surface on the opposite side (inner side) from the wheel cap. In other words, the -60 mm, -50 mm, and 60 mm positions were not in contact with the ground on a new tire. The piezoelectric elements were oriented so that their longitudinal direction coincided with the circumferential direction of the tire. Each electrode of the piezoelectric element was connected to a measurement module similar to that in Experiment 1.

[0148] A wheel was attached to the above tire assembly, and this was incorporated into the experimental apparatus shown in Figure 10 and rotated at a constant speed to acquire time-series data of the voltage generated at each piezoelectric element. Figure 22 is a graph summarizing the voltages generated at the piezoelectric elements by their position on the tire. In the graphs of Figure 22, the upper row corresponds to the opposite (back) side of the wheel cap, and the lower row corresponds to the wheel cap side. The graphs are arranged so that the left side of the paper is closer to the edge of the tire in the width direction, and the right side is closer to the center of the tire in the width direction. The horizontal axis of each graph represents time (seconds), and the vertical axis represents the relative voltage (V). As shown in Figure 22, when comparing the positions in the width direction, it was confirmed that as you approach the center of the tire, relatively small peaks accompanying the maximum peak tend to appear, and as you approach the edge of the tire's contact surface in the width direction, relatively small peaks accompanying the maximum peak tend to appear less frequently.

[0149] Next, similar to Experiment 1, the tire assembly was mounted in the experimental apparatus shown in Figure 10 while varying the tire's internal pressure and wheel load, and the shape of the contact surface when the tire assembly was stationary was measured. The measurement method was the same as in Experiment 1 described above, by transferring the ink from the tread onto paper. There were five combinations of internal pressure and wheel load: (250kPa, 2kN), (250kPa, 2.5kN), (250kPa, 3kN), (200kPa, 2kN), and (150kPa, 2kN). Subsequently, for each combination of internal pressure and wheel load, the tire assembly was rotated at an equivalent of 30km / h (converted rotational speed), and measurement data of the voltage generated at 13 piezoelectric elements was acquired by telemetry. From each acquired measurement data, the average time interval T and time interval Tc were determined, similar to Experiment 1, and the time comparison value Tc / T was calculated. Based on the calculated time comparison value Tc / T and the circumference calculated from the tire diameter, the circumferential length of the tire's contact surface was estimated for each piezoelectric element.

[0150] <Experimental Result 3> Figures 23A to E show graphs for each combination of internal pressure and wheel load, where the circumferential length of the contact surface is plotted on the horizontal axis and the widthwise length on the vertical axis. The graphs superimpose the shape of the contact surface measured when the tire assembly is stationary with the circumferential length of the contact surface estimated based on the measurement data of each piezoelectric element. The plotted points representing the estimated circumferential length are shown on the plane such that the midpoint is 0 on the horizontal axis, and they correspond to the position of the piezoelectric element in the widthwise direction (-60mm to 60mm). Note that the positions -60mm, -50mm, and 60mm in the widthwise direction correspond to positions that do not make contact with the ground in a new tire, but the tire deforms including the non-contacting parts such as the sidewall. Therefore, the measurement data of the voltage generated in these piezoelectric elements showed a first and second peak associated with the rotation of the tire, similar to the graph shown in Figure 22. However, the magnitude of the first and second peaks themselves was small enough to be distinguishable compared to the magnitude of the first and second peaks of other piezoelectric elements corresponding to the contact surface. The graphs in Figures 23A to E also plot the lengths calculated from the measurement data of the piezoelectric elements located at -60mm, -50mm, and 60mm. As can be seen from Figures 23A to E, the circumferential length of the contact surface estimated based on the output of the piezoelectric elements increased as the load increased at the same internal pressure, and increased as the internal pressure decreased at the same load, which was consistent with the change in the shape of the contact surface when stationary. From these results, it was confirmed that the dynamic shape of the contact surface of a rotating tire can be estimated based on the position and output of the piezoelectric elements.

[0151] <Experiment 4> The tire assembly fabricated in Experiment 3 was incorporated into the experimental apparatus shown in Figure 10 and rotated at a constant wheel load and rotational speed. Time-series measurement data of the voltage generated at each piezoelectric element was acquired. For the measurement data of each piezoelectric element, the average value of the first peak value Vp, the average value of the second peak value Vn, the time interval T1 of the first peak, and the time interval Tc between the first and second peaks were calculated. Subsequently, a tire assembly was fabricated with the tread of the tire assembly fabricated in Experiment 3 worn down by approximately 3 mm. This was incorporated into the experimental apparatus shown in Figure 10 and rotated under the same wheel load and rotational speed conditions as the initial experiment. Time-series measurement data of the voltage generated at each piezoelectric element was acquired. For the measurement data of each piezoelectric element, the average value of the first peak value Vp, the average value of the second peak value Vn, the time interval T1 of the first peak, and the time interval Tc between the first and second peaks were calculated.

[0152] <Experimental Result 4> When comparing the peak comparison value Vp / Vn with respect to the position of the piezoelectric element in the width direction for a new tire assembly and a worn tire assembly, the graph shown in Figure 24A was obtained. From the graph in Figure 24A, it was confirmed that the peak comparison value was large when the tire was new, and that the parts where the impact is considered to be greatest during tire rotation (-30mm, 40mm) shifted to the outer positions in the width direction (-40mm, 50mm), respectively, when the tire was worn. In this tire, it is thought that the length of the contact surface in the width direction increased due to wear, and the wheel load came to be supported by the sidewall or its vicinity. Furthermore, when comparing the time comparison value Tc / T1 with respect to the position of the piezoelectric element in the width direction for a new tire assembly and a worn tire assembly, the graph shown in Figure 24B was obtained. From the graph in Figure 24B, it was confirmed that there was no large difference in the time comparison value Tc / T1 between the new and worn tire assemblies at the center of the tread in the width direction, but the difference between the new and worn tire assemblies was relatively large at the width direction edges and their vicinity. Therefore, it was confirmed that when estimating the wear state using the time comparison value Tc / T1, it is sufficient to analyze only the measurement data of the piezoelectric element at the widthwise edge of the tire's contact surface and its vicinity.

[0153] Furthermore, based on the time comparison value Tc / T1 of each piezoelectric element in the tire assembly during wear, the circumferential length of the contact surface relative to the position of each piezoelectric element was estimated and compared with the shape measured while stationary, as shown in Figure 25. Here, a tire circumference that takes wear into account (1652 mm) was adopted as the tire circumference. As mentioned above, the time comparison value Tc / T1 changed significantly at and near the widthwise edge of the tread, so the estimated circumferential length of the contact surface was shorter at and near the widthwise edge (-50 mm and 60 mm) compared to the area near the center in the widthwise direction, and it was confirmed that this trend was consistent with the shape measured while stationary. For reference, Figure 26 (circumferential length 1683 mm) shows a comparison of the circumferential length of the contact surface estimated by a similar experiment for the same tire assembly when new, and the shape measured while stationary (in Figures 25 and 26, as in Experiment 3, the circumferential length estimated based on the peaks appearing in the measurement data for piezoelectric elements at positions that are not considered to be in contact is also plotted, as is the case in each Figure 25). Comparing the estimated circumferential length of the contact surface in Figure 26 and Figure 25, it was confirmed that the position where the estimated circumferential length becomes relatively shorter shifted from -40 mm to -50 mm, and this change was consistent with the change in shape measured while stationary. This confirmed that, according to this method, it is possible to estimate the shape of the contact surface regardless of whether the tire is new or worn, and it is also possible to estimate the tire's wear state based on the change in the shape of the contact surface. [Explanation of Symbols]

[0154] 1.1A~1K generator 6 vehicles 7 Tire Assembly 9 Estimation System 10 First Member 20 Second Member 60 External Computer 70 tires Vp (First Peak Value) Vn 2nd peak value T time interval Tc time interval PE piezoelectric element

Claims

1. At least one power generator that generates voltage in accordance with the deformation of the tire is placed inside the tire, While the tire is rotating, time-series measurement data is acquired, which includes measuring the voltage and at least one of the physical quantities equivalent to the voltage. Identifying the peaks that repeatedly appear in the aforementioned measurement data, To identify at least one of the peak value and the interval between the peaks, Based on at least one of the identified values ​​and intervals, estimate at least one of the tire wear condition and contact condition. Includes, The aforementioned power generator is A first member having a first insulating film that forms a first surface, A second member having a second insulating film that faces the first surface and forms a second surface that contacts the first surface, Equipped with, The first member and the second member are configured such that the true contact area between the first surface and the second surface changes in response to the pressure applied to the first member and the second member. The first insulating film and the second insulating film are configured such that, as the true contact area changes, one becomes positively charged and the other becomes negatively charged. Identifying the aforementioned peaks includes identifying a first peak and a second peak that appears in conjunction with the first peak. Identifying at least one of the peak values ​​and the intervals between the peaks includes identifying at least one of the following: a first peak value which is the value of the first peak, a second peak value which is the value of the second peak, a first interval which is the interval between the first peaks, a second interval which is the interval between the second peaks, and a pair of time intervals between the first and second peaks. Identifying at least one of the peak value and the interval between peaks includes identifying the first peak value, the second peak value, the time interval, and the first or second interval. Estimating at least one of the tire wear state and contact state includes calculating at least one of a peak comparison value comparing the first peak value and the second peak value, and a time comparison value comparing the time interval with the first interval or the second interval, and estimating the tire wear state based on at least one of the calculated peak comparison value and time comparison value. The aforementioned peak comparison value is the ratio of the first peak value to the second peak value. The aforementioned time comparison value is the ratio of the time interval to the first interval or the second interval. Estimating the wear state of the tire includes estimating the wear state of the tire based on the peak comparison value and the time comparison value. Method for estimating the condition of tires.

2. At least one power generator is placed inside the tire, which generates a voltage in accordance with the deformation of the tire, While the tire is rotating, time-series measurement data is acquired, which includes measuring the voltage and at least one of the physical quantities equivalent to the voltage. Identifying the peaks that repeatedly appear in the aforementioned measurement data, To identify at least one of the peak value and the interval between the peaks, Based on at least one of the identified values ​​and intervals, estimate at least one of the tire wear condition and contact condition. Includes, The aforementioned power generator is A first member having a first insulating film that forms a first surface, A second member having a second insulating film that faces the first surface and forms a second surface that contacts the first surface, Equipped with, The first member and the second member are configured such that the true contact area between the first surface and the second surface changes in response to the pressure applied to the first member and the second member. The first insulating film and the second insulating film are configured such that, as the true contact area changes, one becomes positively charged and the other becomes negatively charged. Identifying the aforementioned peaks includes identifying a first peak and a second peak that appears in conjunction with the first peak. Identifying at least one of the peak values ​​and the intervals between the peaks includes identifying at least one of the following: a first peak value which is the value of the first peak, a second peak value which is the value of the second peak, a first interval which is the interval between the first peaks, a second interval which is the interval between the second peaks, and a pair of time intervals between the first and second peaks. Identifying at least one of the peak value and the interval between the peaks includes identifying the time interval and the first interval or the second interval. Estimating at least one of the tire wear state and contact state includes calculating a time comparison value comparing the time interval with the first interval or the second interval, and estimating the tire contact state based on the calculated time comparison value. To obtain the circumference of the aforementioned tire, It further includes, Estimating the contact state of the tire includes estimating the circumferential length of the tire's contact surface based on the calculated time comparison value and the acquired circumference. Method for estimating the condition of tires.

3. Placing at least one power generator inside the tire includes placing at least one power generator at a position outside the width of the contact surface when the tire is new. Identifying at least one of the peak value and the interval between the peaks includes identifying the peak value of the power generator located at the outer position, Estimating at least one of the tire wear condition and contact condition includes estimating at least one of the tire wear condition and contact condition based on the change in the identified value. A method for estimating the condition of a tire according to claim 1 or 2.

4. Placing at least one power generator inside the tire includes placing at least one power generator at the widthwise edge of the contact surface when the tire is new, Identifying at least one of the peak value and the interval between the peaks includes identifying the peak value of the power generator located at the edge position, Estimating at least one of the tire wear condition and contact condition includes estimating at least one of the tire wear condition and contact condition based on the change in the identified value. A method for estimating the condition of a tire according to claim 1 or 2.

5. At least one power generator positioned inside the tire, which generates a voltage in response to the deformation of the tire, A measuring device positioned inside the tire, which measures the voltage and at least one physical quantity equivalent to the voltage while the tire is rotating, and outputs time-series measurement data; An estimation unit that identifies peaks that repeatedly appear in the measurement data, identifies at least one of the peak value and the interval between the peaks, and estimates at least one of the tire wear state and contact state based on at least one of the identified value and interval, Equipped with, The aforementioned power generator is A first member having a first insulating film that forms a first surface, A second member having a second insulating film that faces the first surface and forms a second surface that contacts the first surface, Equipped with, The first member and the second member are configured such that the true contact area between the first surface and the second surface changes in response to the pressure applied to the first member and the second member. The first insulating film and the second insulating film are configured such that, as the true contact area changes, one becomes positively charged and the other becomes negatively charged. Identifying the aforementioned peaks includes identifying a first peak and a second peak that appears in conjunction with the first peak. Identifying at least one of the peak values ​​and the intervals between the peaks includes identifying at least one of the following: a first peak value which is the value of the first peak, a second peak value which is the value of the second peak, a first interval which is the interval between the first peaks, a second interval which is the interval between the second peaks, and a pair of time intervals between the first and second peaks. Identifying at least one of the peak value and the interval between peaks includes identifying the first peak value, the second peak value, the time interval, and the first or second interval. Estimating at least one of the tire wear state and contact state includes calculating at least one of a peak comparison value comparing the first peak value and the second peak value, and a time comparison value comparing the time interval with the first interval or the second interval, and estimating the tire wear state based on at least one of the calculated peak comparison value and time comparison value. The aforementioned peak comparison value is the ratio of the first peak value to the second peak value. The aforementioned time comparison value is the ratio of the time interval to the first interval or the second interval. Estimating the wear state of the tire includes estimating the wear state of the tire based on the peak comparison value and the time comparison value. A system for estimating the condition of tires.

6. At least one power generator positioned inside the tire and generating a voltage in response to the deformation of the tire, A measuring device positioned inside the tire, which measures the voltage and at least one physical quantity equivalent to the voltage while the tire is rotating, and outputs time-series measurement data; An estimation unit that identifies peaks that repeatedly appear in the measurement data, identifies at least one of the peak value and the interval between the peaks, and estimates at least one of the tire wear state and contact state based on at least one of the identified value and interval, Equipped with, The aforementioned power generator is A first member having a first insulating film that forms a first surface, A second member having a second insulating film that faces the first surface and forms a second surface that contacts the first surface, Equipped with, The first member and the second member are configured such that the true contact area between the first surface and the second surface changes in response to the pressure applied to the first member and the second member. The first insulating film and the second insulating film are configured such that, as the true contact area changes, one becomes positively charged and the other becomes negatively charged. Identifying the aforementioned peaks includes identifying a first peak and a second peak that appears in conjunction with the first peak. Identifying at least one of the peak values ​​and the intervals between the peaks includes identifying at least one of the following: a first peak value which is the value of the first peak, a second peak value which is the value of the second peak, a first interval which is the interval between the first peaks, a second interval which is the interval between the second peaks, and a pair of time intervals between the first and second peaks. Identifying at least one of the peak value and the interval between the peaks includes identifying the time interval and the first interval or the second interval. Estimating at least one of the tire wear state and contact state includes calculating a time comparison value comparing the time interval with the first interval or the second interval, and estimating the tire contact state based on the calculated time comparison value. The estimated units are, To obtain the circumference of the aforementioned tire, Further execution, Estimating the contact state of the tire includes estimating the circumferential length of the tire's contact surface based on the calculated time comparison value and the acquired circumference. A system for estimating the condition of tires.

7. At least two of the aforementioned power generators, Energy storage device, Furthermore, The energy storage device is configured to store the charge of some of the power generators among at least two or more power generators. The tire condition estimation system according to claim 5 or 6.

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