Power generation module and tire assembly

Abstract

To provide a power generation module that can be attached to the inner surface of a tire and can generate a large amount of power. [Solution] The tire includes a mounting portion, a first pressure plate, a second pressure plate, and a power generation device (33). The mounting portion is configured to be detachable from the inner surface of the tire and extends along the longitudinal direction. The first pressure plate is fixed to the mounting portion and has a first surface configured to be positioned radially outward of the tire, and a second surface on the back side of the first surface. The second pressure plate (32) extends along the longitudinal direction and is fixed, directly or indirectly, to the mounting portion or the first pressure plate at at least two locations, a first location and a second location, spaced apart in the longitudinal direction. The power generation device is disposed between the first pressure plate and the second pressure plate, and between the first location and the second location. When the power generation module is not attached to the tire, the radius of curvature of the second surface of the first pressure plate is larger than the radius of curvature of the inner surface of the tire.

Description

[Technical Field]

[0001] The present invention relates to a power generation module and a tire assembly. [Background technology]

[0002] Japanese Patent Application Laid-Open Publication No. 2020-200012 (Patent Document 1) discloses a tire assembly incorporating a friction-charged power generator. The power generator includes a first insulating film and a second insulating film. When tire deformation is transmitted to the power generator and the contact area between the first insulating film and the second insulating film changes, the first insulating film and the second insulating film become charged, generating an electromotive force. According to Patent Document 1, a greater amount of power can be generated by making the length of the chargeable surface of the second insulating film along the circumferential direction of the tire shorter than the tire's contact length. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-200012 Summary of the Invention [Problem to be solved by the invention]

[0004] According to Patent Document 1, if the above length exceeds the tire's contact length, the local electromotive forces generated at the point where the tire starts to contact the ground and the point where it leaves the ground cancel each other out, resulting in a decrease in the amount of power generated by the power generator. The tire assembly disclosed in Patent Document 1 aims to improve the amount of power generated by avoiding this situation. However, it is believed that there are other factors that affect the amount of power generated by the power generator, such as those described above, and there is room for further investigation to improve the amount of power generated.

[0005] An object of the present invention is to provide a power generation module or the like that can be attached to the inner surface of a tire and that can generate a larger amount of power. [Means for solving the problem]

[0006] A power generation module according to a first aspect of the present invention is a power generation module that can be attached to the inner surface of a tire, and includes a mounting portion, a first pressure plate, a second pressure plate, and a power generation device. The mounting portion is configured to be detachable from the inner surface of the tire and extends along the longitudinal direction. The first pressure plate is fixed to the mounting portion and has a first surface configured to be positioned radially outward of the tire, and a second surface on the reverse side of the first surface. The second pressure plate extends along the longitudinal direction and is fixed, directly or indirectly, to the mounting portion or the first pressure plate at at least two locations, a first location and a second location, that are spaced apart in the longitudinal direction. The power generation device is disposed between the first pressure plate and the second pressure plate, and between the first location and the second location. The power generation device has a first member and a second member that are charged by friction with each other. When the power generation module is not attached to the tire, the radius of curvature of the second surface of the first pressure plate is greater than the radius of curvature of the inner surface of the tire.

[0007] A power generation module according to a second aspect of the present invention is the power generation module according to the first aspect, wherein the radius of curvature of the second surface is 1 m or more.

[0008] A power generation module according to a third aspect of the present invention is the power generation module according to the first or second aspect, further comprising a fixing member that mechanically fixes the second presser plate to the mounting portion or the first presser plate, and the fixing member is disposed at the first location and the second location.

[0009] A power generation module according to a fourth aspect of the present invention is a power generation module according to any one of the first to third aspects, wherein the length from the first end to the second end in the longitudinal direction of the second pressure plate is at least three times the length from the first location to the second location.

[0010] A power generation module according to a fifth aspect of the present invention is the power generation module according to any one of the first to fourth aspects, further comprising a thickness adjusting sheet between the second pressing plate and the mounting portion.

[0011] A power generation module according to a sixth aspect of the present invention is a power generation module according to any one of the first to fifth aspects, wherein the first member has a first insulating film forming a first contact surface, the second member has a second insulating film forming a second contact surface facing the first contact surface and in contact with the first contact surface, and the first member and the second member are configured such that one becomes positively charged and the other becomes negatively charged due to friction between the first contact surface and the second contact surface in response to pressure applied to the first member and the second member.

[0012] A power generation module according to a seventh aspect of the present invention is the power generation module according to any one of the first to fifth aspects, wherein the second pressing plate is made of fiber reinforced resin.

[0013] A tire assembly according to an eighth aspect of the present invention includes a tire and a power generation module. The tire has a mounting portion extending circumferentially on its inner surface. The power generation module is mounted to the mounting portion and includes a mounting portion, a first presser plate, a second presser plate, and a power generation device. The mounting portion is configured to be attachable to and detachable from the mounting portion of the tire and extends along the longitudinal direction. The first presser plate is fixed to the mounting portion and has a first surface located radially outward of the tire and a second surface behind the first surface. The second presser plate extends along the longitudinal direction and is fixed, directly or indirectly, to the mounting portion or the first presser plate at at least two locations, a first location and a second location, spaced apart in the longitudinal direction. The power generation device includes a first member and a second member that are disposed between the first presser plate and the second presser plate and between the first location and the second location and are electrically charged by friction with each other. When the power generation module is not attached to the tire, the radius of curvature of the second surface of the first pressing plate is larger than the radius of curvature of the inner surface of the tire.

[0014] A tire assembly according to a ninth aspect of the present invention is the tire assembly according to the eighth aspect, further comprising a fixing member that mechanically fixes the second presser plate to the mounting portion or the first presser plate. The fixing member is disposed at the first location and the second location, and the length from the first location to the second location is equal to or less than the length of the contact patch of the tire in the circumferential direction. [Effects of the Invention]

[0015] According to the present invention, a power generation module or the like is provided that can be attached to the inner surface of a tire and can generate a larger amount of power. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is a plan view showing the overall configuration of a power generation module according to an embodiment; [Figure 2] Side view of Figure 1. [Figure 3] FIG. 1 is a cross-sectional view showing a configuration of a power generating device according to an embodiment. [Figure 4] 1 is a longitudinal cross-sectional view of a tire according to an embodiment. [Figure 5] FIG. 2 is a diagram showing the internal configuration of a tire assembly according to one embodiment. [Figure 6] 4A to 4C are diagrams illustrating the behavior of a tire assembly. [Figure 7] FIG. 10 is a side view of a power generation module according to another embodiment. [Figure 8A] 1 is a plan view showing the overall configuration of a power generation module according to an embodiment; [Figure 8B] FIG. 10 is a plan view showing the overall configuration of a power generation module according to a comparative example. [Figure 8C] 5A to 5C are diagrams illustrating a method for manufacturing a power generation module according to a comparative example. [Figure 9] 10 shows measurement results of the contours of the tire inner surface and the second presser plate according to the example and the comparative example. [Figure 10A] 4 is a graph of the output voltage of the tire assembly according to the example. [Figure 10B] 10 is a graph of the output voltage of a tire assembly according to a comparative example. [Figure 11]Graph of output power of each tire assembly versus driving speed. [Figure 12] Graph of output power of each tire assembly versus mileage. [Figure 13] Graph of output power for each tire assembly versus temperature. [Figure 14] Images of the contact patch shape of a tire assembly measured under different loading conditions. [Figure 15] 10 is a graph showing the relationship between the circumferential length of the contact surface relative to the length between the eyelets and the output power. [Figure 16] 10 is a graph showing the relationship between the length between the grommets and the output power relative to the length of the power generation module. [Figure 17A] 4 is a graph of the output voltage of the tire assembly according to the example. [Figure 17B] 4 is a graph of the output voltage of the tire assembly according to the example. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, a power generation module and a tire assembly including the same according to an embodiment of the present invention will be described with reference to the drawings. In the following drawings, for the sake of convenience, some components may be omitted and some dimensions may be exaggerated.

[0018] <1. Power generation module> FIG. 1 is a top view showing the overall configuration of a power generation module 3 according to one embodiment of the present invention, and FIG. 2 is a side view of FIG. 1. The power generation module 3 is configured to be attachable to a tire 2 having an attachment portion 21, which will be described later, and can constitute a tire assembly 1, which will be described later, together with the tire 2. The power generation module 3 includes an attachment portion 35, a first presser plate 31, a second presser plate 32, and a power generation device 33. The power generation module 3 may also include grommets 34. Hereinafter, the left-right direction in FIG. 1 will be referred to as the longitudinal direction of the power generation module 3, and the up-down direction in FIG. 1 will be referred to as the width direction of the power generation module 3. Note that in the tire assembly 1, the longitudinal direction and width direction of the power generation module 3 correspond to the circumferential direction and width direction of the tire 2, respectively.

[0019] [Mounting part] The mounting portion 35 is a strip-shaped member extending in the longitudinal direction. The mounting portion 35 enables the power generation module 3 to be attached to and detached from the mounting base 21 of the tire 2. For example, the mounting base 21 and the mounting portion 35 are each made of a hook-and-loop fastener and have a raised surface that can be joined to other hook-and-loop fasteners. The power generation module 3 including the mounting portion 35 can be attached to the mounting base 21 by joining the raised surface of the mounting base 21 and the raised surface of the mounting portion 35 to each other.

[0020] [First holding plate] The first pressing plate 31 is a plate-like member extending in the longitudinal direction. The first pressing plate 31 according to this embodiment has a first surface 311 and a second surface 312 on the reverse side of the first surface 311, and is fixed on the first surface 311 side to the non-brushed surface of the mounting part 35 (the surface that cannot be coupled to the mounted part 21). The first pressing plate 31 is made of a flexible material so that it can deform in accordance with the deformation of the tire 2.

[0021] The first surface 311 is a surface that faces the inner surface 20 of the tire 2 when the power generation module 3 is attached to the tire 2, and the second surface 312 is a surface that faces the internal space of the tire 2. That is, in the tire assembly 1, the first surface 311 is located on the radially outer side of the tire 2, and the second surface 312 is located on the radially inner side of the tire 2. The first pressing plate 31 according to this embodiment is flat or approximately flat in a side view when no deforming force is applied. Here, the first pressing plate 31 being "flat or approximately flat" means that, when the outline of the second surface 312 along the longitudinal direction is approximated by a circle centered on an imaginary point on the second surface 312 side, the radius of the circle (the radius of curvature of the second surface 312) is larger than the radius of curvature of the inner surface 20 of the tire 2, which will be described later. In addition, in order for the first pressure plate 31 to be considered "flat or generally flat" compared to tires that are generally on the market, the radius of curvature of the second surface 312 is preferably 1 m or more, more preferably 2 m or more, and even more preferably 2.5 m or more.

[0022] [Second holding plate] The second presser plate 32 is a plate-like member extending in the longitudinal direction. Like the first presser plate 31, the second presser plate 32 is made of a flexible material so that it deforms in response to deformation of the tire 2. The second presser plate 32 is fixed to the first presser plate 31 via eyelets 34 so as to face the second surface 312. In addition, the second presser plate 32 is fixed to the first presser plate 31 in regions on both longitudinal sides of the eyelets 34 with an adhesive or pressure-sensitive adhesive. As a result, when the power generation module 3 is attached to the tire 2, the second presser plate 32 is located radially inward of the tire 2 relative to the first presser plate 31. The second presser plate 32 according to this embodiment is flat or approximately flat in a side view when no deforming force is applied to the power generation module 3. Here, the second presser plate 32 being "flat or substantially flat" means that when the outline of the surface of the second presser plate 32 that does not face the second surface 312 along the longitudinal direction is approximated by a circle, the radius of the circle (radius of curvature) is 1 m or more. Note that in Figure 2, the thickness of the power generation device 33 and the curvature of the second presser plate 32 are exaggerated.

[0023] [material] The materials constituting the first and second presser plates 31 and 32 are not particularly limited as long as they are flexible, and examples thereof include resin, metal, rubber, and composite materials thereof. Among these, from the viewpoints of flexural rigidity, flexural strength, heat resistance, and lightweight, the second presser plate 32 is preferably made of fiber-reinforced plastics, such as glass fiber reinforced plastics and carbon fiber reinforced plastics. On the other hand, the first presser plate 31 is preferably made of resin, rubber, or a composite material thereof from the viewpoints of deformability, flexural strength, heat resistance, and lightweight, and is preferably made of carbon fiber reinforced rubber (CFR). Carbon fiber reinforced rubber is a composite material made by bonding a woven carbon fiber fabric with an elastic polymer compound, and has a structure in which the woven carbon fiber fabric is coated with synthetic rubber. Carbon fiber reinforced rubber has a higher tensile strength than steel, and has better shock absorption than a composite material in which the elastic polymer compound is replaced with carbon fiber reinforced plastic. It also has better flexibility than the composite material. Examples of the elastic polymer compound include ethylene propylene rubber, butyl rubber, acrylonitrile rubber, and silicone rubber.

[0024] According to the inventor's investigations, when the first presser plate 31 is made of carbon fiber reinforced rubber, the output of the power generation module 3 is improved compared to when it is made of polycarbonate. This is thought to be because carbon fiber reinforced rubber has higher flexibility. Furthermore, when the first presser plate 31 is made of carbon fiber reinforced rubber and the mounting portion 35 is made of hook-and-loop fasteners and these are fixed entirely using double-sided tape, it is possible to prevent the mounting portion 35 from being stretched in the surface direction due to external forces, thereby improving the durability of the mounting portion 35. This is thought to be because the tensile force of the first presser plate 31 acts on the mounting portion 35, mitigating the external force that stretches the mounting portion 35 in the surface direction.

[0025] Other resins included in the materials constituting the first pressure plate 31 and the second pressure plate 32 include the above-mentioned fiber-reinforced resins as well as engineering plastics such as polypropylene (PP), polyethylene (PE), polyethylene terephthalate (PET), and polycarbonate and polyether ether ketone (PEEK). In addition to the above-mentioned rubbers, examples of rubbers include natural rubber, styrene-butadiene rubber, chloroprene rubber, fluororubber, and other synthetic rubbers. Examples of metals include stainless steel (SUS), carbon steel, aluminum steel, copper, brass, iron, and other alloys. These metals may also be used as spring materials.

[0026] The thickness of the first pressure plate 31 is preferably 0.5 mm or more and 1.5 mm or less from the viewpoint of not impeding the transmission of deformation from the tire 2 to the power generator 33. The thickness of the second pressure plate 32 is preferably 0.2 mm or more and 0.5 mm or less from the viewpoint of maintaining rigidity and efficiently transmitting deformation of the tire 2 to the power generator 33. Note that the first pressure plate 31 and the second pressure plate 32 do not need to be completely plate-shaped, and at least one of through holes, notches, and cutouts may be appropriately formed in them to adjust rigidity and mass.

[0027] The first pressure plate 31 and the second pressure plate 32 according to this embodiment are preferably formed so that their shapes and dimensions match each other when viewed from above, and are fixed so that they are stacked with the same shape. As a result, both longitudinal ends of the first pressure plate 31 and the second pressure plate 32 form the first end 301 and the second end 302 of the power generation module 3, excluding the mounting portion 35. Note that the first pressure plate 31 and the second pressure plate 32 according to this embodiment are fixed to each other in a flat state when viewed from the side (i.e., without any external force being applied in a bending direction).

[0028] [Eyelet] The first and second pressure plates 31 and 32 according to this embodiment are fixed together chemically using an adhesive, pressure-sensitive adhesive, or the like. In addition, it is preferable that they be fixed together mechanically using a fixing member. The eyelets 34 are an example of such a fixing member. Here, "mechanically fixing" refers to preventing the first and second pressure plates 31 and 32 from separating using a tangible member, and does not include fastening the first and second pressure plates 31 and 32 together using an adhesive, pressure-sensitive adhesive, or the like. The material constituting the fixing member is not particularly limited, but is preferably a material that is resistant to deterioration by heat generated inside the tire 2, such as metal, resin, natural fiber, or ceramic. The eyelets 34 according to this embodiment are made of brass.

[0029] The eyelets 34 penetrate the second presser plate 32 and the first presser plate 31, respectively, to secure them together. Here, for example, two eyelets 34 are arranged at a first position P1 and a second position P2 spaced apart in the longitudinal direction in regions near the longitudinal centers of the second presser plate 32 and the first presser plate 31. As a result, a space defined by the first presser plate 31, the second presser plate 32, and the eyelets 34 is formed between the first position P1 and the second position P2. A power generation device 33 that generates electricity through frictional charging is arranged in this space. While the location of the eyelets 34 is not particularly limited, it is preferable to arrange them so that the power generation device 33 can be positioned in the longitudinal center of the power generation module 3. Furthermore, the first position P1 and the second position P2 are preferably located longitudinally outboard of both longitudinal ends of the power generation device 33. Here, the first point P1 is closer to the first end 301 than the second end 302, and the second point P2 is closer to the second end 302 than the first end 301.

[0030] The length Lp from the first end 301 to the second end 302, i.e., the longitudinal length of the first presser plate 31 and the second presser plate 32, is not particularly limited, but is preferably at least three times the length L3, where L3 is the length from the first point P1 to the second point P2. More specifically, if L1 is the length from the first end 301 to the first point P1 and L2 is the length from the second end 302 to the second point P2, then it is preferable that the power generation module 3 satisfy the relationships L1 ≥ L3 and L2 ≥ L3. In other words, if L1 is the length from the first end 301 to the fixing member on the first end 301 side, L2 is the length from the second end 302 to the fixing member on the second end 302 side, and L3 is the length between the fixing members along the longitudinal direction, then it is preferable that the power generation module 3 satisfy the relationships L1 ≥ L3 and L2 ≥ L3. The reason for this will be explained later.

[0031] [Power generation equipment] Fig. 3 is a cross-sectional view showing the configuration of a power generation device 33 according to this embodiment. As shown in Fig. 3, the power generation device 33 includes a first member 331 and a second member 332, with the members stacked in this order. The power generation device 33 according to this embodiment has a rectangular shape in a plan view, but the shape of the power generation device 33 is not limited to this.

[0032] The first member 331 has a first base material 3310, a first electrode 3311, and a first insulating film 3312. These elements are rectangular in plan view, stacked in this order from the outside to the inside of the power generation device 33, and fixed to each other. The first base material 3310 is made of a flexible material or a viscoelastic material, such as a resin or an elastomer, so that it can deform when subjected to an external force. A large number of projections and recesses are formed on the surface of the first base material 3310 that comes into contact with the first electrode 3311. As a result, projections and recesses corresponding to the projections and recesses of the first base material 3310 are reproduced on a first contact surface 3312s formed by the first insulating film 3312 via the first electrode 3311.

[0033] There is no particular limitation on the configuration of the unevenness of first base material 3310. For example, the unevenness may be formed regularly across the surface direction of first base material 3310, or may be formed somewhat randomly. In addition, there is no particular limitation on the cross-sectional shape of the unevenness.

[0034] The first electrode 3311 is a part for extracting the charge generated in the first insulating film 3312 to the outside of the power generation device 33 and is arranged so as to contact the first insulating film 3312 on the back side of the first contact surface 3312s. The first electrode 3311 can be made of a conductive material, examples of which include a conductive film of Ag, Cu, etc., and conductive cloth. The composition of the conductive cloth is not particularly limited, but may be a metal-plated organic fiber cloth made of a polymer material, or a material made of polymer material mixed with metal fibers, etc. The first electrode 3311 is flexible and can deform in response to deformation of the first base material 3310. Furthermore, the surface of the first electrode 3311 that contacts the first insulating film 3312 reproduces unevenness corresponding to the unevenness of the first base material 3310.

[0035] The first insulating film 3312 is a flexible insulating film. In this embodiment, the surface of the first insulating film 3312 opposite the first electrode 3311 corresponds to the first contact surface 3312s. The first base material 3310 forms irregularities on the first contact surface 3312s that correspond to the irregularities of the first base material 3310. The first contact surface 3312s faces a second contact surface 3322s formed by the second insulating film 3322 (described later) and is capable of contacting the second contact surface 3322s. When the actual contact area between the first contact surface 3312s and the second contact surface 3322s changes due to pressure applied to the power generation device 33, the first insulating film 3312 is charged with a polarity opposite to that of the second insulating film 3322. In other words, when the second insulating film 3322 is positively charged, the first insulating film 3312 is negatively charged. Moreover, when the second insulating film 3322 is negatively charged, the first insulating film 3312 is positively charged.

[0036] The ten-point mean roughness of the first contact surface 3312s is preferably 100 μm or more and 2 mm or less, and the ten-point mean roughness is measured in accordance with JIS B 0601:2001.

[0037] Note that when the first contact surface 3312s and the second contact surface 3322s are said to be "in contact," it is sufficient that the first contact surface 3312s and the second contact surface 3322s are in partial contact, and it is also acceptable for there to be portions where the first contact surface 3312s and the second contact surface 3322s are not in contact. In the power generating device 33 of this embodiment, the first contact surface 3312s and the second contact surface 3322s both have a rectangular shape and are configured to overlap entirely. In other words, in the power generating device 33 of this embodiment, friction can be generated entirely between one side of the first insulating film 3312 and one side of the second insulating film 3322.

[0038] The second member 332 has a second base material 3320, a second electrode 3321, and a second insulating film 3322. The elements of the second member 332 have a rectangular shape in a plan view, and are fixed to each other while being stacked in this order from the outside to the inside of the power generation device 33. The configurations of the second base material 3320 and the second electrode 3321 are the same as those of the first base material 3310 and the first electrode 3311, respectively, and therefore will not be described again.

[0039] The second insulating film 3322 is a flexible film made of an insulator different from that of the first insulating film 3312. In this embodiment, the surface of the second insulating film 3322 opposite to the second electrode 3321 corresponds to the second contact surface 3322s. The second base material 3320 forms irregularities on the second contact surface 3322s that correspond to the irregularities of the second base material 3320. The second contact surface 3322s faces the first contact surface 3312s formed by the first insulating film 3312 and is capable of coming into contact with the first contact surface 3312s.

[0040] The ten-point mean roughness of the second contact surface 3322s is preferably 100 μm or more and 2 mm or less, and the ten-point mean roughness is measured in accordance with JIS B 0601:2001.

[0041] The materials constituting the first insulating film 3312 and the second insulating film 3322 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, chlorinated polyether, polyvinylidene chloride, polystyrene, polyethylene, polypropylene, polyimide, polyvinyl chloride, polydimethylsiloxane, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-hexafluoropropylene copolymer (FEP), and other materials containing organic fluorocarbons as their main components. From the viewpoint of increasing the electromotive force of the power generation device 33, it is preferable to select a pair of materials from the above group that are farther apart in the triboelectric series.

[0042] The orientation of the power generation device 33 in the power generation module 3 is not particularly limited. The first member 331 may be disposed so as to face the second presser plate 32, and the second member 332 may be disposed so as to face the first presser plate 31, or the first member 331 may be disposed so as to face the first presser plate 31, and the second member 332 may be disposed so as to face the second presser plate 32. The first base material 3310 and the second base material 3320 are preferably fixed to the first presser plate 31 or the second presser plate 32, respectively, whichever faces them. The fixing method may be a method using an adhesive or a pressure-sensitive adhesive, and is not particularly limited. The first base material 3310 and the second base material 3320 are preferably fixed so that the first contact surface 3312s and the second contact surface 3322s entirely overlap when no deformation force is applied to the power generation module 3. The tire assembly 1 is preferably configured so that when the power generation device 33 is closest to the road surface, the change in the true contact area between the first contact surface 3312s and the second contact surface 3322s is theoretically maximized by the pressing force applied by the second presser plate 32. In the tire assembly 1, of the first member 331 and the second member 332, the one facing the second presser plate 32 is located on the radially inner side of the tire 2, and the one facing the first presser plate 31 is located on the radially outer side of the tire 2.

[0043] <2. Tires> Next, the tire 2 to which the power generation module 3 is attached will be described. FIG. 4 is a longitudinal cross-sectional view of the tire 2 (a cross-sectional view of a cross section along the radial direction of the tire 2). The tire 2 is made of vulcanized rubber or the like and has elasticity. The type and structure of the tire 2 are not particularly limited, but the tire 2 of this embodiment has a tread portion 200, a sidewall portion 201, a shoulder portion 202, and a bead portion 203, as shown in FIG. 4. The tread portion 200 is a portion that defines the circumferential surface of the tire assembly 1 and contacts the road surface to generate friction, thereby moving the vehicle forward. The sidewall portion 201 flexes and bends to absorb impact from the road surface. The shoulder portion 202 is a portion that is continuous with the tread portion 200 and the sidewall portion 201. The bead portion 203 is a portion that is fixed to a wheel rim and contains a bead wire (not shown). The tire 2 further has an inner surface 20 that defines the internal space of the tire 2. Hereinafter, of the inner surface 20, the annular surface corresponding to the back side of the tread portion 200 may be referred to as the inner surface 20a to distinguish it from other portions.

[0044] The tire 2 has an attachment portion 21 on its inner surface 20a to which the power generation module 3 is attached. In this embodiment, the attachment portion 21 is configured with a hook-and-loop fastener that extends along the circumferential direction of the tire 2. The attachment portion 21 according to this embodiment is fixed to the inner surface 20a so as to extend along the entire circumference of the tire 2. This allows the power generation module 3 to be fixed at any position in the circumferential direction relative to the inner surface 20a.

[0045] The hook-and-loop fasteners constituting the attachment portion 21 and the attachment portion 35 are not particularly limited as long as they are fasteners that can be attached and detached from the surface, and may be, for example, one with raised hooks and the other with raised loops, or both with raised hooks and raised loops, or fasteners that are joined in other shapes. However, taking into consideration the environment inside the tire 2, it is preferable that the material of the hook-and-loop fasteners constituting the attachment portion 21 and the attachment portion 35 is heat resistant. The method of attaching the attachment portion 21 to the inner surface 20a is not particularly limited and may be a method using an adhesive, a method using a pressure-sensitive adhesive, or the like.

[0046] <3. Tire assembly> FIG. 5 is a top view of the interior of tire assembly 1. As shown in FIG. 5, tire assembly 1 includes a tire 2 and a power generation module 3. Tire assembly 1 may further include functional components (not shown) other than power generation module 3. Examples of functional components include electronic devices such as a sensor, antenna, transmitter, processor, or memory. These may be connected to power generation device 33 via lead wires (not shown) and may receive power generated by power generation device 33. Tire assembly 1 may also further include a secondary battery or capacitor that stores power generated by power generation device 33. Note that power generation device 33 generates power in conjunction with the rotation of tire 2. For this reason, by detecting a change in the potential difference generated in power generation device 33, power generation device 33 can also be used as a sensor for monitoring at least one of the rotation speed, wear state, road surface state, and ground contact state of tire 2.

[0047] The tire assembly 1 is configured so that the radii of curvature of the first surface 311 and the second surface 312 of the first presser plate 31 are larger than the radius of curvature of the inner surface 20 of the tire 2. The definition of the radius of curvature of the first presser plate 31 is as described above, and is specified in a state where the power generation module 3 is not attached to the tire 2. In other words, the first presser plate 31 itself is not given a curve that follows the curvature of the inner surface 20 of the tire 2. The same is true for the second presser plate 32. The radius of curvature of the inner surface 20 is calculated by dividing the length of one circumference measured in the circumferential direction of the inner surface 20a by 2π.

[0048] Furthermore, it is preferable that the length L3 from the first point P1 to the second point P2 satisfies Lc≧L3, where Lc is the circumferential length of the contact patch of the tire assembly 1. The length Lc is the maximum length along the circumferential direction of the tire assembly 1 of the contact patch where the tread portion 200 comes into contact with a flat surface when the tire assembly 1 is mounted on a wheel with a standard rim, inflated to a predetermined air pressure, and a load corresponding to a predetermined mass is applied. The shape of the contact patch can be a shape created when paint applied to the circumferential surface of the tire assembly 1 is transferred to the flat surface.

[0049] The standard rim is a rim specified in the standard on which the tire 2 is based, and the specified air pressure is 200 kPa. Note that this air pressure is the air pressure at which the tire 2 is filled, and does not include any increase due to use of the tire 2. Furthermore, if the tire 2 is based on the JATMA standard, the specified mass is the mass (kg) corresponding to the load capacity when the air pressure is 200 kPa in the air pressure-load capacity correspondence table specified by the JATMA. If the tire 2 is based on the ETRTO standard (standard), the "specified mass" is the mass (kg) corresponding to the load when the air pressure is 200 kPa in the air pressure-load capacity correspondence table in the ETRTO (standard). If the tire 2 is based on the ETRTO standard (reinforced), the "specified mass" is the mass (kg) corresponding to the load when the air pressure is 200 kPa in the air pressure-load capacity correspondence table in the ETRTO (reinforced).

[0050] <4. Operation of tire assembly> FIG. 6 is a schematic diagram illustrating the behavior of the power generation module 3 when the tire assembly 1 rotates on a road surface. In FIG. 6, the tire assembly 1 is rotating in the direction of arrow A1. The deflection of the second presser plate 32 of the power generation module 3 changes in the order of symbols a to d as the tire assembly 1 rotates. Symbol a represents the point in time before the second presser plate 32 (i.e., the power generation module 3) reaches the ground contact region R of the tire assembly 1. Symbol d represents the point in time when the portion of the power generation module 3 including the first point P1 and the second point P2 is within the ground contact region R. Symbols b and c represent the points in time between symbols a and d, respectively. The ground contact region R is the region inside the tire 2 that corresponds to the ground contact surface of the tire assembly 1.

[0051] At time a, the second presser plate 32 is bent relatively significantly toward the inside in the radial direction of the tire 2 between the eyelets 34 at the first location P1 and the eyelets 34 at the second location P2. In this state, the first contact surface 3312s and the second contact surface 3322s of the power generation device 33 are separated or locally in contact. Thereafter, as time passes through times b and c, the bending of the second presser plate 32 gradually decreases and the second presser plate 32 approaches a flat shape. As a result, the contact area between the first contact surface 3312s and the second contact surface 3322s increases. Then, at time d, the inner surface 20a within the contact region R becomes almost flat, and the first presser plate 31 and the second presser plate 32 return to their flat shapes. As a result, the change in the true contact area between the first contact surface 3312s and the second contact surface 3322s reaches its theoretical maximum.

[0052] The eyelets 34 secure the first presser plate 31 and the second presser plate 32 together while allowing the second presser plate 32 to flex and restore its shape as the tire assembly 1 rotates. This ensures that the power generator 33 deforms as the tire assembly 1 rotates, allowing the power generator 33 to generate greater power. Furthermore, since Lc≧L3, the second presser plate 32 is more likely to return to its original shape after flexing in the ground contact region R, thereby more reliably increasing the true contact area between the first contact surface 3312s and the second contact surface 3322s. Furthermore, since the power generation module 3 satisfies L1≧L3 and L2≧L3, the power generation module 3 is more firmly fixed to the inner surface 20a. Additionally, the portion of the second presser plate 32 from the first end 301 to the first location P1 and the portion of the second presser plate 32 from the second end 302 to the second location P2 are also affected by the deformation of the tire 2 and contribute to the deformation of the second presser plate 32, thereby further increasing the power generated by the power generator 33.

[0053] <5. Features> The power generation module 3 according to the above embodiment can be detachably attached to the inner surface 20 of the tire 2 having the mounting portion 21. This makes it possible to easily configure the tire assembly 1. Furthermore, the power generation module 3 can be reused even when the tire 2 needs to be replaced, thereby enabling effective use of resources.

[0054] In the power generation module 3 according to the above embodiment, the first presser plate 31 and the second presser plate 32 are configured so that they are relatively less curved (flat) with respect to the inner surface 20 of the tire 2 to which they are attached. Therefore, in the tire assembly 1, when the power generation device 33 is positioned in the ground contact region R, the first contact surface 3312s and the second contact surface 3322s can be reliably brought into contact with each other, thereby improving the amount of power generation. In other words, even if the power generation module 3 is applied to a tire 2 having a relatively large diameter, the deflection of the second presser plate 32 is restored in the ground contact region R, promoting contact between the first contact surface 3312s and the second contact surface 3322s, so that a sufficient amount of power generation by the power generation device 33 can be maintained.

[0055] In the power generation module 3 according to the above embodiment, the first pressure plate 31 and the second pressure plate 32 are mechanically fixed via eyelets 34. If the first pressure plate 31 and the second pressure plate 32 were fixed only by chemical methods, the adhesive or pressure-sensitive adhesive would be altered by heat generated in the tire 2, gradually reducing the fixing strength, which could lead to separation between the first pressure plate 31 and the second pressure plate 32. However, in the power generation module 3 according to the above embodiment, the first pressure plate 31 and the second pressure plate 32 are mechanically fixed by the eyelets 34, which are resistant to heat alteration. This makes separation less likely, and the power generation module 3 can be used for a long period of time. Furthermore, because the eyelets 34 can locally fix the first pressure plate 31 and the second pressure plate 32, the second pressure plate 32 is more likely to deform than if they were fixed in a planar manner, which can also promote power generation by the power generation device 33.

[0056] In the power generation module 3 according to the above embodiment, satisfying L1 ≥ L3 and L2 ≥ L3 ensures sufficient length on both longitudinal sides of the eyelets 34, i.e., on both longitudinal sides of the power generation device 33. This allows for more reliable fixation by the eyelets 34. Furthermore, deformation of the first and second presser plates 31, 32 on both longitudinal sides is transmitted, particularly to the region between the first position P1 and the second position P2 of the second presser plate 32. This makes the second presser plate 32 more likely to bend before reaching the ground contact region R and more likely to return to its original shape once it reaches the ground contact region R. In this way, the deformation between the first position P1 and the second position P2 of the second presser plate 32 is greater, thereby more reliably increasing the amount of power generated by the power generation device 33.

[0057] <6. Variations> Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and various modifications are possible without departing from the spirit of the present invention. For example, the following modifications are possible. Furthermore, the gist of the following modifications can be combined as appropriate.

[0058] (1) The power generating device 33 is not limited to the above embodiment as long as it includes a first member and a second member that are charged by friction with each other. For example, the first electrode and the first contact surface may be formed as a single member, or the second electrode and the second contact surface may be formed as a single member. Furthermore, for example, the power generating device 33 may further include a member that is charged by friction in addition to the first member and the second member. Furthermore, when the first pressing plate 31 is formed of carbon fiber reinforced rubber, the first pressing plate 31 may also serve as the first substrate 3310 or the second substrate 3320 of the power generating device 33. In other words, when the first pressing plate 31 is formed of carbon fiber reinforced rubber, the substrate of the first member 331 or the second member 332 that is located on the first pressing plate 31 side can be omitted.

[0059] (2) The mounting portion 21 of the tire 2 and the mounting portion 35 of the power generation module 3 may each be formed of something other than a hook-and-loop fastener. For example, the mounting portion 21 and the mounting portion 35 may be formed of a pair of magnets, a pair of a magnet and a magnetic body, a pair of snap buttons, or the like. In another example, the mounting portion 21 may be formed of one or more protrusions protruding from the inner surface 20 toward the internal space, and the mounting portion 35 of the power generation module 3 may be formed of one or more through-holes corresponding to the one or more protrusions, with the protrusions passing through the corresponding through-holes to secure the power generation module 3 to the tire 2. Furthermore, one of the mounting portion 21 and the mounting portion 35 may be formed of adhesive tape that can be peeled off and then reattached, and the other may be formed of a surface to which the adhesive tape can be attached.

[0060] (3) In the above embodiment, the attachment portion 35 and the first pressure plate 31 may be formed as an integrated member. In other words, the attachment portion 35 itself may double as the first pressure plate 31 of the above embodiment. When the attachment portion 35 is formed from a hook-and-loop fastener, the raised surface of the attachment portion 35 (capable of being coupled to another hook-and-loop fastener) corresponds to the first surface 311, and the non-raised surface of the attachment portion 35 corresponds to the second surface 312. Furthermore, at least one of the first pressure plate 31 and the second pressure plate 32 may be formed from a plurality of laminated plate-like members. In this way, the bending rigidity of the first pressure plate 31 and the second pressure plate 32 can be adjusted. According to the inventor's investigation, increasing the bending rigidity of at least one of the first pressure plate 31 and the second pressure plate 32 allows the amount of power generated by the power generator 33 to peak when the tire assembly 1 rotates in a higher speed range. On the other hand, if the bending rigidity of at least one of the first pressure plate 31 and the second pressure plate 32 is reduced, the amount of power generated by the power generator 33 can peak when the tire assembly 1 rotates in a lower speed range. Therefore, in order to maintain the overall amount of power generated over a wider speed range, the tire assembly 1 may be provided with a plurality of power generation modules 3 in which the bending rigidity of at least one of the first pressure plate 31 and the second pressure plate 32 is different from each other. However, because it is the adjustment of the bending rigidity of the second pressure plate 32 that mainly contributes to adjusting the peak amount of power generated by the power generator 33, it is more effective to adjust the bending rigidity of the second pressure plate 32. The bending rigidity of the first pressure plate 31 and the second pressure plate 32 can also be adjusted by simply changing their thicknesses.

[0061] (4) In this embodiment, four eyelets 34 are used, but the number of eyelets 34 is not limited to four and may be changed as appropriate. Furthermore, the fixing members are not limited to eyelets 34. For example, staples, screws, split pins, thread (for sewing), bolts and nuts, etc. may be used in addition to or instead of the eyelets 34. Note that the fixing members may not only mechanically fix the second presser plate 32 and the first presser plate 31, but may also mechanically fix the mounting portion 35 as well.

[0062] (5) FIG. 7 is a side view of a power generation module 3X according to another embodiment different from the above-described embodiment. The power generation module 3X includes at least a first presser plate 31X, a second presser plate 32X, a power generation device 33X, an attachment portion 35X, and a thickness adjustment sheet 36X. The second presser plate 32X is a plate-shaped member extending in the longitudinal direction, similar to the second presser plate 32, and may be made of, for example, a glass fiber reinforced plastic plate. The power generation device 33X includes a first member 331X and a second member 332X, similar to the power generation device 33. The first member 331X and the second member 332X may have the same configuration as the first member 331 and the second member 332. The attachment portion 35X may be formed of a hook-and-loop fastener, similar to the attachment portion 35. In other words, the second presser plate 32X, the power generation device 33X, and the attachment portion 35X may have the same configuration as the second presser plate 32, the power generation device 33, and the attachment portion 35, respectively. The power generation module 3X differs significantly from the power generation module 3 in that the mounting portion 35X and the second presser plate 32X extend to approximately the same length along the longitudinal direction, but the length of the first presser plate 31X is the same or approximately the same as the length of the power generation device 33X. At least two thickness adjustment sheets 36X are disposed between the second presser plate 32X and the mounting portion 35X so as to sandwich the first presser plate 31X and the power generation device 33X from both sides of the power generation module 3X in the longitudinal direction. The material constituting the thickness adjustment sheets 36X is not particularly limited as long as it can deform in response to the deformation of the tire 2, but the aforementioned carbon fiber reinforced rubber is preferable, for example. In the example shown in FIG. 7, each thickness adjustment sheet 36X is fixed on one side to the second presser plate 32X and on the other side to the mounting portion 35X by double-sided tape 37X. In the example of Figure 7, the first member 331X is fixed to the second presser plate 32X and the second member 332X is fixed to the first presser plate 31X, but the first member 331X may be fixed to the first presser plate 31X and the second member 332X may be fixed to the second presser plate 32X.

[0063] The power generation module 3X may further include fixing members disposed at least at first and second locations spaced apart in the longitudinal direction. The fixing members may be selected from the above-mentioned members as appropriate, but preferably, for example, at least two SUS staples 34X are used. Each staple 34X penetrates the second presser plate 32X, the thickness adjusting sheet 36X, and the mounting portion 35X to secure them together. In the power generation module 3X, the thickness adjusting sheet 36X is interposed between the second presser plate 32X and the mounting portion 35X, so the second presser plate 32X can be said to be indirectly fixed to the mounting portion 35X. The power generation module 3X described above improves the flexural durability between the power generation device 33X and the staples 34X. This improves the durability of the power generation module 3X as a whole. [Example]

[0064] The following describes experiments conducted by the inventors and the results thereof, but the present invention is not limited to these.

[0065] <Experiment 1> A power generation module (Example 1) having the configuration shown in FIG. 8A was fabricated. The first and second pressure plates in Example 1 each measured 250 mm in the longitudinal direction and 40 mm in the width direction. The first pressure plate was a 0.5 mm-thick polycarbonate plate with numerous 2 mm-diameter through-holes. A hook-and-loop fastener (3M SJ-3540J Dual Lock Fastener) was used as the attachment, with the non-brushed side attached to the first surface of the first pressure plate. The second pressure plate was a 0.3 mm-thick glass fiber-reinforced epoxy resin plate. The size of the power generation device was 50 mm in the longitudinal direction and 40 mm in the width direction. A 40 μm-thick porous polyimide film (Tokyo Ohka Kogyo Co., Ltd.) and a 15 μm-thick polyamide film were used as the first and second insulating films of the power generation device (either could be used as the first insulating film or the second insulating film). Conductive nonwoven fabrics were attached to the backsides of the first and second contact surfaces to form the first and second electrodes, respectively. Lead wires for extracting power were connected to the first and second electrodes, respectively, and were extended from both ends of the first and second pressure plates in the width direction. The first and second substrates were made of silicone rubber with numerous cylindrical protrusions on their surfaces, each with a protrusion height of 0.5 mm and a diameter of approximately 1 mm. The surfaces with the protrusions were bonded to the first and second electrodes, respectively. The first and second substrates were fixed to the first and second pressure plates using double-sided tape. The first and second pressure plates were fixed to each other with double-sided tape (VR-5000T, manufactured by Nitto Denko Corporation) while maintaining a flat state without applying any bending force. The fixed locations were from both ends of the first and second pressure plates to positions 20 mm from both ends of the power generator in the longitudinal direction (the shaded areas in Figure 8A). Two 2 mm diameter brass grommets were then attached to each end 20 mm from both ends of the power generator in the longitudinal direction, further securing the first and second pressure plates. In this state, the radius of curvature of the first pressure plate was 1 m or more.

[0066] As Comparative Example 1, a power generation module having the configuration shown in FIGS. 8B and 8C was fabricated. The first and second pressure plates of Comparative Example 1 both measured 150 mm in the longitudinal direction and 40 mm in the width direction. The thickness and materials of the first and second pressure plates, as well as the configuration of the power generation device, were the same as in Example 1. The size of the mounting portion was 150 mm x 40 mm, the same as that of the first pressure plate, and the material was the same as in Example 1. As shown in FIG. 8C , the first and second pressure plates were bent to match the curvature of the inner surface (the back side of the tread portion) of a tire (175 / 60R15), and were fixed to each other using the same double-sided tape as in Example 1. The fixed locations were from both ends of the first and second pressure plates to positions 7.5 mm away from both ends of the power generation device in the longitudinal direction (the shaded areas in FIG. 8B ). Then, two grommets similar to those in Example 1 were attached to each end 7.5 mm away from both ends of the power generation device in the longitudinal direction, further fixing the first and second pressure plates. Even when this power generation module is not mounted on a tire, the radius of curvature of the second surface of the first pressing plate is equal to or smaller than the radius of curvature of the inner surface of the tire.

[0067] The inner surface (backside of the tread portion) of a tire (175 / 60R15) was treated with a primer, and a hook-and-loop fastener (3M SJ-3540J Dual Lock Fastener) was attached using double-sided tape (Nitto Denko VR-5000T) to form a fixed portion. The hook-and-loop fastener of the power generation module according to the example was pressed against this hook-and-loop fastener to prepare a tire assembly (Example 1) without a wheel attached. The hook-and-loop fastener of the power generation module according to the comparative example was pressed against the hook-and-loop fastener of the same tire to prepare a tire assembly (Comparative Example 1) without a wheel attached.

[0068] The contour of the inner surface of the tire assembly according to Example 1 and the contour of the second presser plate of the power generation module were each measured using a contour gauge. The contour of the second presser plate is the contour of the surface facing radially inward of the tire assembly. Measurements were performed in two ways: (I) when the power generation module, particularly the power generation device, was located within the tire's contact patch, and (II) when the power generation module was not located within the tire's contact patch. The contour of the inner surface of the tire assembly according to Comparative Example 1 and the contour of the second presser plate of the power generation module were also measured in the same way as in the Examples. The measured curves are shown in Figure 9.

[0069] <Result 1> From the results in Figure 9, it was confirmed that in the tire assembly according to Example 1, the change in deflection between the eyelets of the second presser plate on which the power generation unit is disposed is greater when the power generation module is located within the ground contact area than when it is not located within the ground contact area. This is thought to be because the power generation module according to Example 1 is fixed to each other while the first presser plate and the second presser plate remain flat. On the other hand, in the tire assembly according to Comparative Example 1, it was confirmed that the change in deflection between the eyelets of the second presser plate on which the power generation unit is disposed is smaller when the power generation module is located within the ground contact area than when it is not located within the ground contact area. From this, it is thought that the power generation module according to Example 1 generates more power when attached to a tire than the power generation module according to Comparative Example 1.

[0070] <Experiment 2> The power generation modules according to Example 1 and Comparative Example 1 were each fixed to a separate tire (175 / 60R15) to produce tire assemblies according to Example 2 and Comparative Example 2. In each tire assembly, three power generation modules were connected in parallel via bridge diodes. The power generation modules of each tire assembly were also connected to a wireless oscilloscope to enable measurement of the output voltage (V) and power (μW) of the entire tire assembly. Each tire assembly was mounted on a wheel, which was then attached to the hub of an automobile, and a running test was conducted.

[0071] <Result 2> 10A and 10B are graphs showing the output voltage of each tire assembly in the running test. As can be seen from FIGS. 10A and 10B, at approximately the same running speed, the output voltage of the tire assembly according to Example 2 was significantly higher than the output voltage of the tire assembly according to Comparative Example 2. Note that the graphs of FIGS. 10A and 10B show voltage waveforms after rectification by a bridge diode, so the output voltages are positive. FIG. 11 is a graph showing the output power of each tire assembly versus the running speed of the automobile. In FIG. 11, the filled circles indicate the results of Example 2 and the open squares indicate the results of Comparative Example 2. As can be seen from FIG. 11, the output power of the tire assembly according to Example 2 was significantly higher than the output power of the tire assembly according to Comparative Example 2 across the entire speed range of approximately 30 km / h to 90 km / h. FIG. 12 is a graph showing the output power of each tire assembly versus the cumulative running distance of the automobile (running speed: 50 km / h to 60 km / h). In FIG. 12, the filled circles indicate the results of Example 2 and the open squares indicate the results of Comparative Example 2. As shown in FIG. 12, it was found that with the tire assembly according to Example 2, even if the mileage increased, the output power did not decrease and was maintained at the initial level.

[0072] <Experiment 3> A power generation module having the same configuration as Comparative Example 1 except that the second pressure plate was changed to a plate made of the same polycarbonate as the first pressure plate was fabricated by fixing the first pressure plate and the second pressure plate in the same manner as Comparative Example 1, and designated Reference Example 1. A power generation module was also fabricated from the power generation module of Reference Example 1, but without the grommets, and designated Reference Example 2. The power generation modules of Reference Examples 1 and 2 were fixed to the inner surface of a tire (145 / 80R12) with a fixed portion formed in the manner described above, and these were designated tire assemblies of Reference Example 1 and Reference Example 2, respectively. Wheels were attached to each tire assembly, and while heating them with a heater, they were installed in a drum-type running test machine and rotated at a constant speed, and the output power (μW) was measured. A wireless oscilloscope for measuring the output power of the power generation module was attached to the inner surface of each tire assembly, and the temperature of the inner surface of the tire was measured using a temperature sensor attached to the wireless oscilloscope.

[0073] <Result 3> FIG. 13 shows a graph of the output power of the tire assemblies according to Reference Example 1 and Reference Example 2 versus temperature. The left vertical axis corresponds to the output power of Reference Example 1, and the right vertical axis corresponds to the output power of Reference Example 2. As can be seen from FIG. 13, in Reference Example 2, in which the first and second pressure plates were not fastened together with grommets, the output power decreased significantly as the temperature increased. This is thought to be because the adhesive strength of the double-sided tape decreased as the temperature increased, weakening the ability of the second pressure plate to hold down the generator in the tire contact area. Note that a decrease in output power with increasing temperature was also observed in Reference Example 1, and this may be due to factors such as an increase in tire air pressure caused by an increase in temperature, shortening the circumferential length of the tire contact area. Furthermore, a significant difference in the magnitude of output power occurred between Reference Example 1 and Reference Example 2. This is thought to be because when the first and second pressure plates are fixed with only double-sided tape, a larger misalignment occurs in the surface direction between the first and second pressure plates, resulting in a smaller degree of shape change during bending and recovery of the second pressure plate.

[0074] <Experiment 4> The power generation module according to Example 1 was fixed to a tire (145 / 80R12) with a fixed portion formed by the above-mentioned method, thereby producing a tire assembly according to Example 3. The tire assembly according to Example 3 was mounted on a wheel, and the air pressure was set to 250 kPa. This tire assembly was installed in a drum-type running test machine, and the circumferential length Ld of the contact patch on the outer peripheral surface of the drum in a stationary state was measured while applying loads of 0.4 kN, 1.0 kN, 1.5 kN, 2.0 kN, and 3.0 kN. The length Ld simulated various contact lengths Lc. The tire assembly was then rotated under each of the above load conditions, and the output power (μW) was measured.

[0075] <Result 4> The shape of the ground contact patch of the tire assembly under each load changed as shown in Fig. 14. Fig. 15 shows a graph plotting the ratio of the length Ld to the distance L3 (= 90 mm) between the eyelets in the tire assembly according to Example 3 versus the output power. As can be seen from Fig. 14, the output power improved as Ld / L3 approached 1, and the output power was maximized when Ld / L3 was less than 1. This confirmed that the output power could be further improved if the distance between the fixing members in the power generation module (the length L3 from the first point P1 to the second point P2) was equal to or less than the circumferential length of the ground contact patch of the tire to which it was fixed.

[0076] <Experiment 5> In the power generation module of Example 1, power generation modules were fabricated in which the lengths (Lp) of the first and second pressure plates were varied to 150 mm, 200 mm, 250 mm, 300 mm, and 350 mm. Each power generation module was fixed to a tire (275 / 80R22.5) with a fixed portion formed using the method described above, to fabricate tire assemblies of Examples 4 to 8. The circumferential length of the contact patch of each tire assembly without the wheel was approximately 95 mm, and the distance L3 between the grommets was 90 mm in all cases. Each tire assembly was rolled by hand, and the output power (μW) of the power generation module was measured.

[0077] FIG. 16 shows a graph plotting the ratio of Lp to L3 for each power generation module versus output power. Because each tire assembly was manually rolled without being mounted on a wheel, the output power was lower than in other experiments. For reference, FIGS. 17A and 17B show the output voltages of the tire assembly according to Example 4 and the tire assembly according to Example 8, respectively. As can be seen from FIG. 16, it was confirmed that increasing Lp / L3 increases the output power. In particular, it was found that the length Lp of the first and second pressure plates is preferably three times or more L3. This is thought to be because the regions on both sides of the eyelets in the longitudinal direction of the first and second pressure plates are deformable in response to tire deformation, further promoting deflection of the second pressure plate between the eyelets. However, it is thought that a ratio of Lp / L3 of approximately three to four times is preferable to prevent an excessive increase in the mass of the entire power generation module. [Explanation of symbols]

[0078] 1 Tire assembly 2 tires 3,3X Power Generation Module 20,20a inner surface 21 Mounting part (hook and loop fastener) 31,31X First holding plate 32,32X Second holding plate 33,33X power generation equipment 34 Eyelets 35,35X Mounting part (hook and loop fastener) 311 Page 1 312 2nd page

Claims

1. A power generation module that can be attached to the inner surface of a tire, an attachment portion configured to be attachable to and detachable from an inner surface of the tire and extending along a longitudinal direction; a first pressing plate fixed to the mounting portion and having a first surface configured to be positioned radially outward of the tire and a second surface on the back side of the first surface; a second pressing plate extending along the longitudinal direction and fixed directly or indirectly to the mounting portion or the first pressing plate at at least two locations, a first location and a second location, spaced apart in the longitudinal direction; a power generating device having a first member and a second member that are arranged between the first pressure plate and the second pressure plate and between the first location and the second location and that are charged by friction with each other; Equipped with When the power generation module is not attached to the tire, the radius of curvature of the second surface of the first pressing plate is larger than the radius of curvature of the inner surface of the tire. Power generation module.

2. The radius of curvature of the second surface is 1 m or more. The power generation module according to claim 1 .

3. a fixing member that mechanically fixes the second pressing plate to the mounting portion or the first pressing plate; Furthermore, The fixing member is disposed at the first location and the second location. The power generation module according to claim 1 .

4. The length from the first end to the second end of the second pressing plate in the longitudinal direction is three times or more the length from the first location to the second location. The power generation module according to claim 3 .

5. a thickness adjusting sheet between the second pressing plate and the mounting portion; Further equipped The power generation module according to claim 1 .

6. the first member has a first insulating film that forms a first contact surface; the second member has a second insulating film that forms a second contact surface that faces the first contact surface and is in contact with the first contact surface; the first member and the second member are configured so that one of them is positively charged and the other is negatively charged due to friction between the first contact surface and the second contact surface in response to pressure applied to the first member and the second member. The power generation module according to any one of claims 1 to 5.

7. The second pressing plate is made of fiber reinforced resin. The power generation module according to any one of claims 1 to 5.

8. a tire having a mounting portion extending circumferentially on an inner surface thereof; A power generation module attached to the attachment portion, a mounting portion configured to be attachable to and detachable from a mounting portion of the tire and extending along a longitudinal direction; a first presser plate fixed to the mounting portion and having a first surface located radially outward of the tire and a second surface on the reverse side of the first surface; a second pressing plate extending along the longitudinal direction and fixed directly or indirectly to the mounting portion or the first pressing plate at at least two locations, a first location and a second location, spaced apart in the longitudinal direction; a power generating device having a first member and a second member that are arranged between the first pressure plate and the second pressure plate and between the first location and the second location and that are charged by friction with each other; a power generation module having Equipped with When the power generation module is not attached to the tire, the radius of curvature of the second surface of the first pressing plate is larger than the radius of curvature of the inner surface of the tire. Tire assembly.

9. a fixing member that mechanically fixes the second pressing plate to the mounting portion or the first pressing plate; Furthermore, the fixing member is disposed at the first location and the second location, and a length from the first location to the second location is equal to or less than a length of the tire contact surface in the circumferential direction. The tire assembly of claim 8.

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