Strain detection device

Abstract

The cover of the frame body of the strain detection device comprises a cylindrical peripheral wall part; a disc-shaped top plate part for closing the upper end of the peripheral wall part; and a reinforcing part protruding from the top plate part. The volume of the cover is 15% or more and less than 40% of the volume of the cylinder including the upper surface of the top plate portion, the outer peripheral surface of the peripheral wall portion, and the bottom surface of the peripheral wall portion. In the strain detection device, the maximum deformation amount of the top plate part of the cover in the central axis direction of the peripheral wall part caused by the differential pressure between the inner pressure of the inner space of the housing sealed by the cover and the air pressure of the tire is 4.1% or less of the outer diameter of the cover.

Description

Technical Field

[0001] The invention relates to a strain detection device. Background Art

[0002] Conventionally, there is known an invention related to a functional component that can be mounted on a tire (see Patent Document 1 below). This conventional functional component includes a structure in which a strain detection unit (strain sensor) for detecting tire strain is provided on the bottom surface (Patent Document 1, Claim 6, Paragraph 0043 and Fig.10 ).

[0003] The above-mentioned conventional functional component includes a frame body, the frame body includes a storage case having a storage space (storage portion) for the module, and a cover that functions as a cover body with respect to the storage case (Patent Document 1, paragraphs 0010-0011, Figure 2 A hole is formed on the circular top of the cover and penetrates the top. When the opening of the storage shell is closed by the cover, the hole can connect the storage space of the storage shell to the outside (ibid., paragraph 0016, Figure 2 ). Prior art literature Patent Literature

[0004] Patent Document 1: Japanese Patent Application Publication No. 2020-055402 Summary of the invention Problem that the invention aims to solve

[0005] The frame of the strain detection device for detecting the strain of the tire is bonded to the inner surface of the tire on the side opposite to the contact surface by an elastic adhesive, for example, by a housing for accommodating a circuit substrate or a battery, and a cover for closing the opening of the housing. Therefore, if a hole is formed in the cover of the frame as in the functional component of the above-mentioned Patent Document 1, the air pressure of the tire will act on the circuit substrate or the battery inside the housing of the frame, or moisture or dust will intrude into the interior of the housing, which may cause a malfunction in the strain detection device.

[0006] However, when the hole of the cover of the frame is sealed to make the frame into a closed structure, a uniform load will act on the cover due to the difference between the internal pressure of the frame and the air pressure of the tire. When the cover is deformed by the uniform load, the stress caused by the deformation of the cover will act on the elastic adhesive between the strain sensor for detecting the strain of the tire and the tire, which may cause the strain sensor to produce a detection error. However, if the thickness of the cover is increased to prevent deformation, the weight of the frame including the cover will increase, the centrifugal force and inertial force acting on the strain detection device will increase, and the alignment adjustment of the tire will become difficult, etc., and the performance and practicality of the device may be reduced.

[0007] The present invention provides a strain detection device which can suppress the increase in weight of a frame including a housing and a cover, and can suppress the deformation of the cover of the frame having a closed structure accommodating a circuit substrate and a battery, thereby improving the strain detection accuracy of a tire. Technical means of solving problems

[0008] One embodiment of the present invention is a strain detection device, which comprises: a housing fixed to the inner circumferential surface of a tire by an elastic adhesive; a strain sensor installed on the outer side of the bottom wall of the housing to detect the strain of the tire via the elastic adhesive; a circuit substrate and a battery, which are accommodated in the internal space of the box; and a resin cover, which closes the opening of the box on the side opposite to the bottom wall to seal the internal space, wherein the cover includes: a cylindrical peripheral wall portion; a circular plate-shaped top plate portion, which closes the upper end of the peripheral wall portion; and a reinforcement portion, which protrudes from the top plate portion, the volume of the cover is not less than 15% and not more than 40% of the volume of the cylinder including the upper surface of the top plate portion, the outer circumferential surface of the peripheral wall portion and the bottom surface of the peripheral wall portion, and the maximum deformation of the top plate portion of the cover in the central axis direction of the peripheral wall portion caused by the differential pressure between the internal pressure of the internal space of the housing sealed by the cover and the air pressure of the tire is not more than 4.1% of the outer diameter of the cover. Effects of the Invention

[0009] According to one of the above-mentioned embodiments of the present invention, a tire strain detection device can be provided, which can suppress the increase in weight of a frame including a casing and a cover, and can suppress the deformation of the cover of the frame having a sealed structure that accommodates a circuit substrate and a battery, thereby improving the strain detection accuracy of the tire. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is an enlarged cross-sectional view showing an embodiment of the strain detection device of the present invention. Figure 2 yes Figure 1 A bottom view and a cross-sectional view of a cover of a frame in a strain detection device. Figure 3 Yes means Figure 2 A bottom view and a cross-sectional view of a modified example 1 of the cover. Figure 4 Yes means Figure 2 A bottom view and a cross-sectional view of a modification 2 of the cover. Figure 5 Yes means Figure 2 A bottom view and a cross-sectional view of a variant example 3 of the cover. Figure 6 Yes means Figure 2 A bottom view and a cross-sectional view of a modification example 4 of the cover. Figure 7 Yes means Figure 2 A bottom view and a cross-sectional view of a modification example 5 of the cover. Figure 8 It means acting on Figures 2 to 7 A graph showing the relationship between stress on the cover and volume ratio. Fig. 9 Yes means Figures 2 to 7 A graph showing the relationship between the outer diameter of the cover and the maximum deformation. Fig.10 Yes means Figure 1 A top view of a modified example of the outer shell of the frame body in the strain detection device. DETAILED DESCRIPTION

[0011] Hereinafter, embodiments of the strain detection device according to the present invention will be described with reference to the drawings.

[0012] Figure 1 1 is an enlarged cross-sectional view showing an embodiment of the strain detection device of the present invention. The strain detection device 100 of this embodiment is mounted on the inner peripheral surface Ti of the tire T of a vehicle such as an automobile, detects the strain of the tire T, and transmits the detection result to the outside of the device through wireless communication. The detection result of the strain transmitted from the strain detection device 100 is received by an external device such as an electronic control unit (ECU) through a communication device mounted on the vehicle, for example.

[0013] The strain detection device 100 includes, for example, a housing 110, a strain sensor 120, an elastic member 130, a battery 140, and a circuit board 150. The housing 110 includes, for example, a bottomed cylindrical housing 111 made of resin and a cover 112 made of resin that closes an opening 111a of the housing 111. From the perspective of enabling wireless communication, the resin material of the housing 111 and the cover 112 may be, for example, polybutylene terephthalate (PBT), polyamide (PA), polycarbonate (PC), etc., having a dielectric constant of less than 4 and a dissipation factor of less than 0.02.

[0014] The housing 111 includes, for example, a cylindrical portion 111c having a circular opening 111a at the upper end and a bottom wall 111b closing the lower end of the cylindrical portion 111c. The housing 111 includes, for example, a skirt-shaped elastic member 130 mounted on the lower end of the cylindrical portion 111c and fixed to the inner circumferential surface Ti of the tire T by an elastic adhesive EA filled inside the elastic member 130.

[0015] The cover 112 is fixed to the upper end of the cylindrical portion 111c of the housing 111 by, for example, an adhesive, and closes the opening 111a of the housing 111 on the opposite side of the bottom wall 111b, thereby sealing the internal space 111d of the housing 111. The cover 112 has a cylindrical peripheral wall portion 112a and a disc-shaped top plate portion 112b that closes the upper end of the peripheral wall portion 112a.

[0016] The strain sensor 120 is mounted on the outer side of the bottom wall 111b of the housing 111 of the frame 110, and detects the strain of the tire T via the elastic adhesive EA. The strain sensor 120 includes, for example, a semiconductor sensor. The semiconductor sensor uses the piezoresistive effect of a diffused resistor formed by ion implantation of impurities into a silicon single crystal, and can detect the strain of the tire T by directly measuring the voltage from the electrode pad of the semiconductor chip. The strain sensor 120 is connected to the circuit board 150, for example, via the wiring 121.

[0017] The lower part of the housing 111 is inserted into the inner side of the cylindrical upper part of the elastic member 130, and the elastic member 130 is fixed to the outer peripheral surface of the lower part of the housing 111. The elastic member 130 has a skirt-shaped lower part that expands downward as it moves away from the cylindrical upper part. The elastic member 130 is made of an elastic resin material such as rubber, and elastically deforms as the tire T deforms.

[0018] The battery 140 is, for example, a button-type battery, which is received in the inner space 111d of the housing 111 through the opening 111a of the housing 111 of the frame 110 and arranged on the bottom wall 111b of the housing 111. The battery 140 is connected to the circuit board 150 via the connection terminals 141 and 142, for example, to supply power to the circuit board 150.

[0019] The circuit board 150 is accommodated in the internal space 111d of the housing 111, for example, from the opening 111a of the housing 111, supported by the step or protrusion on the inner peripheral surface of the housing 111, and arranged on the battery 140. The circuit board 150 includes, for example, a power supply circuit, a signal processing circuit, a wireless communication circuit, and a control circuit. The power supply circuit, for example, supplies the power supplied from the battery 140 to the strain sensor 120. The signal processing circuit, for example, processes the signal input from the strain sensor 120. The wireless communication circuit, for example, transmits the detection result of the strain of the tire T by the strain sensor 120 to an external device through wireless communication. The control circuit, for example, controls the power supply circuit, the signal processing circuit, and the wireless communication circuit.

[0020] Figure 2 The upper and lower figures are Figure 1The top view and cross-sectional view of the cover 112 of the frame 110 in the strain detection device 100 of the present embodiment are characterized by the following structure. The cover 112 includes a cylindrical peripheral wall portion 112a, a circular plate-shaped top plate portion 112b closing the upper end of the peripheral wall portion 112a, and a reinforcement portion 112c protruding from the top plate portion 112b.

[0021] The volume of the cover 112 is 15% or more and less than 40% of the volume of the cylinder or column including the upper surface of the top plate portion 112b, the outer peripheral surface of the peripheral wall portion 112a, and the lower surface of the peripheral wall portion 112a. In addition, the cover 112 is configured so that the maximum deformation amount of the top plate portion 112b of the cover 112 in the central axis direction of the peripheral wall portion 112a caused by the differential pressure between the internal pressure of the internal space 111d of the housing 111 sealed by the cover 112 and the air pressure of the tire T is 4.1% or less of the outer diameter of the cover 112.

[0022] Here, the air pressure of the tire T is about 14 [atm] at maximum in a commercial tire, for example, whereas the internal pressure of the internal space 111d of the housing 111 sealed by the cover 112 is about 1 [atm], for example. Due to the differential pressure between the air pressure of the tire T and the internal pressure of the internal space 111d of the housing 111, a uniform load acts on the upper surface of the top plate portion 112b of the cover 112.

[0023] As described above, the strain detection device 100 of the present embodiment provides the reinforcing portion 112c on the cover 112, and specifies the percentage of the volume of the cover 112 relative to the volume of the cylinder or column defined by the upper surface, the outer peripheral surface, and the bottom surface of the cover 112 having the peripheral wall portion 112a and the top plate portion 112b. Furthermore, the strain detection device 100 of the present embodiment specifies the percentage of the maximum deformation of the cover 112 based on the above-mentioned uniformly distributed load relative to the outer diameter of the cover 112.

[0024] Figure 2 An example of the structure of the cover 112 that satisfies these conditions is shown. Figure 2 In the example shown, the reinforcing portion 112c includes a plurality of ribs 112d extending radially from the center of the lower surface of the top plate portion 112b to the outer edge. The cover 112, for example, has three or more ribs 112d arranged at equal angles in the circumferential direction of the cover 112, based on the conditions of the volume and maximum deformation of the cover 112. Figure 2 In the illustrated example, the protruding heights of the respective ribs 112 d , that is, the heights from the bottom surface of the top plate portion 112 b to the top ends of the ribs 112 d in the protruding directions of the ribs 112 d , are the same.

[0025] Figure 3 The upper and lower figures represent Figure 2 A bottom view and a cross-sectional view of a modification 1 of the cover 112 are shown. Figure 3 The cover 112 shown in the figure satisfies the above volume and maximum deformation conditions, and the reinforcing portion 112c includes a plurality of ribs 112d and a cylindrical protrusion 112e. The cylindrical protrusion 112e is provided on the lower surface of the top plate 112b and is a short-axis cylindrical thick wall portion concentric with the peripheral wall 112a.

[0026] exist Figure 3 In the cover 112 shown, for example, the width w of the rib 112d, the thickness t of the top plate portion 112b, and the protruding height h of the rib 112d are equal (w=t=h). In addition, the radius r2 of the cylindrical protrusion 112e is, for example, more than half of the radius r1 of the cover 112 (r2≥1 / 2×r1). These conditions are, for example, optimal conditions for suppressing deformation of the cover 112 obtained by Computer-Aided Engineering (CAE).

[0027] Figure 4 The upper and lower figures represent Figure 2 A bottom view and a cross-sectional view of a second variation of the cover 112 are shown. Figure 4 The cover 112 shown, for example, satisfies the above volume and maximum deformation conditions, and the reinforcing portion 112c includes a plurality of ribs 112d arranged at equal angles in the circumferential direction of the cover 112. In addition, each rib 112d gradually decreases its protruding height h from the center to the outer edge of the top plate portion 112b.

[0028] Figure 5 The upper and lower figures represent Figure 2 A bottom view and a cross-sectional view of a modification 3 of the cover 112 are shown. Figure 5 The cover 112 shown, for example, satisfies the above-mentioned volume and maximum deformation conditions, and the reinforcing portion 112c includes a plurality of ribs 112d arranged at equal angles in the circumferential direction of the cover 112. In addition, the width w of each rib 112d orthogonal to the radial direction of the cover 112 gradually decreases from the central portion of the top plate portion 112b toward the outer edge portion.

[0029] Figure 6 The upper and lower figures represent Figure 2 A bottom view and a cross-sectional view of a modification example 4 of the cover. Figure 6 The cover 112 shown, for example, satisfies the above-mentioned volume and maximum deformation conditions, and the reinforcing portion 112c includes a conical convex portion 112f having the upper surface of the top plate portion 112b as the bottom surface and being concentric with the top plate portion 112b instead of the plurality of ribs 112d. In addition, the cover 112 may also include a conical convex portion 112f having the bottom surface of the top plate portion 112b as the bottom surface and being concentric with the top plate portion 112b.

[0030] Figure 7The upper and lower figures represent Figure 2 A bottom view and a cross-sectional view of a modification example 5 of the cover. Figure 7 The cover 112 shown, for example, satisfies the above-mentioned volume and maximum deformation conditions, and the reinforcing portion 112 c includes a positive plane filling-shaped lattice structure 112 g instead of the plurality of ribs 112 d. Figure 7 The front plane filling shape of the lattice structure 112g of the cover 112 shown may be, for example, a regular triangle or a square, in addition to a regular hexagon.

[0031] Figure 8 It means acting on Figures 2 to 7 A graph showing the relationship between the maximum stress σ of the top plate portion 112b of the cover 112 and the volume ratio VR of the cover 112 relative to the reference cylinder or reference column. Here, the volume of the reference cylinder or reference cylinder is the volume of the cylinder or column defined by the upper surface of the top plate portion 112b of the cover 112, the outer peripheral surface of the peripheral wall portion 112a, and the bottom surface of the peripheral wall portion 112a.

[0032] In addition, Figure 8 In the graph of FIG. 1 , the hatched area BA indicates the damaged area of ​​the cover 112. In addition, the dotted line and the black triangle mark indicate the comparative example CE of the cover 112 having the peripheral wall portion 112a and the top plate portion 112b, but not having the reinforcing portion 112c for increasing the thickness of the top plate portion 112b. In addition, the solid line and the hollow circle mark indicate Figures 2 to 7 Cover 112 of embodiment E.

[0033] like Figure 8 As shown, in comparative example CE in which the thickness of the top plate portion 112b is increased, if the volume ratio VR exceeds 40%, the cover 112 can be prevented from being damaged. In contrast, in embodiment E in which the cover 112 has a reinforcement portion 112c, the cover 112 can be prevented from being damaged by setting the volume ratio VR to 15% or more. Figures 2 to 7 The cover 112 of Embodiment E can reduce the weight as compared with the cover 112 of Comparative Example CE which can prevent breakage by setting the volume ratio VR to 15% or more and less than 40%.

[0034] Fig. 9 Yes means Figures 2 to 7 A graph showing the relationship between the outer diameter Φ of the cover 112 and the maximum deformation amount DA. Fig. 9 In the graph of , the hatched area BA represents a damaged area of ​​the cover 112. Here, the maximum deformation amount DA of the cover 112 is the maximum deformation amount of the top plate portion 112b of the cover 112 in the central axis direction of the peripheral wall portion 112a caused by the differential pressure between the internal pressure of the internal space 111d of the housing 111 sealed by the cover 112 and the air pressure of the tire T.

[0035] In addition, Fig. 9 The solid lines and hollow circles indicate Figures 2 to 7 Cover 112 of embodiment E. Fig. 9 For example, the graph of FIG. 114 shows that if the outer diameter Φ of the cover 112 is less than 34 [mm], then Figures 2 to 7 The maximum deformation amount DA of the top plate portion 112b of the cover 112 shown is less than 1.4 [mm], which is less than 4.1% of the outer diameter Φ of the cover 112. Such a relationship between the outer diameter Φ of the cover 112 and the maximum deformation amount DA can be derived by CAE, for example.

[0036] Fig.10 Yes means Figure 1 FIG. 1 is a top view of a modified example of the housing 111 of the frame body 110 in the strain detection device 100 . Fig.10 The housing 111 shown in the figure includes: a cylindrical portion 111c, a bottom wall 111b closing the lower end of the housing 111, and a support protruding radially inward from the inner circumferential surface of the cylindrical portion 111c. Figure 3 The cover 112 is shown with a plurality of ribs 111e of the plurality of ribs 112d.

[0037] The supporting protrusion 111e is, for example, Fig.10 As shown, it has a substantially semicircular shape when viewed from the central axis direction of the housing 111, and extends from the opening 111a to the bottom wall 111b along the central axis direction of the cylindrical portion 111c of the housing 111. The plurality of supporting protrusions 111e are arranged at the same angular intervals as the plurality of ribs 112d of the cover 112. Thus, the upper surface of each supporting protrusion 111e of the housing 111 contacts the adjacent end of the peripheral wall portion 112a of the lower surface of each rib 112d of the cover 112. Moreover, each rib 112d of the cover 112 is supported from below by each supporting protrusion 111e of the housing 111.

[0038] Next, the operation of the strain detection device 100 according to the present embodiment will be described.

[0039] As described above, the strain detection device 100 of the present embodiment includes a housing 111, a strain sensor 120, a battery 140, a circuit board 150, and a resin cover 112. The housing 111 is fixed to the inner circumferential surface Ti of the tire T by an elastic adhesive EA. The strain sensor 120 is mounted on the outer side of the bottom wall 111b of the housing 111, and detects the strain of the tire T via the elastic adhesive EA. The battery 140 and the circuit board 150 are accommodated in the internal space 111d of the housing 111. The cover 112 closes the opening 111a on the opposite side of the bottom wall 111b of the housing 111, thereby sealing the internal space 111d. The cover 112 includes a cylindrical peripheral wall portion 112a, a disc-shaped top plate portion 112b that closes the upper end of the peripheral wall portion 112a, and a reinforcing portion 112c protruding from the top plate portion 112b. The volume of the cover 112 is 15% or more and less than 40% of the volume of the cylinder including the upper surface of the top plate portion 112b, the outer peripheral surface of the peripheral wall portion 112a, and the bottom surface of the peripheral wall portion 112a. In addition, in the strain detection device 100, the maximum deformation amount DA of the top plate portion 112b of the cover 112 in the central axis direction of the peripheral wall portion 112a caused by the differential pressure between the internal pressure of the internal space 111d of the housing 111 sealed by the cover 112 and the air pressure of the tire T is 4.1% or less of the outer diameter Φ of the cover 112.

[0040] With such a configuration, the strain detection device 100 of the present embodiment can reinforce the cover 112 by the reinforcement portion 112c. More specifically, by providing the reinforcement portion 112c on the cover 112, the stress distribution when the uniformly distributed load caused by the differential pressure between the internal space 111d of the internal space of the housing 111 and the air pressure of the tire T acts on the cover 112 can be made uniform. Thus, the deformation of the cover 112 caused by the above-mentioned uniformly distributed load can be suppressed. In addition, since the volume of the cover 112 is greater than 15% and less than 40% of the volume of the reference cylinder including the upper surface of the top plate portion 112b, the outer peripheral surface of the peripheral wall portion 112a, and the bottom surface of the peripheral wall portion 112a, the cover 112 can be made lighter than when the top plate portion 112b of the cover 112 is thickened. In addition, by making the maximum deformation amount DA caused by the differential pressure between the internal pressure of the internal space 111d of the housing 111 and the air pressure of the tire T less than 4.1% of the outer diameter Φ of the cover 112, it is possible to prevent the center portion of the cover 112 from being damaged. Therefore, according to this embodiment, it is possible to provide a strain detection device 100 that can suppress the increase in weight of the frame 110 including the housing 111 and the cover 112, and can suppress the deformation of the cover 112 of the frame 110 having a sealed structure that accommodates the circuit board 150 and the battery 140, thereby improving the strain detection accuracy of the tire T.

[0041] In addition, in the strain detection device 100 of this embodiment, Figures 2 to 5As shown, the reinforcing portion 112 c of the cover 112 includes a plurality of ribs 112 d extending radially from a central portion of a lower surface of the top plate portion 112 b toward an outer edge portion.

[0042] With such a configuration, according to the strain detection device 100 of the present embodiment, the mechanical strength of the cover 112 with respect to the uniformly distributed load caused by the differential pressure can be improved by using the plurality of ribs 112d, thereby suppressing deformation of the cover 112. In addition, by using the plurality of ribs 112d to improve the mechanical strength of the cover 112, the portion of the top plate portion 112b where the reinforcement portion 112c is not provided can be made thinner, thereby suppressing an increase in the weight of the cover 112. In addition, by having the cover 112 have three or more ribs 112d, the stress distribution of the cover 112 can be made more uniform, thereby suppressing deformation.

[0043] In addition, in the strain detection device 100 of this embodiment, Figure 3 As shown, the reinforcing portion 112 c of the cover 112 may include a cylindrical protrusion 112 e provided on the lower surface of the top plate portion 112 b and concentric with the peripheral wall portion 112 a .

[0044] With such a configuration, according to the strain detection device 100 of this embodiment, the cylindrical convex portion 112e can be used to reinforce the center portion of the top plate portion 112b of the cover 112 where the deformation caused by the uniformly distributed load generated by the differential pressure is the largest. As a result, the stress distribution when the uniformly distributed load acts on the cover 112 can be made more uniform.

[0045] In addition, in the strain detection device 100 of this embodiment, Figure 4 As shown, the protruding height h of the plurality of ribs 112 d of the cover 112 gradually decreases from the center toward the outer edge of the top plate portion 112 b.

[0046] With such a configuration, according to the strain detection device 100 of the present embodiment, the mechanical strength of the rib 112d relative to the above-mentioned uniformly distributed load acting on the top plate portion 112b of the cover 112 is higher at the center portion than at the peripheral portion of the top plate portion 112b. Thus, the center portion of the top plate portion 112b, which has the largest deformation amount when the above-mentioned uniformly distributed load acts, can be reinforced by the rib 112d having a higher mechanical strength at the center portion than at the peripheral portion. Thus, the stress distribution of the cover 112 can be made more uniform, and the deformation of the top plate portion 112b of the cover 112 can be more effectively suppressed. In addition, by gradually reducing the protruding height h of the rib 112d toward the outer edge of the top plate portion 112b, where the deformation amount decreases when the above-mentioned uniformly distributed load acts, the weight of the reinforcing portion 112c can be reduced, and the weight increase of the cover 112 can be suppressed.

[0047] In addition, in the strain detection device 100 of this embodiment, Figure 5As shown, the width w of the plurality of ribs 112 d of the cover 112 which is perpendicular to the radial direction of the cover 112 gradually decreases from the central portion toward the outer edge portion of the top plate portion 112 b .

[0048] With such a configuration, according to the strain detection device 100 of the present embodiment, the mechanical strength of the rib 112d relative to the above-mentioned uniformly distributed load acting on the top plate portion 112b of the cover 112 is higher at the center portion than at the peripheral portion of the top plate portion 112b. Thus, the center portion of the top plate portion 112b, which has the largest deformation amount when the above-mentioned uniformly distributed load acts, can be reinforced by the rib 112d having a higher mechanical strength at the center portion than at the peripheral portion. Thus, the stress distribution of the cover 112 can be made more uniform, and the deformation of the top plate portion 112b of the cover 112 can be more effectively suppressed. In addition, by gradually reducing the width w of the rib 112d toward the outer edge of the top plate portion 112b, where the deformation amount decreases when the above-mentioned uniformly distributed load acts, the weight of the reinforcing portion 112c can be reduced, and the weight increase of the cover 112 can be suppressed.

[0049] In addition, in the strain detection device 100 of this embodiment, Figure 6 As shown, the reinforcement portion 112 c of the cover 112 may include a conical convex portion 112 f having an upper surface of the top plate portion 112 b as a bottom surface and being concentric with the peripheral wall portion 112 a .

[0050] With such a configuration, according to the strain detection device 100 of the present embodiment, the protruding height of the conical convex portion 112f from the upper surface of the top plate portion 112b increases from the outer edge of the top plate portion 112b toward the center. Therefore, the mechanical strength of the conical convex portion 112f relative to the above-mentioned uniformly distributed load acting on the cover 112 increases from the outer edge to the center of the top plate portion 112b. By reinforcing the top plate portion 112b of the cover 112 with such a conical convex portion 112f, the stress distribution when the above-mentioned uniformly distributed load acts on the cover 112 can be made more uniform, and the deformation of the cover 112 can be more effectively suppressed.

[0051] In addition, in the strain detection device 100 of the present embodiment, the reinforcement portion 112c of the cover 112 may include Figure 7 The front plane is shown to fill the lattice structure 112g.

[0052] With such a configuration, according to the strain detection device 100 of the present embodiment, deformation of the cover 112 can be suppressed by reinforcing the top plate portion 112b of the cover 112 with the lattice structure 112g. In addition, by forming the reinforcing portion 112c with the lattice structure 112g having a plurality of gaps, an increase in the volume of the cover 112 can be suppressed, thereby suppressing an increase in the weight of the cover 112.

[0053] In addition, in the strain detection device 100 of this embodiment, Fig.10As shown, the housing 111 can include: a cylindrical portion 111c; a bottom wall 111b that closes the lower end of the cylindrical portion 111c; and a plurality of supporting protrusions 111e that protrude radially inward from the inner circumference of the cylindrical portion 111c and support the plurality of ribs 112d of the cover 112.

[0054] With such a configuration, according to the strain detection device 100 of the present embodiment, the ends of the ribs 112d adjacent to the peripheral wall portion 112a of the cover 112 can be supported from below by the supporting protrusions 111e of the housing 111. Thus, the deformation of the ribs 112d when the uniform load acts on the cover 112 can be suppressed, and the deformation of the cover 112 can be suppressed. In addition, the cylindrical portion 111c of the housing 111 has a higher mechanical strength against the uniform load caused by the differential pressure than the disc-shaped top plate portion 112b of the cover 112, so that the portion where the cylindrical protrusions 112e are not provided can be thinned, thereby suppressing the increase in the weight of the housing 111.

[0055] As described above, according to the present embodiment, a strain detection device 100 can be provided, which can suppress the increase in weight of the frame 110 including the outer shell 111 and the cover 112, and can suppress the deformation of the cover 112 of the frame 110 having a sealed structure that accommodates the circuit substrate 150 and the battery 140, thereby improving the strain detection accuracy of the tire T.

[0056] Although the embodiments of the strain detection device of the present invention have been described above, the strain detection device of the present invention is not limited to the above-described embodiments, and additions, omissions, substitutions, and other changes in configuration may be made without departing from the spirit of the present invention. Explanation of symbols

[0057] 100 strain detection device 111 Shell 111a Opening 111b Bottom wall 111c Cylinder 111d Interior Space 111e Support projection 112 Cover 112a Peripheral wall 112b Top plate 112c Reinforcement 112d Rib 112e cylindrical convex part 112f Conical convex part 112g Lattice structure 120 Strain Sensor 140 battery 150 circuit board DA maximum deformation EA elastic adhesive T Tire Ti inner surface wWidth hProtrusion height ΦOuter diameter.

Claims

1. A strain detection device, comprising: a housing fixed to the inner circumferential surface of a tire by an elastic adhesive; a strain sensor mounted on the outer side of the bottom wall of the housing to detect the strain of the tire via the elastic adhesive; a circuit board and a battery housed in an internal space of the housing; and a resin cover that closes an opening of the housing on the side opposite to the bottom wall to seal the internal space, wherein the strain detection device is characterized in that: The cover comprises: a cylindrical peripheral wall portion; a disc-shaped top plate portion closing an upper end of the peripheral wall portion; and a reinforcing portion protruding from the top plate portion, The volume of the cover is 15% or more and less than 40% of the volume of the cylinder including the upper surface of the top plate portion, the outer peripheral surface of the peripheral wall portion, and the bottom surface of the peripheral wall portion, The maximum deformation amount of the top plate portion of the cap in the central axis direction of the peripheral wall portion caused by the differential pressure between the internal pressure of the internal space of the housing sealed by the cap and the air pressure of the tire is 4.1% or less of the outer diameter of the cap.

2. The strain detection device according to claim 1, characterized in that: The reinforcing portion includes a plurality of ribs extending in a radial direction from a central portion of a lower surface of the top plate portion toward an outer edge portion.

3. The strain detection device according to claim 2, characterized in that: The reinforcing portion includes a cylindrical protrusion provided on the lower surface of the top plate portion and concentric with the peripheral wall portion.

4. The strain detection device according to claim 2, characterized in that: The protruding heights of the plurality of ribs gradually decrease from the center toward the outer edge of the top plate portion.

5. The strain detection device according to claim 2, characterized in that: The width of the plurality of ribs perpendicular to the radial direction gradually decreases from a central portion toward an outer edge portion of the top plate portion.

6. The strain detection device according to claim 1, characterized in that: The reinforcing portion includes a conical convex portion having an upper surface of the top plate portion as a bottom surface and being concentric with the peripheral wall portion.

7. The strain detection device according to claim 1, characterized in that: The reinforcement portion includes a lattice structure of a positive plane filling shape.

8. The strain detection device according to claim 2, characterized in that: The housing includes: a cylindrical portion; a bottom wall that closes a lower end of the cylindrical portion; and a plurality of supporting protrusions that protrude radially inward from an inner circumferential surface of the cylindrical portion and support the plurality of ribs of the cover.

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