Device for detecting loose screws

Abstract

To provide a looseness detector which can detect looseness of a screw member preferably.SOLUTION: A substrate 100 provided with an acceleration sensor 110 is fixed to a ceiling surface 32 of a nut cap 30 to be attached to a wheel nut. Fixing the substrate 100 so that the acceleration sensor 110 is located at a position of a rotation axis O of the wheel nut allows looseness of the wheel nut to be detected accurately based on a centrifugal acceleration detected by the acceleration sensor 110 regardless of an attachment position of the nut cap 30.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to a device for detecting loosening of a screw member. [Background technology]

[0002] JP 2017-529499 A (Patent Document 1) discloses a nut, particularly a wheel nut or axle nut for a vehicle, that has a recess in which a sensor element made of a piezoelectric element (pressure sensor) is disposed. The nut described in Patent Document 1 is said to detect loosening of the nut by a signal (sensor signal) from the sensor element. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Special Publication No. 2017-529499 Summary of the Invention [Problem to be solved by the invention]

[0004] In the nut described in Patent Document 1, loosening of the nut is detected by detecting changes in the internal stress of the nut. In order to detect loosening of a screw member such as a nut, it is conceivable to use an acceleration sensor. For example, in the case of screw members such as nuts (hub nuts) and bolts (hub bolts) that fasten a fastened member such as a wheel to a rotating body such as a hub (wheel hub), loosening of the screw member can be detected from changes in centrifugal acceleration (centrifugal force) applied to the screw member due to the rotation of the rotating body.

[0005] An object of the present disclosure is to provide a loosening detection device that can suitably detect loosening of a screw member. [Means for solving the problem]

[0006] The device for detecting loosening of a screw member according to the present disclosure is a device for detecting loosening of a screw member that includes an acceleration sensor that rotates in conjunction with the rotation of the screw member and detects acceleration applied along a detection axis that intersects with the rotation axis of the screw member. In the device for detecting loosening of a screw member, the acceleration sensor is fixed so as to be positioned on the rotation axis of the screw member.

[0007] In a screw loosening detector of this configuration, an acceleration sensor that rotates in conjunction with the rotation of the screw and detects acceleration applied along a detection axis that intersects with the rotation axis of the screw is fixed to be located on the rotation axis of the screw. Because the acceleration sensor is fixed to be located on the rotation axis of the screw, the position of the acceleration sensor does not change from the position of the rotation axis even when the screw is tightened (rotated about the rotation axis) during fastening. The position of the acceleration sensor can be kept constant when the screw is completely tightened, allowing for efficient detection of loosening of the screw.

[0008] For example, the acceleration sensor is preferably provided on a substrate, and the substrate is fixed so that the acceleration sensor is positioned on the rotation axis of the screw member. The acceleration sensor may be of a capacitance type, a piezoelectric type, a piezoresistive type, a frequency change type, or the like.

[0009] The screw loosening detector according to the present disclosure is a screw loosening detection device that detects the fastening state of a screw consisting of a hexagonal nut or a hexagonal bolt. The screw loosening detector includes a cap attached to the outer periphery of the hexagonal nut body or the outer periphery of the hexagonal bolt head, a circuit board on which an acceleration sensor is mounted, and a battery, with the circuit board and battery fixed to the side of the cap facing the outer periphery of the hexagonal nut body or the outer periphery of the hexagonal bolt head.

[0010] According to this configuration, the screw loosening detector comprises a cap attached to the outer periphery of the hexagonal nut body or the outer periphery of the hexagonal bolt head, a circuit board with an acceleration sensor, and a battery. The circuit board and battery are fixed to the side of the cap facing the outer periphery of the hexagonal nut body or the outer periphery of the hexagonal bolt head. Because the circuit board with the acceleration sensor and the battery are fixed to the side of the cap, the circuit board and battery can be placed in the gap between the cap and the outer periphery of the hexagonal nut body or the outer periphery of the hexagonal bolt head.

[0011] Preferably, the side of the cap may be formed with a plurality of support portions that abut against the outer periphery of the body of the hexagonal nut or the outer periphery of the head of the hexagonal bolt, and the support portions may abut against the outer periphery of the body or the outer periphery of the head to form spaces for arranging the substrate and battery between the outer periphery of the body or the outer periphery of the head and the side of the cap. In this case, the support portions may abut against at least three of the outer periphery of the body of the hexagonal nut or the outer periphery of the head of the hexagonal bolt, each of which has a central angle of 120 degrees, and the substrate and battery may be arranged in different spaces partitioned by the support portions. [Effects of the Invention]

[0012] According to the present disclosure, it is possible to provide a loosening detection device that can suitably detect loosening of a screw member. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a diagram showing a vehicle equipped with a fastening member detection device according to an embodiment of the present invention; [Figure 2] FIG. 2 is a cross-sectional view of a fastening portion of a wheel. [Figure 3] FIG. [Figure 4] FIG. 2 is a diagram showing an example of a substrate in the present embodiment. [Figure 5] 10A, 10B, and 10C are diagrams showing the relationship between centrifugal acceleration and acceleration detected by an acceleration sensor. [Figure 6]FIG. 10 is a diagram illustrating the influence of the position of the acceleration sensor. [Figure 7] FIG. [Figure 8] 10 is a diagram showing a fixing structure of a substrate according to Modification 1. FIG. [Figure 9] FIG. 10 is a diagram showing a state in which the substrate is rotated in the loosening direction. [Figure 10] 10 is a diagram showing a fixing structure of a substrate in Modification 2. FIG. [Figure 11] 13 is a diagram showing a fixing structure of a substrate in Modification 3. FIG. [Figure 12] FIG. 10 is a cross-sectional view of a wheel nut according to a second embodiment. [Figure 13] 13 is a diagram showing a fixing structure of a substrate in Modification 4. FIG. [Figure 14] FIG. 11 is a perspective view of a nut cap according to a third embodiment. [Figure 15] FIG. [Figure 16] FF cross-sectional view showing the nut cap attached to the wheel nut. [Figure 17] FIG. [Figure 18] FIG. 13 is a bottom view of a nut cap according to a fifth modified example. [Figure 19] FIG. 13 is a bottom view of a nut cap according to a sixth modified example. [Figure 20] FIG. 13 is a bottom view of a nut cap according to Modification 7. [Figure 21] FIG. 13 is a bottom view of a nut cap according to Modification 8. [Figure 22] FIG. 20 is a bottom view of a nut cap according to Modification 9. [Figure 23] FIG. 10 is a diagram illustrating an example of a wheel bolt loosening detector. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals, and description thereof will not be repeated.

[0015] (Embodiment 1) FIG. 1 is a side view showing a wheel 10 fastened by a screw member (wheel nut) 20 according to this embodiment (embodiment 1). The wheel 10 includes a wheel 11 and a tire 12 attached to the wheel 11. The wheel 11 is provided with a wheel hole 11a (see FIG. 2) through which a hub bolt 25 provided on a hub (wheel hub) 40 of a vehicle is inserted, and the wheel 11 is fastened to the hub by threading a plurality of wheel nuts 20 (five in FIG. 1) onto the hub bolt 25. The number of wheel nuts 20 is not limited to the above example and may be, for example, four, six, eight, or ten.

[0016] The wheel 11 (wheel 10) is fastened to the hub 40 by a wheel nut 20 on a predetermined pitch circle (see the dashed line in FIG. 1). The pitch circle diameter (PCD) may be any value, for example, 114.3 mm. The wheel nut 20 may be 275 mm. , Ho Nut caps (nut covers) 30 are attached to the wheel nuts 20 to protect them and to enhance their design. In this embodiment, nut caps are attached to all of the wheel nuts 20. The symbol O denotes the rotation axis (center of rotation) of the hub 40.

[0017] FIG. 2 is a cross-sectional view of the fastening portion of the wheel 11. Note that FIG. 2 shows a cross-sectional view with the nut cap 30 attached, and the threaded portion (thread) is omitted. As shown in FIG. 2, the hub bolt 25 is provided on the hub 40 (the hub bolt 25 is fixed to the hub 40). The hub bolt 25 is inserted into the wheel hole 11a of the wheel 11, and the wheel nut 20 is screwed onto the hub bolt 25, thereby fastening the wheel 11 to the hub 40. Note that the wheel nut 20 is a hexagonal nut.

[0018] The nut cap 30 is fixed to the outer periphery of the wheel nut 20. As a result, the nut cap 30 rotates in conjunction with the rotation of the wheel nut 20 (integrally with the wheel nut 20). In this embodiment, the inner surface (inner side surface) 31 of the nut cap 30 fits into the outer periphery of the wheel nut 20 (the inner surface 31 of the nut cap 30 fits into the outer periphery of the wheel nut 20), thereby fixing the nut cap 30 to the outer periphery of the wheel nut. FIG. 3 is a perspective view of the nut cap 30. As shown in FIGS. 2 and 3, the nut cap 30 has a space C formed by the inner surface 31 and a ceiling surface 32, and a substrate 100 having an acceleration sensor 110 mounted thereon is fixed to the ceiling surface 32. Note that it is sufficient that the nut cap 30 with the substrate 100 fixed to the ceiling surface 32 is attached to at least one wheel nut 20; nut caps without the substrate 100 may be attached to the other wheel nuts 20.

[0019] 4 is a diagram showing an example of a substrate 100 in this embodiment. Substrate 100 is a printed circuit board (printed substrate) 101 on which an acceleration sensor 110, a control device (control circuit) 120, a communication device (communication circuit) 130, etc. are mounted. Acceleration sensor 110 may be of a capacitance type, a piezoelectric type, a piezo-resistance type, a frequency change type, etc., and may output, for example, a voltage value, a change in capacitance or resistance value caused by the displacement of a movable electrode or weight serving as an acceleration detection unit.

[0020] The control device 120 includes, for example, a CPU (Central Processing Unit) and a memory, and detects the fastening state (looseness) of the wheel nuts 20 based on the acceleration detected by the acceleration sensor 110. The communication device 130 is mounted on the printed circuit board 101 as a communication circuit including an antenna, a mixer, a modem, etc., for communication with an ECU (Electronic Control Unit) provided in the vehicle.

[0021] In this embodiment, the centrifugal acceleration (centrifugal force) applied to the wheel nut 20 (nut cap 30) due to the rotation of the wheel 11 (wheel 10) is detected using an acceleration sensor 110 provided on the substrate 100, and the fastening state (looseness) of the wheel nut 20 is detected based on the acceleration detected by the acceleration sensor 110. FIG. 5 is a diagram showing the relationship between centrifugal acceleration and the acceleration Gx detected by the acceleration sensor 110. In FIG. 5, the X-axis represents the acceleration detection axis of the acceleration sensor 110, and extends in a direction intersecting with the rotation axis O. FIG. 5(A) shows a state in which the wheel nut 20 has been fastened with a predetermined fastening torque. FIGS. 5(B) and 5(C) show states in which the wheel nut 20 has been rotated in the loosening direction (counterclockwise).

[0022] Centrifugal acceleration due to the rotation of the wheel 11 is applied to the wheel nut 20 (the nut cap 30 attached to the wheel nut 20). Since the centrifugal acceleration acts in a radial direction from the rotation axis O of the hub 40 (the center of rotation of the wheel 11), which is centered on the rotation axis O, the centrifugal acceleration acts in the direction of the dashed arrows in Figures 5(A), (B), and (C) regardless of the position of the wheel nut 20 (nut cap 30) on the pitch circle. In Figure 5, arrow Gc indicates the vector of centrifugal acceleration, and the vector Gc always points in the radial direction centered on the rotation axis O.

[0023] In FIG. 5A, which shows a state in which the wheel nut 20 has been tightened with a predetermined tightening torque, the X-axis component (the component in the detection axis direction of the acceleration sensor 110) of the vector Gc (centrifugal acceleration) is detected by the acceleration sensor 110 as +Gx1. When the wheel nut 20 rotates in the loosening direction (counterclockwise) and the wheel nut 20 loosens, reaching the state shown in FIG. 5B, the nut cap 30 moves in conjunction with the rotation of the wheel nut 20, so the X-axis component (the component in the detection axis direction of the acceleration sensor 110) of the vector Gc (centrifugal acceleration) is detected by the acceleration sensor 110 as +Gx2. When the wheel nut 20 further rotates in the loosening direction from the state shown in FIG. 5B and reaches the state shown in FIG. 5C, the X-axis component (the component in the detection axis direction of the acceleration sensor 110) of the vector Gc (centrifugal acceleration) is detected by the acceleration sensor 110 as -Gx3. In this way, by detecting the magnitude (or direction (sign)) of the X-axis component (the component in the detection axis direction of the acceleration sensor 110) of the centrifugal acceleration Gc applied to the wheel nut 20 (nut cap 30), it is possible to detect loosening of the wheel nut 20. In this way, in this embodiment, the nut cap 30 equipped with the acceleration sensor 110 functions as a device for detecting loosening of the screw member (wheel nut 20). Note that although FIG. 5 illustrates the acceleration sensor 110 having one acceleration detection axis (X-axis), the acceleration detection axis may be two or more.

[0024] FIG. 6 is a diagram illustrating the influence of the position of the acceleration sensor 110. In FIG. 6, symbol P denotes the rotation axis (center axis of the female thread) of the wheel nut 20 (threaded member) to which the nut cap 30 is fixed. In FIG. 6, when the acceleration detection unit of the acceleration sensor 110 is positioned on the rotation axis P of the wheel nut 20, the distance between the rotation axis O of the wheel 11 and the acceleration sensor 110 is R. The distance between the acceleration detection unit of acceleration sensor 110-1, which is positioned above the rotation axis P, and the rotation axis O is R2, which is longer than R. Furthermore, the distance between the acceleration detection unit of acceleration sensor 110-2, which is positioned below the rotation axis P, and the rotation axis O is R1, which is shorter than R.

[0025] The centrifugal acceleration applied to the acceleration sensor 110 due to the rotation of the wheel 11 is proportional to the distance from the rotation axis O to the acceleration sensor. Therefore, when the wheel 11 is rotating at a predetermined rotational speed, the centrifugal acceleration applied to the acceleration sensor 110-1 is the largest and the centrifugal acceleration applied to the acceleration sensor 110-2 is the smallest.

[0026] When the position of the acceleration detection section of the acceleration sensor 110 on the substrate 100 fixed to the ceiling surface 32 of the nut cap 30 deviates from the position of the rotation axis P, the distance between the rotation axis O and the acceleration sensor 110 changes depending on the attachment position of the nut cap 30. Depending on the attachment position of the nut cap 30, the distance between the rotation axis O and the acceleration sensor 110 becomes, for example, R1 or R2 as shown in FIG. 6, and therefore the centrifugal acceleration acting on the acceleration sensor 110 changes.

[0027] In contrast, if the acceleration detection portion of the acceleration sensor 110 is located on the rotation axis P on the substrate 100 fixed to the ceiling surface 32 of the nut cap 30, the acceleration detection portion of the acceleration sensor 110 will be located on the rotation axis P regardless of the attachment position of the nut cap 30. As a result, the distance between the rotation axis O and the acceleration sensor 110 will be R regardless of the attachment position of the nut cap 30. Therefore, the centrifugal acceleration applied to the acceleration sensor 110 will be the same regardless of the attachment position of the nut cap 30.

[0028] In this embodiment, the substrate 100 is fixed to the ceiling surface 32 of the nut cap 30 so that the acceleration sensor 110 provided on the substrate 100 is positioned on the rotation axis P. This keeps the distance between the rotation axis O and the acceleration sensor 110 constant regardless of the mounting position of the nut cap 30, making it possible to accurately detect looseness of the wheel nut 20.

[0029] 7 is a bottom view of the nut cap 30 (view A in FIG. 3). The nut cap 30 has an inner surface 31 and a ceiling surface 32, which form a space C. The inner surface 31 fits onto the outer peripheral surface of the wheel nut 20, thereby attaching the nut cap 30 to the wheel nut 20. A substrate 100 is fixed to the ceiling surface 32 by adhesive or the like.

[0030] 7, the symbol P indicates the rotation axis (position of the rotation axis) of the wheel nut 20 when the nut cap 30 is attached to the wheel nut 20. The substrate 100 is fixed to the ceiling surface 32 so that the acceleration sensor 110 provided on the substrate 100 is positioned on the rotation axis P. In particular, it is preferable to fix the substrate 100 to the ceiling surface 32 so that the acceleration detection portion of the acceleration sensor 110 is positioned on the rotation axis P.

[0031] According to this embodiment, the substrate 100 is fixed to the ceiling surface 32 of the nut cap 30 so that the acceleration sensor 110 is positioned on the rotation axis P of the wheel nut 20. Therefore, regardless of the mounting position of the nut cap 30, the distance between the rotation axis O of the wheel 11 and the acceleration sensor 110 can be kept constant, so that loosening of the wheel nut 20 can be detected with high accuracy.

[0032] (Variation 1) In the above embodiment, the substrate 100 is fixed to the ceiling surface 32 of the nut cap 30 by adhesive or the like. In the first modification, the substrate 100 is fixed to the ceiling surface 32 of the nut cap 30 by using a machine screw (basic).

[0033] FIG. 8 is a diagram showing a fixing structure of the substrate 100 according to the first modification. Two screw holes 321 and 322 are provided in the ceiling surface 32 of the nut cap 30, into which machine screws (screws) S are threaded. The substrate 100 (printed circuit board 101) is formed with insertion holes 102 and 103, through which the machine screws S are inserted, at positions corresponding to the screw holes 321 and 322. The insertion hole 102 has a diameter slightly larger than the thickness (nominal diameter) of the shank of the machine screw S. On the other hand, the insertion hole 103 is an elongated hole to improve assembly, taking into account variations (tolerances) in the screw holes 321 and 322 and the insertion holes 102 and 103. The machine screws S are inserted into the insertion holes 102 and 103 and threaded into the screw holes 321 and 322, thereby fixing the substrate 100 to the ceiling surface 32 at two points.

[0034] The elongated hole shape of one of the insertion holes 103 is shaped (tapered) so that the spacing between the long sides becomes shorter when the substrate 100 rotates around the insertion hole 102 in the direction in which the wheel nut 20 loosens (the loosening direction indicated by the arrow in FIG. 8). FIG. 9 is a diagram showing the state in which the substrate 100 has rotated in the loosening direction. As shown in FIG. 9, when the fastening by the machine screw S loosens and the substrate 100 rotates in the loosening direction, the shank of the machine screw S abuts against the part of the insertion hole 103 where the spacing between the long sides is shorter and bites into the substrate 100, thereby fixing the substrate 100.

[0035] According to this first modification, even if one of the insertion holes (insertion hole 103) is an elongated hole, when the fastening of the machine screw S loosens, the shank of the machine screw S abuts against the portion of the long side with the narrow spacing and bites into the board 100, thereby fixing the board 100. Furthermore, the elongated shape of the insertion hole is shaped (tapered) so that the spacing between the long sides becomes shorter when the board 100 rotates in the direction in which the wheel nut 20 loosens (the loosening direction indicated by the arrow in FIG. 8 ). This prevents the shank of the machine screw S from rotating in the loosening direction beyond the position where it abuts against the portion of the long side of the insertion hole 103 with the narrow spacing. This prevents the acceleration sensor 110 from moving in the loosening direction of the wheel nut 20, which would otherwise result in an erroneous detection of loosening of the wheel nut 20. When assembling the substrate 100 to the ceiling surface 32 (when fixing using the small screw S), the substrate 100 may be fixed to the ceiling surface 32 so that the shank of the small screw S abuts against the part of the long side of the insertion hole 103 with the shorter spacing (as shown in Figure 9).

[0036] (Variation 2) Fig. 10 is a diagram showing a fixing structure of substrate 100 in Modification 2. Modification 2 is obtained by changing insertion hole 103 in Modification 1 to insertion hole 104. As shown in Fig. 10, insertion hole 104 is formed as an elongated hole to improve the ease of assembling substrate 100. The elongated shape of insertion hole 104 is such that the long side of the elongated hole extends in the direction of straight line L connecting screw hole 321 and screw hole 322.

[0037] According to this variant example 2, in order to improve the assembly of the substrate 100, even if the insertion hole 104 is an elongated hole, if the fastening by the small screw S becomes loose, the shank of the small screw S abuts against the long side of the insertion hole 104, thereby preventing the substrate 100 from rotating around the insertion hole 102.

[0038] (Variation 3) Fig. 11 is a diagram showing a fixing structure of the substrate 100 in Modification 3. In Modification 3, in addition to the fixing structure of the substrate 100 of Modification 1, a positioning convex portion is formed on the ceiling surface 32 of the nut cap 30. In Fig. 11, a convex portion (rib) 35 and a convex portion (rib) 36 that abut against the side surface of the substrate 100 are formed on the ceiling surface 32. In Fig. 11, convex portion 35 is formed at a position that abuts against the upper side surface (upper edge) of the substrate 100 (printed circuit board 101), and convex portion 36 is formed at a position that abuts against the right side surface (right edge) of the substrate 100.

[0039] The protrusions 35 and 36 are formed at positions where, when the insertion hole 102 overlaps with the screw hole 321 and the center of the insertion hole 103 overlaps with the screw hole 322, the protrusion 35 abuts against the upper edge of the substrate 100 and the protrusion 36 abuts against the right edge of the substrate 100. This allows the protrusions 35 and 36 to function as positioning members that position the substrate 100. Furthermore, because the protrusions 35 and 36 abut on two edges of the substrate 100, it is also possible to prevent the substrate 100 from rotating about the insertion hole 102.

[0040] In variant example 3, the convex portion formed on the ceiling surface 32 only needs to abut two sides of the substrate 100; for example, instead of convex portion 36, convex portion 37 may be formed that abuts the left side (left side surface) of the substrate 100.

[0041] (Embodiment 2) 12 is a cross-sectional view of a wheel nut 50 according to the second embodiment. In the first embodiment, a substrate 100 provided with an acceleration sensor 110 is fixed to the ceiling surface 32 of the nut cap 30 to constitute a screw member loosening detector. stomach In the second embodiment, the wheel nut 20 in the first embodiment is configured as a cap nut, and a substrate 100 is fixed to the top surface of the cap nut, thereby being used as a screw loosening detector.

[0042] 12, wheel nut 50 is a cap nut (cap nut) having a hexagonal nut configuration with one side closed, and includes ceiling surface 52. A threaded portion (internal threaded portion) 55 that screws onto hub bolt 25 is formed on the main body of wheel nut 50, and space C is formed between inner surface 51 and ceiling surface 52. A substrate 100 having an acceleration sensor 110 is fixed to ceiling surface 52. As in the first embodiment, substrate 100 is fixed to ceiling surface 52 so that acceleration sensor 110 is positioned on rotation axis P of wheel nut 50. Note that the method of fixing (attaching) substrate 100 to ceiling surface 52 may be adhesive, which may be the same as in the first to third modifications described above.

[0043] If the position of the acceleration detection unit of the acceleration sensor 110 deviates from the position of the rotation axis P, the distance between the rotation axis O and the acceleration sensor 110 will change depending on the tightening completion position of the wheel nut 50, as explained using Figure 6. However, if the acceleration detection unit of the acceleration sensor 110, which is fixed to the top surface 52 of the wheel nut 50, is located on the rotation axis P, the acceleration detection unit of the acceleration sensor 110 will be located on the rotation axis P regardless of the tightening completion position of the wheel nut 50, and the distance between the rotation axis O and the acceleration sensor 110 will not change. As a result, regardless of the tightening completion position of the wheel nut 50, the distance between the rotation axis O and the acceleration sensor 110 remains constant, making it possible to accurately detect loosening of the wheel nut 50.

[0044] (Variation 4) 13 is a diagram showing a fixing structure of the substrate 100 in Modification 4. In Modification 4, resin M is injected into the space C by potting, insert molding, molding, or the like to fix the substrate 100 to the ceiling surface 52 and seal the substrate 100. The resin M may be, for example, urethane or epoxy resin.

[0045] According to the fourth modification, the substrate 100 is fixed to the ceiling surface 52 and sealed with the resin M, so that the substrate 100 can be protected.

[0046] (Embodiment 3) Fig. 14 is a perspective view of a nut cap 60 according to a third embodiment. Fig. 15 is a bottom view of the nut cap 60 (view A in Fig. 14). Fig. 16 is a cross-sectional view taken along line FF in Fig. 15, showing the nut cap 60 attached to the wheel nut 20. As shown in Figs. 14 and 15, the nut cap 60 is hexagonal and has an inner surface (inner side surface) 61 and a ceiling surface 62. 61 and ceiling surface 62 form a space C. In Fig. 15, the dashed dotted line represents the outer periphery (outer periphery surface) of the wheel nut 20 (see Fig. 2). Ribs (protrusions) 63a, 63b that come into contact with the outer periphery surface of the wheel nut 20 are formed on the inner surface 61 of the nut cap 60. The ribs 63a, 63b formed on the inner surface 61 come into contact with and fit into the outer periphery surface of the wheel nut 20 (the outer periphery surface of the main body of the wheel nut 20), thereby attaching the nut cap 60 to the wheel nut 20. Note that the ribs 63a, 63b are not shown in Fig. 14.

[0047] The ribs 63a, 63b are formed so as to abut on three outer peripheral surfaces of the wheel nut 20, the three surfaces being spaced apart by a central angle of 120°. In this embodiment, the inner surface 61 of the nut cap 60 has six surfaces 61-1 to 61-6 that face the outer peripheral surface of the wheel nut 20, and the ribs 63a, 63b are formed on three surfaces 61-1, 61-3, 61-5, the three surfaces being spaced apart by a central angle of 120°. The ribs 63a and 63b are formed on one surface of the inner surface 61, and in this embodiment, the ribs 63a and 63b form a support portion 63.

[0048] As shown in FIGS. 15 and 16, a substrate 200 provided with an acceleration sensor is fixed to the inner surface 61 (surface 61-2) of the nut cap 60. Also, as shown in FIG. 15, a battery 300 is fixed to the inner surface 61 (surface 61-4). The inner surfaces 61 (surface 61-2) and 61-4 are surfaces facing the outer periphery (outer periphery) of the wheel nut 20 and correspond to the "side surfaces" in this disclosure. Similar to the substrate 100, an acceleration sensor is mounted on the substrate 200. The acceleration detection axis of the acceleration sensor provided on the substrate 200 is oriented in a direction that allows it to detect centrifugal acceleration applied to the wheel nut 20 due to the rotation of the wheel 11. Also, the battery 300 may be, for example, a button-type battery.

[0049] The substrate 200 and the battery 300 are fixed, for example, by adhesive, to the inner surface 61 (surfaces 61-2 and 61-4) on which the support portions 63 are not formed. The substrate 200 and the battery 300 may be fixed and sealed using resin, as in Variation 4. When the support portions 63 abut the outer peripheral surface of the wheel nut 20, a space is formed between the outer peripheral surface of the wheel nut 20 and the inner surface 61 (surfaces 61-2 and 61-4) of the nut cap 60, and the substrate 200 and the battery 300 are fixed to the inner surface 61 so that they are located in this space. The support portions 63 are located between the substrate 200 and the battery 300 on the inner surface 61 of the nut cap 60, and the space in which the substrate 200 is located and the space in which the battery 300 is located are separated by the support portions 63. The substrate 200 and the battery 300 are connected by lead wires (not shown).

[0050] 15, on the inner surface 61 of the nut cap 60, the support portion 63 is not formed, and on surface 61-6, which is the surface to which the substrate 200 and the battery 300 are not fixed, the support portion 63 (ribs 63a, 63b) may be formed as shown by the dashed line. Furthermore, when the support portion 63 is not formed on surface 61-6, for example, a switch for turning on / off the power supply from the battery 300 to the substrate 200 may be provided, and a resilient member (spring member) 64 shown in FIG. 17 may be provided.

[0051] Figure 17 is a partial perspective view of the nut cap 60 as seen from the direction of arrow B in Figure 15. A tongue-shaped spring member 64 is formed on surface 61-6 of the inner surface 61 of the nut cap 60. The spring member 64 may be, for example, a leaf spring. The spring member 64 abuts against the outer peripheral surface of the wheel nut 20, and its resilience prevents the nut cap 60 from easily coming off the wheel nut 20. A stopper portion 95 is formed on surface 61-6 adjacent to the spring member 64, preventing the spring member 64 from being bent beyond an allowable range.

[0052] According to the third embodiment, a plurality of support portions 63 that abut against the outer periphery (outer peripheral surface) of the wheel nut 20 are formed on the inner surface 61 of the nut cap 60, and a space for arranging the substrate 200 and the battery 300 is formed between the outer peripheral surface of the wheel nut 20 and the inner surface 61 of the nut cap 60. Therefore, the substrate 200 and the battery 300 can be fixed to the inner surface 61, and the substrate 200 and the battery 300 can be arranged in the gap (space) between the nut cap 60 and the wheel nut 20.

[0053] The support portion 63 is formed to abut at least three of the outer peripheral surfaces of the wheel nut 20, each having a central angle of 120°, and the nut cap 60 is supported at at least three points, allowing the nut cap 60 to be attached to the wheel nut 20 well.

[0054] (Variation 5) Fig. 18 is a bottom view of a nut cap 70 in Modification 5. While the nut cap 60 of Embodiment 3 is hexagonal, the nut cap 70 is triangular. The nut cap 70 has an inner surface (inner side surface) 71 and a ceiling surface 72, and the inner surface 71 and the ceiling surface 72 form a space C. In Fig. 18, the dashed dotted line represents the outer periphery (outer periphery) of the wheel nut 20 (see Fig. 2). The inner surface 71 of the nut cap 70 abuts against the outer periphery of the wheel nut 20 at abutment portions 71a, 71b, and 71c. These abutment portions 71a to 71c abut against and fit into the outer periphery of the wheel nut 20 (the outer periphery of the main body of the wheel nut 20), thereby attaching the nut cap 70 to the wheel nut 20.

[0055] When nut cap 70 is attached to wheel nut 20, space C is divided into space C1 between contact portions 71a and 71b, space C2 between contact portions 71a and 71c, and space C3 between contact portions 71b and 71c. Substrate 200 having an acceleration sensor mounted thereon is adhesively fixed to inner surface 71 facing space C1, and battery 300 is adhesively fixed to inner surface 71 facing space C2.

[0056] In this fifth modification, similarly to the third embodiment, the circuit board 200 and the battery 300 can be placed in the gap (space) between the nut cap 70 and the wheel nut 20.

[0057] (Variation 6) FIG. 19 is a bottom view of a nut cap 80 in Modification 6. The nut cap 80 is triangular and has an inner surface (inner side surface) 81 and a ceiling surface 82, with the inner surface 81 and the ceiling surface 82 forming a space C. In FIG. 18, the dashed dotted line represents the outer periphery (outer periphery) of the wheel nut 20 (see FIG. 2). Ribs (protrusions) 83a and 83b that come into contact with the outer periphery of the wheel nut 20 are formed on each side of the inner surface 81 of the nut cap 80. In Modification 6, the ribs 83a and 83b form a support portion 83. The ribs 83a and 83b are formed so that a corner of the outer periphery of the wheel nut 20 is located between the ribs 83a and 83b.

[0058] The nut cap 80 is attached to the wheel nut 20 by the support portions 83 (ribs 83a, 83b) abutting against and fitting to the outer peripheral surface of the wheel nut 20 (the outer peripheral surface of the main body of the wheel nut 20). When the nut cap 80 is attached to the wheel nut 20, the support portions 83 divide the space C into three spaces. Of the three divided spaces, the substrate 200 is fixed to the inner surface 81 of one space, and the battery 300 is fixed to the inner surface 81 of the other space. In this sixth modification, as in the third embodiment, the substrate 200 and the battery 300 can be placed in the gap (space) between the nut cap 80 and the wheel nut 20.

[0059] (Variation 7) FIG. 20 is a bottom view of a nut cap 90 in Modification 7. The nut cap 90 is hexagonal and has an inner surface (inner side surface) 91 and a ceiling surface 92, with the inner surface 91 and ceiling surface 92 forming a space C. In FIG. 19, the dashed dotted line represents the outer periphery (outer periphery) of the wheel nut 20 (see FIG. 2). Ribs (protrusions) 93a, 93b that come into contact with the outer periphery of the wheel nut 20 are formed on each of the two opposing inner surfaces 91 of the nut cap 90. In Modification 7, the ribs 93a and 93b form a support portion 93. The ribs 93a and 93b are formed so that the corners of the outer periphery of the wheel nut 20 are positioned between the ribs 93a and 93b.

[0060] The nut cap 90 is attached to the wheel nut 20 by the support portions 93 (ribs 93a, 93b) abutting against and fitting into the outer peripheral surface of the wheel nut 20 (the outer peripheral surface of the main body of the wheel nut 20). When the nut cap 90 is attached to the wheel nut 20, the space C is divided into two spaces by the support portions 93. Of the two divided spaces, the substrate 200 is fixed to the inner surface 91 of one space, and the battery 300 is fixed to the inner surface 91 of the other space. In this seventh modification, as in the third embodiment, the substrate 200 and the battery 300 can be placed in the gap (space) between the nut cap 90 and the wheel nut 20.

[0061] (Variation 8) FIG. 21 is a bottom view of a nut cap 400 in Modification 8. The nut cap 400 has an inner surface (inner side surface) 401 and a ceiling surface 402, and the inner surface 401 and the ceiling surface 402 form a space C. In FIG. 20, the dashed dotted line represents the outer periphery (outer periphery) of the wheel nut 20 (see FIG. 2). The nut cap 400 is hexagonal, and protrusions 403 are formed on three inner surfaces 401, each having a central angle of 120°, so as to abut against the outer periphery of the wheel nut 20. The protrusions 403 abut against and fit into the outer periphery of the wheel nut 20, thereby attaching the nut cap 400 to the wheel nut 20. In Modification 8, the protrusions 403 correspond to the "support portion" of the present disclosure.

[0062] When nut cap 400 is attached to wheel nut 20, space C is divided into three spaces by protrusions 403. Of the three divided spaces, substrate 200 is fixed to the inner surface 401 of one space, and battery 300 is fixed to the inner surface 401 of the other space. In this sixth modification, as in the third embodiment, substrate 200 and battery 300 can be placed in the gap (space) between nut cap 400 and wheel nut 20.

[0063] (Variation 9) FIG. 22 is a bottom view of a nut cap 500 in Modification 9. The nut cap 500 has a cylindrical outer shape and has an inner surface (inner side surface) 501 and a ceiling surface 502, with the inner surface 501 and the ceiling surface 502 forming a space C. In FIG. 21, the dashed dotted line represents the outer periphery (outer periphery) of the wheel nut 20 (see FIG. 2). The inner surface 501 of the nut cap 500 is formed with a wavy portion 503 into which corners of the outer periphery of the wheel nut 20 fit. The nut cap 500 is attached to the wheel nut 20 by fitting the corners of the outer periphery of the wheel nut 20 into this wavy portion 503. In Modification 9, the wavy portion 503 corresponds to the "support portion" of the present disclosure.

[0064] On the inner surface 501 of the nut cap 500, a flat portion is formed between adjacent wavy portions 503. By fixing the substrate 200 and the battery 300 to this flat portion, the substrate 200 and the battery 300 are disposed in the gap (space) between the flat portion and the outer periphery (outer periphery) of the wheel nut 20. In this ninth modification, as in the third embodiment, the substrate 200 and the battery 300 can be disposed in the gap (space) between the nut cap 500 and the wheel nut 20.

[0065] In the above embodiment and modified examples, the nut caps 30, 60, 70, 80, 90, 400, and 500, to which the substrates 100 and 200 having acceleration sensors are fixed, function as devices for detecting loosening of the screw member (wheel nut 20). However, when the screw member is a wheel bolt, a cap (bolt cap) attached to the head of the bolt may be used as a detector for detecting loosening of the screw member (wheel bolt).

[0066] Fig. 23 is a diagram showing an example of a detector for detecting looseness of a wheel bolt 600. In Fig. 22, a threaded hole 41 into which the wheel bolt 600 is threaded is formed in the hub 40, and the wheel 11 is fastened to the hub 40 by threading the threaded portion 600a of the wheel bolt 600 into the threaded hole 41 and tightening it.

[0067] 23, the dashed double-dashed line indicates a cap (bolt cap) attached to the head of wheel bolt 600, and has substantially the same configuration as any of nut caps 30, 60, 70, 80, 90, 400, and 500 described above. In this way, a cap (bolt cap) attached to the head of wheel bolt 600 may be used as a loosening detector for a screw member (wheel bolt). In this case, in a cap (bottle cap) equivalent to nut caps 60, 70, 80, 90, 400, and 500, board 200 and battery 300 are disposed in the gap (space) between the side of the cap (bolt cap) and the outer periphery of the head of wheel bolt 600.

[0068] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0069] 10 Wheel, 11 Wheel, 12 Tire, 20 Wheel nut, 25 Hub bolt, 30,60,70,80,90,400,500 Nut cap, 40 Hub, 50 Wheel nut, 63,83,93 Support part, 31,51,61,71,81,91,401,501 Inner surface, 32,52,62,72,82,92,402,502 Ceiling surface, 100,200 Circuit board, 110 Acceleration sensor, 300 Battery, 600 Wheel bolt.

Claims

1. an acceleration sensor that rotates in conjunction with the rotation of the screw member and detects acceleration applied along a detection axis that intersects with the rotation axis of the screw member; the acceleration sensor is provided on a substrate, and the substrate is fixed so that the acceleration sensor is located on the rotation axis of the screw member; the screw member is a nut or a bolt, the loosening detection device is composed of a cap attached to the body of the nut or the head of the bolt, The substrate is fixed to the ceiling surface of the cap, and is a screw member loosening detection device.

2. an acceleration sensor that rotates in conjunction with the rotation of the screw member and detects acceleration applied along a detection axis that intersects with the rotation axis of the screw member; the acceleration sensor is provided on a substrate, and the substrate is fixed so that the acceleration sensor is located on the rotation axis of the screw member; the screw member is a cap nut, The loosening detection device is configured to include the cap nut, The substrate is a screw member loosening detection device that is fixed to the ceiling surface of the cap nut.

3. Two holes through which machine screws are inserted are formed in the substrate, and the substrate is fixed to the ceiling surface at two points by the machine screws that pass through the holes, 3. The screw loosening detection device according to claim 1, wherein one of the holes provided in the substrate is an elongated hole.

4. 4. The device for detecting loosening of a screw according to claim 3, wherein the elongated hole is formed so that the distance between the long sides of the elongated hole becomes shorter when the substrate rotates in the direction in which the screw loosens.

5. 3. The screw loosening detection device according to claim 1, wherein a positioning member for positioning the board is formed on the ceiling surface.

6. 3. The screw loosening detection device according to claim 1, wherein the substrate is sealed and fixed to the ceiling surface with a resin.

7. A screw member loosening detection device that detects the fastening state of a screw member consisting of a hexagonal nut or a hexagonal bolt, a cap attached to the outer periphery of the body of the hexagonal nut or the outer periphery of the head of the hexagonal bolt; a substrate on which an acceleration sensor is provided; a battery; The device for detecting loosening of a screw member, wherein the substrate is fixed to a side surface of the cap that faces the outer periphery of the main body or the outer periphery of the head.

8. A screw member loosening detection device as described in Claim 7, wherein the battery is fixed to the side of the cap that faces the outer periphery of the main body or the outer periphery of the head.

9. a plurality of support portions are formed on the side surface of the cap, the support portions being in contact with the outer periphery of the main body or the outer periphery of the head; A screw member loosening detection device as described in claim 7, wherein the support portion abuts against the outer periphery of the main body or the outer periphery of the head, thereby forming a space between the outer periphery of the main body or the outer periphery of the head and the side of the cap, and the substrate is positioned in the space.

10. A screw member loosening detection device as described in Claim 9, wherein the battery is placed in the space.

11. 11. The screw loosening detection device according to claim 9 or 10, wherein the support portion abuts against at least three of the outer peripheral surfaces of the main body outer peripheral portion or the outer peripheral surface of the head outer peripheral portion, the three outer peripheral surfaces having central angles of 120 degrees each.

12. The screw loosening detection device according to claim 10 , wherein the substrate and the battery are arranged in different spaces defined by the support portion.

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