Detection device and detection method

Abstract

A detection apparatus and a detection method are provided. A sensor device (detection device) (100) is provided with an acceleration sensor (sensor unit) (1) that detects X-axis acceleration and Y-axis acceleration. Furthermore, the sensor device (100) is provided with a signal processing unit (state detection unit) (2). And a signal processing unit (2) that detects the fastening state of the nut (240) on the basis of the result of comparison between the rotation angle of the sensor device (100) calculated on the basis of the X-axis acceleration and the Y-axis acceleration, and the initial value of the rotation angle of the sensor device (100) calculated on the basis of the initial values (reference acceleration) of the X-axis acceleration and the Y-axis acceleration. The signal processing unit (2) defines, as an initial value of acceleration, an acceleration greater than zero value detected by the acceleration sensor (1) after the X-axis acceleration and the Y-axis acceleration each have a value that can be regarded as zero value.

Description

Technical Field

[0001] The present disclosure relates to a detection device and a detection method. Background Art

[0002] Japanese Patent Application Laid-Open No. 2005-329907 (Patent Document 1) discloses a detection device that detects the mounting state of a tire (a nut fastening a wheel) based on a detection value of a detector (acceleration sensor (G sensor)) mounted on the tire or wheel.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2005-329907

[0004] In the detection device described in the above-mentioned patent document 1, the looseness of the nut fastened to the wheel is detected based on the detection value of the acceleration sensor. However, the vibration of the wheel generated when the nut is loose may change depending on the type of vehicle or tire. Therefore, in order to detect the looseness of the nut (fastening member) regardless of the type of vehicle or tire (rotating body), it is possible to consider detecting the looseness of the nut based on the change in the value obtained based on the rotation angle of the nut. In this case, in order to detect the looseness of the nut, it is necessary to set a reference value (initial value) based on the value obtained based on the rotation angle of the nut. Therefore, it is desired to have a detection device and a detection method that can easily set a reference value based on the value of the rotation angle of the nut (fastening member). Summary of the invention

[0005] The present disclosure has been made to solve such a problem, and an object of the present disclosure is to provide a detection device and a detection method that can easily set a reference value of a value obtained based on the rotation angle of a fastening member.

[0006] The detection device of the first aspect of the present disclosure is a detection device for detecting the fastening state of a fastening member that fastens a predetermined member to a rotating body having a rotation axis that intersects with the direction of gravity, and comprises: a sensor unit that detects acceleration along at least one axis that intersects with each other in a plane that intersects with the rotation axis of the rotating body in a state in which the predetermined member has been fastened to the rotating body by the fastening member; and a state detection unit that detects the fastening state of the fastening member based on a comparison result between a value obtained based on the acceleration detected by the sensor unit and a value obtained based on a reference acceleration that is defined as a reference value of the acceleration, and the state detection unit defines a value obtained based on the absolute value of the acceleration detected by the sensor unit that is greater than 0 as the reference acceleration after the absolute value of the acceleration along at least one axis becomes a value that can be regarded as a 0 value.

[0007] In the detection device of the first aspect of the present disclosure, as described above, after the absolute value of the acceleration along at least one axis becomes a value that can be regarded as a zero value, the acceleration detected by the sensor unit that is greater than a zero value is defined as a reference acceleration. Here, in the case where the fastening member is temporarily removed from the rotating body in order to fasten the fastening member and the fastener is placed horizontally to the ground, the acceleration of the sensor unit on at least one axis becomes zero. Moreover, after the operation of fastening the fastening member is completed, a centrifugal acceleration greater than a predetermined magnitude is applied to the fastening member by starting the rotation of the rotating body. Therefore, the acceleration of the fastening member when the operation of fastening the fastening member is completed and the rotation of the rotating body is started is automatically set as the reference acceleration. As a result, the trouble of the user can be reduced compared to the case where the reference acceleration of the fastening member is set by, for example, a predetermined operation by the user. As a result, the reference value of the acceleration of the fastening member (a value obtained based on the rotation angle) can be easily set.

[0008] The detection method according to the second aspect of the present disclosure is a detection method for detecting the tightening state of a fastening member that fastens a predetermined member to a rotating body having a rotation axis that intersects the direction of gravity, and comprises: an acceleration detection step, using a sensor unit that detects the acceleration on at least one axis along a plane that intersects the rotation axis of the rotating body in a state where the predetermined member has been tightened to the rotating body by the fastening member, to detect the acceleration on at least one axis; a prescribed step, after the absolute value of the acceleration along at least one axis becomes a value that can be regarded as a zero value, a value obtained based on the absolute value of the acceleration detected by the sensor unit that is greater than a zero value is prescribed as a reference acceleration; and a tightening state detection step, detecting the tightening state of the fastening member based on a comparison result between a value obtained based on the acceleration on at least one axis detected by the sensor unit and a value obtained based on the reference acceleration.

[0009] In the detection method of the second aspect of the present disclosure, as described above, after the absolute value of the acceleration along at least one axis becomes a value that can be regarded as 0, the acceleration detected by the sensor unit that is greater than 0 is defined as the reference acceleration. Thus, a detection method that can easily set the reference value of the acceleration (value obtained based on the rotation angle) of the fastening member can be provided.

[0010] According to the present disclosure, it is possible to easily set a reference value of a value obtained based on the rotation angle of the fastening member. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a diagram showing a vehicle provided with a sensor device according to one embodiment.

[0012] Figure 2 This is a cross-sectional view of a nut according to one embodiment.

[0013] Figure 3 It is a diagram showing the structure of a sensor device according to one embodiment.

[0014] Figure 4 This is a functional block diagram of a signal processing unit according to one embodiment.

[0015] Figure 5 This is a front view showing the structure of a tire (initial state) of a vehicle according to an embodiment.

[0016] Figure 6 This is a diagram showing the relationship between the acceleration and the rotation angle of the wheel when the centrifugal force is 0.

[0017] Figure 7 This is a diagram showing the relationship between the acceleration and the rotation angle of the wheel when the centrifugal force is 6G.

[0018] Figure 8 This is a front view showing the structure of a tire of a vehicle (in a state where the nut is loosened) according to one embodiment.

[0019] Fig. 9 This is a diagram showing the relationship between the acceleration and the wheel angle when the centrifugal force is 6 G in a state where the nut is loose.

[0020] Fig. 10A This is a diagram showing the relationship between the average value of acceleration and the sensor angle when the centrifugal force is 6 G.

[0021] Fig. 10B This is a diagram showing the relationship between the average value of acceleration and the sensor angle when the centrifugal force is 10G.

[0022] Fig.11 This is a flowchart showing a method for detecting a tightening state of a nut using a sensor device according to an embodiment.

[0023] Fig.12 This is a diagram showing a state where the sensor device according to one embodiment is placed horizontally on the ground.

[0024] Fig.13 It is a cross-sectional view of a nut according to a first modified example of one embodiment.

[0025] Fig.14 It is a cross-sectional view of a nut according to a second modified example of one embodiment. DETAILED DESCRIPTION

[0026] Hereinafter, the embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. In addition, the same reference numerals are given to the same or corresponding parts in the drawings, and their description will not be repeated.

[0027] Figure 1 The sensor device 100 (see Figure 2 ) is a diagram of a vehicle 200. The vehicle 200 includes a plurality of wheels 210. In addition, the vehicle 200 includes a communication terminal 201 that can communicate with a communication unit 3 described later and includes a display unit not shown. In addition, the sensor device 100 is an example of a "detection device" of the present disclosure.

[0028] The wheel 210 includes a wheel 220 and a tire 230 mounted on the wheel 220. The wheel 220 is provided with a plurality of ( Figure 1 5) nuts 240 are fastened to the hub 250a (refer to Figure 2 ). In addition, the number of nuts 240 is not limited to the above example. In addition, the hub 250a is an example of the "predetermined member" and the "vehicle body" of the present disclosure. In addition, the wheel 220 and the nut 240 are examples of the "rotating body" and the "fastening member" of the present disclosure, respectively.

[0029] like Figure 2 As shown in FIG. 2 , the nut 240 fastens the bolt 250 to the wheel 220. Specifically, the wheel 220 is provided with a plurality of (five) wheel holes 221 through which the bolt 250 is inserted (penetrated). The nut 240 fastens the bolt 250 (see FIG. 2 ) in the state of being inserted into the wheel hole 221. Figure 2 ) is fastened to the wheel 220. In addition, the bolt 250 is fixed to the wheel hub 250a.

[0030] Figure 2 In the example of a dual tire, the wheel 220 is composed of an inner wheel 222 and an outer wheel 223 .

[0031] One side of the nut 240 is open. In addition, a nut cover 241 is attached to the nut 240. The sensor device 100 may be indirectly provided on the nut 240 by being attached to the nut cover 241, for example. In addition, the nut 240 is an example of a "fastening member" in the present disclosure.

[0032] Specifically, the nut cover 241 includes a top portion 241a and a side portion 241b. The side portion 241b is provided to surround the portion of the bolt 250 that passes through the wheel hole 221 in a circumferential shape. The top portion 241a is provided to face the terminal end portion 251 of the bolt 250 (in the insertion direction of the bolt 250). The top portion 241a and the side portion 241b are provided continuously. In addition, a washer 243 may be provided between the nut 240 and the wheel 220.

[0033] The sensor device 100 is attached (bonded) to the inner surface 241c of the top portion 241a of the nut cover 241. Therefore, the sensor device 100 is disposed in the space S of the nut cover 241 for accommodating the bolt 250.

[0034] The sensor device 100 is provided on a part of the nuts 240 provided on each wheel 210. Alternatively, the sensor device 100 may be provided on all of the nuts 240 provided on each wheel 210.

[0035] like Figure 3 As shown, the sensor device 100 includes an acceleration sensor 1, a signal processing unit 2, a communication unit 3, and a power supply unit 4. The acceleration sensor 1 and the signal processing unit 2 are examples of the “sensor unit” and the “state detection unit” in the present disclosure, respectively.

[0036] like Figure 5 As shown, the acceleration sensor 1 is aligned with the rotation axis (along the axis of rotation) of the wheel 220 (not shown). Figure 5 The acceleration sensor 1 detects acceleration on each of the X-axis and the Y-axis that are orthogonal to each other in a plane that is orthogonal to an axis extending in a direction perpendicular to the paper surface. The acceleration detected by the acceleration sensor 1 has a positive or negative magnitude (direction). Figure 5 The arrows indicating the X-axis and Y-axis respectively indicate the positive directions of the X-axis and Y-axis respectively. Figure 5 On the paper shown, the positive direction is the direction in which the Y axis is rotated 90 degrees clockwise relative to the X axis.

[0037] also, Figure 5 The Z direction shown indicates the vertical direction (up and down direction). In addition, due to the rotation of the wheel 210, a centrifugal acceleration corresponding to the rotation speed of the wheel 210 is applied to the nut 240A. In this embodiment, in order to simplify the description, the case where the centrifugal acceleration is a value sufficiently larger than the gravitational acceleration is described (the case where the gravitational acceleration can be ignored is used for description). In addition, Figure 5 In the embodiment, the nut 240 located closest to the Z1 side among the five nuts 240 is referred to as the nut 240A. In the following description, the sensor device 100 is oriented in the direction of Figure 5 When in the state, the angle (rotation angle) of the sensor device 100 is set to 0 degrees.

[0038] The signal processing unit 2 detects the state (tightening state) of the nut 240 based on the detection signal of the acceleration sensor 1. Figure 4 As shown, the signal processing unit 2 includes a root mean square calculation unit 2a, a normalization unit 2b, a rotation angle calculation unit 2c, a tightening state detection unit 2d, an initial value setting unit 2e, and a sensing detection cycle setting unit 2f. Figure 4The RMS calculation unit 2a, normalization unit 2b, rotation angle calculation unit 2c, tightening state detection unit 2d, initial value setting unit 2e and sensing cycle setting unit 2f are software that modularizes the functional features of the signal processing unit 2. Details of each function will be described later.

[0039] The communication unit 3 transmits the processing result of the signal processing unit 2 or information obtained based on the processing result to the communication terminal 201 of the vehicle 200 (see Figure 1 ).

[0040] The power supply unit 4 supplies power to the acceleration sensor 1 , the signal processing unit 2 , and the communication unit 3 .

[0041] When the hub 250a is fastened to the wheel 220 by the nut 240, the acceleration sensor 1 detects the acceleration (vector) on the X-axis, i.e., the X-axis acceleration (Xg), and the acceleration (vector) on the Y-axis, i.e., the Y-axis acceleration (Yg). The X-axis acceleration and the Y-axis acceleration are respectively represented by G values ​​(values ​​in which the gravitational acceleration is recorded as 1G).

[0042] Figure 6 It is a coordinate diagram showing the relationship between the rotation angle centered on the rotation axis of the tire 230 (wheel 220) and the X-axis acceleration and the Y-axis acceleration when the vehicle 200 has a speed of 0 (the centrifugal force acting on the nut 240 is 0). In this case, the X-axis acceleration and the Y-axis acceleration each change in a sinusoidal wave within the range of ±1G. This is because the X-axis and the Y-axis each contain only the acceleration component obtained based on the gravitational acceleration formed in the Z2 direction. In addition, Figure 6 It means setting Figure 5 A graph of the results of the sensor device 100 for the nut 240A is shown.

[0043] Figure 7 It is a coordinate diagram showing the relationship between the rotation angle of the tire 230 (wheel 220) and the X-axis acceleration and the Y-axis acceleration when a centrifugal force of 6G acts on the nut 240 due to a predetermined vehicle speed. In addition, in the present disclosure, there is a case where the magnitude of the centrifugal force is represented by a G value. On the one hand, in Figure 5 The Y-axis orientation shown has no centrifugal force component on the Y-axis, so the Y-axis acceleration is Figure 6 On the other hand, the centrifugal force is applied to the X-axis, so the X-axis acceleration becomes Figure 6 The value is obtained by adding 6G to the X-axis acceleration. In this case, the waveform of the root mean square of the X-axis acceleration and the Y-axis acceleration is the same as the waveform of the X-axis acceleration. Figure 7In order to facilitate understanding, the waveform of the X-axis acceleration and the waveform of the root mean square are slightly offset in the figure. Figure 7 It means setting Figure 5 A graph of the results of the sensor device 100 for the nut 240A is shown.

[0044] Figure 8 It means that the nut 240 is Figure 5 FIG. 2 is a diagram of a state in which the nut 240 is rotated 135 degrees clockwise from the state in which the nut 240 is loosened and rotated 225 degrees counterclockwise. Fig. 9 It means in Figure 8 The coordinate diagram is a relationship between the angle of the tire 230 (wheel 220) and the X-axis acceleration and the Y-axis acceleration when a centrifugal force of 6G acts on the nut 240. In this case, on the one hand, the amplitude of the waveform of the X-axis acceleration and the Y-axis acceleration is Figure 7 On the other hand, the average values ​​of the X-axis acceleration and the Y-axis acceleration are Figure 7 On the one hand, the average values ​​of the X-axis acceleration and the Y-axis acceleration reflect the rotation angle of the nut 240 (sensor device 100). On the other hand, the waveform of the root mean square of the X-axis acceleration and the Y-axis acceleration is different from Figure 7 The same situation is the same, and does not change due to the rotation angle of the nut 240 (sensor device 100). In addition, Fig. 9 It means setting Figure 8 A graph of the results of the sensor device 100 for the nut 240A is shown.

[0045] Fig. 10A : is a graph showing the average value of acceleration with respect to the angle (rotation angle) of the sensor device 100 when the centrifugal force is 6G. Fig. 10B : is a graph showing the average value of the acceleration relative to the angle (rotation angle) of the sensor device 100 when the centrifugal force is 10G. Fig. 10A and Fig. 10B As shown in FIG. 1 , the waveforms of the average values ​​of the X-axis acceleration and the Y-axis acceleration have amplitudes corresponding to the centrifugal force (the scales on the vertical axis are different from each other), but have the same shape. Fig. 10A and Fig. 10B The root mean square of the average values ​​of the X-axis acceleration and the Y-axis acceleration is a constant value corresponding to the centrifugal force. Therefore, the value obtained by dividing the average values ​​of the X-axis acceleration and the Y-axis acceleration by the root mean square is equal regardless of the magnitude of the centrifugal force.

[0046] The signal processing unit 2 (RMS calculation unit 2a) of this embodiment calculates the RMS of the X-axis acceleration (Xg) and the Y-axis acceleration (Yg). In addition, the signal processing unit 2 (normalization unit 2b) calculates the X-axis normalization value by dividing the X-axis acceleration by the RMS. In addition, the signal processing unit 2 (normalization unit 2b) calculates the Y-axis normalization value by dividing the Y-axis acceleration by the RMS.

[0047] Then, the signal processing unit 2 (rotation angle calculation unit 2c) detects the rotation angle of the nut 240 (sensor device 100) based on both the X-axis normalized value and the Y-axis normalized value. Fig. 10A and Fig. 10B As described above, when the vehicle speed is above a constant value, the values ​​of the X-axis normalized value and the Y-axis normalized value become values ​​obtained based on the sensor angle and are independent of the centrifugal force (vehicle speed). Therefore, by using the X-axis normalized value and the Y-axis normalized value, the rotation angle of the nut 240 can be detected regardless of the vehicle speed. In addition, the signal processing unit 2 (rotation angle calculation unit 2c) obtains information on the X-axis acceleration and the Y-axis acceleration from the acceleration sensor 1 at every predetermined time (for example, every 20 seconds to 120 seconds) and calculates the rotation angle of the nut 240. In addition, the rotation angle of the nut 240 is an example of a "value obtained based on acceleration" in the present disclosure.

[0048] In addition, the signal processing unit 2 (tightening state detection unit 2d) detects the tightening state of the nut 240 based on the difference between the rotation angle of the nut 240 calculated this time and the rotation angle of the nut 240 until the last time. On the one hand, if the above difference is outside the predetermined allowable range, the signal processing unit 2 (tightening state detection unit 2d) determines that the nut 240 is loose (not fixed). In this case, the signal processing unit 2 sends a signal to the communication unit 3 (refer to Figure 3 ) to the communication terminal 201 (refer to Figure 1 ) notifies that the nut 240 has loosened. Thus, a warning may be displayed on a display unit (not shown) of the communication terminal 201, causing the communication terminal 201 to generate a warning sound. On the other hand, if the above-mentioned difference is within a predetermined allowable range, the signal processing unit 2 (tightening state detection unit 2d) determines that the nut 240 is fixed. In this case, the signal processing unit 2 does not notify the communication terminal 201. In addition, the above-mentioned rotation angle up to the last time may also be the last rotation angle, or may be the average value of the rotation angles of several times in the past including the last time.

[0049] In addition, when the detection value of the X-axis acceleration and the Y-axis acceleration detected by the acceleration sensor 1, whichever has the larger absolute value, is within the range of ±1G, the signal processing unit 2 (tightening state detection unit 2d) determines that the rotation of the wheel 220 (tire 230) has stopped. In addition, the detection value until the last time may be the detection value of the last time, or may be the average value of the detection values ​​of the past several times including the last time. In addition, it is also possible to determine that the rotation of the wheel 220 (tire 230) has stopped based on either the X-axis acceleration or the Y-axis acceleration. In addition, it is also possible to determine that the rotation of the wheel 220 (tire 230) has stopped when the detection value of both the X-axis acceleration and the Y-axis acceleration is within the range of ±1G.

[0050] When the signal processing unit 2 determines that the rotation of the wheel 220 (tire 230 ) has stopped, the signal processing unit 2 performs processing to lengthen the cycle (the above-mentioned predetermined time) of sensing detection by the sensor device 100 (for example, to a 30-minute cycle).

[0051] In addition, the signal processing unit 2 obtains information about the X-axis acceleration and the Y-axis acceleration detected by the acceleration sensor 1. The signal processing unit 2 (initial value setting unit 2e) defines the X-axis acceleration and the Y-axis acceleration as initial values ​​when the absolute value of at least the larger one of the X-axis acceleration and the Y-axis acceleration becomes a predetermined value (e.g., 2G) greater than the zero value after the X-axis acceleration and the Y-axis acceleration each become values ​​that can be regarded as the zero value. In addition, the initial value is an example of the "reference acceleration" of the present disclosure. In addition, the value that can be regarded as the zero value refers to a value within a predetermined range (e.g., 0±0.1G) centered on the zero value.

[0052] For example, when the nut 240 is tightened by torque, when the nut 240 is temporarily removed from the wheel 220 and placed horizontally on the ground, the X-axis acceleration and the Y-axis acceleration are 0. Afterwards, after the nut 240 is mounted on the wheel 220, the vehicle 200 travels at a predetermined speed or higher, and a centrifugal acceleration of 3G or higher is applied to the nut 240. At this time, the X-axis acceleration and the Y-axis acceleration are each set to an initial value.

[0053] Specifically, after the X-axis acceleration and the Y-axis acceleration are each in a state that can be regarded as a zero value for a predetermined time or longer (for example, more than 30 minutes), the signal processing unit 2 (initial value setting unit 2e) sets the X-axis acceleration and the Y-axis acceleration when the absolute value of at least the larger absolute value of the X-axis acceleration and the Y-axis acceleration becomes greater than the predetermined value as initial values. Thus, it is possible to suppress the situation in which the initial value is set when the X-axis acceleration and the Y-axis acceleration each become 0 due to erroneous detection (momentary) of the acceleration sensor 1.

[0054] Specifically, in a plurality of detections after the X-axis acceleration and the Y-axis acceleration each become 0, when the absolute value of at least the larger absolute value of the X-axis acceleration and the Y-axis acceleration becomes greater than the predetermined value, the average value of the X-axis acceleration and the average value of the Y-axis acceleration in the plurality of detections are each set as the initial value. In addition, the plurality of detections may also be continuous plurality of detections.

[0055] After the X-axis acceleration and the Y-axis acceleration each become 0, the signal processing unit 2 (sensing detection cycle setting unit 2f) performs control to lengthen the sensing detection cycle. For example, the signal processing unit 2 changes the sensing detection cycle from 20 to 120 seconds to 30 minutes (constant value).

[0056] In addition, the signal processing unit 2 (tightening state detection unit 2d) detects the tightening state of the nut 240 based on the difference between the current rotation angle of the nut 240 (sensor device 100) and the rotation angle of the nut 240 (sensor device 100) calculated based on the above initial value. Specifically, it is also possible that in the case where the above difference becomes outside the predetermined allowable range, the signal processing unit 2 (tightening state detection unit 2d) determines that the nut 240 is loose (not fixed). In this case, the signal processing unit 2 detects the tightening state of the nut 240 through the communication unit 3 (refer to Figure 3 ) to the communication terminal 201 (refer to Figure 1 ) notifies that the nut 240 has been loosened. Thus, a warning may be displayed on a display unit (not shown) of the communication terminal 201, or the communication terminal 201 may generate a warning sound.

[0057] (Method for detecting the tightening state of a nut)

[0058] Next, refer to Fig.11 The method of detecting the tightening state of the nut 240 is described with reference to the flowchart of FIG.

[0059] First, in step S1, a process is performed to arrange the nut 240 (nut cover 241) on a horizontal plane 900 perpendicular to the vertical direction (see Fig.12). As a result, the X-axis acceleration and the Y-axis acceleration detected by the acceleration sensor 1 are each 0. Next, in step S2, the signal processing unit 2 obtains information indicating that the X-axis acceleration and the Y-axis acceleration are each 0 (can be regarded as a zero value) from the acceleration sensor 1. Next, in step S3, the signal processing unit 2 (sensing detection cycle setting unit 2f) changes the sensing detection cycle from, for example, 20 to 120 seconds to 30 minutes.

[0060] Next, in step S4 , it is assumed that the signal processing unit 2 detects, based on the information from the acceleration sensor 1 , that the state in which the X-axis acceleration and the Y-axis acceleration are each 0 continues for a predetermined time (for example, 30 minutes) or longer.

[0061] Thereafter, in step S5, a process is performed to make at least one of the X-axis acceleration and the Y-axis acceleration equal to or greater than the predetermined value (e.g., 2G) while the wheel hub 250a is fastened to the wheel 220 by the nut 240. Specifically, while the wheel hub 250a is fastened to the wheel 220 by the nut 240, the vehicle 200 is driven at a speed equal to or greater than a predetermined speed, thereby applying a centrifugal acceleration equal to or greater than a predetermined magnitude to the nut 240.

[0062] Next, in step S6 , the signal processing unit 2 acquires information indicating that at least one of the X-axis acceleration and the Y-axis acceleration is equal to or greater than the predetermined value.

[0063] Next, in step S7, the signal processing unit 2 (initial value setting unit 2e) sets the X-axis acceleration and the Y-axis acceleration as initial values ​​when at least one of the X-axis acceleration and the Y-axis acceleration is detected to be greater than the predetermined value (when the information of step S6 is obtained). Specifically, the signal processing unit 2 (initial value setting unit 2e) sets the average value of the X-axis acceleration and the Y-axis acceleration calculated in multiple (for example, three) sensing detections after the information of step S6 is obtained as the initial value.

[0064] Then, in step S8, the signal processing unit 2 (tightening state detection unit 2d) detects the tightening state of the nut 240 based on the initial values ​​of the X-axis acceleration and the Y-axis acceleration set in step S7. Specifically, the signal processing unit 2 (tightening state detection unit 2d) detects the loosening state of the nut 240 based on the difference between the rotation angle of the nut 240 calculated based on the current X-axis acceleration and the Y-axis acceleration and the rotation angle of the nut 240 calculated based on the above initial values.

[0065] Note that the above-mentioned steps S1 and S5 are processes performed by the user, and the other steps are processing steps performed by the signal processing unit 2 .

[0066] As described above, in this embodiment, after the X-axis acceleration and the Y-axis acceleration each become values ​​that can be regarded as 0, the X-axis acceleration and the Y-axis acceleration are each set as initial values ​​when the absolute value of at least the one with the larger absolute value becomes a predetermined value greater than 0. Thus, the initial values ​​of the X-axis acceleration and the Y-axis acceleration are automatically set, thereby reducing the trouble of the user. As a result, the initial values ​​of the X-axis acceleration and the Y-axis acceleration can be easily set.

[0067] Furthermore, since a mechanical switch or the like for registering the initial value is not required, the number of components of vehicle 200 can be reduced and the structure of vehicle 200 can be simplified. In addition, in order to register the initial value, a mechanical switch or a switch that switches on and off by magnetic force may be provided in the vehicle.

[0068] In addition, in the above-mentioned embodiment, an example is shown in which the signal processing unit 2 sets the sensing detection period to 30 minutes (constant value) after the X-axis acceleration and the Y-axis acceleration are each regarded as a zero value, but the present disclosure is not limited to this. It is also possible that after the X-axis acceleration and the Y-axis acceleration are each regarded as a zero value, the signal processing unit 2 gradually lengthens the sensing detection period. For example, the signal processing unit 2 may also gradually lengthen the sensing detection period to 1 minute, 5 minutes, 30 minutes, 2 hours, 6 hours (thereafter every 6 hours). In addition, in the above-mentioned embodiment, an example is shown in which the above-mentioned initial value is set when the state in which the X-axis acceleration and the Y-axis acceleration can each be regarded as a zero value lasts for, for example, more than 30 minutes, but in the case of gradually lengthening the sensing detection period as described above, the above-mentioned initial value may also be set when the above-mentioned state lasts for more than 5 minutes.

[0069] In addition, in the above-mentioned embodiment, an example is shown in which the acceleration sensor 1 detects the X-axis acceleration and the Y-axis acceleration, but the present disclosure is not limited to this. For example, the acceleration sensor may detect accelerations of more than three axes that intersect each other in a plane orthogonal to the rotation axis of the wheel 220. In addition, the acceleration sensor may detect only one of the X-axis acceleration and the Y-axis acceleration.

[0070] In addition, in the above embodiment, an example is shown in which the average value of the X-axis acceleration and the Y-axis acceleration detected multiple times after the X-axis acceleration and the Y-axis acceleration each become 0 is set as the initial value, but the present disclosure is not limited to this. Alternatively, the X-axis acceleration and the Y-axis acceleration calculated in one sensing detection after the X-axis acceleration and the Y-axis acceleration each become 0 may be set as the initial value.

[0071] In addition, in the above-mentioned embodiment, an example of detecting the tightening state of the nut 240 provided on the wheel 220 of the vehicle 200 is shown, but the present disclosure is not limited thereto. For example, it is also possible to detect the tightening state of the fastening member such as the nut installed on the pulley of the elevator, the pulley of the conveyor belt, the rotating coffee cup and the carousel provided in the amusement park, and the rotating amusement equipment provided in the park. In addition, in the case of the rotating body rotating along the plane perpendicular to the gravity in the above-mentioned example, the centrifugal force is not affected by the gravity, so the tightening state of the fastening member can be easily detected even when the centrifugal acceleration is small. In the case of the rotating body rotating along the plane perpendicular to the gravity, the X-axis acceleration (Y-axis acceleration) becomes 0 during the stop of the rotating body. In this case, the reset condition (the condition corresponding to the above-mentioned step S2) is always established during the stop of the rotating body. Therefore, in this modified example, it is preferred to interchange the above-mentioned reset condition with the initial value setting condition (the condition corresponding to the above-mentioned step S6).

[0072] In addition, in the above-mentioned embodiment, an example in which the nut cover 241 is installed on the nut 240 is shown, but the present disclosure is not limited thereto. Fig.13 As shown, the sensor device 100 may be mounted on a nut 340 which is a cap nut. The nut 340 is an example of a "fastening member" in the present disclosure.

[0073] In addition, Fig.14 In the second modified example shown, the nut 440 is open on one side but does not include a nut cover. In this example, the sensor device 100 may be provided on the side surface 441 of the nut 440 (provided to be a surface orthogonal to the wheel 220). In addition, the nut 440 is an example of a "fastening member" disclosed in the present invention.

[0074] In addition, in the above embodiment, an example in which the sensor device 100 is provided on the nut 240 is shown, but the present disclosure is not limited to this. Alternatively, the sensor device 100 may be provided on a bolt (a bolt independent of the wheel hub). The bolt in this case is an example of a "fastening member" in the present disclosure.

[0075] In addition, in the above-mentioned embodiment, an example is shown in which the looseness of the nut 240 is detected by the signal processing unit 2 provided in the sensor device 100, but the present disclosure is not limited thereto. For example, the detection value of the acceleration sensor 1 may be sent to the ECU (Electronic Control Unit) provided in the vehicle 200 through the communication unit 3, and the ECU may detect the looseness of the nut 240 based on the detection value.

[0076] In addition, in the above-mentioned embodiment, an example of detecting the tightening state (looseness) of the nut 240 based on the change of the rotation angle of the nut 240 is shown, but the present disclosure is not limited to this. Alternatively, the tightening state (looseness) of the nut 240 may be detected based on the comparison between the change amount of at least one of the X-axis normalized value (X-axis acceleration) and the Y-axis normalized value (Y-axis acceleration) and a predetermined threshold value. In this case, the X-axis normalized value (X-axis acceleration) and the Y-axis normalized value (Y-axis acceleration) are an example of "acceleration-based values" of the present disclosure.

[0077] In addition, in the above-mentioned embodiment, an example of setting the initial value based on the situation that the X-axis acceleration and the Y-axis acceleration each become a value that can be regarded as a zero value is shown, but the present disclosure is not limited to this. It is also possible to set the initial value based on the situation that any one of the X-axis acceleration and the Y-axis acceleration becomes a value that can be regarded as a zero value. In addition, instead of detecting that the X-axis acceleration and the Y-axis acceleration become values ​​that can be regarded as zero values, the initial value can be set by detecting that the acceleration in the Z-axis direction parallel to the gravity direction becomes 1G. In addition, it is also possible to set the initial value by detecting that the composite vector of the X-axis acceleration, the Y-axis acceleration, and the Z-axis acceleration becomes 1G in the direction of gravity acceleration.

[0078] In the above embodiment, an example of setting the initial value of the X-axis acceleration (Y-axis acceleration) is shown, but the present disclosure is not limited thereto. The initial value of the rotation angle of the nut 240 calculated based on the X-axis acceleration (Y-axis acceleration) may also be set.

[0079] In addition, in the above-mentioned embodiment, an example in which the X-axis and the Y-axis are orthogonal to each other is shown, but the present disclosure is not limited to this, and the X-axis and the Y-axis may intersect each other instead of being orthogonal to each other.

[0080] In the above embodiment, an example is shown in which the plane provided with the X-axis and the Y-axis is orthogonal to the rotation axis of the wheel 220, but the present disclosure is not limited thereto. The plane may intersect the rotation axis instead of being orthogonal.

[0081] In addition, in the above-mentioned embodiment, an example of using the X-axis normalized value and the Y-axis normalized value to detect the tightening state of the nut 240 is shown, but the present disclosure is not limited to this. It is also possible that, when the X-axis and the Y-axis are orthogonal to each other, the tightening state of the nut 240 is detected using the inverse trigonometric function of the X-axis acceleration and the Y-axis acceleration. The inverse trigonometric function includes the inverse tangent function (arctan), the inverse sine function (arcsin), the inverse cosine function (arccos), the inverse cotangent function (arccot), the inverse cosecant function (arccsc), and the inverse secant function (arcsec). In addition, it is also possible to detect the tightening state of the nut 240 based on the ratio between the X-axis acceleration and the Y-axis acceleration.

[0082] Furthermore, in the above-described embodiment, the number of sensor devices 100 for one wheel 220 may be appropriately changed as long as it is one or more.

[0083] The above-described embodiment and the above-described modified examples can be appropriately combined within a range where no technical contradiction occurs.

[0084] The embodiments disclosed this time should be considered as illustrative in all aspects and not restrictive. The scope of the present disclosure is indicated by the claims rather than the above description, and is intended to include all modifications within the meaning and scope equivalent to the claims.

[0085] Description of Reference Numerals

[0086] 1...acceleration sensor (sensor unit); 2...signal processing unit (state detection unit); 100...sensor device (detection device); 220...wheel (rotating body); 240, 340, 440...nut (fastening member); 250a...wheel hub (predetermined member) (vehicle body).

Claims

1. A detection device for detecting a fastening state of a fastening member fastening a predetermined member to a rotating body having a rotation axis intersecting a gravity direction, the detection device comprising: a sensor portion that detects acceleration on at least one axis along a plane intersecting with a rotation axis of the rotating body in a state where the predetermined member has been fastened to the rotating body by the fastening member; and a state detection unit that detects a fastening state of the fastening member based on a comparison result between a value obtained based on the acceleration detected by the sensor unit and a value obtained based on a reference acceleration specified as a reference value of the acceleration, After the absolute value of the acceleration on the at least one axis becomes a value that can be regarded as a zero value, the state detection unit defines a value obtained based on an absolute value of the acceleration detected by the sensor unit that is greater than the zero value as the reference acceleration.

2. The detection device according to claim 1, characterized in that: For the state detection unit, acquiring the acceleration of the at least one axis of the fastening member at every predetermined time, After the absolute value of the acceleration on the at least one axis becomes a value that can be regarded as the zero value, an average value of values ​​obtained based on the absolute values ​​of acceleration greater than the zero value detected multiple times by the sensor unit is defined as the reference acceleration.

3. The detection device according to claim 1 or 2, characterized in that: For the state detection unit, acquiring the acceleration of the at least one axis of the fastening member at every predetermined time, And after the absolute value of the acceleration on the at least one axis becomes a value that can be regarded as the zero value, control is performed to lengthen the predetermined time.

4. The detection device according to claim 3, characterized in that: The state detection unit performs control to gradually lengthen the predetermined time after the absolute value of the acceleration on the at least one axis reaches a value that can be regarded as zero.

5. The detection device according to claim 1 or 2, characterized in that: The sensor unit is provided on a nut that fixes the wheel to the vehicle body.

6. The detection device according to claim 1 or 2, characterized in that: The at least one axis includes a first axis and a second axis that intersect each other, The state detection unit defines the acceleration on the first axis and the acceleration on the second axis as the reference acceleration when the absolute value of the acceleration on at least one of the first axis and the second axis becomes greater than a predetermined value greater than the zero value, after the absolute value of the acceleration on each of the first axis and the second axis becomes a value that can be regarded as the zero value.

7. A detection method for detecting a fastening state of a fastening member fastening a predetermined member to a rotating body having a rotation axis intersecting a gravity direction, the detection method comprising: an acceleration detection step of detecting the acceleration on at least one axis along a plane intersecting the rotation axis of the rotating body in a state where the predetermined member is fastened to the rotating body by the fastening member, using a sensor unit that detects the acceleration on at least one axis along a plane intersecting the rotation axis of the rotating body; a step of defining, after the absolute value of the acceleration along the at least one axis becomes a value that can be regarded as a zero value, defining a value obtained based on the absolute value of the acceleration detected by the sensor unit and greater than the zero value as a reference acceleration; as well as The fastening state detecting step detects the fastening state of the fastening member based on a comparison result between a value based on the acceleration on the at least one axis detected by the sensor unit and a value based on the reference acceleration.

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