Determination device, information transmission device, and determination system

Abstract

To provide a determination device capable of determining abnormality in a wheel before large influence is exerted on traveling.SOLUTION: A determination device 21 determines presence or absence of abnormality in a wheel based on transition of a variation value which is difference between pre-processing wheel speed detected by a wheel speed sensor 15 for detecting rotational speed of the wheel included in a vehicle and post-processing wheel speed obtained by applying low-pass filter processing to the pre-processing wheel speed.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a determination device, an information transmission device, and a determination system. [Background technology]

[0002] Patent Document 1 describes a determination device that determines whether a wheel has an abnormality using the rotation speed of the wheel. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6526818 Summary of the Invention [Problem to be solved by the invention]

[0004] An abnormality in a wheel has a significant impact on the running of a vehicle, so it is desirable to be able to determine an abnormality in a wheel before it has a significant impact on running. [Means for solving the problem]

[0005] The determination device for solving the above problem determines whether or not there is an abnormality in the wheel based on the trend in the fluctuation value, which is the difference between the pre-processing wheel speed detected by a wheel speed sensor that detects the rotational speed of the wheel equipped on the vehicle and the post-processing wheel speed obtained by applying low-pass filter processing to the pre-processing wheel speed.

[0006] The information transmission device for solving the above problem acquires a pre-processing wheel speed detected by a wheel speed sensor that detects the rotational speed of a wheel provided on a vehicle. The information transmission device calculates a variation value that is the difference between the acquired pre-processing wheel speed and a post-processing wheel speed obtained by applying low-pass filtering to the pre-processing wheel speed. The information transmission device transmits the calculated variation value to a determination device.

[0007] A determination system for solving the above problem comprises an information transmission device and a determination device. In the determination device, the information transmission device acquires a pre-processing wheel speed detected by a wheel speed sensor that detects the rotational speed of a wheel equipped on a vehicle. In the determination system, the information transmission device calculates a fluctuation value that is the difference between the acquired pre-processing wheel speed and a processed wheel speed obtained by applying low-pass filter processing to the pre-processing wheel speed. In the determination system, the information transmission device transmits the calculated fluctuation value to the determination device. In the determination system, the determination device determines whether or not there is an abnormality in the wheel based on the transition of the received fluctuation value. In the determination system, when the determination device determines that there is an abnormality in the wheel, it notifies the user of the vehicle that there is an abnormality in the wheel. [Effects of the Invention]

[0008] The determination device, information transmission device, and determination system make it possible to determine an abnormality in a wheel before it has a significant impact on driving. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a determination system according to an embodiment. [Figure 2] FIG. 2 is a sequence diagram showing a communication mode in the determination system of the embodiment. [Figure 3] FIG. 3 is a graph showing an example of the transition of the pre-processing wheel speed when there is no looseness in the fastening between the wheel and the hub. [Figure 4] FIG. 4 is a graph showing an example of the transition of the pre-processing wheel speed when there is looseness in the fastening between the wheel and the hub. [Figure 5] FIG. 5 is a graph showing an example of the transition of the pre-processing wheel speed when traveling on a road surface with large irregularities. [Figure 6] FIG. 6 is a graph showing an example of the transition of the pre-processing wheel speed and the post-processing wheel speed. [Figure 7]FIG. 7 is a graph showing an example of the transition of the amount of fluctuation when there is no looseness in the fastening between the wheel and the hub. [Figure 8] FIG. 8 is a graph showing an example of the transition of the amount of fluctuation when there is looseness in the fastening between the wheel and the hub. [Figure 9] FIG. 9 is a graph showing an example of the transition when an upper limit value is set for the amount of fluctuation when there is no looseness in the fastening between the wheel and the hub. [Figure 10] FIG. 10 is a graph showing an example of the transition when an upper limit value is set for the amount of fluctuation when there is looseness in the fastening between the wheel and the hub. [Figure 11] FIG. 11 is a graph showing an example of the transition of the cumulative total of the time integral value of the fluctuation amount over a predetermined period. [Figure 12] FIG. 12 is a sequence diagram showing a mode of communication in the determination system of the first modified example. [Figure 13] FIG. 13 is a graph showing an example of the transition of the cumulative total of the time integral value before and after the occurrence of loosening in the fastening between the wheel and the hub. [Figure 14] FIG. 14 is a table showing past gradients stored for determining threshold values ​​in the determination system of the second modified example. [Figure 15] FIG. 15 is a graph showing an example of the transition of the cumulative total of the time integral values ​​for a plurality of wheels of a vehicle, both for wheels with no looseness in the fastening to the hub and for wheels with looseness. [Figure 16] FIG. 16 is a graph showing an example of the transition of the amount of fluctuation when there is no loosening in the fastening between the wheel and the hub, and the relationship with the specified range. [Figure 17] FIG. 17 is a graph showing an example of the transition of the amount of fluctuation when there is looseness in the fastening between the wheel and the hub, and the relationship with the specified range. [Figure 18] FIG. 18 is a sequence diagram showing a mode of communication in the determination system of the fourth modified example. [Figure 19] FIG. 19 is a graph showing the transition of the number of convergences in the determination system of the fifth modified example. [Figure 20]FIG. 20 is a table showing the number of past convergences stored for determining a threshold value in the determination system of the fifth modified example. [Figure 21] FIG. 21 is a graph showing an example of the transition of the number of convergences for a plurality of wheels of a vehicle, both for wheels with no looseness in fastening to the hub and for wheels with looseness. DETAILED DESCRIPTION OF THE INVENTION

[0010] An embodiment of the determination system will be described below with reference to FIGS. <Configuration of Determination System 100> As shown in FIG. 1, the determination system 100 is configured by an information transmission device provided in a vehicle 10 and a determination device 21.

[0011] The vehicle 10 has four wheels, namely, a front left wheel 17, a front right wheel 18, a rear right wheel 19, and a rear right wheel 20, and an information transmitting device. The front left wheel 17 is a wheel located on the front right side of the vehicle 10. The front left wheel 18 is a wheel located on the front left side of the vehicle 10. The rear right wheel 19 is a wheel located on the rear left side of the vehicle 10.

[0012] As shown in Fig. 1, the wheels of the vehicle 10 are fastened to hubs. The front wheel 17 is fastened to the front wheel hub 24. The front wheel 18 is fastened to the front wheel hub 25. The rear wheel 19 is fastened to the rear wheel hub 26. The rear wheel 20 is fastened to the rear wheel hub 27.

[0013] 1, the information transmission device includes a plurality of electronic control units (ECUs) and a wheel speed sensor 15. The information transmission device includes a brake ECU 11 and a central ECU 12 as the electronic control units.

[0014] 1, the central ECU 12 includes a storage device 14 that stores programs, and a processing circuit 13 that executes the programs stored in the storage device 14 to perform various processes. The processing circuit 13 includes a processor. The central ECU 12 is connected to the brake ECU 11 so as to be able to communicate with each other.

[0015] As shown in Fig. 1, four wheel speed sensors 15 are installed on the vehicle 10 so as to correspond to the respective wheels, namely, FR wheels 17, FL wheels 18, RR wheels 19, and RL wheels 20. As shown in Fig. 1, each wheel speed sensor 15 is wired and connected to the brake ECU 11 via a communication line 16. In this way, the brake ECU 11 is an electronic control device directly connected to the wheel speed sensors 15.

[0016] Each wheel speed sensor 15 detects the rotation speed of the wheel corresponding to it. Then, each wheel speed sensor 15 transmits the detected rotation speed as a pre-processing wheel speed to the brake ECU 11 via the communication line 16. In this way, the brake ECU 11 obtains the pre-processing wheel speed detected by the wheel speed sensor 15.

[0017] 1, the determination device 21 includes a storage device 23 in which a program is stored, and a processing circuit 22 that executes various processes by executing the program stored in the storage device 23. The processing circuit 22 includes a processor.

[0018] The determination device 21 is connected to the information transmitting device so as to be able to communicate with the central ECU 12. Based on the information received from the information transmitting device, the determining device 21 determines whether or not there is an abnormality in the wheels of the vehicle 10. The determining device 21 determines whether or not there is loosening of the fastening between the wheel and the hub as the abnormality in the wheel.

[0019] 2 shows a mode of communication between an information transmitting device, which is constituted by the brake ECU 11, the central ECU 12, and the wheel speed sensor 15, and a determination device 21 in the determination system 100. In FIG. 2, the processing executed by the central ECU 12 is executed by a processing circuit 13. Also, in FIG. 2, the processing executed by the determination device 21 is executed by a processing circuit 22.

[0020] The sequence diagram of FIG. 2 will be described below with reference to FIGS. <Outline of pre-processing wheel speed> 2, in the determination system 100, the wheel speed sensor 15 transmits the pre-processing wheel speed to the brake ECU 11. The characteristics of the pre-processing wheel speed will be described below with reference to FIGS.

[0021] Fig. 3 shows an example of the transition of pre-processing wheel speed when there is no looseness in the connection between the wheel and the hub. The graph shown in Fig. 3 shows the pre-processing wheel speed of the front wheel rear wheel 17, for example, detected by the wheel speed sensor 15 corresponding to the front wheel rear wheel 17.

[0022] In the graph of Fig. 3, the vertical axis represents pre-processing wheel speed. Also, in the graph of Fig. 3, the horizontal axis represents time. Therefore, Fig. 3 shows the transition of pre-processing wheel speed over time. The vertical and horizontal axes of the graph are the same for Figs. 4 and 5.

[0023] The pre-processing wheel speed fluctuates minutely due to the influence of small irregularities on the road surface, the influence of the wheel tread pattern, etc. Therefore, the pre-processing wheel speed shown in Figure 3 fluctuates minutely over time.

[0024] Fig. 4 shows an example of the transition of the pre-processing wheel speed when there is loosening in the fastening between the wheel and the hub. The graph shown in Fig. 4 shows the pre-processing wheel speed of the FR wheel 17 detected by the wheel speed sensor 15 corresponding to the FR wheel 17 when, for example, the bolt fastening the FR wheel 17 to the FR hub 24 is loosened by one turn. Note that the pre-processing wheel speed shown in Fig. 4 is assumed to be detected under the same conditions as when the pre-processing wheel speed shown in Fig. 3 was detected, except for the loosening of the bolt. In other words, the pre-processing wheel speed shown in Fig. 4 is the pre-processing wheel speed detected when the vehicle 10 travels at the same speed at the same location as when the pre-processing wheel speed shown in Fig. 3 was detected.

[0025] Comparing Figure 3 and Figure 4, the amplitude of the graph is larger in Figure 4. In other words, the pre-processing wheel speed when there is looseness in the fastening between the wheel and hub has a larger change amount than the pre-processing wheel speed when there is no looseness.

[0026] FIG. 5 shows an example of the transition of the pre-processing wheel speed when the vehicle 10 travels on a road surface that is more uneven than the situation in FIG. 3 with no loosening in the fastening between the wheel and the hub. The graph shown in FIG. 5 shows the pre-processing wheel speed of the front wheel rear wheel 17 detected by the wheel speed sensor 15 corresponding to the front wheel rear wheel 17 when, for example, the vehicle 10 travels on a road surface that is more uneven than the road surface on which the pre-processing wheel speed shown in FIG. 3 was detected. Note that the pre-processing wheel speed shown in FIG. 5 is assumed to be detected under the same conditions as the pre-processing wheel speed shown in FIG. 3, except that the road surface traveled on is more uneven. In other words, the pre-processing wheel speed shown in FIG. 5 is the pre-processing wheel speed detected when the vehicle 10 travels at the same speed as when the pre-processing wheel speed shown in FIG. 3 was detected.

[0027] In Fig. 5, the area surrounded by the dotted line reflects the pre-processing wheel speed when the vehicle 10 travels on a road surface that is more uneven than the road surface in Fig. 3. On the other hand, in the area not surrounded by the dotted line in Fig. 5, the vehicle 10 travels on a road surface with approximately the same degree of unevenness as the road surface traveled in Fig. 3.

[0028] As shown in Fig. 5, the amplitude of the graph is approximately the same in the areas not surrounded by the dotted line as in the graph in Fig. 3, because the magnitude of the unevenness of the road surface on which the vehicle is traveling is approximately the same. On the other hand, the amplitude of the area surrounded by the dotted line in Fig. 5 is larger than that in the graph in Fig. 3. In other words, even if there is no looseness in the connection between the wheel and the hub, the larger the unevenness of the road surface, the larger the amount of change in the pre-processing wheel speed.

[0029] As shown and explained in Figure 3, the pre-processing wheel speed fluctuates slightly due to the influence of small irregularities in the road surface, the influence of the wheel tread pattern, etc. And, as shown and explained in Figure 4, when there is looseness in the fastening between the wheel and hub, the amount of change in the pre-processing wheel speed is larger than when there is no looseness. On the other hand, as shown and explained in Figure 5, even if there is no looseness in the fastening between the wheel and hub, when the road surface is large, the amount of change in the pre-processing wheel speed is larger than when the unevenness is small.

[0030] As described with reference to FIG. 2, the wheel speed sensor 15 transmits the pre-processing wheel speed having such characteristics to the brake ECU 11. <Outline of the fluctuation value and fluctuation amount calculated in the determination system 100> As shown in the upper part of FIG. 2, the brake ECU 11 receives the pre-processing wheel speed and calculates a fluctuation value and a fluctuation amount from the received pre-processing wheel speed.

[0031] The fluctuation value and the fluctuation amount will be described below with reference to FIGS. Fig. 6 shows an example of the transition between the pre-processing wheel speed and the post-processing wheel speed calculated based on the pre-processing wheel speed. In Fig. 6, the graph shown by the dotted line is the same as the graph of the pre-processing wheel speed shown in Fig. 3. On the other hand, in Fig. 6, the graph shown by the solid line shows the transition of the post-processing wheel speed calculated based on the pre-processing wheel speed in Fig. 3. In Fig. 6, the horizontal axis represents time, as in Fig. 3.

[0032] The processed wheel speed is a value obtained by applying low-pass filtering to the unprocessed wheel speed. Specifically, the processed wheel speed shown in Fig. 6 indicates a value obtained by applying 2 Hz low-pass filtering to the unprocessed wheel speed shown in Fig. 3. Note that the filter value used for the low-pass filtering is not limited to 2 Hz.

[0033] The processed wheel speed, which is obtained by applying low-pass filtering to the unprocessed wheel speed, is a value that removes small fluctuations in the unprocessed wheel speed. In other words, the processed wheel speed is a value that reflects rough fluctuations in the unprocessed wheel speed. Therefore, as shown in Figure 6, the unprocessed wheel speed fluctuates up and down around the unprocessed wheel speed.

[0034] In the upper part of FIG. 2, the brake ECU 11 calculates a fluctuation value and a fluctuation amount from the pre-processing wheel speed and the post-processing wheel speed as shown in FIG. The fluctuation value is a value indicating the difference between the pre-processing wheel speed and the post-processing wheel speed, that is, the fluctuation value indicates minute fluctuations in the pre-processing wheel speed.

[0035] The amount of fluctuation is the absolute value of the fluctuation value. Figures 7 and 8 are graphs showing an example of the change in the amount of fluctuation over time. In Figures 7 and 8, the horizontal axis represents time, as in Figure 3.

[0036] Specifically, Fig. 7 shows the transition of the amount of fluctuation, which is the absolute value of the fluctuation value, which is the difference between the pre-processing wheel speed and the post-processing wheel speed shown in Fig. 6. In Fig. 7, where the amplitude is large, the deviation between the solid line and the dotted line in Fig. 6 at the same time is also large. On the other hand, in Fig. 7, where the value is zero, the solid line and the dotted line in Fig. 6 at the same time overlap.

[0037] The fluctuation amounts shown in Fig. 7 are calculated based on the pre-processing wheel speeds shown in Fig. 3. In other words, the fluctuation amounts shown in Fig. 7 show an example of how the fluctuation amounts change when there is no loosening in the fastening between the wheel and the hub.

[0038] On the other hand, Fig. 8 shows the change in the amount of fluctuation calculated based on the pre-processing wheel speed shown in Fig. 4. In other words, the amount of fluctuation shown in Fig. 8 shows an example of the change in the amount of fluctuation when there is looseness in the fastening between the wheel and the hub.

[0039] As can be seen from a comparison of Figure 7 and Figure 8, the amplitude of the graph of the amount of fluctuation shown in Figure 8 tends to be larger than the amplitude of the graph of the amount of fluctuation shown in Figure 7. In this way, the amount of fluctuation is larger when there is looseness in the fastening between the wheel and the hub than when there is no looseness.

[0040] The determination device 21 uses these characteristics of the fluctuation amount to determine whether or not there is loosening in the fastening between the wheel and the hub based on the transition of the fluctuation value. As mentioned above, the fluctuation value indicates small fluctuations in the pre-processing wheel speed. Therefore, by using the transition of the fluctuation value, the determination device 21 can determine whether loosening has occurred in the fastening between the wheel and the hub at the stage when changes in the fluctuation amount begin to appear.

[0041] As shown in the upper part of Fig. 2, the brake ECU 11 calculates the fluctuation value and fluctuation amount having the above-described characteristics based on the pre-processing wheel speed received from the wheel speed sensor 15. Then, in the determination system 100, the determination device 21 determines whether or not there is an abnormality in the wheel based on the transition of the fluctuation value calculated by the brake ECU 11, which is directly connected to the wheel speed sensor 15. Because the brake ECU 11 is directly connected to the wheel speed sensor 15 via the communication line 16, it can acquire the pre-processing wheel speed with high resolution. Therefore, the brake ECU 11 can calculate a precise fluctuation value.

[0042] <Outline of time integral value calculated in determination system 100> 2, the brake ECU 11 calculates the fluctuation value and the fluctuation amount, and then calculates the time integral value of the fluctuation amount over a predetermined period of time. At this time, the brake ECU 11 periodically calculates the time integral value.

[0043] The time integral value will be described below with reference to FIGS. The time integral value of the amount of fluctuation over a predetermined period when there is looseness in the fastening between the wheel and the hub is larger than when there is no looseness, because the amount of fluctuation is larger when there is looseness in the fastening between the wheel and the hub than when there is no looseness.

[0044] As shown in FIG. 5 and explained above, even if there is no loosening in the fastening between the wheel and the hub, when the road surface is rough, the amount of change in the pre-processing wheel speed is larger than when the roughness is small. For example, when a large bump is passed over, the amplitude of the fluctuation value may momentarily increase. Even in such a momentary event, if the amplitude is very large, the time integral value of the fluctuation amount may become large, which may result in an erroneous judgment. For this reason, an upper limit is set for the amount of fluctuation used by the judgment device 21 to calculate the time integral value used for judgment.

[0045] Fig. 9 shows an amount of fluctuation with an upper limit value that is referenced in the determination system 100 in order to calculate a time integral value from the amount of fluctuation shown in Fig. 7 when the amount of fluctuation is calculated. As shown in Fig. 9, the upper limit value is set to 0.04 in the determination system 100. In the present invention, the upper limit value is not limited to 0.04.

[0046] The upper limit value set in the determination system 100 is set in consideration of the characteristics of the vehicle 10. The characteristics of the vehicle 10 are characteristics that affect the fluctuation value of the wheels. Examples of the characteristics of the vehicle 10 include the size and weight of the wheels equipped on the vehicle 10. Examples of the characteristics of the vehicle 10 may include the weight of the vehicle 10 itself and the vibration transmissibility of the suspension equipped on the vehicle 10.

[0047] For example, if the characteristics of the vehicle 10 make it easy to reduce the amount of fluctuation, the upper limit value is set low. Such an upper limit value may be set in advance in accordance with the characteristics of the vehicle 10. Furthermore, a value calculated based on the history of past changes in the amount of fluctuation may be set as such an upper limit value.

[0048] The determination device 21 determines whether or not there is loosening in the fastening between the wheel and the hub based on the time integral of the amount of variation over a predetermined period as shown in Fig. 9. In the determination system 100, for example, in order for the determination device 21 to make a determination, the period T1 shown in Fig. 9 is set as the predetermined period and the time integral of the amount of variation shown in Fig. 9 over this predetermined period is calculated. In this way, the time integral used by the determination device 21 to make a determination is a value calculated using multiple amounts of variation over a predetermined period in which any amount of variation that exceeds an upper limit value is replaced with a value equal to the upper limit value.

[0049] Fig. 10 shows an upper limit-attached variation amount that is referenced by the determination system 100 in order to calculate a time integral value from the variation amount when the variation amount shown in Fig. 8 is calculated. Similarly, in Fig. 10, the period T1 is set as a predetermined period, and the time integral value of the variation amount for the predetermined period is calculated.

[0050] The time integral value of the fluctuation amount with an upper limit value in a predetermined period shown in Fig. 10 is greater than the time integral value of the fluctuation amount with an upper limit value shown in Fig. 9. In this way, even when an upper limit value is introduced into the fluctuation amount, the time integral value of the fluctuation amount when there is looseness in the fastening between the wheel and the hub is greater than when there is no looseness.

[0051] As shown in the upper part of Figure 2, the brake ECU 11 periodically calculates a time integral value from the amount of fluctuation. The determination device 21 then uses the time integral value of the amount of fluctuation over a predetermined period to determine whether or not the fastening between the wheel and the hub has loosened. As mentioned above, the pre-processing wheel speed may fluctuate significantly instantaneously due to external factors such as road surface irregularities. By making a determination using the time integral value, which is a value that summarizes information on the magnitude of the amount of fluctuation over a predetermined period, a more accurate determination can be made.

[0052] <Outline of gradient calculated in determination system 100> As shown in the upper part of FIG. 2, the brake ECU 11 calculates the time integral value, and then calculates the gradient of the calculated time integral value.

[0053] The gradient will be explained below with reference to FIG. FIG. 11 shows an example of the transition of the cumulative total of the time integral value calculated by the determination system 100. In FIG.

[0054] As described above, the time integral value is calculated periodically. Specifically, the brake ECU 11 calculates the time integral value for each predetermined period T1 shown in Fig. 9 and Fig. 10. The points shown in Fig. 11 indicate the cumulative total of the time integral values ​​calculated by the brake ECU 11 for each predetermined period. Therefore, the value indicated by each point in Fig. 11 is the value indicated by the previous point plus the calculated time integral value.

[0055] As shown in Fig. 11, the brake ECU 11 accumulates the time integral values ​​calculated for each predetermined period. Then, the brake ECU 11 calculates the gradient of the time integral value for the calculation period using multiple time integral values ​​calculated for a calculation period longer than the predetermined period. In this embodiment, the calculation period is the period TA shown in Fig. 11.

[0056] The brake ECU 11 calculates the gradient from the cumulative total of the time integrals calculated during the period TA, which is the period to be included in the calculation. The straight line shown in Fig. 11 represents the regression line of the cumulative total of the time integrals. The brake ECU 11 calculates the gradient of the regression line as the gradient of the time integrals during the period to be included in the calculation. The determination device 21 determines whether there is loosening of the connection between the wheel and the hub based on the gradient calculated in this way.

[0057] As mentioned above, the time integral value of the amount of fluctuation over a predetermined period when there is looseness in the fastening between the wheel and the hub is larger than when there is no looseness, so the gradient of the time integral value over the included period is larger when there is looseness than when there is no looseness.

[0058] Based on these characteristics, the determination device 21 can determine that there is looseness in the connection between the wheel and the hub when it determines that the gradient calculated by the brake ECU 11 is large. As shown in the upper part of Figure 2, the brake ECU 11, which has calculated the gradient, transmits the calculated gradient to the central ECU 12.

[0059] <Processing in the central ECU 12> Hereinafter, with reference to FIG. 2, a description will be given of the manner in which the central ECU 12 and the determination device 21 communicate with each other so that the determination device 21 can determine whether or not there is loosening in the fastening between the wheel and the hub based on the gradient.

[0060] 2, the central ECU 12, upon receiving the gradient, executes a threshold setting process. As will be described later, the determination device 21 compares the gradient with a threshold to determine whether or not there is loosening of the fastening between the wheel and the hub. In the threshold setting process, the central ECU 12 sets a threshold to be used by the determination device 21.

[0061] For example, the central ECU 12 stores a reference threshold value in advance in the storage device 14. Then, in the threshold value setting process, the central ECU 12 sets a threshold value by applying a correction based on the characteristics of the vehicle 10 to the threshold value stored in the storage device 14. The central ECU 12 may calculate the reference threshold value based on the history of past gradients for the vehicle 10, rather than storing the reference threshold value in advance in the storage device 14.

[0062] In the threshold setting process, the central ECU 12 sets the threshold taking into consideration the characteristics of the vehicle 10. For example, if the characteristics of the vehicle 10 are such that the amount of fluctuation is likely to increase, the threshold is set high.

[0063] In the threshold setting process, the central ECU 12 may set a common threshold for the FR wheels 17, the FL wheels 18, the RR wheels 19, and the RL wheels 20. Note that in the threshold setting process, the central ECU 12 may set different thresholds for each of the FR wheels 17, the FL wheels 18, the RR wheels 19, and the RL wheels 20.

[0064] 2, after executing the threshold setting process, the central ECU 12 transmits the gradient received from the brake ECU 11 to the determination device 21. Also, as shown in the middle part of FIG. 2, the central ECU 12 transmits the threshold set in the threshold setting process to the determination device 21.

[0065] 2, when transmitting the gradient, the central ECU 12 transmits information indicating the state of the vehicle 10. The state of the vehicle 10 is information regarding the traveling state of the vehicle 10 during the period included in the calculation of the gradient transmitted in the middle part of FIG.

[0066] The central ECU 12 transmits information about the functions that the vehicle 10 was operating during the calculation period as information indicating the state of the vehicle 10. For example, if the vehicle 10 had an anti-lock brake system activated, the central ECU 12 transmits information indicating that the vehicle 10 had the anti-lock brake system activated as information indicating the state of the vehicle. For example, if the vehicle 10 had a traction control system activated, the central ECU 12 transmits information indicating that the vehicle 10 had the traction control system activated as information indicating the state of the vehicle. For example, if the vehicle 10 had a vehicle stability control system activated, the central ECU 12 transmits information indicating that the vehicle 10 had the vehicle stability control system activated as information indicating the state of the vehicle.

[0067] The central ECU 12 transmits information indicating that the vehicle 10 was traveling on a rough road during the calculation period as information indicating the state of the vehicle 10. At this time, the central ECU 12 determines that the vehicle 10 is traveling on a rough road, for example, from information from a camera provided on the vehicle 10. The central ECU 12 may also determine that the vehicle 10 is traveling on a rough road, for example, from a change in the traveling speed of the vehicle 10.

[0068] In this way, the information transmitting device acquires the pre-processing wheel speed detected by the wheel speed sensor 15 that detects the rotational speed of the wheels equipped on the vehicle 10. Then, the information transmitting device calculates a fluctuation value, which is the difference between the acquired pre-processing wheel speed and the post-processing wheel speed obtained by applying low-pass filter processing to the pre-processing wheel speed. Thereafter, the information transmitting device transmits the calculated fluctuation value to the determination device 21.

[0069] The information transmitting device also periodically calculates a time integral of the amount of fluctuation, which is the absolute value of the fluctuation, over a predetermined period. The information transmitting device then calculates the gradient of the time integral over the inclusion period using multiple time integrals calculated over an inclusion period longer than the predetermined period. The information transmitting device then transmits the calculated gradient to the determination device 21.

[0070] <Processing Mode of Determination Device 21> As shown in the lower part of Figure 2, the determination device 21 receives the gradient, threshold value, and information indicating the state of the vehicle 10 from the central ECU 12, and determines whether it is possible to determine whether there is loosening in the connection between the wheel and the hub.

[0071] In determining whether or not the determination is possible, the determination device 21 checks the received information indicating the state of the vehicle 10. For example, if the vehicle 10 is not in a normal running state, such as when the vehicle 10 suddenly decelerates, the pre-processing wheel speed detected by the wheel speed sensor 15 will also be different from the normal one. Based on the fluctuation value calculated in such a state, the determination device 21 cannot make an accurate determination.

[0072] When the vehicle 10 suddenly decelerates, the vehicle 10 activates the anti-lock brake system. In this way, the functions activated by the vehicle 10 may reflect that the vehicle 10 is not in a normal driving state. When the vehicle 10 is in a state where a function that is activated when the vehicle 10 is not in a normal driving state is activated, the vehicle 10 does not determine whether there is loosening of the fastening with the wheel hub. For example, when the received information indicating the vehicle state indicates that the vehicle 10 is activating an anti-lock brake system, a traction control system, a vehicle stability control system, or the like, the determination device 21 does not determine whether there is loosening of the fastening with the wheel hub.

[0073] In this way, the determination device 21 does not use the transition of the fluctuation value calculated based on the pre-processing wheel speed detected by the wheel speed sensor 15 while the vehicle 10 is operating the anti-lock brake system to determine whether or not there is an abnormality in the wheel. Furthermore, the determination device 21 does not use the transition of the fluctuation value calculated based on the pre-processing wheel speed detected by the wheel speed sensor 15 while the vehicle 10 is operating the traction control system to determine whether or not there is an abnormality in the wheel. Furthermore, the determination device 21 does not use the transition of the fluctuation value calculated based on the pre-processing wheel speed detected by the wheel speed sensor 15 while the vehicle 10 is operating the vehicle stability control system to determine whether or not there is an abnormality in the wheel.

[0074] As mentioned above, even if there is no looseness in the fastening between the wheel and the hub, if the road surface is very uneven, the amount of change in the pre-processing wheel speed will be larger than if the road surface is only slightly uneven. Therefore, on a bad road with a very uneven road surface, the determination device 21 cannot make an accurate determination.

[0075] When the vehicle 10 receives information indicating that the vehicle 10 has been traveling on a rough road as information indicating the vehicle state, the vehicle 10 does not determine whether the fastening between the wheel and the hub has loosened. In this way, the determination device 21 does not use the transition of the fluctuation value calculated based on the pre-processing wheel speed detected by the wheel speed sensor 15 while the vehicle 10 is traveling on a rough road to determine whether there is an abnormality in the wheel.

[0076] As shown in the lower part of Fig. 2, when the determination device 21 determines that it is possible to determine whether or not there is looseness in the fastening between the wheel and the hub, it executes a looseness determination process. In the looseness determination process, the determination device 21 compares the gradient received in the middle part of Fig. 2 with a threshold value. Then, if the gradient is equal to or greater than the threshold value, the determination device 21 determines that there is looseness in the fastening between the wheel and the hub for the wheel whose pre-processing wheel speed that is the basis of the gradient has been detected.

[0077] As shown in the lower part of FIG. 2 , if the determination device 21 determines that there is looseness between a wheel and a hub of the vehicle 10, it sends a warning to the central ECU 12. In the looseness determination process, the determination device 21 compares the gradients of the FR wheels 17, FL wheels 18, RR wheels 19, and RL wheels 20 with a threshold value. If the determination device 21 determines that there is looseness between the hub and any of the FR wheels 17, FL wheels 18, RR wheels 19, and RL wheels 20, it sends a warning to the central ECU 12. At this time, the determination device 21 sends a warning that includes information about the wheel determined to have looseness between the hub and the wheel and a message indicating that there is a possibility that there is looseness in the wheel's connection to the hub. The central ECU 12, for example, displays a warning message on the display of the vehicle 10 based on the received information. In this way, when the determination device 21 determines that there is an abnormality in a wheel, it notifies the user of the vehicle 10 that there is an abnormality in the wheel.

[0078] <Operation of this embodiment> The pre-processing wheel speed fluctuates minutely due to factors such as small irregularities in the road surface and the wheel tread pattern. The processed wheel speed, which is obtained by applying low-pass filtering to the pre-processing wheel speed, is a value that excludes these small fluctuations. In other words, the processed wheel speed is a value that reflects the rough fluctuations in the pre-processing wheel speed. When an abnormality occurs in the wheel, the amount of fluctuation, which is the absolute value of the fluctuation value, becomes large. By using the transition of the fluctuation value, which is a value that indicates the fine fluctuations in the pre-processing wheel speed, it is possible to determine the occurrence of an abnormality when a change in the amount of fluctuation begins to appear.

[0079] <Effects of this embodiment> (1) The above-described determination device 21 can determine whether or not there is an abnormality in the wheel before it significantly affects the running of the vehicle.

[0080] (2) The determination device 21 determines whether or not there is looseness in the fastening between the wheel and the hub as an abnormality in the wheel. If there is looseness in the fastening between the wheel and the hub, the amount of fluctuation increases. As the looseness progresses gradually, the amount of fluctuation increases gradually. The determination device 21 determines whether or not there is looseness using the transition of the fluctuation value, and therefore can determine the occurrence of looseness while the looseness is progressing, that is, before it has a significant impact on the running of the vehicle 10.

[0081] (3) The determination device 21 determines whether or not the fastening between the wheel and the hub has loosened using the time integral of the amount of variation, which is the absolute value of the variation, over a predetermined period of time. The time integral of the amount of variation when the fastening between the wheel and the hub is loose will be larger than when there is no abnormality in the wheel. The time integral of the amount of variation is a value that summarizes information on the magnitude of the amount of variation over a predetermined period of time. The pre-processing wheel speed may fluctuate greatly instantaneously due to external factors such as unevenness of the road surface. The determination device 21 determines whether or not the fastening between the wheel and the hub has loosened based on the time integral of the amount of variation. This allows the determination device 21 to prevent erroneous determinations from being made based on instantaneous changes in the value of the variation.

[0082] (4) An upper limit is set for the amount of fluctuation used to calculate the time integral value. The time integral value used by the determination device 21 is a value calculated using multiple amounts of fluctuation over a predetermined period, in which any amount of fluctuation exceeding the upper limit is replaced with a value equal to the upper limit.

[0083] For example, when the vehicle 10 passes over a large bump, the amplitude of the fluctuation value may momentarily increase. Even in such a momentary event, if the amplitude is very large, the time integral value of the fluctuation amount may become large, which may cause the determination device 21 to make an erroneous determination. In contrast, the time integral value used by the determination device 21 for determination is a value calculated using multiple fluctuation amounts over a predetermined period in which fluctuation amounts exceeding an upper limit value are replaced with a value equal to the upper limit value. Therefore, even if the amplitude of the fluctuation value momentarily increases, the time integral value reflects a value limited by the upper limit value. Therefore, the determination device 21 can suppress the influence of momentary events on the determination and make a highly accurate determination.

[0084] (5) The time integral value is calculated periodically. The determination device 21 determines whether or not there is loosening of the fastening between the wheel and the hub based on the gradient of the time integral value during the calculation period, which is calculated using multiple time integral values ​​calculated during the calculation period that is longer than the predetermined period.

[0085] If driving continues with looseness between the wheel and hub, the loosening will gradually progress. As a result, the time integral value of the amount of variation will gradually increase. Therefore, if looseness progresses, a change will appear in the gradient of the time integral value during the calculation period. The determination device 21 uses the gradient of the time integral value to determine whether there is looseness between the wheel and hub. The determination device 21 can detect looseness as it progresses by monitoring changes that appear in the gradient.

[0086] (6) When the gradient is equal to or greater than a threshold, the determination device 21 determines that there is loosening in the fastening between the wheel and the hub. The determination device 21 can detect that the loosening is progressing based on the increase in the gradient and determine that loosening has occurred.

[0087] (7) The determination device 21 does not use the change in the fluctuation value calculated based on the pre-processing wheel speed detected by the wheel speed sensor 15 while the vehicle 10 is operating the anti-lock brake system to determine whether or not there is an abnormality in the wheel.

[0088] The determination device 21 may not be able to accurately determine whether or not there is an abnormality in the wheel depending on the running state of the vehicle 10, such as when the vehicle 10 is suddenly decelerating. Therefore, it is desirable that the vehicle 10 is in a normal running state when the determination device 21 determines whether or not there is an abnormality in the wheel.

[0089] When the vehicle 10 is suddenly decelerating, the antilock brake system of the vehicle 10 is activated. The determination device 21 does not determine whether there is an abnormality in the wheel when the vehicle 10 is activating the antilock brake system. This allows the determination device 21 to suppress erroneous determinations.

[0090] (8) The determination device 21 does not use the trend in the fluctuation value calculated based on the pre-processing wheel speed detected by the wheel speed sensor 15 while the vehicle 10 is operating the traction control system to determine whether or not there is an abnormality in the wheel.

[0091] When the traction control system is activated, the vehicle 10 is not in a normal driving state, and therefore the determination device 21 cannot make an accurate determination. When the traction control system is activated, the determination device 21 does not determine whether there is an abnormality in the wheels. This allows the determination device 21 to suppress erroneous determinations.

[0092] (9) The determination device 21 does not use the trend in the fluctuation value calculated based on the pre-processing wheel speed detected by the wheel speed sensor 15 while the vehicle 10 is operating the vehicle stability control system to determine whether or not there is an abnormality in the wheel.

[0093] When the vehicle 10 is operating the vehicle stability control system, the vehicle is not in a normal driving state and therefore an accurate determination cannot be made. When the vehicle 10 is operating the vehicle stability control system, the determination device 21 does not determine whether there is an abnormality in the wheel. This allows the determination device 21 to suppress erroneous determinations.

[0094] (10) The determination device 21 does not use the change in the fluctuation value calculated based on the pre-processing wheel speed detected by the wheel speed sensor 15 while the vehicle 10 is traveling on a rough road to determine whether or not there is an abnormality in the wheel.

[0095] When the vehicle 10 is traveling on a rough road, the determination device 21 cannot make an accurate determination. When the vehicle 10 is traveling on a rough road, the determination device 21 does not determine whether there is an abnormality in the wheel. This allows the determination device 21 to suppress erroneous determination.

[0096] (11) The vehicle 10 includes a brake ECU 11, which is an electronic control device directly connected to the wheel speed sensor 15. The determination device 21 determines whether or not there is an abnormality in the wheel based on the transition of the fluctuation value calculated by the brake ECU 11.

[0097] The brake ECU 11 is directly connected to the wheel speed sensor 15, and therefore can acquire a pre-processing wheel speed value with high resolution. This allows the brake ECU 11 to calculate an accurate fluctuation value. The determination device 21 determines whether or not there is an abnormality in the wheel based on the fluctuation value calculated by the brake ECU 11. This allows the determination device 21 to make a more accurate determination.

[0098] (12) The information transmitting device acquires a pre-processing wheel speed detected by the wheel speed sensor 15 that detects the rotational speed of the wheels equipped on the vehicle 10. The information transmitting device calculates a fluctuation value, which is the difference between the acquired pre-processing wheel speed and a post-processing wheel speed obtained by applying low-pass filter processing to the pre-processing wheel speed. The information transmitting device transmits the calculated fluctuation value to the determination device 21.

[0099] The information transmitting device transmits a variation value required to determine whether or not there is an abnormality in the wheel to the determining device 21. In this way, the information transmitting device can cause the determining device 21 to determine whether or not there is an abnormality in the wheel.

[0100] (13) The information transmitting device periodically calculates a time integral of the amount of fluctuation, which is the absolute value of the fluctuation, over a predetermined period. The information transmitting device calculates the gradient of the time integral over the period using multiple time integrals calculated over a period longer than the predetermined period. The information transmitting device transmits the calculated gradient to the determination device 21.

[0101] The information transmitting device transmits the gradient of the time integral value to the determining device 21. In this way, the information transmitting device can cause the determining device 21 to determine the presence or absence of an abnormality in the wheel based on the gradient of the time integral value.

[0102] (14) The determination system 100 is composed of an information transmission device and a determination device 21. The information transmission device acquires a pre-processing wheel speed detected by a wheel speed sensor 15 that detects the rotational speed of the wheels equipped on the vehicle 10. The information transmission device calculates a fluctuation value, which is the difference between the acquired pre-processing wheel speed and a post-processing wheel speed obtained by applying low-pass filter processing to the pre-processing wheel speed. The information transmission device transmits the calculated fluctuation value to the determination device 21. The determination device 21 determines whether or not there is an abnormality in the wheel based on the change in the received fluctuation value. When the determination device 21 determines that there is an abnormality in the wheel, it notifies the user of the vehicle 10 that there is an abnormality in the wheel.

[0103] The determination system 100 determines whether or not there is an abnormality in the wheel by observing the transition of the variable value. In this way, the determination system 100 can notify the user of the existence of an abnormality in the wheel before it significantly affects driving.

[0104] (15) In the determination system 100, the determination device 21 determines whether or not there is loosening between the wheel and the hub as an abnormality in the wheel. This allows the determination system 100 to warn the user of the occurrence of loosening while the loosening is progressing, that is, before it significantly affects the running of the vehicle 10.

[0105] <Example of change> This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0106] In the above embodiment, the determination device 21 determines whether or not there is looseness between the wheel and the hub as an abnormality in the wheel. However, the abnormality in the wheel determined by the determination device 21 is not limited to whether or not there is looseness between the wheel and the hub. For example, the determination device 21 can also detect an abnormality in the wheel when the air pressure in the wheel is inappropriate or when only one wheel of the vehicle 10 is equipped with a studless tire.

[0107] In the above embodiment, the determination device 21 determines whether there is looseness between the FR wheels 17, FL wheels 18, RR wheels 19, and RL wheels 20 and the hubs. However, the number of wheels for which the determination device 21 determines whether there is looseness is not limited to that in the above embodiment. For example, the determination device 21 may determine whether there is looseness between the FR wheels 17 and the FR hub 24 after calculating the gradient only for the FR wheels 17. In this case, the information transmission device does not need to be equipped with wheel speed sensors 15 corresponding to wheels other than the FR wheels 17.

[0108] In the above embodiment, as shown in FIG. 1, the brake ECU 11 is connected to the wheel speed sensor 15 via a wired connection via the communication line 16. However, the brake ECU 11 may be connected to the wheel speed sensor 15 wirelessly.

[0109] In the above embodiment, as shown in FIG. 2 and explained, the determination device 21 determines whether or not the determination can be made before performing the slack determination process. On the other hand, in the determination system 100, the determination whether or not the determination can be made may be made by the information transmission device. For example, the central ECU 12 in the information transmission device determines whether or not the determination device 21 can perform the slack determination process based on information indicating the state of the vehicle 10. Then, the central ECU 12 may adopt a configuration in which, if the determination device 21 determines that the slack determination process cannot be performed, the central ECU 12 does not transmit information such as the gradient to the determination device 21.

[0110] In the above embodiment, as shown in FIG. 2 and explained, the determination device 21 determines whether or not the determination can be made before performing the loosening determination process. On the other hand, the determination device 21 does not have to determine whether or not the determination can be made. In other words, the determination device 21 may always make a determination without determining whether or not the determination can be made. In this case, the central ECU 12 does not need to transmit information indicating the characteristics of the vehicle 10 in the middle part of FIG. 2.

[0111] In the above embodiment, as shown in FIG. 2, the brake ECU 11 calculates the fluctuation value and the fluctuation amount. However, it is not necessary for the brake ECU 11 to calculate the fluctuation value and the fluctuation amount. For example, the central ECU 12 may calculate the fluctuation value and the fluctuation amount from the pre-processing wheel speed. Also, for example, the determination device 21 may calculate the fluctuation value and the fluctuation amount from the pre-processing wheel speed.

[0112] In the above embodiment, as shown in FIG. 2, the brake ECU 11 calculates the time integral value. However, it is not necessary for the brake ECU 11 to calculate the time integral value. For example, the central ECU 12 may calculate the time integral value from the amount of fluctuation. Also, for example, the determination device 21 may calculate the time integral value from the amount of fluctuation.

[0113] In the above embodiment, as shown in FIG. 2 and described above, the brake ECU 11 calculates the gradient. However, it is not necessary for the brake ECU 11 to calculate the gradient. For example, the central ECU 12 may calculate the gradient from a time integral value. Also, for example, the determination device 21 may calculate the gradient from a time integral value.

[0114] In the above embodiment, the central ECU 12 sets the threshold value as described with reference to Fig. 2. Alternatively, the determination device 21 may set the threshold value. 12 shows a mode of communication between an information transmitting device constituted by the brake ECU 11, the central ECU 12, and the wheel speed sensor 15, and the determination device 21 in the determination system 100 of the first modified example. In FIG. 12, the processing executed by the central ECU 12 is executed by the processing circuit 13. Also, in FIG. 12, the processing executed by the determination device 21 is executed by the processing circuit 22.

[0115] In FIG. 12, the communication mode from when the wheel speed sensor 15 transmits the unprocessed wheel speed until when the brake ECU 11 transmits the gradient is the same as in FIG. 12, the central ECU 12 receives the gradient and transmits the received gradient, information indicating the characteristics of the vehicle 10, and information indicating the state of the vehicle 10 to the determination device 21. Then, the determination device 21, having received the information from the central ECU 12, determines whether or not it is possible to determine whether or not there is loosening in the fastening between the wheel and the hub. At this time, the processing executed by the determination device 21 is the same as the processing executed by the determination device 21 in the lower part of FIG.

[0116] As shown in the lower part of Fig. 12, when the determination device 21 determines that it is possible to determine whether or not there is loosening in the fastening between the wheel and the hub, it executes a threshold setting process. The determination device 21, for example, stores a reference threshold in advance in the storage device 23. Then, in the threshold setting process, the determination device 21 sets a threshold by applying a correction based on the characteristics of the vehicle 10 to the threshold stored in the storage device 23. The determination device 21 may calculate the reference threshold based on the history of past gradients for the vehicle 10, rather than storing the reference threshold in the storage device 23 in advance.

[0117] In the threshold setting process, the determination device 21 sets a common threshold for the FR wheels 17, FL wheels 18, RR wheels 19, and RL wheels 20. Note that in the threshold setting process, the determination device 21 may set a threshold for each of the FR wheels 17, FL wheels 18, RR wheels 19, and RL wheels 20.

[0118] As shown in the lower part of Fig. 12, the determination device 21 executes a threshold setting process and then executes a looseness determination process. In the looseness determination process, the determination device 21 compares the gradient received in the middle part of Fig. 12 with the threshold set in the lower part of Fig. 12. If the gradient is equal to or greater than the threshold, the determination device 21 determines that there is looseness in the fastening between the wheel and the hub for which the pre-processing wheel speed used in calculating the gradient was detected.

[0119] 2, when the determination device 21 determines that there is looseness in the fastening between the wheel and the hub of the vehicle 10, the determination device 21 transmits a warning to the central ECU 12. The processing executed here is the same as the processing in the lower part of FIG. 2 in which the determination device 21 transmits a warning to the central ECU 12.

[0120] In the above embodiment, as shown in the middle part of Fig. 2, the central ECU 12 executes a threshold setting process. In the threshold setting process, the central ECU 12 sets a threshold by correcting a reference threshold. Alternatively, the central ECU 12 may determine an abnormality based on a comparison with a past gradient of the wheel being determined.

[0121] Fig. 13 shows an example of the transition of the cumulative total of the time integral values ​​calculated in the determination system 100 of the second modified example. In Fig. 14, the period TA is the same as the period TA shown in Fig. 11. Also, in Fig. 13, the periods TB, TC, TD, TE, and TF each indicate a period of the same length as the period TA shown in Fig. 11. Thus, in Fig. 13, TA, TB, TC, TD, TE, and TF each indicate a period of the same length as the period TA shown in Fig. 11.

[0122] Hereinafter, it is assumed that the transition of the cumulative time integral value shown in Fig. 13 is calculated from the pre-processing wheel speed detected at the FR wheel 17. In Fig. 13, the loosening of the fastening between the FR wheel 17 and the FR hub 24 starts to progress midway through the TD period.

[0123] As shown in Figure 13, the gradient calculated from the time integral value at the FR wheel 17 begins to increase from the period TD. Furthermore, the gradient calculated from the time integral value at the FR wheel 17 gradually increases after TD. This is because if driving continues with looseness between the wheel and the hub, the looseness gradually progresses, and the time integral value of the amount of variation gradually increases. In this way, the gradient calculated from the time integral value at the wheel increases as the looseness progresses, once the wheel becomes loose.

[0124] The determination device 21 can determine that loosening has occurred in the fastening between the wheel and the hub when the gradient of the time integral value calculated for the wheel being determined becomes larger than the past gradient for the same wheel.

[0125] 14 shows data that the central ECU 12 stores in the storage device 14 to set the threshold value in the determination system 100 of the second modified example. As shown in FIG. 14, the central ECU 12 stores in the storage device 14 the gradient of the time integral value of the wheel to be determined during the calculation period.

[0126] In Fig. 14, the gradient in the time period TA in Fig. 13 is A1. In Fig. 14, the gradients calculated in each calculation period in Fig. 13 are represented by symbols such as A1, A2, A3, etc. In the determination system 100 of the second modified example, when the central ECU 12 makes a determination for each of the FR wheels 17, FL wheels 18, RR wheels 19, and RL wheels 20, the central ECU 12 stores the gradient for each wheel.

[0127] As explained with reference to the upper part of FIG. 2, the brake ECU 11 transmits the gradient calculated by itself to the central ECU 12. The central ECU 12 sets the threshold value by using a moving average of the received gradients. The central ECU 12 stores the three most recent gradients received from the brake ECU 11. The central ECU 12 then sets the threshold value based on the three stored gradients. For example, the central ECU 12 sets the threshold value to a value greater than the average of the three stored gradients.

[0128] An example will be described below. For example, assume that the central ECU 12 has stored the gradients at TA, TB, and TC shown in FIG. 14 and receives the gradient at TD from the brake ECU 11. In this case, in the threshold setting process shown in FIG. 2, the central ECU 12 sets a value greater than the average of A1, A2, and A3 shown in FIG. 14 as the threshold. Thereafter, the central ECU 12 discards A1, which is the gradient at TA, and stores A4, which is a new gradient at TD, in the storage device 14. In this way, the central ECU 12 sets the threshold based on the stored gradient while updating the gradient stored in the storage device 14.

[0129] The number of gradients stored in the central ECU 12 is not limited to that in the second modified example. Furthermore, the manner in which the central ECU 12 sets the threshold value based on past gradients is not limited to the manner in which the threshold value is set to a value greater than the average of the gradients stored.

[0130] In the second modified example, the central ECU 12 sets the threshold value. On the other hand, as in the first modified example, the determination device 21 may set the threshold value based on the past gradient of the wheel to be determined. In this case, the determination device 21 sets the threshold value based on the gradient stored in the storage device 23.

[0131] In this way, the determination device 21 can determine whether or not there is loosening in the fastening between the wheel and the hub, using a threshold value that is set based on the past gradient of the wheel that is the subject of the determination. In this case, the determination device 21 uses a threshold value set based on the past gradient of the wheel being determined. As loosening progresses, the gradient of the time integral value increases. Based on data obtained from the wheel being determined, the determination device 21 can detect that loosening is progressing and determine whether loosening has occurred on that wheel.

[0132] In the above embodiment, the central ECU 12 executes a threshold setting process as shown in the middle part of Figure 2. In the threshold setting process, the central ECU 12 sets a threshold by correcting a reference threshold. Alternatively, the central ECU 12 may set a threshold based on the gradient of the time integral value of a wheel that is not a target of the determination, among the multiple wheels equipped on the vehicle 10.

[0133] Fig. 15 shows an example of the progress of the accumulation of the time integral value calculated in the determination system 100 of the third modified example. In the time integral value shown in Fig. 15, the period TA is the same as the included period TA shown in Fig. 11. Also, in the time integral value shown in Fig. 15, the periods TB, TC, TD, TE, and TF each indicate a period of the same length as the included period TA shown in Fig. 11. Thus, in Fig. 15, TA, TB, TC, TD, TE, and TF each indicate an included period.

[0134] 15 collectively shows the transition of the time integral values ​​for the FR wheel 17 and the FL wheel 18 of the vehicle 10. In FIG. 16, similar to FIG. 14, the loosening of the fastening between the FR wheel 17 and the FR hub 24 begins to progress midway through the TD period.

[0135] As shown in Figure 15, the gradient of the FR wheel 17 before the TD period is similar to the gradient of the FL wheel 18 during the same time period. Some factors that affect the pre-processing wheel speed affect the pre-processing wheel speed of each wheel on the vehicle 10 in the same manner. For example, changes in road surface conditions affect the pre-processing wheel speed of each wheel on the same vehicle in the same manner. Therefore, the gradient of the FR wheel 17 will be similar to the gradient of the other wheels on the vehicle 10 during the same time period as long as factors that affect the pre-processing wheel speed of a specific wheel on the vehicle 10 are not significantly affecting it.

[0136] As shown in Fig. 15, the gradient calculated from the time integral value for the FR wheel 17 increases after the TD period. The gradient for the FR wheel 17 after the TD period is greater than the gradient for the FL wheel 18 in the same time period. In this way, if loosening occurs in the fastening of one of multiple wheels on the same vehicle to the hub, the gradient for that wheel will be greater than the gradient for the other wheels.

[0137] The determination device 21 can determine that loosening has occurred in the fastening of the wheel to the hub when the gradient of the time integral value calculated for the wheel being determined becomes larger than the gradient for the same time period for other wheels equipped with that wheel.

[0138] The following describes the processes executed in the determination system 100 of the third modified example. In the determination system 100 of the third modified example, the central ECU 12 acquires the gradients for the FR wheels 17, FL wheels 18, RR wheels 19, and RL wheels 20 in the same time period. As described with reference to the upper part of Fig. 2, the brake ECU 11 transmits the calculated gradients to the central ECU 12. In the third modified example, the central ECU 12 starts executing the threshold setting process when the gradients for the FR wheels 17, FL wheels 18, RR wheels 19, and RL wheels 20 in the same time period are aligned.

[0139] In the threshold setting process, the central ECU 12 calculates the average gradient for the same time period for the wheels that are not the target of the determination among the multiple wheels of the vehicle 10. For example, when setting a threshold for determination for the FR wheels 17, the central ECU 12 calculates the average gradient for the FL wheels 18, RR wheels 19, and RL wheels 20 for the same time period. Then, the central ECU 12 sets the threshold based on the calculated average gradient. For example, the central ECU 12 sets a value greater than the calculated average gradient as the threshold for the FR wheels 17.

[0140] The manner in which the central ECU 12 sets the threshold value based on the gradient of the time integral value of a wheel that is not the target of the determination among the multiple wheels equipped on the vehicle 10 is not limited to the third modified example. For example, the central ECU 12 may set a value that is greater than the gradient of the FL wheel 18 in the same time period as the threshold value corresponding to the FR wheel 17.

[0141] In the third modified example, the central ECU 12 sets the threshold value. On the other hand, as in the first modified example, the determination device 21 may set the threshold value. In this case, the determination device 21 acquires information on the gradients of the multiple wheels of the vehicle 10 from the brake ECU 11.

[0142] In this way, the determination device 21 can determine whether or not there is loosening of the fastening between the wheel and the hub using a threshold value set based on the gradient at the same time period for a wheel that is not the subject of the determination among the multiple wheels equipped on the vehicle 10.

[0143] In this case, the determination device 21 uses as the threshold a value set based on the gradient of a wheel, among the multiple wheels of the vehicle 10, that is not the target of the determination during the same time period. If loosening occurs in the fastening of any of the multiple wheels to the hub, the gradient of the time integral value of the wheel with loosening will be larger than the gradient of the time integral value of the other wheels. Some factors that affect the pre-processing wheel speed, such as changes in road surface conditions, have a similar effect on the pre-processing wheel speed of each wheel on the same vehicle. The determination device 21 determines the presence or absence of loosening by comparing the gradients of the wheels of the same vehicle. This allows the determination device 21 to prevent erroneous determinations due to factors that have a similar effect on the pre-processing wheel speed of each wheel.

[0144] In the above embodiment, the determination device 21 determines whether or not there is looseness in the fastening between the wheel and the hub based on the gradient of the time integral value calculated from the amount of fluctuation in the wheel. However, the determination device 21 does not necessarily have to calculate the time integral value or gradient in order to determine whether or not there is looseness in the fastening between the wheel and the hub. For example, the determination device 21 may determine whether or not there is looseness in the fastening between the wheel and the hub based on the number of times the fluctuation value converges.

[0145] The number of convergences will be described below with reference to FIGS. Fig. 16 is the same graph as the change in the amount of fluctuation shown in Fig. 7. In other words, the amount of fluctuation shown in Fig. 16 shows an example of the change in the amount of fluctuation when there is no looseness in the fastening between the wheel and the hub.

[0146] A specified range is set for the transition of the fluctuation amount shown in Fig. 16. The specified range is a range set for the fluctuation value centered around zero. In Fig. 18, the fluctuation amount, which is the absolute value of the fluctuation value, is shown, and the specified range is shown corresponding to it.

[0147] In FIG. 16, the limit value of the specified range is 0.04. The limit value of the specified range is set in consideration of the characteristics of the vehicle 10. For example, if the characteristics of the vehicle 10 make it easy to reduce the amount of fluctuation, the limit value of the specified range is set low. Such a value may be set in advance in accordance with the characteristics of the vehicle 10. Furthermore, such a value may be set to a value calculated based on the history of past changes in the amount of fluctuation.

[0148] The form of the specified range is not limited to the specified range shown in Fig. 16. The limit value of the specified range is not limited to 0.04. In Fig. 16, the specified range is set for the amount of fluctuation obtained by converting the fluctuation value into an absolute value. On the other hand, for example, by setting two values, 0.04 and -0.04, as the limit values ​​of the specified range, the specified range can also be set for the fluctuation value.

[0149] The number of convergences is the sum of the number of times the fluctuation value changed from outside the specified range to within the specified range and the number of times it changed from within the specified range to outside the specified range within the counting period. In Figure 16, T1 indicates the counting period. In Figure 16, the points where the fluctuation amount changed from outside the specified range to within the specified range and the points where it changed from within the specified range to outside the specified range are highlighted with circles. The number of convergences is the number of circles in Figure 16.

[0150] The number of convergences may include the cases where the fluctuation value reaches a limit value of the specified range from outside the specified range and then changes back out of the specified range.Similarly, the number of convergences may include the cases where the fluctuation value reaches a limit value of the specified range from inside the specified range and then changes back into the specified range.

[0151] Fig. 17 is the same graph as the change in the amount of variation shown in Fig. 8. That is, the amount of variation shown in Fig. 17 shows an example of the change in the amount of variation when there is looseness in the fastening between the wheel and the hub. In Fig. 17, a specified range is set, just like in Fig. 16. Also in Fig. 17, just like in Fig. 16, points where the amount of variation changes from outside the specified range to within the specified range and points where the amount of variation changes from within the specified range to outside the specified range are highlighted with circles.

[0152] As can be seen from a comparison of Figure 16 and Figure 17, the number of convergences in Figure 17 is less than the number of convergences in Figure 16. In this way, the number of convergences is less when there is looseness in the fastening between the wheel and the hub than when there is no looseness.

[0153] Fig. 18 shows a mode of communication between an information transmission device constituted by the brake ECU 11, central ECU 12, and wheel speed sensor 15, and a determination device 21 in a determination system 100 of the fourth modified example. In Fig. 18, the processing performed by the central ECU 12 is executed by a processing circuit 13. Also, in Fig. 18, the processing performed by the determination device 21 is executed by a processing circuit 22. In the determination system 100 of the fourth modified example, the determination device 21 determines whether or not there is loosening of the fastening between the wheel and the hub of the vehicle 10 based on the number of convergences.

[0154] As shown in the upper part of Fig. 18, in the determination system 100 of the fourth modified example, the wheel speed sensor 15 transmits the pre-processing wheel speed to the brake ECU 11. Then, the brake ECU 11, which has received the pre-processing wheel speed, calculates the fluctuation value and the fluctuation amount from the received pre-processing wheel speed. Note that in the determination system 100 of the fourth modified example, if a specified range is set for the fluctuation value, it is not necessary to calculate the fluctuation amount.

[0155] 18, the brake ECU 11, which has calculated the fluctuation value and the fluctuation amount, calculates the number of convergences in the count period. The brake ECU 11, which has calculated the number of convergences, transmits the number of convergences to the central ECU 12.

[0156] As shown in the middle part of Fig. 18, upon receiving the convergence count, the central ECU 12 executes a threshold setting process. The processing performed by the central ECU 12 in the threshold setting process is similar to the processing shown in Fig. 2. That is, the central ECU 12 stores, for example, a reference threshold in advance in the storage device 14. Then, in the threshold setting process, the central ECU 12 sets a threshold by applying a correction based on the characteristics of the vehicle 10 to the threshold stored in the storage device 14. The central ECU 12 may calculate the reference threshold based on the history of the past convergence count for the vehicle 10, rather than storing the reference threshold in the storage device 14 in advance.

[0157] As shown in the middle part of Fig. 18, the central ECU 12, which has set the threshold value, transmits the number of convergences, the threshold value, and information indicating the state of the vehicle 10. The information indicating the state of the vehicle 10 transmitted by the central ECU 12 in the middle part of Fig. 18 is the same as that shown in the middle part of Fig. 2. In this way, the information transmission device calculates the number of convergences. Then, the information transmission device, which has calculated the number of convergences, transmits the obtained number of convergences to the determination device 21.

[0158] 18, the determination device 21 receives the number of convergences, the threshold value, and information indicating the state of the vehicle 10 from the central ECU 12, and determines whether or not it is possible to determine whether or not there is loosening in the fastening between the wheel and the hub. The manner in which the determination device 21 determines whether or not it is possible to make the determination is the same as the manner shown in the lower part of FIG.

[0159] As shown in the lower part of Fig. 18, when it is determined that it is possible to determine whether or not there is loosening in the fastening between the wheel and the hub, the determination device 21 executes looseness determination processing. In the looseness determination processing, the determination device 21 compares the number of convergences received in the middle part of Fig. 18 with a threshold value.

[0160] As described above, the number of convergences is lower when there is looseness in the fastening between the wheel and the hub than when there is no looseness. Therefore, the determination device 21 can determine that there is looseness in the fastening between the wheel and the hub when the number of convergences is low. When the number of convergences is equal to or less than a threshold, the determination device 21 determines that there is looseness in the fastening between the wheel and the hub for the wheel whose pre-processing wheel speed was detected as the basis for the number of convergences. In this way, the determination device 21 determines whether the number of convergences is low by comparing the received number of convergences with the threshold.

[0161] 18, when the determination device 21 determines that there is looseness in the fastening between the wheel and the hub of the vehicle 10, the determination device 21 transmits a warning to the central ECU 12. The manner in which the determination device 21 transmits the warning is the same as the manner shown in the lower part of FIG.

[0162] In this way, in the determination system 100 of the fourth modified example, the determination device 21 can determine whether or not there is loosening in the fastening between the wheel and the hub based on the number of convergences. In this case, the determination device 21 determines whether or not there is looseness in the fastening between the wheel and the hub based on the number of convergences, which is the sum of the number of times the variation value changes from outside the specified range centered on zero to within the specified range and the number of times it changes from within the specified range to outside the specified range, during the counting period. If looseness occurs, the variation value will be less likely to converge to a value close to zero. Therefore, if looseness occurs, the number of convergences will be smaller. Therefore, as described above, the determination device 21 can determine whether or not there is looseness based on the number of convergences.

[0163] In this case, the determination device 21 determines that there is loosening in the fastening between the wheel and the hub when the number of convergences becomes equal to or less than a threshold value. The determination device 21 can detect that the loosening is progressing based on the decrease in the number of convergences, and determine that loosening has occurred.

[0164] In this case, the information transmitting device calculates the number of convergences, which is the sum of the number of times the fluctuation value has changed from outside the specified range centered on zero to within the specified range and the number of times the fluctuation value has changed from within the specified range to outside the specified range, within the counting period.The information transmitting device then transmits the calculated number of convergences to the determination device 21.

[0165] The information transmitting device transmits the number of convergences to the determining device 21. In this way, the information transmitting device can cause the determining device 21 to determine the presence or absence of an abnormality in the wheel based on the number of convergences.

[0166] In the fourth modified example, the central ECU 12 executes the threshold setting process as shown in the middle part of Fig. 18. In the threshold setting process, the central ECU 12 sets the threshold by correcting the reference threshold. Alternatively, the central ECU 12 may determine an abnormality based on a comparison with the past number of convergences for the wheel being determined.

[0167] Fig. 19 shows an example of the transition of the number of convergences acquired in the determination system 100. In the number of convergences shown in Fig. 19, T1, T2, T3, T4, T5, and T6 indicate count periods.

[0168] Hereinafter, it is assumed that the transition of the convergence count shown in Fig. 19 is calculated from the pre-processing wheel speed detected at the FR wheel 17. In Fig. 19, loosening of the fastening between the FR wheel 17 and the FR hub 24 begins to progress midway through the period T4.

[0169] 19, the number of convergences at the FR wheel 17 decreases sharply from the period T4 onwards. The number of convergences at the FR wheel 17 also gradually decreases after the period T4. In this way, the number of convergences at the wheel decreases as the loosening progresses once the loosening occurs in the fastening between the wheel and hub.

[0170] In this way, the determination device 21 can determine that loosening has occurred in the fastening between the wheel and the hub when the number of convergences obtained for the wheel being determined becomes smaller than the number of convergences in the past for the same wheel.

[0171] FIG. 20 shows data that the central ECU 12 stores in the storage device 14 to set threshold values ​​in the determination system 100 of the fifth modified example. As shown in FIG. 20, the central ECU 12 stores the number of convergences within a count period for a wheel to be determined in the storage device 14. In FIG. 20, the number of convergences in time period T1 in FIG. 19 is B1. Thus, in FIG. 20, the number of convergences obtained in each count period in FIG. 19 is represented by symbols such as B1, B2, and B3. Note that in the determination system 100 of the fifth modified example, when determining each of the FR wheels 17, FL wheels 18, RR wheels 19, and RL wheels 20, the central ECU 12 stores the number of convergences for each wheel.

[0172] As explained with reference to the upper part of FIG. 18, the brake ECU 11 transmits the acquired convergence count to the central ECU 12. The central ECU 12 sets a threshold value by using a moving average of the received convergence counts. The central ECU 12 stores the three most recent convergence counts received from the brake ECU 11. The central ECU 12 then sets a threshold value based on the three stored convergence counts. For example, the central ECU 12 sets a value smaller than the average of the three stored convergence counts as the threshold value.

[0173] An example will be described below. For example, assume that the central ECU 12 stores the number of convergences at T1, T2, and T3 shown in FIG. 20 and receives the number of convergences at T4 from the brake ECU 11. In this case, in the threshold setting process shown in FIG. 18, the central ECU 12 sets a value smaller than the average of B1, B2, and B3 shown in FIG. 20 as the threshold. Thereafter, the central ECU 12 discards B1, which is the number of convergences at T1, and stores B4, which is the number of convergences at T4, in the storage device 14. In this way, the central ECU 12 sets the threshold based on the number of convergences stored while updating the number of convergences stored in the storage device 14.

[0174] The number of convergence times stored by the central ECU 12 is not limited to that of the fifth modified example. Furthermore, the manner in which the central ECU 12 sets the threshold value based on the past convergence times is not limited to the manner in which the threshold value is set to a value smaller than the average of the stored convergence times.

[0175] In the fifth modified example, the central ECU 12 sets the threshold value. On the other hand, as in the first modified example, the determination device 21 may set the threshold value based on the number of past convergences for the wheel to be determined. In this case, the determination device 21 sets the threshold value based on the number of convergences stored in the storage device 23.

[0176] In this way, the determination device 21 can determine whether or not there is loosening of the fastening between the wheel and the hub, using a threshold value set based on the number of past convergences for the wheel being the target of determination.

[0177] In this case, the determination device 21 uses a threshold value set based on the number of past convergences for the wheel being determined. As loosening progresses, the number of convergences decreases. The determination device 21 can detect the progression of loosening based on data obtained from the wheel being determined, and determine whether loosening has occurred in the fastening of the wheel to the hub.

[0178] In the fourth modified example, as shown in the middle part of Fig. 18, the central ECU 12 executes a threshold setting process. In the threshold setting process, the central ECU 12 sets a threshold by correcting a reference threshold. Alternatively, the central ECU 12 may set a threshold based on the number of convergences for a wheel that is not a target of the determination, among the multiple wheels of the vehicle 10.

[0179] Fig. 21 shows an example of the transition of the number of convergences acquired in the determination system 100. In the number of convergences shown in Fig. 21, T1, T2, T3, T4, T5, and T6 indicate count periods.

[0180] Fig. 21 shows the number of convergences for the FR wheel 17 and the FL wheel 18 equipped on the vehicle 10. In Fig. 21, the white circles indicate the number of convergences for the FR wheel 17. On the other hand, in Fig. 21, the black circles indicate the number of convergences for the FL wheel 18. In Fig. 21, as in Fig. 19, the loosening of the fastening between the FR wheel 17 and the FR hub 24 begins to progress midway through the T4 period.

[0181] The number of convergences before T4 for the FR wheel 17 is not significantly different from the number of convergences in the same time period for the FL wheel 18. As described above, some of the factors that affect the pre-processing wheel speed have the same effect on the pre-processing wheel speed of each wheel on the vehicle 10. Therefore, the number of convergences for the FR wheel 17 behaves in the same way as the number of convergences in the same time period for the other wheels on the vehicle 10, as long as there are no significant factors that affect the pre-processing wheel speed of a specific wheel on the vehicle 10.

[0182] As shown in Figure 21, the number of convergences for the FR wheel 17 decreases after T4. The number of convergences for the FR wheel 17 after T4 is also less than the number of convergences for the FL wheel 18 in the same time period. In this way, if loosening occurs in the fastening of only one of multiple wheels on the same vehicle to the hub, the number of convergences for only that wheel will be less than the other wheels.

[0183] The determination device 21 can determine that loosening of the fastening between the wheel and the hub has occurred in the wheel when the number of convergences obtained for the wheel being determined becomes lower than the number of convergences for the same time period for other wheels equipped with that wheel.

[0184] The following describes the processing that is performed in the determination system 100 of the sixth modified example. In the determination system 100 of the sixth modified example, the central ECU 12 acquires the number of convergences in the same time period for the FR wheels 17, FL wheels 18, RR wheels 19, and RL wheels 20. As explained with reference to the upper part of Fig. 18, the brake ECU 11 transmits the calculated number of convergences to the central ECU 12. In the sixth modified example, the central ECU 12 starts executing the threshold setting process when the number of convergences in the same time period for the FR wheels 17, FL wheels 18, RR wheels 19, and RL wheels 20 have all been acquired.

[0185] In the threshold setting process, the central ECU 12 calculates the average number of convergences in the same time period for wheels that are not the target of determination among the multiple wheels equipped on the vehicle 10. For example, when setting a threshold for determination for the FR wheels 17, the central ECU 12 calculates the average number of convergences in the same time period for the FL wheels 18, the RR wheels 19, and the RL wheels 20. Then, the central ECU 12 sets the threshold based on the calculated average value. For example, the central ECU 12 sets a value smaller than the calculated average value as the threshold for the FR wheels 17.

[0186] The manner in which the central ECU 12 sets the threshold value based on the number of convergences for wheels that are not the target of the determination among the multiple wheels of the vehicle 10 is not limited to the sixth modified example. For example, the central ECU 12 may set a value that is smaller than the number of convergences for the FL wheels 18 in the same time period as the threshold value for the FR wheels 17.

[0187] In the sixth modified example, the central ECU 12 sets the threshold value. However, as in the first modified example, the determination device 21 may set the threshold value. In this case, the determination device 21 acquires information on the number of convergences of the plurality of wheels of the vehicle 10 from the brake ECU 11.

[0188] In this way, the determination device 21 can determine whether or not there is loosening of the fastening between the wheel and the hub using a threshold value set based on the number of convergences during the same time period for wheels that are not the subject of determination among the multiple wheels equipped on the vehicle 10.

[0189] In this case, the determination device 21 uses, as the threshold value, a value that is set based on the number of convergences in the same time period for wheels that are not the target of determination, among the plurality of wheels provided on the vehicle 10. If any of the multiple wheels has loosened from the hub, the convergence count for the wheel with the loosened connection will be lower than the convergence count for the other wheels. Some factors that affect the pre-processing wheel speed, such as changes in road conditions, have a similar effect on the pre-processing wheel speeds of all wheels on the same vehicle. The determination device 21 determines whether or not there is looseness by comparing the convergence counts for wheels on the same vehicle. This allows the determination device 21 to reduce erroneous determinations due to factors that have a similar effect on the pre-processing wheel speeds of all wheels.

[0190] <Additional Notes> The technical ideas that can be understood from the above-described embodiment and modified examples will be described. [Appendix 1] A determination device that determines whether or not there is an abnormality in a wheel based on the transition of a fluctuation value, which is the difference between a pre-processing wheel speed detected by a wheel speed sensor that detects the rotational speed of a wheel equipped on a vehicle and a post-processing wheel speed obtained by applying low-pass filter processing to the pre-processing wheel speed.

[0191] [Appendix 2] The determination device described in [Appendix 1] determines whether or not there is loosening of the fastening between the wheel and the hub as an abnormality in the wheel. [Appendix 3] The determination device described in [Appendix 2] determines whether or not there is loosening in the fastening between the wheel and the hub using the time integral value of the fluctuation amount over a predetermined period, which is the absolute value of the fluctuation value.

[0192] [Appendix 4] A determination device as described in [Appendix 3], in which an upper limit value is set for the fluctuation amount used to calculate the time integral value, and the time integral value is a value calculated using multiple fluctuation amounts for the specified period in which the fluctuation amount exceeding the upper limit value is replaced with a value equal to the upper limit value.

[0193] [Appendix 5] A determination device as described in [Appendix 3] or [Appendix 4], in which the time integral value is calculated periodically, and the presence or absence of loosening of the fastening between the wheel and the hub is determined based on the gradient of the time integral value during the calculation period calculated using multiple time integral values ​​calculated during a calculation period longer than the predetermined period.

[0194] [Appendix 6] The determination device described in [Appendix 5] determines that there is loosening in the fastening between the wheel and the hub when the gradient is equal to or greater than a threshold value. [Appendix 7] The determination device according to [Appendix 6], wherein the threshold value is a value set based on the past gradient of the wheel being determined.

[0195] [Appendix 8] The determination device described in [Appendix 6] uses, as the threshold value, a value set based on the gradient during the same time period for a wheel that is not the subject of determination among the plurality of wheels equipped on the vehicle.

[0196] [Appendix 9] The determination device described in [Appendix 2] determines whether or not the fastening between the wheel and the hub has loosened based on the number of convergences, which is the sum of the number of times the fluctuation value changes from outside a specified range centered on zero to within the specified range and the number of times the fluctuation value changes from within the specified range to outside the specified range within a counting period.

[0197] [Appendix 10] The determination device according to [Appendix 9], which determines that there is loosening in the fastening between the wheel and the hub when the number of convergences is equal to or less than a threshold value. [Appendix 11] The determination device according to [Appendix 10], wherein the threshold value is a value set based on the number of past convergences for the wheel to be determined.

[0198] [Appendix 12] The determination device described in [Appendix 10] uses, as the threshold value, a value set based on the number of convergences in the same time period for a wheel that is not the subject of determination among the plurality of wheels equipped on the vehicle.

[0199] [Appendix 13] A determination device described in any one of [Appendix 1] to [Appendix 12], wherein the change in the fluctuation value calculated based on the pre-processing wheel speed detected by the wheel speed sensor while the vehicle is operating the anti-lock brake system is not used to determine whether or not there is an abnormality in the wheel.

[0200] [Appendix 14] A determination device described in any one of [Appendix 1] to [Appendix 13], wherein the change in the fluctuation value calculated based on the pre-processing wheel speed detected by the wheel speed sensor while the vehicle is operating the traction control system is not used to determine whether or not there is an abnormality in the wheel.

[0201] [Appendix 15] A determination device described in any one of [Appendix 1] to [Appendix 14], wherein the change in the fluctuation value calculated based on the pre-processing wheel speed detected by the wheel speed sensor while the vehicle is operating a vehicle stability control system is not used to determine whether or not there is an abnormality in the wheel.

[0202] [Appendix 16] A determination device described in any one of [Appendix 1] to [Appendix 15], wherein the change in the fluctuation value calculated based on the pre-processing wheel speed detected by the wheel speed sensor while the vehicle is traveling on a rough road is not used to determine whether or not there is an abnormality in the wheel.

[0203] [Appendix 17] The vehicle is equipped with an electronic control unit directly connected to the wheel speed sensor, and the determination device described in any one of [Appendix 1] to [Appendix 16] determines whether or not there is an abnormality in the wheel based on the trend of the fluctuation value calculated by the electronic control unit. [Explanation of symbols]

[0204] 10...Vehicle 11...Brake ECU 12...Central ECU 13...Processing circuit 14...Storage device 15...Wheel speed sensor 16...Communication line 17...FR wheels 18…FL wheels 19…RR wheels 20...RL wheels 21...Judgment device 22...Processing circuit 23…Storage device 24…FR hub 25...FL hub 26...Rear wheel drive hub 27...RL hub 100...Judgment system

Claims

1. Based on the transition of a fluctuation value which is the difference between a pre-processing wheel speed detected by a wheel speed sensor which detects the rotation speed of a wheel provided on the vehicle and a post-processing wheel speed obtained by performing low-pass filtering on the pre-processing wheel speed, Determine whether there is an abnormality in the wheel Judgment device.

2. As an abnormality in the wheel, whether or not there is looseness between the wheel and the hub is determined. The determination device according to claim 1 .

3. The time integral value of the amount of fluctuation, which is the absolute value of the fluctuation value, over a predetermined period is used to determine whether or not there is loosening of the fastening between the wheel and the hub. The determination device according to claim 2 .

4. an upper limit value is set for the amount of fluctuation used to calculate the time integral value, The time integral value is a value calculated using a plurality of the fluctuation amounts for the predetermined period in which the fluctuation amount exceeding the upper limit value is replaced with a value equal to the upper limit value The determination device according to claim 3 .

5. the time integral value is calculated periodically, The presence or absence of loosening of the fastening between the wheel and the hub is determined based on a gradient of the time integral value during the included period, the gradient being calculated using a plurality of the time integral values ​​calculated during the included period that is longer than the predetermined period. The determination device according to claim 3 .

6. When the gradient is equal to or greater than a threshold value, it is determined that there is looseness in the fastening between the wheel and the hub. The determination device according to claim 5 .

7. The threshold value is A value set based on the past gradient of the wheel to be judged is used. The determination device according to claim 6.

8. The threshold value is A value set based on the gradient in the same time period for a wheel that is not a target of the determination among the plurality of wheels provided on the vehicle is used. The determination device according to claim 6.

9. The presence or absence of loosening of the fastening between the wheel and the hub is determined based on the number of convergences, which is the sum of the number of times the fluctuation value changes from outside a specified range centered around zero to within the specified range and the number of times the fluctuation value changes from within the specified range to outside the specified range, within a counting period. The determination device according to claim 2 .

10. When the number of convergences is equal to or less than a threshold value, it is determined that there is looseness in the fastening between the wheel and the hub. The determination device according to claim 9 .

11. The threshold value is A value set based on the number of past convergences for the wheel to be determined is used. The determination device according to claim 10.

12. The threshold value is A value set based on the number of convergences in the same time period for a wheel that is not a target of the determination among the plurality of wheels provided on the vehicle is used. The determination device according to claim 10.

13. Regarding the transition of the fluctuation value calculated based on the pre-processing wheel speed detected by the wheel speed sensor while the antilock brake system of the vehicle is activated, It is not used to determine whether there is an abnormality in the wheel. The determination device according to claim 1 .

14. Regarding the transition of the fluctuation value calculated based on the pre-processing wheel speed detected by the wheel speed sensor while the traction control system of the vehicle is activated, It is not used to determine whether there is an abnormality in the wheel. The determination device according to claim 1 .

15. Regarding the transition of the fluctuation value calculated based on the pre-processing wheel speed detected by the wheel speed sensor while the vehicle is operating a vehicle stability control system, It is not used to determine whether there is an abnormality in the wheel. The determination device according to claim 1 .

16. Regarding the transition of the fluctuation value calculated based on the pre-processing wheel speed detected by the wheel speed sensor while the vehicle is traveling on a rough road, It is not used to determine whether there is an abnormality in the wheel. The determination device according to claim 1 .

17. The vehicle is an electronic control unit directly connected to the wheel speed sensor; The electronic control unit determines whether or not there is an abnormality in the wheel based on the transition of the fluctuation value calculated by the electronic control unit. The determination device according to claim 1 .

18. A pre-processing wheel speed detected by a wheel speed sensor that detects the rotation speed of a wheel provided on the vehicle is acquired; calculating a fluctuation value that is a difference between the acquired pre-processing wheel speed and a processed wheel speed obtained by performing low-pass filtering on the pre-processing wheel speed; The calculated variation value is transmitted to the determination device according to claim 1. Information transmission device.

19. periodically calculating a time integral of the amount of fluctuation, which is the absolute value of the fluctuation value, over a predetermined period of time; calculating a gradient of the time integral value during the inclusion period using a plurality of the time integral values ​​calculated during the inclusion period that is longer than the predetermined period; The calculated gradient is transmitted to the determination device.

19. The information transmitting device according to claim 18.

20. Calculating the number of convergences, which is the sum of the number of times the fluctuation value has changed from outside a specified range centered on zero to within the specified range and the number of times the fluctuation value has changed from within the specified range to outside the specified range, within a counting period; The calculated number of convergences is transmitted to the determination device.

19. The information transmitting device according to claim 18.

21. A determination system including an information transmission device and a determination device, The information transmitting device A pre-processing wheel speed detected by a wheel speed sensor that detects the rotation speed of a wheel provided on the vehicle is acquired; calculating a fluctuation value that is a difference between the acquired pre-processing wheel speed and a processed wheel speed obtained by performing low-pass filtering on the pre-processing wheel speed; transmitting the calculated variation value to the determination device; The determination device determining whether or not there is an abnormality in the wheel based on the transition of the received fluctuation value; When it is determined that there is an abnormality in the wheel, the user of the vehicle is notified that there is an abnormality in the wheel. Judging system.

22. The determination device As an abnormality in the wheel, whether or not there is looseness between the wheel and the hub is determined. The determination system according to claim 21.

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