Tire failure determination method and tire failure determination device

Abstract

A tire failure determination method according to the present disclosure is executed by a computer and includes: acquiring a thermal image of a tire captured by a thermographic camera; acquiring the internal temperature of the tire; and estimating the depth of a damaged portion of the tire in the thermal image on the basis of the surface temperature of the damaged portion and the internal temperature at a time when the thermal image was captured.

Description

Tire failure detection method and tire failure detection device

[0001] The present disclosure relates to a tire malfunction detection method and a tire malfunction detection device.

[0002] There are known technologies for determining tire damage. For example, Patent Literature 1 discloses a tire damage detection system that detects the size of a damaged portion of a tire based on the diameter of a rim wheel, based on image data of the tire mounted on the rim wheel.

[0003] Patent Publication No. 2019-202729

[0004] However, there is a need for further improvements in the usefulness of technology for determining tire failure. For example, if a mining vehicle used at a mining site experiences a sudden tire failure, productivity is reduced due to the need to transport the vehicle and change the tire. In addition, regular tire inspections by workers to prevent sudden failures are a cost burden. Therefore, there is a need for automation of tire failure determination.

[0005] In view of the above circumstances, an object of the present disclosure is to provide a tire fault determination method and a tire fault determination device that improve the usefulness of the technology for determining tire faults.

[0006] [1] A tire fault determination method according to one embodiment of the present disclosure is a computer-implemented tire fault determination method, which includes acquiring a thermal image of a tire taken with a thermographic camera, acquiring the tire cavity temperature, and estimating the depth of the damaged portion based on the surface temperature of the damaged portion of the tire in the thermal image and the tire cavity temperature at the time the thermal image was taken.

[0007] [2] A tire fault determination method according to one embodiment of the present disclosure is the tire fault determination method described in [1] above, further comprising detecting, as the damaged portion, a portion of the outer surface of the tire captured in the thermal image that has a temperature higher than the surrounding portion by a threshold temperature or more, and it is preferable that the threshold temperature is changed depending on the inner cavity temperature at the time the thermal image is captured.

[0008] [3] A tire fault determination method according to one embodiment of the present disclosure is the tire fault determination method described in [1] or [2] above, wherein estimating the depth of the damaged portion preferably includes correcting the depth of the damaged portion according to the inner cavity temperature at the time the thermal image was captured.

[0009] [4] A tire fault determination method according to one embodiment of the present disclosure is the tire fault determination method described in [3] above, wherein estimating the depth of the damaged portion preferably includes correcting the depth of the damaged portion such that the higher the inner cavity temperature when the thermal image is captured, the greater the correction amount of the depth of the damaged portion.

[0010] [5] A tire fault determination method according to one embodiment of the present disclosure is the tire fault determination method described in any one of [1] to [4] above, wherein estimating the depth of the damaged portion preferably includes correcting the depth of the damaged portion depending on the position of the damaged portion in the tire.

[0011] [6] A tire failure determination method according to one embodiment of the present disclosure is the tire failure determination method described in any one of [1] to [5] above, and preferably further includes determining whether the damaged portion is within an acceptable range of durability for the tire.

[0012] [7] A tire fault determination method according to one embodiment of the present disclosure is the tire fault determination method described in [6] above, wherein the determining preferably includes, when multiple damaged portions are detected in the tire, determining whether the depths of the multiple damaged portions are within the allowable range based on the relative depths of the multiple damaged portions.

[0013] [8] A tire failure determination method according to one embodiment of the present disclosure is the tire failure determination method described in [6] or [7] above, further comprising obtaining the travel distance or travel time of a vehicle equipped with the tire, wherein the determination comprises determining whether the depth of the damaged portion is within the allowable range based on the depth of the damaged portion and the travel distance or the travel time of the vehicle, and it is preferable that the allowable range is set such that the deeper the depth of the damaged portion and the shorter the travel distance or the travel time of the vehicle, the more likely the depth of the damaged portion is to fall outside the allowable range.

[0014] [9] A tire fault determination device according to one embodiment of the present disclosure includes a control unit configured to acquire a thermal image of a tire taken with a thermographic camera, acquire the tire cavity temperature, and estimate the depth of the damaged portion based on the surface temperature of the damaged portion of the tire in the thermal image and the tire cavity temperature at the time the thermal image was taken.

[0015] According to the present disclosure, it is possible to provide a tire fault determination method and a tire fault determination device that can improve the usefulness of the technology for determining tire faults.

[0016] Fig. 1 is a diagram showing a schematic configuration of a tire malfunction determination system according to an embodiment of the present disclosure. Fig. 2 is a block diagram showing the configuration of a server shown in Fig. 1. Fig. 3 is a sequence diagram showing the operation of the tire malfunction determination system shown in Fig. 1. Fig. 4 is a diagram showing an example of a thermo image of a tire. Fig. 5 is a graph showing the change in temperature of a damaged portion of a tire according to the tire cavity temperature.

[0017] A tire fault determination system according to an embodiment of the present disclosure will be described below with reference to the drawings. Common components and parts in each drawing are designated by the same reference numerals. However, please note that the drawings are schematic, and the proportions of each dimension may differ from those in reality.

[0018] (Configuration of Tire Failure Determination System) First, an overview of a tire failure determination system 1 according to this embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing the schematic configuration of the tire failure determination system 1. As shown in Fig. 1, the tire failure determination system 1 includes a server 10, an imaging device 20, a measuring device 30, and a terminal device 40. Note that Fig. 1 shows one server 10, one imaging device 20, one measuring device 30, and one terminal device 40. However, the tire failure determination system 1 may include any number of servers 10, one imaging device 20, one measuring device 30, and one terminal device 40.

[0019] The server 10 is configured with one or more computers. In this embodiment, the server 10 is described as being configured with one computer. However, the server 10 may be configured with multiple computers, such as in a cloud computing system. In this disclosure, the server 10 is also referred to as a "tire malfunction determination device."

[0020] The imaging device 20 is configured with a computer including one or more cameras. The imaging device 20 is equipped with, for example, a thermographic camera capable of capturing thermal images. However, the imaging device 20 is not limited to a thermographic camera, and may be equipped with a camera capable of capturing any image, such as a visible light camera or an infrared camera. The image captured by the imaging device 20 may be a still image such as a photograph, or may be a video. The imaging device 20 generates a thermographic image of the tire 2 and transmits it to the server 10. In this embodiment, the thermographic image of the tire 2 captures at least a portion of the tire 2. Note that the thermographic image of the tire 2 may also capture at least a portion of the vehicle 3 on which the tire 2 is mounted, in addition to at least a portion of the tire 2.

[0021] The imaging device 20 may be, for example, a fixed imaging device 20 installed on the travel route of the vehicle 3 at the mine site. This allows the imaging device 20 to capture images of the vehicle 3 traveling on the travel route, and is less likely to reduce the operating rate of the vehicle 3 and productivity at the mine. However, the imaging device 20 is not limited to a fixed imaging device 20, and may be an imaging device 20 mounted on a drone or a mobile imaging device 20 such as a tablet terminal that can be carried by a person.

[0022] The measurement device 30 is configured with a computer including one or more sensors. The sensors may be, but are not limited to, a digital tachograph, a tire pressure monitoring system (TPMS), an electronic control unit (ECU), a car navigation device, or the like. The measurement device 30 acquires time-series data regarding the tire 2 mounted on the vehicle 3 and transmits the data to the server 10. Therefore, the measurement device 30 may be installed on the vehicle 3 or the tire 2.

[0023] The time-series data regarding the tire 2 mounted on the vehicle 3 includes measurement values ​​regarding the tire 2, the measurement dates and times, etc. For example, if the measurement device 30 includes a TPMS installed on the tire 2, the measurement values ​​regarding the tire 2 may include tire condition information of the tire 2, such as the internal pressure (air pressure), cavity temperature, or thermal history of the tire 2. The thermal history of the tire 2 is the history of heat applied to the tire 2 as the tire 2 is used. The thermal history of the tire 2 is used to evaluate how much energy has been applied to the tire 2 since the tire 2 was first used. Generally, the greater the thermal history, the more severe the deterioration of the tire 2. The thermal history can be calculated, for example, by applying the cavity temperature of the tire 2 to the Arrhenius equation. Furthermore, for example, if the measurement device 30 includes a digital tachograph installed on the vehicle 3, the measurement values ​​regarding the tire 2 may include driving information of the vehicle 3, such as the driving time, driving distance, speed, acceleration, or number of rotations of the tire 2.

[0024] The terminal device 40 is a computer such as a smartphone, a tablet terminal, or a personal computer.

[0025] The network 50 is any communication network that allows communication between the server 10, the imaging device 20, the measuring device 30, and the terminal device 40. The network 50 in this embodiment may be, for example, the Internet, a mobile communication network, a local area network (LAN), or a combination of these.

[0026] The tire failure determination system 1 is used to determine a failure in one or more tires 2. In the tire failure determination system 1, the server 10 acquires a thermographic image of the tire 2 captured by a thermographic camera from, for example, an imaging device 20. The server 10 then acquires the cavity temperature of the tire 2 from a measuring device 30. The server 10 estimates the depth of the damaged portion based on the surface temperature of the damaged portion of the tire in the thermographic image and the cavity temperature at the time the thermographic image was captured. In this way, the tire failure determination system 1 can more accurately estimate the depth of the damaged portion by using the cavity temperature of the tire 2 in addition to the surface temperature of the damaged portion of the tire 2 in the thermographic image.

[0027] In the present disclosure, the tire 2 is not particularly limited, but may be an OR (Off The Road) tire mounted on a mining vehicle such as a transport vehicle, construction vehicle, work vehicle, or heavy equipment vehicle used at a mining site, etc. However, the tire 2 may be a tire other than an OR tire.

[0028] In the present disclosure, the vehicle 3 is, for example, a mining vehicle used at a mining site, etc. However, the vehicle 3 is not limited to the above-described mining vehicle, and may be any vehicle on which the tire 2 can be mounted, such as a transport vehicle, a construction vehicle, a work vehicle or heavy machinery vehicle, a bus, a passenger car, a motorcycle, a bicycle, or an airplane.

[0029] Next, the configuration of the server 10, which is a tire malfunction determination device, will be described in detail with reference to Fig. 2. Fig. 2 is a block diagram showing the configuration of the server 10. As shown in Fig. 2, the server 10 includes a communication unit 11, an output unit 12, an input unit 13, a storage unit 14, and a control unit 15. In the server 10, the communication unit 11, the output unit 12, the input unit 13, the storage unit 14, and the control unit 15 are connected to each other via wire or wirelessly so as to be able to communicate with each other.

[0030] The communication unit 11 includes a communication module for connecting to the network 50. The communication module is a communication module compatible with mobile communication standards such as 4G (4th Generation) or 5G (5th Generation). The communication module may be a communication module compatible with standards such as wired LAN or wireless LAN. The communication module may be a communication module compatible with short-range wireless communication standards such as Wi-Fi (registered trademark), Bluetooth (registered trademark), or infrared communication. In this embodiment, the server 10 is connected to the network 50 via the communication unit 11. This allows the server 10 to communicate with the imaging device 20, the measurement device 30, the terminal device 40, other computers, etc.

[0031] The output unit 12 includes one or more output devices, such as a display, a speaker, a lamp, etc. As a result, the output unit 12 outputs an image, sound, light, etc.

[0032] The input unit 13 includes one or more input devices, such as a touch panel, a camera, a microphone, etc. The input unit 13 receives input operations by the user of the server 10, for example.

[0033] The storage unit 14 is, for example, a semiconductor memory, a magnetic memory, an optical memory, or the like. The storage unit 14 functions, for example, as a main storage device, an auxiliary storage device, or a cache memory. The storage unit 14 stores any information used in the operation of the server 10. For example, the storage unit 14 stores a system program, an application program, embedded software, a database, or the like. The information stored in the storage unit 14 may be updatable with information obtained from the network 50 via the communication unit 11, for example.

[0034] For example, the storage unit 14 may store tire identification information of one or more tires 2 that are the target of failure determination. In the present disclosure, tire identification information is also referred to as a tire ID (Identifier). The tire identification information of a tire 2 is information that can uniquely identify the tire 2. The tire identification information of a tire 2 is, for example, uniquely issued by the server 10, but is not limited to this and may be the manufacturing number of the tire 2 or the vehicle number of the vehicle 3 on which the tire 2 is mounted, etc. Furthermore, the storage unit 14 may store information related to the tire 2 in association with the tire identification information of the tire 2.

[0035] The information about the tire 2 includes any information about the tire 2. The information about the tire 2 may include, for example, the time-series data about the tire 2 described above, damage information about the tire 2, configuration information about the tire 2, information about the vehicle 3 on which the tire 2 is mounted, or position information about the location of the tire 2 on the vehicle 3. The damage information about the tire 2 may be information including, for example, the position, shape, depth, and registration date and time of damage previously sustained by the tire 2. The configuration information about the tire 2 includes, for example, the type, model number, material properties, tread pattern, belt angle, size, or weight of the tire 2. The information about the vehicle 3 on which the tire 2 is mounted includes identification information, type, model number, engine displacement, number of tires mounted, or number of shafts of the vehicle 3.

[0036] The control unit 15 includes one or more processors. The processor may be, for example, a general-purpose processor such as a CPU (Central Processing Unit) or a dedicated processor specialized for specific processing. The control unit 15 is not limited to a processor and may include one or more dedicated circuits. The dedicated circuits may be, for example, an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit). The control unit 15 controls each component to realize the functions of the server 10, including the functions of the components such as the communication unit 11, the output unit 12, the input unit 13, and the memory unit 14 described above.

[0037] (Operation of Tire Failure Determination System) The operation of the tire failure determination system 1 will be described with reference to Figures 3, 4, and 5. Figure 3 is a sequence diagram showing the operation of the tire failure determination system 1. Figure 4 is a diagram showing an example of a thermographic image 60 of the tire 2. Figure 5 is a graph showing changes in temperature of a damaged portion 70 of the tire 2 according to the cavity temperature of the tire 2. The sequence diagram shown in Figure 3 shows the operations of the server 10, imaging device 20, measuring device 30, and terminal device 40 included in the tire failure determination system 1. Therefore, the description of this operation corresponds to a tire failure determination method executed by the tire failure determination system 1, and also corresponds to a tire failure determination method executed by each of the server 10, imaging device 20, measuring device 30, or terminal device 40 included in the tire failure determination system 1.

[0038] For the purpose of explaining this operation, it is assumed that the control unit 15 of the server 10 stores, in the memory unit 14, the tire identification information of the tire 2 and information about the tire 2 associated with the tire identification information of the tire 2.

[0039] In this operation example, an operation will be described in which the server 10 detects a damaged portion 70 on the outer surface of the side of the tire 2 based on the thermo image 60 shown in Fig. 4. In this case, the imaging device 20 may be installed in a position on the travel path of the vehicle 3 at the mining site where it can capture the thermo image 60 of the side of the vehicle 3.

[0040] Referring to FIG. 3, in step S101 , the measurement device 30 acquires time-series data related to the tire 2 mounted on the vehicle 3 and transmits the data to the server 10 .

[0041] Specifically, the measurement device 30 uses a sensor to acquire time-series data related to the tire 2 at a predetermined timing. The measurement device 30 may associate the acquired time-series data related to the tire 2 with identification information of the tire 2 and transmit the data to the server 10. For example, the measurement device 30 may transmit time-series data related to the tire 2 to the server 10 each time the measurement device 30 acquires the time-series data. Alternatively, the measurement device 30 may collectively transmit time-series data measured over a predetermined period to the server 10. In this operation example, the measurement device 30 includes a digital tachograph and a TPMS. Therefore, the time-series data related to the tire 2 may include tire condition information of the tire 2, such as the internal pressure (air pressure), cavity temperature, and thermal history of the tire 2, as well as driving information of the vehicle 3, such as the driving time and driving distance of the vehicle 3. However, the time-series data transmitted from the measurement device 30 is not limited to the information described above.

[0042] In step S102, the control unit 15 of the server 10 acquires time-series data related to the tire 2, including the temperature of the tire cavity and the like.

[0043] Specifically, the control unit 15 of the server 10 receives time series data related to the tire 2 from the measuring device 30 via the communication unit 11. However, the control unit 15 may receive time series data related to the tire 2 acquired by the measuring device 30 via a computer other than the measuring device 30. The control unit 15 may store the received time series data related to the tire 2 in the storage unit 14 in association with the identification information of the tire 2.

[0044] In step S103 , the imaging device 20 transmits a thermographic image 60 of the tire 2 captured by the thermography camera to the server 10 .

[0045] Specifically, the imaging device 20 uses a thermographic camera to capture an image of the tire 2 and generate a thermographic image 60 of the tire 2. In this operation example, as shown in FIG. 4 , the thermographic image 60 is described as a single still image, but it may be a plurality of continuously captured still images or a video. The imaging device 20 transmits the captured thermographic image 60 to the server 10 along with information on the capture time of the thermographic image 60. However, the image transmitted from the imaging device 20 is not limited to the thermographic image 60. For example, the imaging device 20 may transmit a photograph taken with a visible light camera to the server 10 along with the thermographic image 60. Furthermore, the thermographic image 60 of the tire 2 may include at least a portion of the tire 2 as well as at least a portion of the vehicle 3 on which the tire 2 is mounted. The thermographic image 60 shown in FIG. 4 captures the tire 2 and a portion of the vehicle 3 on which the tire 2 is mounted.

[0046] Referring back to FIG. 3, in step S104, the control unit 15 of the server 10 acquires a thermo image 60 of the tire 2.

[0047] Specifically, the control unit 15 of the server 10 receives a thermo image 60 of the tire 2 from the imaging device 20 via the communication unit 11, together with information on the time the thermo image 60 was captured. However, the control unit 15 may receive the thermo image 60 captured by the imaging device 20 via a computer other than the imaging device 20. The control unit 15 may store the received thermo image 60 and its capture time in the memory unit 14 in association with the identification information of the tire 2.

[0048] In step S104, the control unit 15 of the server 10 may further specify, from the thermographic image 60, the identification information of the tire 2 captured in the thermographic image 60. This allows the control unit 15 to identify the tire 2 from the thermographic image 60 even if the tire 2 captured in the thermographic image 60 has not been identified in advance. Specifically, the control unit 15 extracts a display portion indicating the identification information of the tire 2 from the thermographic image 60 by image processing. The display portion may be, for example, a two-dimensional code such as a QR (Quick Response) Code (registered trademark) attached to the tire 2 or the vehicle 3. In such a case, the control unit 15 can read the identification information of the tire 2 from the display portion which is a two-dimensional code. However, the display portion is not limited to a two-dimensional code and may be any display information such as a character string, a symbol, a figure, a color, a pattern, or a one-dimensional code.

[0049] The display portion indicating the identification information of the tire 2 may be displayed in any position. For example, the display portion may be provided on the outer surface of the tire 2, such as on the side of the tire 2. In this case, even if the tire 2 is remounted from one vehicle 3 to another vehicle 3 due to tire rotation or the like, the identification information of the tire 2 can be continuously identified based on the same display portion. However, the display portion may also be provided on the body of the vehicle 3 on which the tire 2 is mounted. In this case, since the display portion is provided on the body of the vehicle 3, the visibility of the display portion is less likely to decrease even if the outer surface of the tire 2 is soiled with mud or damaged. In this operation example, the control unit 15 of the server 10 is described as identifying the identification information of the tire 2 captured in the thermal image 60 from the thermal image 60, but this is not limited thereto. For example, if a photograph taken with a visible light camera is received from the imaging device 20 along with the thermal image 60, the control unit 15 may identify the identification information of the tire 2 from the photograph.

[0050] In step S105 , the control unit 15 of the server 10 detects the damaged portion 70 on the outer surface of the tire 2 captured in the thermal image 60 .

[0051] Any method can be used to detect the damaged portion 70. For example, the control unit 15 of the server 10 may store in advance in the storage unit 14 an image analysis algorithm for identifying the damaged portion 70 of the tire 2 captured in the thermal image 60.

[0052] Specifically, the control unit 15 of the server 10 uses an image analysis algorithm to detect, as a damaged portion 70, a cut, crack, or other part of the outer surface of the tire 2 captured in the thermal image 60, where the temperature is higher than the surrounding area by at least a threshold value. Generally, the temperature of the tire cavity rises as the vehicle 3 travels. The damaged portion 70 on the outer surface of the tire 2 is closer to the tire cavity than other areas, resulting in a higher surface temperature. Therefore, the thermal image 60 can be used to detect the location and depth of the damaged portion 70 on the outer surface of the tire 2. By using the thermal image 60, damage detection accuracy is less likely to decrease, even when the outer surface of the captured tire 2 is dirty or the tire 2 is photographed at night, which would otherwise reduce the accuracy of damage detection in a photograph taken with a visible light camera. In this operation example, the control unit 15 detects, as a damaged portion 70, a part of the thermal image 60 shown in FIG. 4 that is higher in temperature than the surrounding area. However, if multiple damaged portions 70 exist on the tire 2, the control unit 15 may detect all of the multiple damaged portions 70. The control unit 15 may store information such as the position and number of the detected damaged portions 70 as damage information of the tire 2 in the storage unit 14 in association with the identification information of the tire 2. Note that in the thermo image 60 shown in Fig. 4, the detected damaged portions 70 are highlighted and surrounded by a square frame, but this is not limited to this.

[0053] The threshold temperature used to detect the damaged portion 70 may be, for example, a fixed value. The threshold temperature may be determined using outliers derived by a statistical method such as the 3σ method. In this case, the control unit 15 of the server 10 can detect, as the damaged portion 70, a portion of the outer surface of the tire 2 captured in the thermal image 60 that has a temperature higher than the surrounding portion by at least the threshold value. However, the threshold temperature is not limited to a fixed value and may be changed by the control unit 15 depending on the cavity temperature of the tire 2 (or the thermal history calculated from the cavity temperature) when the thermal image 60 was captured. For this purpose, the control unit 15 may store information correlating the threshold temperature with the cavity temperature of the tire 2 in the storage unit 14 in advance. Referring to FIG. 5 , the temperature (surface temperature) of multiple damaged portions 70 at different positions and depths in the tire 2 changes in accordance with changes in the cavity temperature of the tire 2. In FIG. 5 , the temperatures of the multiple damaged portions 70 are represented by dots, and the cavity temperature of the tire 2 is represented by a line. 5 , the temperature of the damaged portion 70 of the tire 2 changes depending on the cavity temperature of the tire 2. Therefore, by changing the threshold temperature used to detect the damaged portion 70 depending on the cavity temperature of the tire 2, the accuracy of detecting the damaged portion 70 can be improved.

[0054] Specifically, as shown by the arrows in FIG. 5 , the tire cavity temperature and the temperature of the damaged portion 70 behave nonlinearly over time. In the illustrated example, as the tire cavity temperature increases over time, the deviation between the tire cavity temperature and the temperature of the damaged portion 70 increases. Therefore, the threshold temperature may be set so that the higher the tire cavity temperature, the smaller the increase in the threshold temperature. This can further improve the accuracy of detecting the damaged portion 70 of the tire 2. In the present disclosure, the tire cavity temperature "when the thermoimage 60 is captured" may be the tire cavity temperature of the tire 2 at the time of capturing the thermoimage 60 or at a point in time closest to the time of capturing the thermoimage 60 in the time series data. Alternatively, it may be the tire cavity temperatures of multiple tires 2 over a predetermined period (e.g., one hour immediately before the time of capturing the thermoimage 60) based on the time of capturing the thermoimage 60. The tire cavity temperatures of multiple tires 2 over a predetermined period may be all time series data of the tire cavity temperatures measured within the predetermined period, or may be time series data from which singular points have been removed.

[0055] In this embodiment, the image analysis algorithm and the threshold temperature calculation algorithm may be constructed using a statistical method such as machine learning or deep learning. For example, these algorithms may be constructed using a statistical method using a thermographic image 60 of the tire 2 and a damaged portion 70 in the tire 2 identified by a human or the like as training data. This allows the accumulation of training data to improve the accuracy of detecting the damaged portion 70 on the outer surface of the tire 2. However, the image analysis algorithm and the calculation algorithm may include predetermined arithmetic processing that does not rely on a statistical method.

[0056] Referring again to FIG. 3, in step S106, the control unit 15 of the server 10 estimates the depth of the damaged portion 70 on the outer surface of the tire 2 captured in the thermal image 60.

[0057] Any method can be used to estimate the depth of the damaged portion 70. For example, the control unit 15 of the server 10 may estimate the depth of the damaged portion 70 from the surface temperature of the damaged portion 70 of the tire 2 detected in step S105. The control unit 15 may store in advance in the storage unit 14 a depth estimation algorithm for estimating the depth of the damaged portion 70 from the surface temperature of the damaged portion 70 on the outer surface of the tire 2. The control unit 15 estimates the depth of the damaged portion 70 from the surface temperature of the damaged portion 70 using the depth estimation algorithm. The depth of the damaged portion 70 may be set to, for example, a depth corresponding to the portion of the damaged portion 70 of the tire 2 with the highest surface temperature.

[0058] At this time, the control unit 15 of the server 10 may estimate the depth of the damaged portion 70 using not only the surface temperature of the damaged portion 70 of the tire 2 in the thermal image 60 but also the cavity temperature of the tire 2 included in the time-series data related to the tire 2 acquired from the measuring device 30. More specifically, in estimating the depth of the damaged portion 70 shown in the thermal image 60, the depth of the damaged portion 70 is corrected to a different value depending on the cavity temperature at the time the thermal image 60 was captured. That is, estimating the depth of the damaged portion 70 in step S106 includes correcting the depth of the damaged portion 70 depending on the cavity temperature at the time the thermal image 60 was captured. As shown in FIG. 5 , the surface temperature of the damaged portion 70 of the tire 2 changes depending on the cavity temperature of the tire 2. Therefore, by correcting the surface temperature of the damaged portion 70 using the relative relationship with the cavity temperature of the tire 2, the accuracy of estimating the depth of the damaged portion 70 can be improved.

[0059] As described above, in order to correct the depth of the damaged portion 70 estimated from the surface temperature of the damaged portion 70 on the outer surface of the tire 2 using the cavity temperature of the tire 2, the control unit 15 of the server 10 may store in advance in the storage unit 14 information correlating the surface temperature and depth of the damaged portion 70 with the cavity temperature of the tire 2. In the example shown in FIG. 5 , as indicated by the arrow, as the vehicle 3 travels and the cavity temperature of the tire 2 increases, the deviation between the temperature of the damaged portion 70 and the cavity temperature of the tire 2 increases. Therefore, in estimating the depth of the damaged portion 70, the control unit 15 may correct the depth of the damaged portion 70 such that the higher the cavity temperature of the tire 2 when the thermal image 60 is captured, the greater the correction amount for the depth of the damaged portion 70. In this way, by performing correction using the relative relationship between the surface temperature of the damaged portion 70 and the cavity temperature of the tire 2, the accuracy of estimating the depth of the damaged portion 70 can be improved.

[0060] In this embodiment, the depth estimation algorithm may be constructed using a statistical method such as machine learning or deep learning. For example, the depth estimation algorithm may be constructed using a statistical method using training data that includes the characteristics of the damaged portion 70 of the tire 2 and the depth of the damaged portion 70 measured by a human or the like. This allows the accumulation of training data to improve the accuracy of estimating the depth of the damaged portion 70 of the tire 2. However, the depth estimation algorithm may include a predetermined calculation process that does not rely on a statistical method.

[0061] Furthermore, estimating the depth of the damaged portion 70 in step S106 may include correcting the depth of the damaged portion 70 depending on the position of the damaged portion 70 in the tire 2. The position of the damaged portion 70 in the tire 2 may be expressed, for example, as a distance from the rotation axis R of the tire 2 in the tire radial direction, as shown in FIG. 4 . Here, the "tire radial direction" refers to a direction perpendicular to the rotation axis R of the tire. Even if the damaged portion 70 is at the same depth, the temperature (surface temperature) of the damaged portion 70 may differ depending on the position of the damaged portion 70 in the tire 2. For example, when a turned-up portion of the carcass ply of the tire 2 is present on the inner cavity side of the damaged portion 70, the surface temperature of the damaged portion 70 is higher than when no turned-up portion is present. This is because heat from the inner cavity of the tire 2 is absorbed by the turned-up portion of the carcass ply and is more easily transmitted to the damaged portion 70. In this way, the way in which the temperature of the cavity of the tire 2 is transmitted to the surface of the damaged portion 70 varies depending on, for example, differences in the internal structure such as the thickness of the rubber in the damaged portion 70 and the presence or absence of a carcass ply, or differences in the physical properties, such as thermal conductivity, of the components located on the cavity side of the damaged portion 70. Therefore, by taking into account the structural characteristics of the inside of the tire 2 that differ depending on the distance from the rotation axis R of the tire 2 in the tire radial direction, it is possible to further improve the accuracy of estimating the depth of the damaged portion 70.

[0062] The control unit 15 may store the estimated depth of the damaged portion 70 in the storage unit 14 as damage information of the tire 2 in association with the identification information of the tire 2. Note that if multiple damaged portions 70 are detected in the tire 2 captured in the thermal image 60, the control unit 15 may estimate the depth of each of the multiple damaged portions 70 in this step.

[0063] Referring back to FIG. 3, in step S107, the control unit 15 of the server 10 determines whether the depth of the damaged portion 70 of the tire 2 is within the allowable range of durability of the tire 2.

[0064] In the determination in step S107, the allowable range of durability of the tire 2 may be determined arbitrarily. For example, the allowable range of durability of the tire 2 may be determined as a range of the depth of the damaged portion 70 of the tire 2. For example, if the depth of the damaged portion 70 is deeper than a value determined as the allowable range of durability of the tire 2, the control unit 15 of the server 10 can determine that the depth of the damaged portion 70 of the tire 2 is outside the allowable range of durability of the tire 2. This allows the control unit 15 of the server 10 to automatically determine whether the tire 2 is within the allowable range of durability based on the depth of the damaged portion 70 of the tire 2. If multiple damaged portions 70 are detected in the tire 2 captured in the thermal image 60, the control unit 15 may perform this determination based on the damaged portion 70 estimated to be the deepest among the multiple damaged portions 70, or may perform this determination based on the total or average depth of the multiple damaged portions 70.

[0065] Furthermore, when multiple damaged portions 70 are detected in the tire 2 captured in the thermal image 60, the control unit 15 of the server 10 may determine whether the depths of the multiple damaged portions 70 are within an acceptable range based on the relative depths of the multiple damaged portions 70. Specifically, if the depth of any of the multiple damaged portions 70 detected in the tire 2 is relatively deeper than the other damaged portions 70, the progression of that damaged portion 70 is considered to be rapid. Therefore, when a damaged portion 70 that is relatively deeper than the other damaged portions 70 exists in the tire 2, the depth of the damaged portion 70 may be set to be more likely to exceed the acceptable range. For example, the control unit 15 may change the depth range of the damaged portions 70 of the tire 2, which is determined as the acceptable range for durability of the tire 2, in accordance with the average value or standard deviation of the depths of the multiple damaged portions 70. This can further improve the accuracy of determining whether the tire 2 is within the acceptable range for durability based on the depths of the damaged portions 70 of the tire 2.

[0066] Alternatively, the control unit 15 of the server 10 may change the depth range of the damaged portion 70 of the tire 2, which is determined as the allowable range of durability of the tire 2, depending on the position of the damaged portion 70 in the tire 2. As described above, the position of the damaged portion 70 in the tire 2 may be expressed, for example, by the distance from the rotation axis R of the tire 2 in the tire radial direction. For example, the durability of the damaged portion 70 varies depending on the internal structure, such as the thickness of the rubber in the damaged portion 70 and the presence or absence of a carcass ply. Therefore, by taking into account the internal structural characteristics of the tire 2, which differ depending on the distance from the rotation axis R of the tire 2 in the tire radial direction, it is possible to further improve the accuracy of determining whether the tire 2 is within the allowable range of durability.

[0067] Furthermore, in the determination in step S107, the allowable range of durability of the tire 2 may be determined in a composite manner using other factors in addition to the depth of the damaged portion 70 of the tire 2. The other factors may be, for example, information included in the time-series data related to the tire 2 acquired from the measuring device 30. As an example, the control unit 15 of the server 10 may determine whether the depth of the damaged portion 70 of the tire 2 is within the allowable range of durability of the tire 2 based on the depth of the damaged portion 70 of the tire 2 and the travel distance or travel time of the vehicle 3 equipped with the tire 2. Specifically, if the depth of the damaged portion 70 of the tire 2 is deep despite the vehicle 3 having a short travel distance or travel time, it is considered that the progression of the damaged portion 70 is rapid. Therefore, the allowable range may be set so that the deeper the depth of the damaged portion 70 of the tire 2 is and the shorter the travel distance or travel time of the vehicle 3 equipped with the tire 2 is, the more likely the depth of the damaged portion 70 is to fall outside the allowable range. This further improves the accuracy of determining whether the tire 2 is within the allowable range of durability based on the depth of the damaged portion 70 of the tire 2.

[0068] As another example, the control unit 15 of the server 10 may determine whether the depth of the damaged portion 70 of the tire 2 is outside the allowable range for durability of the tire 2, based on the depth of the damaged portion 70 of the tire 2 and the thermal history of the tire 2. Specifically, if the thermal history of the tire 2 is large, it is considered that the tire 2 has already deteriorated and the progression of the damaged portion 70 of the tire 2 is rapid. Therefore, the allowable range may be set so that the deeper the depth of the damaged portion 70 of the tire 2 is and the larger the thermal history of the tire 2, the more likely the depth of the damaged portion 70 is to fall outside the allowable range. This can improve the accuracy of determining whether the damaged portion 70 of the tire 2 exceeds the allowable range for durability of the tire 2.

[0069] The tolerance range of the durability of the tire 2 may be set in multiple stages. For example, the tolerance range of the durability of the tire 2 may be set in stages, such as a level at which the tire 2 needs to be replaced immediately, a level at which the tire 2 needs to be replaced within one month, a level at which the tire 2 needs to be replaced within two months, etc. This allows the tire failure determination system 1 to perform different processing, such as sending different warning messages, depending on the level of the tolerance range of durability.

[0070] In step S108, if the control unit 15 of the server 10 determines that the damaged portion 70 of the tire 2 is outside the acceptable range, it outputs damage information of the tire 2, including the position, number, or depth of the damaged portion 70.

[0071] Any method can be adopted for outputting the damage information of the tire 2. For example, the control unit 15 of the server 10 may display the damage information of the tire 2 via the output unit 12, such as a display. Alternatively, the control unit 15 may transmit a request to display the damage information of the tire 2 to the terminal device 40 via the communication unit 11. In such a case, the terminal device 40 can display the damage information of the tire 2 via a display or the like based on the request received from the server 10 in step S109. The damage information of the tire 2 includes, for example, the depth of the damaged portion 70 of the tire 2. However, the damage information of the tire 2 is not limited to the depth of the damaged portion 70 of the tire 2, and may include any information such as the position, number, and warning message of the damaged portion 70. As a result, a user of the tire malfunction determination system 1 can easily grasp the depth of the damaged portion 70 on the outer surface of the tire 2 and can plan inspection, repair, replacement, etc. of the tire 2 before the tire 2 malfunctions. In particular, when the tire 2 is replaced, the tire 2 may be replaced with a different tire 2 depending on the damage information of the tire 2. For example, if the surface temperature of the damaged portion 70 of the tire 2 is higher than the temperature limit set for the tire 2, the tire 2 may be replaced with a different type of tire 2 that has higher heat resistance. Alternatively, if the number of damaged portions 70 of the tire 2 is greater than a predetermined number, the tire 2 may be replaced with a different type of tire 2 that is less susceptible to the formation of damaged portions 70. In this way, the user of the tire failure determination system 1 can select tires 2 that are suitable for use at mining sites based on the damage information of the tires 2.

[0072] As described above, in this embodiment, the server 10, which is a tire malfunction determination device, acquires a thermographic image 60 of the tire 2 captured by a thermographic camera, and also acquires the cavity temperature of the tire 2. The server 10 estimates the depth of the damaged portion 70 based on the surface temperature of the damaged portion 70 of the tire 2 in the thermographic image 60 and the cavity temperature at the time the thermographic image 60 was captured.

[0073] According to this configuration, the server 10 can more accurately estimate the depth of the damaged portion 70 by using the inner cavity temperature of the tire 2 in addition to the surface temperature of the damaged portion 70 of the tire 2 in the thermal image 60. Therefore, according to this embodiment, the usefulness of the technology for determining a fault in the tire 2 can be improved.

[0074] In the above-described operational example, the tire malfunction determination system 1 detects a damaged portion 70 on the outer surface of the side of the tire 2. However, this is not limiting. The outer surface of the tire 2 processed by the tire malfunction determination system 1 may include at least one of the outer surface of the side or the outer surface of the tread of the tire 2. That is, the tire malfunction determination system 1 may be used to detect a damaged portion 70 on the outer surface of the tread of the tire 2 in addition to or instead of the side of the tire 2. In such a case, the imaging device 20 may be installed in a position capable of capturing an image of the front or rear of the vehicle 3 in order to capture an image of the tread of the tire 2. As in the above-described operational example, the server 10 acquires a thermal image 60 of the tread of the tire 2 from the imaging device 20 and also acquires the cavity temperature of the tire 2. The server 10 estimates the depth of the damaged portion 70 based on the surface temperature of the damaged portion 70 of the tire 2 in the thermal image 60 and the cavity temperature at the time the thermal image 60 was captured. This allows the server 10 to determine the depth of the damaged portion 70 on the outer surface of the tread portion of the tire 2 in addition to / instead of the side portion of the tire 2.

[0075] Although the present disclosure has been described based on the drawings and embodiments, it should be noted that those skilled in the art can make various modifications and alterations based on the present disclosure. Therefore, it should be noted that these modifications and alterations are included within the scope of the present disclosure. For example, the configurations or functions included in each embodiment can be rearranged so as not to cause logical inconsistencies. Furthermore, the configurations or functions included in each embodiment can be used in combination with other embodiments, and multiple configurations or functions can be combined into one, divided, or partially omitted.

[0076] Also, for example, an embodiment is possible in which a general-purpose computer functions as the server 10 according to the above-described embodiment. Specifically, a program describing the processing content for realizing each function of the server 10 according to the above-described embodiment is stored in the memory of the general-purpose computer, and the program is read and executed by a processor. Therefore, the present disclosure can also be realized as a program executable by a processor or a non-transitory computer-readable medium storing the program. Examples of non-transitory computer-readable media include a magnetic recording device, an optical disk, a magneto-optical recording medium, and a semiconductor memory.

[0077] According to the present disclosure, it is possible to provide a tire fault determination method and a tire fault determination device that can improve the usefulness of the technology for determining tire faults.

[0078] 1: Tire failure determination system, 2: Tire, 3: Vehicle, 10: Server (tire failure determination device), 11: Communication unit, 12: Output unit, 13: Input unit, 14: Storage unit, 15: Control unit, 20: Imaging device, 30: Measuring device, 40: Terminal device, 50: Network, 60: Thermographic image, 70: Damaged part, R: Rotating shaft

Claims

1. A tire fault determination method executed by a computer, comprising: acquiring a thermographic image of a tire taken with a thermographic camera; acquiring the tire cavity temperature; and estimating the depth of the damaged portion based on the surface temperature of the damaged portion of the tire in the thermographic image and the tire cavity temperature at the time the thermographic image was taken.

2. A tire fault detection method as described in claim 1, further comprising detecting, as the damaged portion, a portion of the outer surface of the tire captured in the thermographic image that has a temperature higher than a threshold value or more than the surrounding portions, wherein the threshold temperature is changed depending on the inner cavity temperature at the time the thermographic image is captured.

3. A tire fault determination method as described in claim 1 or 2, wherein estimating the depth of the damaged portion includes correcting the depth of the damaged portion according to the inner cavity temperature at the time the thermal image was captured.

4. A tire fault determination method as described in claim 3, wherein estimating the depth of the damaged portion includes correcting the depth of the damaged portion such that the higher the inner cavity temperature when the thermoimage is captured, the greater the correction amount of the depth of the damaged portion.

5. A tire fault determination method as described in claim 1 or 2, wherein estimating the depth of the damaged portion includes correcting the depth of the damaged portion depending on the position of the damaged portion in the tire.

6. The tire fault determination method according to claim 1 or 2, further comprising determining whether the depth of the damaged portion is within an acceptable range for durability of the tire.

7. The tire fault detection method of claim 6, wherein the determining step includes, when multiple damaged portions are detected in the tire, determining whether or not the depths of the multiple damaged portions are within the tolerance range based on relative depths of the multiple damaged portions.

8. A tire failure determination method as described in claim 6, further comprising obtaining a travel distance or a travel time of a vehicle equipped with the tire, and wherein said determining includes determining whether or not the depth of the damaged portion is within the tolerance range based on the depth of the damaged portion and the travel distance or the travel time of the vehicle, and wherein said tolerance range is set such that the greater the depth of the damaged portion is and the shorter the travel distance or the travel time of the vehicle, the more likely it is that the depth of the damaged portion will deviate from the tolerance range.

9. A tire malfunction determination device comprising a control unit configured to: acquire a thermographic image of a tire taken with a thermographic camera; acquire the tire cavity temperature; and estimate the depth of the damaged portion based on the surface temperature of the damaged portion of the tire in the thermographic image and the tire cavity temperature at the time the thermographic image was taken.

Images