Leakage monitoring device, leakage monitoring method and leakage monitoring system

Abstract

To improve a technique for determining air leakage of a tire.SOLUTION: A leakage monitoring device for monitoring air leakage in a tire, includes a communication unit and a control unit. The communication unit is capable of receiving internal pressure information indicating internal pressures of a plurality of tires mounted on a vehicle. The control unit divides a plurality of tires mounted on the vehicle into a plurality of groups. The control unit acquires an internal pressure of each tire via the communication unit during traveling of the vehicle and estimates an internal temperature of each tire, based on the internal pressure. The control unit compares the estimated internal temperatures of the plurality of tires belonging to the same group to determine whether or not there is a possibility of the occurrence of air leakage in any of the tires.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a leak monitoring device, a leak monitoring method, and a leak monitoring system. [Background technology]

[0002] There are two types of drop in air pressure inside a tire: a sudden drop, as typified by a puncture or burst, and a gradual drop known as a slow leak. Historical data on tire air pressure can be monitored to determine the occurrence of a slow leak. However, monitoring changes in air pressure for each tire can lead to erroneous determinations due to differences in vehicle operating conditions. For this reason, a technique has been proposed for determining the occurrence of a slow leak by taking into account drops in internal pressure in other tires mounted on the same vehicle (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2022-90477 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the cited document 1, although the change in air pressure of other tires is compared, the occurrence of a slow leak is basically determined by setting a threshold value for the amount of decrease in internal pressure for one tire. However, the amount of gas inside a tire is also affected by the internal temperature of the tire. For this reason, there is room for improvement in the accuracy of the slow leak determination in the cited document 1. Also, in the cited document 1, for example, a representative value (e.g., average, median or mode) of the air pressure of each tire is calculated for a relatively long period measured in days, and the decrease in this representative value is used as the degree of decrease in air pressure for each tire. For this reason, the method disclosed in the cited document 1 makes it difficult to respond to air leaks in tires that occur in real time while driving.

[0005] Therefore, an object of the present disclosure, which has been made in light of these points, is to improve the technology for determining air leakage from a tire. [Means for solving the problem]

[0006] (1) A leak monitoring device according to one aspect of the present disclosure is a leak monitoring device that monitors air leakage from tires, and includes a communication unit configured to receive internal pressure information indicating the internal pressure of multiple tires mounted on a vehicle, and a control unit that divides multiple tires mounted on a vehicle into multiple groups, acquires the internal pressure information for each tire via the communication unit while the vehicle is traveling, estimates the internal temperature of each tire based on the internal pressure, and compares the estimated internal temperatures of the multiple tires belonging to the same group to determine whether or not there is a possibility of air leakage in any tire. According to the leak monitoring device according to one aspect of the present disclosure, it is possible to improve the technology for determining air leakage from tires. In particular, this leak monitoring device can determine whether or not there is a possibility of air leakage from a tire without using temperature data from a temperature sensor with low measurement accuracy while the vehicle is traveling. Furthermore, this leak monitoring device can handle monitoring of air leakage from tires that occurs in real time while the vehicle is traveling.

[0007] (2) A leak monitoring device according to an embodiment of the present disclosure is the leak monitoring device described in (1) above, wherein the communication unit is further configured to receive measurements of the internal temperatures of the tires, and the control unit acquires the measurements of the internal temperatures and the internal pressure information for each of the tires under conditions where the measurement accuracy of the internal temperatures of the tires is high before estimating the internal temperatures of each of the tires while the vehicle is running, calculates a proportionality coefficient between the internal temperature and the internal pressure for each of the tires, and estimates the internal temperature of each of the tires while the vehicle is running based on the internal pressure and the proportionality coefficient acquired while the vehicle is running. A leak monitoring device having such a configuration makes it possible to estimate the internal temperature of a tire while the vehicle is running with high accuracy when there is no air leakage.

[0008] (3) A leak monitoring device according to an embodiment of the present disclosure is the leak monitoring device described in (1) or (2) above, wherein the control unit is capable of determining that there is a possibility of air leakage in the first tire when a difference between the estimated internal temperature of a first tire and an average value of the estimated internal temperatures of other tires in a group to which the first tire belongs is equal to or greater than a predetermined threshold. With a leak monitoring device having such a configuration, the possibility of air leakage from a tire can be clearly determined using a threshold, and the accuracy of air leakage determination and the frequency of occurrence of determination errors can be adjusted by changing the threshold.

[0009] (4) A leak monitoring device according to an embodiment of the present disclosure is the leak monitoring device described in any one of (1) to (3) above, in which the control unit can divide the tires into two groups: a group of tires mounted on the front side of the vehicle and a group of tires mounted on the rear side of the vehicle. A leak monitoring device having such a configuration can monitor tire air leakage with high accuracy regardless of the weight of the cargo loaded on the vehicle.

[0010] (5) A leak monitoring device according to an embodiment of the present disclosure is the leak monitoring device described in any one of (1) to (3) above, wherein the control unit can divide the tires into three groups: a group of tires mounted on the front side of the vehicle, a group of tires mounted on the outer rear side of the vehicle, and a group of tires mounted on the inner rear side of the vehicle. A leak monitoring device having such a configuration can monitor tire air leakage with even higher accuracy regardless of the weight of the cargo loaded on the vehicle.

[0011] (6) A leak monitoring device according to an embodiment of the present disclosure is the leak monitoring device described in any one of (1) to (5) above, wherein the control unit can group the plurality of tires based on the previously estimated internal temperatures of each tire included in the plurality of tires. A leak monitoring device having such a configuration can group the tires even if the positional relationship between each tire and a sensor unit that detects the internal pressure is not stored.

[0012] (7) A leak monitoring device according to an embodiment of the present disclosure is the leak monitoring device according to any one of (1) to (5), in which the control unit provisionally groups the plurality of tires based on a median value of the internal temperature estimated in the past for each tire included in the plurality of tires, selects one reference tire from the plurality of second tires provisionally grouped into the same group, and determines whether each of the second tires belongs to the same group based on at least one of the difference in slope of an approximation line obtained by plotting the estimated internal temperature of the reference tire at the same time as the X-axis value and the estimated internal temperature of the second tire as the Y-axis value for each of the second tires and the difference in Y-intercept of the approximation line. According to the leak monitoring device having such a configuration, when the positional relationship between each tire and a sensor unit that detects the internal pressure is not stored, the accuracy of grouping the plurality of tires of a vehicle can be improved.

[0013] (8) A leak monitoring method according to one aspect of the present disclosure is a leak monitoring method for monitoring air leakage from tires, executed by a computer, and includes: grouping a plurality of tires mounted on a vehicle into a plurality of groups; acquiring internal pressure information indicating the internal pressure of each tire while the vehicle is traveling, estimating the internal temperature of each tire based on the internal pressure; and determining whether or not there is a possibility of air leakage in any tire by comparing the estimated internal temperatures of the plurality of tires belonging to the same group. According to the leak monitoring method according to one aspect of the present disclosure, it is possible to improve the technology for determining air leakage from tires. In particular, this leak monitoring method can determine whether or not there is a possibility of air leakage from a tire without using temperature data from a temperature sensor with low measurement accuracy while the vehicle is traveling. Furthermore, this leak monitoring method can handle monitoring of air leakage from tires that occurs in real time while the vehicle is traveling.

[0014] (9) A leak monitoring system according to an embodiment of the present disclosure includes a sensor for detecting the internal pressure of a plurality of tires mounted on a vehicle, and a control unit for dividing the plurality of tires mounted on the vehicle into a plurality of groups, acquiring internal pressure information indicating the internal pressure of each tire detected by the sensor while the vehicle is traveling, estimating the internal temperature of each tire based on the internal pressure, and comparing the estimated internal temperatures of the plurality of tires belonging to the same group to determine whether or not there is a possibility of air leakage in any tire. According to the leak monitoring system according to an embodiment of the present disclosure, it is possible to improve the technology for determining air leakage in a tire. In particular, this leak monitoring system can determine whether or not there is a possibility of air leakage in a tire without using temperature data from a temperature sensor with low measurement accuracy while the vehicle is traveling. Furthermore, this leak monitoring system can handle monitoring of air leakage in tires that occurs in real time while the vehicle is traveling. Effect of the Invention

[0015] According to the present disclosure, the technology for determining tire air leakage can be improved. [Brief description of the drawings]

[0016] [Figure 1] 1 is a block diagram showing a schematic configuration of a leak monitoring system 1 according to an embodiment of the present disclosure. [Diagram 2] FIG. 2 is a diagram showing an example of tire arrangement on the vehicle of FIG. 1. [Diagram 3] FIG. 1 shows the balance of loads applied to each tire of a vehicle, where (a) shows the balance of loads applied to each tire when the vehicle is empty, and (b) shows the balance of loads applied to each tire when the vehicle is loaded with cargo. [Figure 4] FIG. 11 is a diagram showing another example of tire grouping. [Diagram 5] 13 is a graph showing an image of the distribution of the internal temperature of each tire relative to the internal temperature of a reference tire, where (a) is a graph for all tires, (b) is a graph for the tires in the front wheel group, (c) is a graph for the tires in the inner rear wheel group, and (d) is a graph for the tires in the outer rear wheel group. [Figure 6] 4 is a flowchart showing an example of a procedure for detecting air leakage from a tire. [Figure 7] FIG. 4 is a diagram illustrating a change in internal temperature of a tire. [Figure 8] 10 is a flowchart showing an example of a procedure for grouping tires. [Figure 9] FIG. 1 is a diagram illustrating a difference in frequency distribution of the internal temperature of a tire. [Figure 10] FIG. 13 is a diagram showing an example of grouping using the median value of the internal temperature of a tire. [Figure 11] FIG. 13 is a diagram illustrating a method for determining whether tires belong to the same group. [Figure 12] 4 is a flowchart showing an example of a procedure for determining air leakage from a tire. [Figure 13] FIG. 11 is a diagram showing an example of a change in an estimated tire internal temperature over time. [Figure 14]FIG. 13 is a diagram showing an example of tire arrangement and grouping in another vehicle. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0018] (Overall configuration of leak monitoring system) A leak monitoring system 1 according to an embodiment of the present disclosure is a system that monitors a slow leak in a tire 11 of a vehicle 10. A slow leak refers to an air leak (leak) accompanied by a drop in internal pressure of approximately more than 50 kPa per month. As shown in FIG. 1, the leak monitoring system 1 includes a vehicle 10 and a leak monitoring device 20.

[0019] The vehicle 10 is a large vehicle, such as a large truck, capable of carrying a large amount of cargo. The leak monitoring device 20 is a computer capable of communicating with the vehicle 10 via a communication network 30. The leak monitoring device 20 may be a server personal computer (PC), a workstation, or other computer. The communication network 30 may include a network such as the Internet, a fourth generation mobile communication system (4G (4th Generation)) such as LTE (Long Term Evolution) and / or a fifth generation mobile communication system (5G (5th Generation)).

[0020] The vehicle 10 is equipped with a plurality of tires 11. The tires 11 are pneumatic tires. The number of tires 11 equipped on one vehicle 10 may be, for example, 6, 8, 10, 12, etc., but is not limited thereto. In the following description, the number of tires 11 on the vehicle 10 is 12, as shown in FIG. 2. In each drawing and the following description, when each tire 11 is to be distinguished from the others, a code for identifying the tire 11 is added in parentheses after the code 11 representing the tire, such as 11(1R) and 11(1L). For example, the tire 11(1R) is the right tire attached to the first axle from the front of the vehicle 10. Also, for example, the tire 11(3L1) is the first tire from the outside on the left side attached to the third axle.

[0021] (Sensor unit configuration) A sensor unit 12 is attached to each tire 11 of the vehicle 10. The sensor unit 12 is, for example, a tire pressure monitoring system (TPMS). The TPMS is attached, for example, to a valve body or a valve cap of the wheel of the tire 11. This method is called a valve-type TPMS. The TPMS is also attached, for example, by wrapping it around the wheel rim of the tire 11. This method is called a band-type TPMS.

[0022] As shown in FIG. 1, the sensor unit 12 includes an internal pressure sensor 13, a temperature sensor 14, a control unit 15, a storage unit 16, a battery 17, and a sensor communication unit 18.

[0023] The internal pressure sensor 13 is a sensor that measures the air pressure inside the tire 11. The air pressure inside the tire 11 is called the internal tire pressure P. The internal tire pressure P is the air pressure in the inner cavity of the tire 11. The internal pressure sensor 13 can be any pressure sensor. The pressure sensor may be, for example, a piezo-resistance type sensor or a capacitance type sensor.

[0024] The temperature sensor 14 is a sensor that measures the internal temperature of the tire 11. The internal temperature T of the tire 11 is the temperature of the gas, for example, the air, inside the cavity of the tire 11. Any temperature sensor can be adopted as the temperature sensor 14. The temperature sensor 14 may be, for example, a sensor using a thermocouple or a sensor using a resistance temperature detector.

[0025] The control unit 15 executes various processes performed by the sensor unit 12. The control unit 15 may include one or more processors such as a CPU (Central Processing Unit). The control unit 15 may read a control program for the sensor unit 12 from the storage unit 16 and execute the program.

[0026] The memory unit 16 can store various information necessary for processing by the control unit 15. The memory unit 16 may include semiconductor memory such as a read only memory (ROM) and a random access memory (RAM). The memory unit 16 may store identification information unique to the sensor unit 12. The memory unit 16 may temporarily store the internal pressure P of the tire 11 detected by the internal pressure sensor 13 and the internal temperature T of the tire 11 detected by the temperature sensor 14.

[0027] The battery 17 supplies power required for operation to each component of the sensor unit 12. As the battery 17, a known battery such as a lithium battery can be used.

[0028] The sensor communication unit 18 includes a communication device capable of wireless communication with the outside of the tire 11. The communication device may include a transmission / reception circuit and an antenna. The sensor communication unit 18 may support any communication method such as Bluetooth (registered trademark), BLE (Bluetooth Low Energy), and NFC (Near Field Communication). The sensor communication unit 18 receives a transmission request from a vehicle communication device 19 provided in the vehicle 10, and transmits information on the measurement values ​​of the internal pressure P and internal temperature T of the tire 11, as well as identification information of the sensor unit 12, etc. to the vehicle communication device 19.

[0029] The vehicle communication device 19 of the vehicle 10 communicates with the sensor unit 12 and the leak monitoring device 20. The vehicle communication device 19 is an information processing device equipped with a short-range wireless communication interface for communicating with the sensor unit 12 and a wireless communication interface for communicating with the leak monitoring device 20 via the communication network 30. The wireless communication interface may include a communication interface compatible with a fourth generation mobile communication system (4G) and / or a fifth generation mobile communication system (5G). The vehicle communication device 19 can collect various information from the vehicle 10 periodically or based on a request from the leak monitoring device 20 and transmit the collected information to the leak monitoring device 20. The vehicle communication device 19 can transmit information on the measurement values ​​of the internal pressure P and internal temperature T of the tire 11 collected from the sensor unit 12, identification information of the sensor unit 12, and the like to the leak monitoring device 20. Furthermore, the vehicle communication device 19 may transmit to the leak monitoring device 20, for example, information on whether the engine of the vehicle 10 is ON / OFF, information on whether the vehicle is moving or not, location information by GPS (Global Positioning System), and the like.

[0030] (Leak monitoring device configuration) As shown in FIG. 1, the leak monitoring device 20 includes a communication unit 21, a control unit 22, a storage unit 23, and an output unit 24.

[0031] The communication unit 21 includes a communication interface compatible with wired communication and / or wireless communication. The communication unit 21 can transmit and receive information to and from devices external to the leak monitoring device 20 via the communication network 30. The communication unit 21 can obtain internal pressure information indicating the internal pressure P of the tire 11 detected by the sensor unit 12, a measurement value of the internal temperature T, identification information of the sensor unit 12, and the like from the vehicle communication device 19 of the vehicle 10 via the communication network 30.

[0032] The control unit 22 includes, for example, one or more processors. The processor may be a general-purpose processor such as a CPU (Central Processing Unit) that executes a program that defines a control procedure, or may be a dedicated processor specialized for a specific process. The control unit 22 performs calculations for executing each function of the leak monitoring device 20 and controls each component of the leak monitoring device 20.

[0033] The storage unit 23 is one or more memories. The memory may be, for example, a semiconductor memory, a magnetic memory, or an optical memory, but is not limited to these and may be any memory. The semiconductor memory may include a volatile memory such as a random access memory (RAM), and a non-volatile memory such as a read only memory (ROM) and a flash memory. The magnetic memory may include, for example, a hard disk and a magnetic tape. The optical memory may include, for example, a compact disc (CD) and a digital versatile disc (DVD).

[0034] The storage unit 23 may store a program for operating a computer as the leak monitoring device 20. The control unit 22 operates as the leak monitoring device 20 by reading the program stored in the storage unit 23. The program for the leak monitoring device 20 may be provided in a form stored in a non-transitory storage medium such as a CD-ROM (Compact Disk Read Only Memory), a DVD-ROM (Digital Versatile Disk Read Only Memory), or a USB (Universal Serial Bus) memory. The program for the leak monitoring device 20 may also be downloaded from an external device via the communication network 30.

[0035] The output unit 24 includes a device that outputs information generated as a result of processing by the control unit 22. The output unit 24 includes, for example, a display and / or a speaker. The display includes, for example, a liquid crystal display (LCD), an organic electro-luminescence (EL) display, and an inorganic EL display, but is not limited to these. When the control unit 22 causes the communication unit 21 to output information to an external device, the communication unit 21 may function as the output unit 24.

[0036] (Principle of determining air leakage) The amount of gas inside the tire 11 can be determined by the pressure, temperature, and volume of the gas. In the range of slow leaks that are the subject of detection in this disclosure, the volume of the cavity of the tire 11 can be considered constant. In the following, for simplicity, the equation of state for an ideal gas will be used. The equation of state for an ideal gas is expressed as follows: PV=nRT (1) Here, P is the internal pressure of the tire 11, V is the volume of the inner cavity of the tire 11, n is the amount of substance in moles, R is the gas constant, and T is the internal temperature of the tire 11 expressed in absolute temperature.

[0037] Since the amount of substance n is the amount of gas inside the tire 11, the leakage of air from the tire 11 means a decrease in the amount of substance n. When the volume V is constant, the amount of substance n can be determined from the internal pressure P and internal temperature T of the tire 11. This is the same when an actual gas is used. In other words, if the internal pressure P and internal temperature T of the tire 11 can be continuously monitored, air leakage from the tire 11 can be monitored.

[0038] However, when using a conventional sensor unit 12 such as a TPMS, it may not be possible to accurately measure the temperature while the vehicle 10 is running. In particular, in valve-type and band-type TPMS, the sensor is cooled by the outside air, so the temperature measured by the temperature sensor 14 is lower than the actual internal temperature T of the tire 11. Therefore, it is difficult to accurately monitor air leakage from the tire 11 using the output of the temperature sensor 14 of the sensor unit 12.

[0039] On the other hand, the temperature of the tires 11 while traveling changes depending on the load applied to the tires 11. The load applied to the tires 11 differs depending on the mounting position of the tires 11 on the vehicle 10. FIG. 3 shows the ratio of the load applied to each tire 11 for one model case of the vehicle 10, quantified. FIG. 3(a) shows the load applied to each tire 11 when the vehicle is empty, i.e., unloaded. FIG. 3(b) shows the load applied to each tire 11 when the vehicle is loaded with cargo close to the maximum load. Both are expressed as a ratio to the load 1 of the front tire 11 (1R).

[0040] 3(a) and (b), the loads applied to the tires 11(1R), 11(2R), 11(1L), and 11(2L) on the front side of the vehicle 10 are approximately the same when the vehicle is empty and when it is loaded. Hereinafter, these tires 11(1R), 11(2R), 11(1L), and 11(2L) are referred to as the front wheel group G1. Since the loads applied to the tires 11(1R), 11(2R), 11(1L), and 11(2L) of the front wheel group G1 are always approximately the same, the temperatures during driving are also approximately the same.

[0041] 3(a) and (b), the loads applied to the rear tires 11(3R1), 11(3R2), 11(3L1), 11(3L2), (4R1), 11(4R2), 11(4L1), and 11(4L2) of the vehicle 10 are substantially the same when the vehicle is empty and when it is loaded. Hereinafter, these tires 11(3R1), 11(3R2), 11(3L1), 11(3L2), (4R1), 11(4R2), 11(4L1), and 11(4L2) will be referred to as the rear wheel group G2. The loads of the tires 11(3R1), 11(3R2), 11(3L1), 11(3L2), (4R1), 11(4R2), 11(4L1), and 11(4L2) of the rear wheel group G2 are always approximately equal to each other, and therefore the temperatures during driving are also approximately equal to each other.

[0042] Therefore, in the leak monitoring system 1 of the present disclosure, air leakage from a tire 11 of a vehicle 10 is determined by measuring and comparing the internal pressure of each tire 11 within a group of tires 11 of the same vehicle 10 that have the same temperature change tendency. In addition, as a method of comparison, the internal temperature T of multiple tires 11 belonging to the same group is estimated on the assumption that there is no air leakage. Any tire 11 in the same group is set as a first tire. If the estimated internal temperature T of the first tire is lower than the average internal temperature T of the other tires 11 by a predetermined threshold or more, it is estimated that the amount of substance n has decreased in the first tire, contrary to the assumption. Therefore, in this case, it is determined that air leakage has occurred in the first tire with the lower internal temperature T.

[0043] The grouping of the tires 11 of the vehicle 10 is not limited to the method of grouping into two groups, the front wheel group G1 and the rear wheel group G2, as shown in FIG. 3. For example, if the load balance is intentionally set according to each axle or tire position in the vehicle design, the tires can be grouped according to the balance setting. Also, if there is a tendency of the load balance due to the habit of the vehicle body, the tires can be grouped based on the tendency. For example, as shown in FIG. 4, the rear wheel group G2 may be further divided into an outer rear wheel group G2-1 and an inner rear wheel group G2-2. The outer rear wheel group G2-1 is made up of the tires 11(3R1), 11(3L1), 11(4R1), and 11(4L1) on the outer rear side of the vehicle 10. The inner rear wheel group G2-2 is made up of the tires 11(3R2), 11(3L2), 11(4R2), and 11(4L2) on the inner rear side of the vehicle 10. Such grouping can be applied when a particular type of vehicle 10 is set or tends to be set such that the tires 11 in the inner rear group G2-2 are subjected to a larger load than the tires 11 in the outer rear group G2-1. If there is no air leakage, the tires 11 in the outer rear group G2-1 and the tires 11 in the inner rear group G2-2 will have approximately the same temperature change within each group.

[0044] FIG. 5(a) is a graph showing an image of tires 11 in each group of a vehicle 10, for example, a tire 11 selected from the front wheel group G1 as a reference tire, the internal temperature of the reference tire during driving is taken on the horizontal axis, and the internal temperature of each tire 11 is taken on the vertical axis. Even for the same vehicle 10, the points on the graph are not arranged in a linear manner, but are distributed with variation. The main cause of such variation is that the balance of the load applied to each tire 11 changes depending on the loading situation, even for the same vehicle. FIG. 5(b) is an image of a graph created similar to FIG. 5(a) only for tires 11 in the front wheel group G1. FIG. 5(c) is an image of a graph created similar to FIG. 5(a) for each tire 11 in the rear inner wheel group G2-1 as a reference tire. FIG. 5(d) is an image of a graph similar to FIG. 5(a) created for each tire 11 in the rear outer group G2-2, with a tire 11 selected from the rear outer group G2-2 as the reference tire. In FIG. 5(b) to FIG. 5(d), the tires 11 in the group are distributed in a narrow range in an almost linear manner. FIG. 5(b) to FIG. 5(d) show that the internal temperatures of the tires 11 in the same group are almost equal to each other even during driving. This is because the loads applied to the tires in the same group are almost the same, and the conditions such as the speed and the outside air temperature are also almost the same. In addition, the tires of the vehicle 10 can be grouped so that the relationship between the temperature of the reference tire and the temperatures of the other tires in each group is linear, as shown in FIG. 5(b) to FIG. 5(d).

[0045] (Leak monitoring procedure) An example of a procedure executed by the control unit 22 of the leak monitoring device 20 in the leak monitoring system 1 of the present disclosure will be described with reference to the flowchart of Fig. 6. The flowchart of Fig. 6 illustrates a leak monitoring method executed by the leak monitoring device 20.

[0046] First, the control unit 22 acquires information on the measurement values ​​of the internal temperature T0 and the internal pressure P0 for each of the multiple tires 11 under conditions where the measurement accuracy of the internal temperature T of the tire 11 is high (step S101). The conditions where the measurement accuracy of the internal temperature T of the tire 11 is high are, for example, a state where the vehicle 10 has been parked for a predetermined time or more, or a state where the internal temperature T of the tire 11 has not yet increased, immediately after starting to run after being parked for a predetermined time or more. The control unit 22 can use the internal temperature T0 and the internal pressure P0 of the tire 11 acquired, for example, from two or three days ago to two weeks ago, at a time when it is estimated that there was no air leakage in the tire 11.

[0047] As described above, the internal temperature T of the tire 11 measured by the temperature sensor 14 of the sensor unit 12 while the vehicle 10 is running is low in measurement accuracy and lacks precision. However, when the vehicle 10 is stopped for a certain period of time or more, the internal temperature T of the tire 11 becomes almost equal to the outside air temperature. The certain period of time is, for example, three hours. This will be described with reference to FIG. 7. The graph in FIG. 7 shows an example of the change in the internal temperature T of the tire 11 over time. The solid line portion of the graph indicates that the vehicle 10 is in operation, and the dashed line portion indicates that the vehicle 10 is stopped. In the solid line portion, the internal temperature T of the tire 11 rises due to the running of the vehicle 10, but the temperature detected by the temperature sensor 14 is an inaccurate temperature due to the influence of the outside air. On the other hand, after the vehicle is stopped, the temperature of the tire 11 gradually drops to the outside air temperature as shown by the dashed line. At this time, the temperature measured by the temperature sensor 14 also becomes almost equal to the outside air temperature.

[0048] In the case of a vehicle 10 such as a large truck used in the transportation industry, the vehicle may be stopped with the engine running for the driver to take a rest, or may be stopped with the engine turned off. After a certain period of time has passed in these states, or immediately after the vehicle starts traveling after a certain period of time has passed in these states, the temperature sensor 14 can measure the internal temperature T of the tire 11 with high measurement accuracy.

[0049] The vehicle communication device 19 may periodically transmit the ON / OFF state of the engine of the vehicle 10, the running state of the vehicle 10, and / or the location information of the vehicle 10 to the leak monitoring device 20. Alternatively, the vehicle communication device 19 may not transmit information to the leak monitoring device 20 when the engine is OFF. The control unit 22 of the leak monitoring device 20 may determine that the vehicle 10 is stopped based on information received from the vehicle communication device 19 of the vehicle 10 or based on the absence of reception of information from the vehicle 10. For example, the control unit 22 may determine that the vehicle 10 is stopped when the location information received from the vehicle 10 does not change. Furthermore, the control unit 22 may determine that the vehicle 10 is stopped with the engine OFF when no information is received from the vehicle 10.

[0050] Next, the control unit 22 calculates a proportionality coefficient k0 between the internal temperature T and internal pressure P of each tire 11 using the measured value of the internal temperature T0 of the tire 11 and the information on the internal pressure P0 acquired in step S101 (step S102). The control unit 22 calculates a proportionality coefficient k0 between the internal temperature T and internal pressure P of each tire 11 using the internal pressure P0 and internal temperature T0 of each tire 11 acquired via the communication unit 21. From formula (1), when k0=T0 / P0=(V / n0R) (n0 is the amount of gas in the cavity of the tire 11 when the internal pressure P0 and internal temperature T0 of the tire 11 were measured in step S101), the internal temperature T and internal pressure P of the tire 11 are expressed by the following formula (2). T=k0P (2) By using the formula (2), it is possible to estimate the internal temperature T of the tire 11 while the vehicle 10 is running, assuming that there is no air leakage, from the internal pressure P of the tire 11. k0 and n0 are variables that differ for each tire 11.

[0051] The control unit 22 can calculate the converted value of the internal pressure P of the tire 11 at a predetermined temperature (for example, 25°C) based on the formula (2). The control unit 22 can calculate the converted value of the internal pressure P of the tire 11 at a predetermined temperature every time the vehicle 10 stops for a predetermined time or more, and can confirm that no abnormal leak has occurred in the most recent past period. If the internal pressure has not decreased by more than 50 kPa per month, for example, the control unit 22 can determine that the air leakage of the tire 11 is within the range of natural leakage and that a slow leak has not occurred. Conversely, if it is determined that the internal pressure has decreased by more than 50 kPa per month, the control unit 22 can determine that an abnormal air leakage has occurred in the tire 11 and generate a warning using the output unit 24. In that case, the control unit 22 may stop executing steps after step S103.

[0052] The control unit 22 divides the tires 11 of the vehicle 10 being monitored into a plurality of groups according to the mounting positions of the tires 11 (step S103). The control unit 22 divides the tires 11 into groups according to the identification information of the sensor units 12 acquired from the sensor units 12 mounted on the tires 11. When the position of each tire 11 of the vehicle 10 is associated with the identification information of the sensor units 12, the control unit 22 can divide the tires 11 having the sensor units 12 mounted thereon into groups based on the positions of the tires 11 determined from the identification information. Such association information may be stored in the storage unit 23 in the form of a table or the like.

[0053] However, in a large vehicle 10 such as a truck, tire rotation is frequently performed, so the position of the tire 11 and the identification information of the sensor unit 12 may not be stored in association with each other. Although there are systems that automatically detect the position of the sensor unit 12, in the case of a large vehicle 10, it may be difficult to identify the position of the sensor unit 12 using such a system due to factors such as dual wheels and low radio wave permeability inside the tire. In such a case, the control unit 22 may execute a grouping procedure exemplified in Fig. 8. The flowchart of Fig. 8 will be described below.

[0054] The control unit 22 provisionally groups the multiple tires 11 based on data on the median value of the internal temperature T estimated going back a certain period of time (step S201). The certain period of time can be, for example, one week or two weeks going back from the present, but is not limited to these. It is assumed that no air leakage has occurred in the tires 11 during the certain period of time. By going back a certain period of time, data that is judged to have no air leakage can be used.

[0055] The estimated value of the internal temperature T of each tire 11 can be estimated using the internal pressure P of the tire 11 as shown in Equation (2). The internal pressure P of the tire 11 may be periodically obtained from the sensor unit 12 of the vehicle 10.

[0056] For example, the control unit 22 generates a frequency distribution of the estimated internal temperature T of the tire 11 for all the tires 11 of the vehicle 10. In the case of the tires 11 of the front wheel group G1, the load is generally large, so that the internal temperature T is generally high as shown by the solid line in FIG. 9. On the other hand, in the tires 11 of the rear wheel group G2, which is generally smaller in load than the tires 11 of the front wheel group G1, the internal temperature T is generally low as shown by the dashed line in FIG. 9. FIG. 9 shows an example of the median value of the internal temperature T of the tires 11 of the front wheel group G1 and an example of the median value of the internal temperature T of the tires 11 of the rear wheel group G2. Note that, in the case of the tires 11 of the rear wheel group G2, as described in FIG. 3, the load applied to the tires 11 is significantly different between when the vehicle is empty and when the vehicle is loaded with cargo up to the maximum load. Accordingly, the temperature of the tires 11 during traveling is also significantly different between when the vehicle is empty and when the vehicle is loaded with cargo. Therefore, the frequency distribution of the dashed line has two peaks, one on the high temperature side and one on the low temperature side.

[0057] 10 is a one-dimensional graph in which the medians of the estimated internal temperatures T of the tires 11 are arranged from the right side in descending order. The control unit 22 ranks the tires according to the highest median of the estimated internal temperatures T. For example, the control unit 22 may provisionally estimate that the four tires 11 with the highest median of the internal temperatures T belong to the front wheel group G1. The control unit 22 may estimate that the other eight tires 11 belong to the rear wheel group G2.

[0058] 4, the controller 22 may further estimate that the four tires 11 having the highest median internal temperatures T among the tires 11 belonging to the rear wheel group G2 provisionally belong to the inner rear wheel group 2G-2. The controller 22 may estimate that the other four tires 11 belong to the outer rear wheel group G2-1.

[0059] The control unit 22 repeats the following steps S203 to S207 for each group of the tires 11 that have been provisionally grouped (step S202). Steps S202 to S208 are procedures for verifying the correctness of the provisional grouping in step S201. Note that the groups may be determined based on the provisional grouping performed in step S201 without performing steps S202 to S208.

[0060] The control unit 22 selects a reference tire from the multiple tires 11 in the same group that have been provisionally grouped (step S203). The multiple tires 11 in the same group that have been provisionally grouped are second tires. The control unit 22 may select the tire 11 in the same group that has the highest median internal temperature T as the reference tire. However, the reference tire does not have to be the tire 11 with the highest median internal temperature T.

[0061] The control unit 22 plots points having the estimated internal temperature T of the reference tire at the same time as the X coordinate value and the estimated internal temperature T of each tire 11 in the same group as the Y coordinate value, and calculates an approximation line corresponding to each tire 11 (step S204). The control unit 22 plots a large number of points based on a large number of internal pressure measurement data for each tire 11. The approximation line can be calculated using a known method such as the least squares method.

[0062] Since tires 11 belonging to the same group undergo approximately the same temperature change, the approximation lines of tires 11 belonging to the same group approximately coincide with a line that passes through the origin and has a slope of 1. If a tire 11 from another group is included among the tires 11 that have been provisionally classified as the same group, the approximation line of that tire 11 deviates from the line that passes through the origin and has a slope of 1, as shown by the dashed line in FIG. 11. The control unit 22 determines whether or not each tire 11 belongs to the same group based on the difference in the slope and / or the Y-intercept of each approximation line (step S205). The control unit 22 can make the determination by setting a threshold value for the difference in the slope of the approximation lines and / or the difference in the Y-intercept.

[0063] When it is determined in step S205 that there is a tire 11 that does not belong to the same group (step S206: Yes), the control unit 22 replaces the tire 11 determined not to belong to the same group with a tire 11 in the next group. For example, when it is determined that one of the four tires 11 provisionally grouped into the front wheel group G1 does not belong to the front wheel group G1, the control unit 22 may select the tire 11 with the highest median internal temperature T from the rear wheel group G2 for replacement.

[0064] After step S207, the control unit 22 may return to step S203 and perform a process of verifying that the multiple tires 11 grouped into the same group after the swapping belong to the same group.

[0065] When it is determined in step S205 that there are no tires 11 that do not belong to the same group (step S206: No), the control unit 22 proceeds to the process of steps S203 to S207 for the next group of tires 11.

[0066] After performing the processes of steps S203 to S207 for all groups, the control unit 22 returns to the process of the flowchart in Fig. 7 (step S208). Through the process of Fig. 8, the identification information of each sensor unit 12 is associated with a group indicating the position of the tire on the vehicle 10. The process of grouping the tires 11 in step S103 may be performed, for example, when the tires 11 of the vehicle 10 are first targeted for monitoring by the leak monitoring device 20, or after the tires 11 of the vehicle 10 have been rotated.

[0067] The control unit 22 sequentially acquires the internal pressure P1 of each tire 11 while the vehicle 10 is traveling. The control unit 22 can estimate the internal temperature T1 of each tire 11 by using the internal pressure P1 of each tire 11 and a proportionality coefficient k0 of each tire 11 according to equation (2) (step S104). That is, the internal temperature T1 of each tire 11 during traveling is calculated by the following equation using the internal pressure P1 of each tire 11 sequentially acquired and a proportionality coefficient k0 calculated in advance for each tire 11. T1 = k0P1(3)

[0068] The control unit 22 compares the calculated internal temperature T1 of the tire 11 within the same group to determine whether there is a possibility of air leakage in any of the tires 11 (step S105). The process of step S105 will be further described with reference to the flowchart of FIG. 12.

[0069] First, the control unit 22 executes the processes of steps S302 to S306 in the flowchart of FIG. 12 for each group of the tires 11 (step S301).

[0070] The control unit 22 designates the tire 11 that deviates the most from the average value of the estimated internal temperatures T1 of all the tires 11 within the same group as the first tire (step S302). As described above, the internal temperatures T of the tires 11 within the same group are actually approximately equal. However, if there is air leakage in the first tire, the proportionality coefficient k0 = V / n0R deviates from the correct value due to the change in the amount of substance n0 of the gas inside the tire. Therefore, the internal temperature T2 of the first tire estimated on the premise that the proportionality coefficient k0 does not change is lower than the estimated internal temperatures T1 of the other tires 11. The reason for this will be briefly explained below.

[0071] Assume that the amount of substance of the gas inside the tire 11 has decreased to n1 (<n0) due to air leakage. In this case, according to the state equation after the decrease in the amount of substance, when k1 = V / n1R, the internal temperature T of the tire 11 in which air leakage has occurred is expressed by the following mathematical formula. T = k1P (4)

[0072] Here, since k0 = V / n0R, k1 = V / n1R, and n1 < n0, k1 > k0. When the internal temperature of the tire 11 in which air leakage has occurred is obtained from the internal pressure P2 of the tire 11 using the correct proportionality coefficient k1, the internal temperature becomes almost the same as the internal temperatures T1 of the other tires 11 in the same group. Therefore, the following equation holds. T1=k1P2(5)

[0073] On the other hand, when the internal temperature T2 of the tire 11 in which air leakage occurs due to the internal pressure P2 is estimated using the proportionality coefficient k0 before the amount of substance n changes, the estimated internal temperature T2 is expressed by the following formula from equation (2). T2=k0P2(6) Here, since k1>k0, the estimated value of the internal temperature T2 of the tire 11 that has experienced air leakage using equations (5) and (6) will be lower than the estimated value of the internal temperature T1 of the other tires 11 in the same group.

[0074] After step S302, the control unit 22 compares the estimated internal temperature T2 of the first tire with the average value of the internal temperatures T1 of the other tires 11 in the same group (step S303).

[0075] The control unit 22 determines whether the difference between the estimated internal temperature T2 of the first tire and the average internal temperature T1 of the other tires 11 in the same group, as the comparison result of step S303, is less than a predetermined threshold value (step S304). The predetermined value may be, for example, 10 degrees. 10 degrees corresponds to 20% of 50 degrees, which is a typical temperature rise of the tire 11 when the load applied to the tire 11 is at its maximum. The threshold value is not limited to 10 degrees, and an appropriate value selected according to various conditions may be set. By changing the threshold value, the accuracy of the air leakage determination and the frequency of occurrence of determination errors can be adjusted.

[0076] In step S304, if the control unit 22 determines that the difference between the estimated internal temperature T2 of the first tire and the average internal temperature T1 of the other tires 11 in the same group is less than the threshold (step S304: Yes), it determines that there is no tire 11 that is leaking air (step S305). In step S304, if the control unit 22 determines that the difference between the estimated internal temperature T2 of the first tire and the average internal temperature T1 of the other tires 11 in the same group is equal to or greater than the threshold (step S304: No), it determines that there is a possibility that air leakage is occurring in the first tire (step S305). The control unit 22 may store the determination result in the memory unit 23.

[0077] After step S305 or step S306, if there is a next group to be determined, the control unit 22 returns to step S302, and if there is no next group, the control unit 22 proceeds to step S308 (step S307).

[0078] The control unit 22 notifies the manager of the leak monitoring device 20 and / or the driver of the vehicle 10 of the determination result (step S308). The control unit 22 may perform the notification only when it is determined in step S306 that there is a possibility of air leakage. The control unit 22 may display the possibility of air leakage in the tire 11 of the vehicle 10 to the manager of the leak monitoring device 20 using a display included in the output unit 24. The control unit 22 may further generate an audio warning using a speaker included in the output unit 24. When notifying the driver of the vehicle 10, the control unit 22 may transmit a signal indicating the possibility of air leakage to the vehicle communication device 19 of the vehicle 10 via the communication unit 21. In this case, the communication unit 21 functions as the output unit 24. The vehicle 10 may be provided with a display, and may be configured to display a warning to the driver when the vehicle communication device 19 receives a signal indicating the possibility of air leakage. Furthermore, the control unit 22 may notify the driver of the vehicle 10 of the possibility of air leakage by e-mail or the like to an information terminal carried by the driver of the vehicle 10. Methods for notifying the driver of the vehicle 10 from the leak monitoring device 20 include various methods other than the above-mentioned methods.

[0079] The control unit 22 may sequentially and repeatedly execute the processes of steps S104 and S105 of the flowchart in Fig. 6 while the vehicle 10 is traveling. Fig. 13 is a diagram showing an example of a change in the estimated internal temperature T of each tire 11 in the same group after the vehicle 10 starts traveling. After a time t1 has elapsed from the start of traveling, the estimated internal temperature of one tire 11 in the group has decreased. Therefore, the control unit 22 can determine that there is a possibility that air leakage is occurring in the tire 11 whose estimated internal temperature is lower than the other tires 11.

[0080] As described above, according to the leak monitoring system 1 of the present disclosure, the tires 11 mounted on the vehicle 10 are divided into a plurality of groups. Then, while the vehicle 10 is traveling, the control unit 22 compares the internal temperature T2 of the tire 11 estimated from the internal pressure P1 of the first tire with the estimated internal temperatures T1 of the tires 11 belonging to the same group, thereby determining whether or not there is air leakage from the tire 11. In this manner, it is possible to determine whether or not there is a possibility of air leakage from the tire 11 while the vehicle 10 is traveling, without using internal temperature information measured by the temperature sensor 14, which has low measurement accuracy.

[0081] Furthermore, according to the leak monitoring system 1 of the present disclosure, the presence or absence of the possibility of air leakage from the tire 11 can be determined using the internal pressure P of the tire 11 sequentially acquired by the sensor unit 12 while the vehicle 10 is traveling. Therefore, the leak monitoring system 1 of the present disclosure can respond to monitoring of air leakage from the tire 11 that occurs in real time while the vehicle 10 is traveling.

[0082] Furthermore, according to the leak monitoring system 1 of the present disclosure, under conditions where the measurement accuracy of the internal temperature T of the tire 11 is high, the measurement value of the internal temperature T0 and information on the internal pressure P0 are acquired for each of the multiple tires 11, and the proportionality coefficient k0 between the internal temperature T and the internal pressure P is calculated. This makes it possible to estimate with high accuracy the internal temperature T of the tire 11 while the vehicle 10 is running based on the internal pressure P in the absence of air leakage.

[0083] In addition, in the leak monitoring system 1 of the present disclosure, the tires 11 of the vehicle 10 are grouped into two groups, a front wheel group G1 and a rear wheel group G2. The tires 11 in the front wheel group G1 and the tires 11 in the rear wheel group G2 are subjected to substantially equal loads even if the weight of the load loaded on the vehicle 10 changes. This makes it possible for the leak monitoring system 1 to monitor the air leaks of the tires 11 regardless of the weight of the load loaded on the vehicle 10. It is also possible to group the tires 11 of the vehicle 10 into three groups, the front wheel group G1, the outer rear wheel group G2-1, and the inner rear wheel group G2-2. In this case, it is expected that the air leaks of the tires 11 can be monitored with even higher accuracy.

[0084] Furthermore, since the leak monitoring device 20 of the present disclosure can group the tires 11 based on the internal temperature T estimated in the past for each tire 11, it is possible to group the tires 11 even if the relationship between the position of the tire 11 and the sensor unit 12 is not stored in the memory unit 23. Also, it is possible to group the tires 11 even if it is difficult to automatically determine the mounting position of the sensor unit 12 due to poor radio wave transparency of the material inside the tire 11 and / or due to dual wheels, etc.

[0085] Furthermore, the control unit 22 of the leak monitoring device 20 of the present disclosure provisionally groups the multiple tires 11 of the vehicle 10 based on the median value of the internal temperatures T estimated in the past, and selects a reference tire from the tires 11 included in the same group. Then, the estimated internal temperatures T of the reference tire at the same time are plotted as the X-axis value, and the estimated internal temperatures T of the other tires 11 are plotted as the Y-axis value to determine an approximate line. Furthermore, the control unit 22 determines whether each tire 11 belongs to the same group based on the difference in the slope of the approximate line and / or the difference in the Y-intercept of the approximate line. This can improve the accuracy of grouping the multiple tires 11 of the vehicle 10.

[0086] Although the embodiments according to the present disclosure have been described based on the drawings and examples, it should be noted that those skilled in the art can easily make various modifications or corrections based on the present disclosure. Therefore, it should be noted that these modifications or corrections are included in the scope of the present disclosure. For example, the functions included in each component or each step can be rearranged so as not to be logically inconsistent, and multiple components or steps can be combined into one or divided. Although the embodiments according to the present disclosure have been described mainly with respect to the device, the embodiments according to the present disclosure can also be realized as a method including steps executed by each component of the device. The embodiments according to the present disclosure can also be realized as a method, a program, or a non-transitory storage medium on which a program is recorded, which is executed by a processor provided in the device. The program may be downloaded from an external device via a network. It should be understood that these are also included in the scope of the present disclosure.

[0087] For example, in the above embodiment, the vehicle 10 is exemplified as a four-axle (12-wheel) vehicle 10 in Figs. 2 to 4. However, the vehicle 10 may have a number of axles other than four. For example, the vehicle 10 may be a three-axle (10-wheel) vehicle 10 as shown in Fig. 14. In this case, the tires 11(1R) and 11(1L) located at the front of the vehicle 10 may be the front wheel group G1. In addition, the tires 11(2R1), 11(2L1), 11(3R1), and 11(3L1) may be the outer rear wheel group G2-1, and the tires 11(2R2), 11(2L2), 11(3R1), and 11(3L2) may be the inner rear wheel group G2-2.

[0088] In the above embodiment, each group of tires 11 includes four tires 11, but the number of tires 11 included in one group is not limited to four. A group may be composed of two tires 11, such as the front wheel group G1 of the vehicle 10 in FIG. 14. In that case, in step S302 in FIG. 12, the control unit 22 compares the internal temperatures of the two tires 11 and sets the tire with the lower internal temperature as the first tire. Furthermore, in steps S303 and S304, the control unit 22 may compare the estimated values ​​of the internal temperatures of the first tire and the other tires and determine whether the difference between the internal temperatures is less than a threshold value. The number of tires 11 included in one group may be any number equal to or greater than two.

[0089] In the above embodiment, the leak monitoring device 20 is a computer capable of communicating with the vehicle 10 via the communication network 30. However, the leak monitoring device 20 may be disposed inside the vehicle 10. That is, an information processing device mounted on the vehicle 10 may have the functions of the leak monitoring device 20. Furthermore, the functions of the leak monitoring device 20 may be shared and executed by an information processing device mounted on the vehicle 10 and a computer external to the vehicle 10. [Explanation of symbols]

[0090] 1. Leak Monitoring System 10 Vehicles 11 Tires 12 Sensor unit 13 Internal pressure sensor 14 Temperature Sensor 15 Control section 16 Memory section 17 Battery 18 Sensor communication unit 19 Vehicle communication device 20 Leak monitoring device 21 Communications Department 22 Control section 23 Memory section 24 Output section 30 Network

Claims

1. A leak monitoring device for monitoring air leakage from a tire, comprising: A communication unit configured to receive internal pressure information indicating the internal pressures of a plurality of tires mounted on a vehicle; a control unit that divides a plurality of tires mounted on a vehicle into a plurality of groups, acquires the internal pressure information for each tire via the communication unit while the vehicle is traveling, estimates the internal temperature of each tire based on the internal pressure, and determines whether or not there is a possibility of air leakage in any tire by comparing the estimated internal temperatures of the plurality of tires belonging to the same group; Leak monitoring device including:

2. The communication unit is further configured to receive measurement values ​​of the internal temperatures of the tires, 2. The leak monitoring device according to claim 1, wherein, before estimating the internal temperature of each of the tires while the vehicle is traveling, the control unit acquires the measured internal temperature and the internal pressure information for each of the plurality of tires under conditions where the measurement accuracy of the internal temperature of the tires is high, calculates a proportionality coefficient between the internal temperature and the internal pressure for each of the tires, and estimates the internal temperature of each of the tires while the vehicle is traveling based on the internal pressure acquired while the vehicle is traveling and the proportionality coefficient.

3. 2. The leak monitoring device according to claim 1, wherein the control unit determines that there is a possibility of air leakage in the first tire when a difference between the estimated internal temperature of the first tire and an average value of the estimated internal temperatures of other tires in a group to which the first tire belongs is equal to or greater than a predetermined threshold value.

4. 2. The leak monitoring device according to claim 1, wherein the control unit divides the plurality of tires into two groups: a group of tires mounted on a front side of the vehicle and a group of tires mounted on a rear side of the vehicle.

5. 2. The leak monitoring device according to claim 1, wherein the control unit divides the plurality of tires into three groups: a group of tires mounted on a front side of the vehicle, a group of tires mounted on an outer rear side of the vehicle, and a group of tires mounted on an inner rear side of the vehicle.

6. The leak monitor of claim 1 , wherein the control unit groups the plurality of tires based on the previously estimated internal temperatures of each tire included in the plurality of tires.

7. The control unit is provisionally grouping the plurality of tires based on the median of the previously estimated internal temperatures of each tire in the plurality of tires; selecting a reference tire from the plurality of second tires provisionally grouped into the same group; 2. The leak monitoring device according to claim 1, wherein the leak monitoring device determines whether or not each of the second tires belongs to the same group based on at least one of a difference in slope of an approximation line obtained by plotting the estimated internal temperature of a reference tire at the same time as the X-axis value and the estimated internal temperature of the second tire as the Y-axis value for each of the second tires and a difference in a Y-intercept of the approximation line.

8. 1. A computer-implemented leak monitoring method for monitoring air leakage from a tire, comprising: Grouping a plurality of tires mounted on a vehicle into a plurality of groups; acquiring internal pressure information indicating an internal pressure of each tire while the vehicle is traveling, and estimating an internal temperature of each tire based on the internal pressure; comparing the estimated internal temperatures of the plurality of tires belonging to the same group to determine whether or not any of the tires may have an air leak; A leak monitoring method comprising:

9. A sensor for detecting internal pressures of a plurality of tires mounted on a vehicle; a control unit that divides a plurality of tires mounted on the vehicle into a plurality of groups, acquires internal pressure information indicating the internal pressure of each of the tires detected by the sensor while the vehicle is traveling, estimates an internal temperature of each of the tires based on the internal pressure, and determines whether or not there is a possibility of air leakage in any of the tires by comparing the estimated internal temperatures of the plurality of tires belonging to the same group; A leak monitoring system comprising:

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