Tire condition monitoring system and tire condition monitoring method

Abstract

A tire condition monitoring system according to the present invention includes an acquisition device and a control device. The acquisition device is configured to repeatedly acquire the pressure and temperature inside the tire. The control device is configured to: calculate a representative value of the ratio in a first period based on the ratio between the pressure and temperature acquired in the first period; and compare the ratio between the pressure and temperature acquired in a second period after the first period with the representative value to determine whether the pressure inside the tire has dropped.

Description

Technical Field

[0001] The present invention relates to a tire condition monitoring system and a tire condition monitoring method. Background Art

[0002] Conventionally, tire condition monitoring systems are known that monitor tire conditions based on information acquired by sensors installed in the tires. Technologies are known to improve the accuracy of determining a drop in tire pressure using the temperature inside the tire in such systems. For example, JP2010-254018A (Patent Document 1) discloses a tire pressure monitoring system that detects a drop in tire pressure based on pressure thresholds set for various tire temperatures.

[0003] Reference List

[0004] Patent Literature

[0005] Patent Document 1: JP2010-254018A Summary of the Invention

[0006] Problems to be solved by the invention

[0007] However, in conventional technology, depending on the installation position of the sensor in the tire, the temperature inside the tire cannot be accurately acquired. In this case, the pressure drop inside the tire may not be properly judged using the temperature inside the tire.

[0008] Therefore, it may be helpful to provide a tire condition monitoring system and a tire condition monitoring method that can improve the accuracy of determining a pressure drop inside a tire.

[0009] Solutions for solving problems

[0010] A tire condition monitoring system according to the present invention includes an acquisition device and a control device. The acquisition device is configured to repeatedly acquire the pressure and temperature inside the tire, and the control device is configured to: calculate a representative value of the ratio in a first period of time based on the ratio between the pressure and temperature acquired in the first period of time; and compare the ratio between the pressure and temperature acquired in a second period of time after the first period of time with the representative value to determine whether the pressure inside the tire has dropped.

[0011] A tire condition monitoring method according to the present invention includes: repeatedly acquiring the pressure and temperature inside the tire; calculating a representative value of the ratio in the first period based on the ratio between the pressure and temperature acquired in the first period; and comparing the ratio between the pressure and temperature acquired in a second period after the first period with the representative value to determine whether the pressure inside the tire has dropped.

[0012] Effects of the Invention

[0013] Therefore, it is possible to provide a tire condition monitoring system and a tire condition monitoring method that can improve the accuracy of determining a pressure drop inside a tire. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In the attached figure:

[0015] Figure 1 is a schematic diagram showing a tire condition monitoring system according to an embodiment of the present invention;

[0016] Figure 2 It is schematically shown Figure 1 Functional block diagram of the structure of the acquisition device;

[0017] Figure 3 is a flow chart illustrating the operation of the acquisition device;

[0018] Figure 4 It is schematically shown Figure 1 Functional block diagram of the structure of the control device;

[0019] Figure 5 is a flowchart illustrating the operation of the control device; and

[0020] Figure 6 is an example of a scatter plot of the temperature and pressure inside the tire acquired during the first period. DETAILED DESCRIPTION

[0021] The embodiments of the present invention will be described below with reference to the accompanying drawings. In the accompanying drawings, the same reference numerals are given to the same or corresponding parts. In the following description of this embodiment, the description of the same or corresponding parts is appropriately omitted or simplified.

[0022] (Structure of Tire Condition Monitoring System)

[0023] The following will refer to Figure 1 An overview of a tire condition monitoring system 1 according to an embodiment of the present invention is described. Figure 1 1 is a schematic diagram showing a tire condition monitoring system 1 according to this embodiment. Tire condition monitoring system 1 includes an acquisition device 2 and a control device 3 .

[0024] The tire condition monitoring system 1 is used to monitor the condition of the tire 5 of the vehicle 4. In this embodiment, the condition of the tire 5 includes the pressure inside the tire 5. However, the condition of the tire 5 is not limited to the pressure inside the tire 5 and may include the temperature of the tire 5, whether the tire 5 has damage or deformation, etc.

[0025] The vehicle 4 is, for example, an automobile such as a passenger car, a truck, a bus, or a two-wheeled vehicle, etc. The vehicle 4 is not limited to an automobile, and may be any vehicle 4 having tires 5 .

[0026] The tire 5 is, for example, a pneumatic tire. In this case, the tire 5 is mounted on the rim 6A of the wheel 6 and filled with air to a predetermined internal pressure. The tire 5 is not limited to a pneumatic tire and can be filled with any fluid (including gas such as nitrogen, liquid, or gel-like substances) to a predetermined internal pressure.

[0027] The acquisition device 2 is mounted at a location where it can acquire the pressure and temperature inside the tire 5. In this embodiment, the acquisition device 2 is mounted on the rim 6A of the wheel 6 of the vehicle 4. For example, the acquisition device 2 is secured to the radially outer side of the rim 6A of the wheel 6 by a belt or the like, so that it faces the interior of the tire 5 when the tire 5 is mounted on the rim 6A of the wheel 6. In this specification, the wheel radial direction refers to a direction orthogonal to the rotation axis of the wheel 6. The side closer to the rotation axis of the wheel 6 in the wheel radial direction is referred to as the "wheel radially inner side," and the side farther from the rotation axis of the wheel 6 in the wheel radial direction is referred to as the "wheel radially outer side."

[0028] The acquisition device 2 repeatedly acquires the pressure and temperature inside the tire 5 and wirelessly transmits the pressure and temperature. The acquisition device 2 can operate in multiple operating modes. For example, the multiple operating modes include a normal mode, in which the pressure and temperature inside the tire 5 are repeatedly transmitted in situations where the state of the tire 5 is likely to change (such as when the vehicle 4 is traveling), and a power saving mode, in which the pressure and temperature inside the tire 5 are transmitted at longer time intervals than in the normal mode in situations where the state of the tire 5 is unlikely to change (such as when the vehicle 4 is stopped). Changing the operating mode of the acquisition device 2 can change the time interval at which the acquisition device 2 acquires and transmits the pressure and temperature inside the tire 5.

[0029] The control device 3 is installed in a vehicle body 4A of the vehicle 4. The control device 3 may be any computer installed in the vehicle 4, such as an electronic control unit (ECU) of the vehicle 4 or a car navigation system.

[0030] The control device 3 receives the pressure and temperature inside the tire 5 sent from the acquisition device 2 , and determines whether the pressure inside the tire 5 has dropped based on the ratio between the received pressure and temperature inside the tire 5 .

[0031] Specifically, the fact that the pressure and temperature inside the tire 5 follow the Boyle-Charles relationship is used to determine whether the pressure inside the tire 5 has dropped. The Boyle-Charles relationship is represented by the following formula (1):

[0032] PV = kT Formula (1)

[0033] Wherein, P is the absolute pressure (gauge pressure + 100 kPa), V is the volume, k is a constant, and T is the absolute temperature (degrees Celsius + 273°C).

[0034] According to the Boyle-Charles relationship, assuming that the volume of the fluid inside the tire 5 is constant, the ratio between the pressure and temperature inside the tire 5 can be considered constant. Under this assumption, the control device 3 determines whether the pressure inside the tire 5 has dropped based on the ratio between the pressure and temperature inside the tire 5.

[0035] Figure 1 The positions and numbers of the acquisition device 2, control device 3, tires 5, and wheels 6 in the vehicle 4 shown in FIG are examples and can be freely set according to usage, etc. For example, a plurality of acquisition devices 2 may be included in the tire condition monitoring system 1 depending on the number of tires 5 included in the vehicle 4.

[0036] Next, the acquisition device 2 and the control device 3 in the tire condition monitoring system 1 are described in detail below.

[0037] (Structure of Acquisition Device)

[0038] The following will refer to Figure 2 The structure of the acquisition device 2 according to this embodiment will be described. Figure 2 2 is a functional block diagram schematically showing the structure of the acquisition device 2. Figure 2 As shown, the acquisition device 2 includes a pressure sensor 21, a temperature sensor 22, a communication unit 23, a storage device 24, and a controller 25. The pressure sensor 21, the temperature sensor 22, the communication unit 23, the storage device 24, and the controller 25 are connected to each other by wire or wirelessly so as to be communicable.

[0039] The pressure sensor 21 obtains the pressure inside the tire 5. In the case where the tire 5 is a pneumatic tire, the pressure sensor 21 obtains the air pressure inside the air chamber of the tire 5.

[0040] The temperature sensor 22 acquires the temperature inside the tire 5. When the tire 5 is a pneumatic tire, the temperature sensor 22 acquires the temperature inside the air chamber of the tire 5.

[0041] The communication unit 23 includes one or more wireless communication modules. Examples of the wireless communication module include wireless LAN and wireless (Bluetooth)( is a registered trademark in Japan, other countries, or both). Thus, the acquisition device 2 can wirelessly communicate with the control device 3 and the like via the communication unit 23. In addition to the wireless communication module, the communication unit 23 may also include a wired communication module such as a wired LAN communication module.

[0042] Storage device 24 is, for example, a semiconductor memory, a magnetic memory, or an optical memory. Storage device 24 can function as, for example, a main memory device, an auxiliary memory device, or a cache memory. Storage device 24 stores any information used to operate acquisition device 2. For example, storage device 24 can store system programs, application programs, embedded software, and the like.

[0043] The controller 25 includes one or more processors. Examples of processors include general-purpose processors such as central processing units (CPUs) and dedicated processors dedicated to specific processing. The controller 25 is not limited to processors and may include one or more dedicated circuits. Examples of dedicated circuits include field programmable gate arrays (FPGAs) and application-specific integrated circuits (ASICs).

[0044] The controller 25 controls components such as the pressure sensor 21, the temperature sensor 22, the communication unit 23, and the storage device 24 to implement the above-mentioned functions of the acquisition device 2. The controller 25, as a function of the acquisition device 2, includes a timing function such as a real-time clock (RTC) or a timer to obtain the time to perform processing or perform processing at predetermined time intervals.

[0045] Reference below Figure 3 The operation of the acquisition device 2 achieved by the controller 25 controlling each function of the acquisition device 2 will be described. Figure 3 is a flowchart illustrating the operation of acquisition device 2. This operation corresponds to the method implemented in the tire condition monitoring method using acquisition device 2. Controller 25 starts this process, for example, when acquisition device 2 is powered on or when receiving a control instruction to start this process from control device 3.

[0046] In step S101 , the controller 25 obtains the pressure and temperature inside the tire 5 .

[0047] Specifically, the controller 25 obtains the pressure inside the tire 5 through the pressure sensor 21 and the temperature inside the tire 5 through the temperature sensor 22. The controller 25 may store the obtained pressure and temperature inside the tire 5 in the storage device 24 in association with the time of obtaining the pressure and temperature.

[0048] In step S102 , the controller 25 transmits the acquired pressure and temperature inside the tire 5 .

[0049] Specifically, the controller 25 controls the communication unit 23 to transmit the acquired data including the acquired pressure and temperature inside the tire 5. In addition to the pressure and temperature inside the tire 5, the acquired data may also include the acquisition time of the pressure and temperature.

[0050] In step S103 , the controller 25 determines whether to continue the present process.

[0051] For example, the controller 25 can determine whether to continue this process based on whether the acquisition device 2 is powered off or whether a control instruction to terminate this process has been received from the control device 3. If the controller 25 determines to continue this process (step S103: Yes), the controller 25 repeats this process from step S101 at predetermined time intervals. The predetermined time intervals are, for example, 5-minute intervals or 10-minute intervals. The predetermined time intervals can vary depending on the operating mode of the acquisition device 2 described above. For example, the controller 25 can determine the operating mode of the acquisition device 2 based on the control instruction received from the control device 3 and repeat this process at time intervals corresponding to the operating mode.

[0052] The predetermined time interval is not limited to the aforementioned example and can be freely determined. For example, the predetermined time interval can be determined based on the judgment cycle (described in detail later) used by the control device 3 to determine whether the pressure inside the tire 5 has dropped. For example, in the case of a slow leak, which is a long-term pressure drop inside the tire 5, the judgment cycle can be extended, and the predetermined time interval can be extended accordingly. For example, if the judgment cycle is one month, the predetermined time interval can be a six-hour interval. This allows the acquisition device 2 to acquire a sufficient number of samples (e.g., 100 samples) in each judgment cycle while saving power consumption.

[0053] When the controller 25 determines not to continue the present process (step S103 : NO), the controller 25 ends the present process.

[0054] (Structure of control device)

[0055] The following will refer to Figure 4 The structure of the control device 3 according to this embodiment will be described. Figure 4 : is a functional block diagram schematically showing the structure of the control device 3. Figure 4 As shown, the control device 3 includes a communication unit 31, a notification unit 32, a storage device 33, and a controller 34. The communication unit 31, the notification unit 32, the storage device 33, and the controller 34 are connected to each other by wire or wirelessly so as to be communicable with each other.

[0056] The communication unit 31 includes one or more wireless communication modules. Examples of wireless communication modules include those that comply with communication standards such as wireless LAN and Bluetooth. This allows the control device 3 to wirelessly communicate with the acquisition device 2 and the like via the communication unit 31. In addition to wireless communication modules, the communication unit 31 may also include wired communication modules such as a wired LAN communication module.

[0057] The notification unit 32 notifies information through images, sounds, vibrations, etc. The notification unit 32 may include, for example, a display, a speaker, or a vibrator.

[0058] Storage device 33 is, for example, a semiconductor memory, a magnetic memory, or an optical memory. For example, storage device 33 can function as a main memory device, an auxiliary memory device, or a cache memory. Storage device 33 stores any information used to control the operation of device 3. For example, storage device 33 can store system programs, application programs, embedded software, and the like.

[0059] The controller 34 includes one or more processors. Examples of processors include general-purpose processors such as CPUs and dedicated processors dedicated to specific processing. The controller 34 is not limited to a processor and may include one or more dedicated circuits. Examples of dedicated circuits include FPGAs and ASICs.

[0060] The controller 34 controls components such as the communication unit 31, the notification unit 32, and the storage device 33 to implement the above-mentioned functions of the control device 3. The controller 34, as a function of the control device 3, includes a timing function such as a real-time clock (RTC) or a timer to obtain the time to perform processing or to perform processing at predetermined time intervals.

[0061] The following will refer to Figure 5 The operation of the control device 3 achieved by the controller 34 controlling each function of the control device 3 will be described. Figure 5 : is a flowchart showing the operation of the control device 3. This operation corresponds to a method implemented using the control device 3 in the tire condition monitoring method.

[0062] The controller 34 repeatedly performs this operation in each predetermined judgment cycle to determine whether the pressure inside the tire 5 has dropped. In this description of the operation, after the first period (the past judgment cycle) has ended, the controller 34 uses the information acquired during the first period (the current judgment cycle) to determine whether the pressure inside the tire 5 has dropped. The lengths of the first and second periods are, for example, one month. The first and second periods may be continuous or discontinuous in time.

[0063] In step S201 , the controller 34 receives the pressure and temperature inside the tire 5 .

[0064] Specifically, the controller 34 receives acquired data including the pressure and temperature inside the tire 5 from the acquisition device 2 via the communication unit 31. If the acquired data includes the acquisition time of the pressure and temperature, the controller 34 stores the pressure, temperature, and acquisition time in the storage device 33 as one of the acquired data sets acquired during the second period. If the acquired data does not include the acquisition time, the controller 34 may set the time of receiving the acquired data as the acquisition time, and store the pressure, temperature, and acquisition time in the storage device 33 as one of the acquired data sets acquired during the second period.

[0065] In step S202 , the controller 34 calculates a representative value of the ratio in the first period based on the ratio between the pressure and the temperature inside the tire 5 acquired in the first period.

[0066] Specifically, the controller 34 calculates the ratio between the pressure and temperature included in each of the plurality of acquired data sets acquired in the first period. In this embodiment, the ratio between the pressure and the temperature is the ratio of pressure to temperature and is represented by the following formula (2):

[0067] R PT = P / T Formula (2)

[0068] Among them, R PT is the ratio between pressure and temperature (pressure to temperature ratio), P is the absolute pressure (gauge pressure + 100 kPa), and T is the absolute temperature (degrees Celsius + 273°C).

[0069] The controller 34 calculates a representative value of the ratio in the first period based on the ratio between the pressure and the temperature acquired in the first period. Figure 6 An example of a scatter diagram of the temperature and pressure inside the tire 5 obtained in the first period is shown. For example, the controller 34 uses the lowest ratio of pressure to temperature among the ratios between pressure and temperature obtained in the first period as a representative value of the ratios in the first period. The lowest ratio of pressure to temperature is R PT The minimum value of . Figure 6 In FIG. 1 , the straight line with the smallest slope among the straight lines connecting each acquired data set and the origin (the straight line with the smallest R PT The slope of this straight line is the representative value of the ratio in the first period. Calculating the representative value in this manner is effective when the temperature acquired by acquisition device 2 is lower than the actual temperature inside tire 5 due to the installation position of acquisition device 2 (for example, when acquisition device 2 is installed on rim 6A of wheel 6, which is cooled by contact with outside air while vehicle 4 is traveling).

[0070] The method for calculating the representative value of the ratio in the first time period is not limited to the method described above. For example, the controller 34 may set the representative value of the ratio in the first time period as a statistical value based on the values ​​in a predetermined range, in order from the lowest ratio of pressure to temperature, among the ratios between pressure and temperature acquired in the first time period. The statistical value is a value calculated by a statistical method, and examples thereof include the average, median, and mode. The predetermined range may be, for example, 10% of the total number of acquired data sets in the first time period. The predetermined range is more preferably 5% of the total number of acquired data sets in the first time period. By calculating the representative value in this manner, even when the temperature acquired by the acquisition device 2 includes extreme values, it is possible to prevent a decrease in the accuracy of using the temperature inside the tire 5 to determine the pressure drop inside the tire 5.

[0071] The controller 34 may set a statistical value as a representative value for the ratio during the first period, based on values ​​within a predetermined range of pressure-to-temperature ratios acquired during the first period, in ascending order of the pressure-to-temperature ratios, excluding the lowest value. The predetermined range excluding the lowest value may, for example, be a range of 5% to 20% of the total number of acquired data sets in ascending order of the pressure-to-temperature ratios. Specifically, if the total number of acquired data sets is 100, the representative value for the ratio during the first period is calculated using the 5th to 20th values ​​in ascending order of the pressure-to-temperature ratios. More preferably, the predetermined range excluding the lowest value is a range of 5% to 10% of the total number of acquired data sets in ascending order of the pressure-to-temperature ratios. By excluding the lowest value from the calculation of the representative value in this manner, even when the temperature acquired by the acquisition device 2 includes extreme values, it is possible to prevent a decrease in the accuracy of determining a pressure drop within the tire 5 using the temperature within the tire 5.

[0072] Controller 34 can calculate a representative value for the ratios during the first period using only those ratios between pressure and temperature acquired during the first period that satisfy a predetermined condition. For example, controller 34 can calculate a representative value for the ratios during the first period based on those ratios corresponding to temperatures not exceeding a predetermined temperature among the ratios between pressure and temperature within tire 5 acquired during the first period. Therefore, even if the temperature acquired by acquisition device 2 includes an abnormal value due to, for example, a malfunction of temperature sensor 22, it is possible to prevent a decrease in the accuracy of using the temperature within tire 5 to determine a pressure drop within tire 5. The predetermined temperature can be the upper limit of the expected endpoint temperature of tire 5. For example, the predetermined temperature is 80 degrees Celsius. Therefore, for a typical tire 5 whose internal temperature does not exceed 80 degrees Celsius while vehicle 4 is traveling, a decrease in the accuracy of using the temperature within tire 5 to determine a pressure drop within tire 5 can be prevented, and the versatility of tire condition monitoring system 1 can be improved. If the temperature within tire 5 is expected to exceed 80 degrees Celsius, such as in the case of racing tires, a specific predetermined temperature can be set for tire 5.

[0073] As another example, the controller 34 may set the ratio between the pressure and temperature at the lowest temperature among the ratios between the pressure and temperature inside the tire 5 acquired during the first period as a representative value of the ratios during the first period. The state in which the temperature inside the tire 5 is lowest can be considered a state in which the temperature inside the tire 5 is substantially equal to the temperature of the outside air, such as a state in which time has elapsed since the vehicle 4 stopped. In other words, the state in which the temperature inside the tire 5 is lowest can be considered a state in which the temperature acquired by the acquisition device 2 is less susceptible to the influence of the outside air. Therefore, if the temperature acquired by the acquisition device 2 is lower than the actual temperature inside the tire 5, a simple method can be used to prevent a decrease in the accuracy of determining a pressure drop inside the tire 5 using the temperature inside the tire 5.

[0074] Return Reference Figure 5 In step S203, the controller 34 compares the ratio between the pressure and temperature inside the tire 5 obtained in the second period (current judgment cycle) after the first period with the representative value of the ratio in the first period to determine whether the pressure inside the tire 5 has dropped.

[0075] Specifically, the controller 34 calculates the ratio between the pressure and temperature inside the tire 5 received in step S201. The controller 34 stores the calculated ratio in the storage device 33 as one of the ratios between the pressure and temperature inside the tire 5 during the second period. If the calculated ratio is outside the range set based on the representative value of the ratio during the first period, the controller 34 determines that the pressure inside the tire 5 has dropped. In this embodiment, if the obtained ratio is lower than the representative value of the ratio during the first period, the controller 34 determines that the pressure inside the tire 5 has dropped.

[0076] The controller 34 may determine that the pressure inside the tire 5 has dropped if the ratio between the pressure and the temperature inside the tire 5 acquired during the second period is outside the range of the representative value based on the ratio during the first period multiple times. This prevents the controller 34 from erroneously determining that the pressure inside the tire 5 has dropped.

[0077] Controller 34 can determine whether the pressure inside tire 5 has dropped only when a predetermined condition is satisfied. For example, controller 34 can determine whether the pressure inside tire 5 has dropped when the number of pairs of pressure and temperature inside tire 5 acquired during the first period is greater than or equal to a predetermined number. The predetermined number is, for example, 100. This can prevent controller 34 from erroneously determining that the pressure inside tire 5 has dropped due to the use of a representative value of a ratio during the first period calculated based on an insufficient number of samples of acquired data.

[0078] Alternatively, the controller 34 may determine whether the pressure inside the tire 5 has dropped if the degree of dispersion of the acquisition times of the pressure and temperature inside the tire 5 acquired during the first period exceeds a predetermined threshold. This prevents the controller 34 from erroneously determining that the pressure inside the tire 5 has dropped due to the use of a representative value of the ratio for the first period calculated based on biased acquisition data. Specifically, the controller 34 determines whether the pressure inside the tire 5 has dropped if there is a predetermined time difference between the earliest acquisition time and the latest acquisition time among the acquisition times of the pressure and temperature inside the tire 5 acquired during the first period. The predetermined time difference is, for example, greater than or equal to half the length of the determination period. The degree of dispersion of the acquisition times is not limited to this specific example and may be a value calculated using statistical methods such as the variance or standard deviation of the acquisition times.

[0079] If the controller 34 determines in step S203 that the pressure inside the tire 5 has dropped (step S203: YES), in step S204, the controller 34 notifies the user of the vehicle 4 of the drop in pressure inside the tire 5 via the notification unit 32. For example, the controller 34 causes the display to display a notification that the pressure inside the tire 5 has dropped. This allows the user of the vehicle 4 to replace or inspect the tire 5.

[0080] If the controller 34 determines in step S203 that the pressure inside the tire 5 has not dropped or has not yet determined whether the pressure inside the tire 5 has dropped (step S203: No), the controller 34 proceeds to step S205. The controller 34 may notify the notification unit 32 that the pressure inside the tire 5 has not dropped.

[0081] In step S205 , the controller 34 determines whether to continue the present process.

[0082] Specifically, the controller 34 determines whether to continue this process based on whether the current time has reached the end time of the current judgment cycle. When the current time has not reached the end time of the current judgment cycle, the controller 34 determines to continue this process (step S205: Yes), and repeats the process from step S101.

[0083] If the current time has reached the end time of the current judgment cycle, the controller 34 determines to end the present process (step S205: No), and ends the present process. After ending the present process, the controller 34 may start the present process in a new judgment cycle.

[0084] As described above, the tire condition monitoring system 1 according to an embodiment of the present invention includes an acquisition device 2 and a control device 3. Acquisition device 2 is configured to repeatedly acquire the pressure and temperature inside tire 5, and control device 3 is configured to: calculate a representative value of the ratio between the pressure and temperature acquired during a first period of time based on the ratio between the pressure and temperature acquired during the first period of time; and compare the ratio between the pressure and temperature acquired during a second period of time subsequent to the first period of time with the representative value to determine whether the pressure inside tire 5 has dropped. With this configuration, even if acquisition device 2 cannot accurately acquire the temperature inside tire 5 due to, for example, the mounting position of acquisition device 2 on tire 5 or wheel 6, control device 3 can improve the accuracy of determining a drop in pressure inside tire 5 using the temperature inside tire 5.

[0085] Preferably, in tire condition monitoring system 1 according to an embodiment of the present invention, control device 3 is configured to set the lowest pressure-to-temperature ratio among the ratios between pressure and temperature acquired during the first period as the representative value. With this configuration, even in situations where the temperature acquired by acquisition device 2 is lower than the actual temperature inside tire 5 due to the installation position of acquisition device 2 (such as when acquisition device 2 is installed on rim 6A of wheel 6), the accuracy of determining a pressure drop inside tire 5 using the temperature inside tire 5 can be further improved.

[0086] Preferably, in tire condition monitoring system 1 according to an embodiment of the present invention, control device 3 is configured to set as a representative value a statistical value based on values ​​within a predetermined range, sequentially starting from the lowest pressure-to-temperature ratio, among the ratios between pressure and temperature acquired during the first period. With this configuration, even if the temperature acquired by acquisition device 2 is lower than the actual temperature inside tire 5, or the temperature acquired by acquisition device 2 includes extreme values, it is possible to prevent a decrease in the accuracy of determining a pressure drop inside tire 5 using the temperature inside tire 5.

[0087] Preferably, in tire condition monitoring system 1 according to an embodiment of the present invention, control device 3 is configured to set a statistical value as a representative value, the statistical value being based on values ​​within a predetermined range, excluding the lowest value, in ascending order of the pressure-to-temperature ratio, of the ratios between pressure and temperature acquired during the first period. With this configuration, even if the temperature acquired by acquisition device 2 is lower than the actual temperature inside tire 5, the temperature acquired by acquisition device 2 includes extreme values, thereby preventing a decrease in the accuracy of determining a pressure drop inside tire 5 using the temperature inside tire 5.

[0088] Preferably, in tire condition monitoring system 1 according to an embodiment of the present invention, control device 3 is configured to set the ratio between pressure and temperature at the lowest temperature, among the ratios between pressure and temperature acquired during the first period, as the representative value. With this configuration, if the temperature acquired by acquisition device 2 is lower than the actual temperature inside tire 5, a reduction in the accuracy of determining a pressure drop inside tire 5 using the temperature inside tire 5 can be prevented using a simple method.

[0089] Preferably, in tire condition monitoring system 1 according to an embodiment of the present invention, control device 3 is configured to determine whether the pressure inside tire 5 has dropped if the number of pressure and temperature pairs acquired during the first period is greater than or equal to a predetermined number. With this configuration, it is possible to prevent control device 3 from erroneously determining that the pressure inside tire 5 has dropped due to the use of a representative value of the ratio during the first period calculated based on an insufficient number of samples of acquired data.

[0090] Preferably, in tire condition monitoring system 1 according to an embodiment of the present invention, control device 3 is configured to determine whether the pressure inside tire 5 has dropped if the degree of dispersion in the acquisition times of the pressure and temperature acquired during the first period is greater than a predetermined threshold. This configuration prevents control device 3 from erroneously determining that the pressure inside tire 5 has dropped due to the use of a representative value of the ratio during the first period calculated based on biased acquired data.

[0091] Preferably, in tire condition monitoring system 1 according to an embodiment of the present invention, control device 3 is configured to determine whether the pressure inside tire 5 has dropped when a predetermined time difference exists between the earliest and latest acquisition times of the pressure and temperature acquired during the first period. This configuration can simply prevent control device 3 from using a representative value of the ratio during the first period, calculated based on biased acquired data, to determine whether the pressure inside tire 5 has dropped.

[0092] Preferably, in tire condition monitoring system 1 according to an embodiment of the present invention, control device 3 is configured to calculate a representative value based on each ratio of the pressure and temperature acquired during the first period corresponding to a temperature that does not exceed a predetermined temperature. With this configuration, even when the temperature acquired by acquisition device 2 includes an abnormal value, it is possible to prevent a decrease in the accuracy of determining a pressure drop within tire 5 using the temperature within tire 5.

[0093] Preferably, in tire condition monitoring system 1 according to an embodiment of the present invention, the predetermined temperature is 80 degrees Celsius. With this configuration, for typical tires 5 whose internal temperature does not exceed 80 degrees Celsius while vehicle 4 is traveling, it is possible to prevent a decrease in the accuracy of determining a pressure drop within tire 5 using the internal temperature of tire 5, thereby improving the versatility of tire condition monitoring system 1.

[0094] Preferably, in tire condition monitoring system 1 according to an embodiment of the present invention, control device 3 is configured to determine that the pressure inside tire 5 has dropped if the ratio between the pressure and temperature acquired during the second period falls outside the range based on the representative value multiple times. With this configuration, control device 3 can be prevented from erroneously determining that the pressure inside tire 5 has dropped.

[0095] The tire condition monitoring method according to an embodiment of the present invention includes: repeatedly acquiring the pressure and temperature inside the tire 5; calculating a representative value of the ratio in the first period based on the ratio between the pressure and temperature acquired in the first period; and comparing the ratio between the pressure and temperature acquired in a second period after the first period with the representative value to determine whether the pressure inside the tire 5 has dropped. With this configuration, even when the temperature inside the tire 5 cannot be accurately acquired, it is possible to improve the accuracy of determining a pressure drop inside the tire 5 using the temperature inside the tire 5.

[0096] Although the technology of the present invention has been described above through the embodiments and drawings, a person skilled in the art may make various changes and modifications based on the present invention. Such changes and modifications are therefore included in the scope of the present invention. For example, the structures, functions, etc. included in the various embodiments or examples may be rearranged without logical contradiction. The structures, functions, etc. included in the various embodiments may be used in conjunction with another embodiment or example, and multiple structures, functions, etc. may be combined into one structure, function, etc., one structure, function, etc. may be divided into multiple structures, functions, etc., or part of the structure, function, etc. may be omitted.

[0097] For example, all or part of the functions or processes described as the functions of the acquisition device 2 or the functions of the control device 3 in the above embodiments can be implemented by a program. The program can be recorded in a computer-readable non-transitory recording medium. Examples of computer-readable non-transitory recording media include magnetic recording devices, optical discs, magneto-optical recording media, and semiconductor memories. For example, the program is distributed by selling, transmitting, or leasing a portable recording medium (such as a digital versatile disc (DVD) or a compact disc read-only memory (CD-ROM)) on which the program is recorded. Alternatively, the program can be stored in a storage device of a certain server and transmitted from the certain server to another computer to distribute the program. The program can be provided as a program product.

[0098] For example, the processor in acquisition device 2 or control device 3 once stores a program recorded on a portable recording medium or transmitted from a server in memory, then reads the program stored in memory and executes processing based on the read program. A program includes information equivalent to the program to be processed by the processor. For example, data that is not a direct command to the processor but has properties that define the processing of the processor is "equivalent to the program."

[0099] Alternatively, all or part of the functions or processes described as the functions or processes of the control device 3 in the above embodiments may be implemented as the functions or processes of the acquisition device 2. In this case, a program describing the functions or processes of the control device 3 according to the embodiment may be stored in, for example, a memory in the acquisition device 2, and read and executed by, for example, a processor in the acquisition device 2. Likewise, all or part of the functions or processes described as the functions or processes of the acquisition device 2 may be implemented as the functions or processes of the control device 3.

[0100] Although the above embodiment describes a case where the acquisition device 2 is mounted on the rim 6A of the wheel 6 of the vehicle 4, the present invention is not limited thereto. For example, the acquisition device 2 may be mounted anywhere on the tire 5 or wheel 6, such as inside the tire 5 of the vehicle 4 or at the valve of the tire 5.

[0101] While the above embodiment describes a case where the control device 3 is installed in the vehicle body 4A of the vehicle 4, the present invention is not limited thereto. For example, the control device 3 may be installed in the tire 5 or wheel 6 of the vehicle 4, as in the acquisition device 2. Alternatively, the control device 3 may be installed outside the vehicle 4, and the functions or processing of the control device 3 may be provided to the user as a service such as SaaS (Software as a Service). In this case, instead of notifying the user of a decrease in pressure inside the tire 5 via the notification unit 32, the control device 3 may communicate with a computer such as a smartphone owned by the user via the communication unit 31, and notify the user of the decrease in pressure inside the tire 5 through the computer.

[0102] Although the above embodiment describes the case where the ratio between pressure and temperature is the ratio of pressure to temperature, the present invention is not limited thereto. The ratio between pressure and temperature may be the ratio of temperature to pressure, and may be expressed by the following formula (3):

[0103] R TP = T / P Formula (3)

[0104] Among them, R TP is the ratio between pressure and temperature (temperature to pressure ratio), P is the absolute pressure (gauge pressure + 100 kPa), and T is the absolute temperature (degrees Celsius + 273°C).

[0105] In this case, the lowest ratio of pressure to temperature in the above embodiment is R TP For example, the controller 34 in the control device 3 may obtain the ratio R between the pressure and the temperature in the second period. TP Higher than the ratio R in the first period TP When the representative value is , it is determined that the pressure inside the tire 5 has dropped.

[0106] Reference Signs List

[0107] 1Tire condition monitoring system

[0108] 2 Obtaining the device

[0109] 21 pressure sensor

[0110] 22 temperature sensors

[0111] 23 Ministry of Communications

[0112] 24 storage devices

[0113] 25 controllers

[0114] 3 Control device

[0115] 31 Ministry of Communications

[0116] 32 Notification Department

[0117] 33 Storage device

[0118] 34 controllers

[0119] 4 vehicles

[0120] 4A body

[0121] 5 tires

[0122] 6 wheels

[0123] 6A rims

Claims

1. A tire condition monitoring system comprising an acquisition device and a control device, in, The acquisition device is configured to repeatedly acquire the pressure and temperature inside the tire, and The control device is configured to: calculating a representative value of the ratio in the first period based on the ratio between the pressure and the temperature acquired in the first period; and comparing a ratio between pressure and temperature acquired in a second period following the first period with the representative value to determine whether the pressure inside the tire has dropped, The control device is configured to set, as the representative value, the ratio between the pressure and the temperature at the lowest temperature among the ratios between the pressure and the temperature acquired in the first period.

2. The tire condition monitoring system according to claim 1, wherein: The control device is configured to determine whether the pressure inside the tire has dropped if the number of pairs of pressure and temperature acquired in the first period is greater than or equal to a predetermined number.

3. The tire condition monitoring system according to claim 1 or 2, wherein: The control device is configured to determine whether the pressure inside the tire has dropped if a dispersion of acquisition times of the pressure and temperature acquired in the first period is greater than a predetermined threshold.

4. The tire condition monitoring system according to claim 3, wherein: The control device is configured to determine whether the pressure inside the tire has dropped if there is a predetermined time difference between an earliest acquisition time and a latest acquisition time among acquisition times of the pressure and temperature acquired in the first period.

5. The tire condition monitoring system according to claim 1 or 2, wherein: The control device is configured to calculate the representative value based on each of the ratios between the pressure and the temperature acquired in the first period corresponding to a temperature not exceeding a predetermined temperature.

6. The tire condition monitoring system according to claim 5, wherein: The predetermined temperature is 80 degrees Celsius.

7. The tire condition monitoring system according to claim 1 or 2, wherein: The control device is configured to determine that the pressure inside the tire has dropped if the ratio between the pressure and the temperature acquired in the second period is outside a range based on the representative value a plurality of times.

8. A tire condition monitoring method, comprising: Repeatedly obtain the pressure and temperature inside the tire; calculating a representative value of the ratio in the first period based on the ratio between the pressure and the temperature acquired in the first period; as well as comparing a ratio between pressure and temperature acquired in a second period following the first period with the representative value to determine whether the pressure inside the tire has dropped, Among the ratios between pressure and temperature acquired in the first period, the ratio between pressure and temperature at the lowest temperature is set as the representative value.

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