Pressure management devices, pressure management methods and pressure management procedures

Abstract

The air pressure management device (10) according to this embodiment includes: a temperature-to-pressure calculation unit (17) that calculates the temperature-to-pressure of the tire based on the obtained tire temperature and air pressure; an air pressure drop rate calculation unit (18) that calculates the air pressure drop rate, which is used to indicate the tendency of the tire air pressure to drop, based on the change in temperature-to-pressure within a preset period; an air pressure drop rate threshold setting unit (20) that sets an air pressure drop rate threshold corresponding to the obtained thermal process amount using a threshold table (20a) that specifies an air pressure drop rate threshold corresponding to the tire-related thermal process amount; and a first determination unit (22) that determines whether the tire air pressure is abnormal based on the calculated air pressure drop rate and the set air pressure drop rate threshold.

Description

Technical Field

[0001] This invention relates to a tire pressure management device, a tire pressure management method, and a tire pressure management procedure. Background Technology

[0002] Vehicle stability is ensured by filling multiple tires mounted on a vehicle with appropriate air pressure. The air pressure of these tires typically decreases over time due to natural leakage. The absolute value of the pressure drop depends on the tire pressure; for example, in the case of tires used on trucks and buses, the pressure may sometimes drop by about 30 to 50 kPa per month. Furthermore, in addition to the aforementioned natural leakage, tire pressure can also drop rapidly due to problems such as tire blowouts, valve malfunctions, and wheel damage. Therefore, a technique has been proposed to calculate the tire pressure drop rate, which indicates the tendency of tire pressure to drop, and based on this tire pressure drop rate, to estimate the time required for the pressure to drop back to a set pressure, while simultaneously informing the driver of the estimated drop time (e.g., see Patent Document 1).

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 2006-327554 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] However, the tire pressure drop rate, used to indicate the tendency of tire pressure to drop, varies greatly due to factors such as tire specifications, operating environment (operating temperature), and the inflation pressure. Therefore, when determining whether an abnormality is present by comparing the tire pressure drop rate with a threshold, it is difficult to make a high-precision determination using a predetermined threshold.

[0008] The present invention was made in view of the above circumstances, and its purpose is to provide a tire pressure management device, tire pressure management method and tire pressure management program that can accurately determine whether there is an abnormality in tire pressure.

[0009] Technical solution

[0010] To solve the aforementioned technical problems and achieve the objective, the tire pressure management device according to the present invention includes: a temperature-to-pressure calculation unit that calculates the temperature-to-pressure of the tire based on the obtained tire temperature and pressure; a pressure drop rate calculation unit that calculates the pressure drop rate, representing the tendency of tire pressure to drop, based on the change in temperature-to-pressure within a preset period; a pressure drop rate threshold setting unit that sets a pressure drop rate threshold corresponding to the obtained physical quantity using a threshold table that specifies a pressure drop rate threshold corresponding to a preset physical quantity related to the tire; and a first determination unit that determines whether the tire pressure is abnormal based on the calculated pressure drop rate and the set pressure drop rate threshold.

[0011] In the above-mentioned air pressure management device, preferably, the physical quantity is any one of the tire's thermal process quantity, temperature, or air pressure.

[0012] Furthermore, preferably, in the above-mentioned air pressure management device, the air pressure drop rate calculation unit calculates the air pressure drop rate of a pair of tires according to the wheel position of the vehicle on which the tires are installed. The air pressure management device includes a second determination unit, which determines whether the air pressure of one of the tires in the pair is abnormal based on the deviation of each air pressure drop rate.

[0013] Furthermore, preferably, the above-mentioned air pressure management device includes a table updating unit, which is used to obtain the physical quantities of the tire and the air pressure drop rate, and update the threshold table according to the obtained physical quantities and air pressure drop rate.

[0014] Furthermore, preferably, in the above-mentioned air pressure management device, the table update unit obtains the physical quantity and air pressure drop rate of a tire of the same specification as the tire stored in the external device.

[0015] Furthermore, preferably, the above-mentioned air pressure management device includes a notification unit, which, when the first determination unit determines that the tire pressure is abnormal, notifies the time until the tire pressure drops to the limit pressure when the tire continues to be used at the calculated rate of pressure drop.

[0016] Furthermore, the tire pressure management method according to the present invention includes: a step of calculating tire temperature-converted tire pressure based on the obtained tire temperature and tire pressure; a step of calculating the tire pressure drop rate based on the change in tire pressure within a preset period; a step of setting a tire pressure drop rate threshold corresponding to the obtained physical quantity using a threshold table that specifies a tire pressure drop rate threshold corresponding to a preset physical quantity related to the tire; and a step of determining whether the tire pressure is abnormal based on the calculated tire pressure drop rate and the set tire pressure drop rate threshold.

[0017] Furthermore, the air pressure management program according to the present invention causes the air pressure management device to perform the following steps: a step of calculating the tire temperature-converted air pressure based on the obtained tire temperature and air pressure; a step of calculating the air pressure drop rate based on the change in temperature-converted air pressure within a preset period; a step of setting an air pressure drop rate threshold corresponding to the obtained physical quantity using a threshold table that specifies an air pressure drop rate threshold corresponding to a preset physical quantity related to the tire; and a step of determining whether the tire air pressure is abnormal based on the calculated air pressure drop rate and the set air pressure drop rate threshold.

[0018] Invention Effects

[0019] According to the present invention, the tire pressure drop rate is determined to be abnormal based on the pressure drop rate threshold and the pressure drop rate set according to the physical quantity corresponding to the current situation, thus the tire pressure drop rate can be determined with high precision. Attached Figure Description

[0020] Figure 1 A schematic diagram illustrating a vehicle equipped with the air pressure management device according to this embodiment.

[0021] Figure 2 A block diagram illustrating the functional structure of the air pressure management device and the server device.

[0022] Figure 3 A flowchart illustrating the operating sequence of the air pressure management device.

[0023] Figure 4 A graph showing the relationship between the temperature detected and the detection frequency during a predetermined period.

[0024] Figure 5 A graph showing the relationship between the temperature acceleration coefficient and temperature.

[0025] Figure 6 A schematic diagram of a threshold table illustrating the relationship between thermal process quantities and pressure drop thresholds.

[0026] Figure 7 A graph showing the estimated time for the pressure to drop before reaching the limit pressure.

[0027] Figure 8 A diagram illustrating the process of generating a threshold table based on information related to thermal processes and the rate of pressure drop.

[0028] Figure 9 This is a schematic diagram of a threshold table illustrating the relationship between air pressure and the air pressure drop threshold. Detailed Implementation

[0029] Hereinafter, embodiments of the air pressure management device of the present invention will be described based on the accompanying drawings. It should be noted that the present invention is not limited to these embodiments. Furthermore, the constituent elements in these embodiments include constituent elements that can be substituted by those skilled in the art and are readily conceived of, or substantially the same structural elements.

[0030] Figure 1 A schematic diagram illustrating a vehicle equipped with the air pressure management device according to this embodiment. Figure 2 This is a block diagram illustrating the functional structure of the air pressure management device and the server device. According to this embodiment, the air pressure management device 10 is installed in a vehicle 1 to manage the air pressure of a plurality of tires 2 of the vehicle 1. Specifically, as part of air pressure management, the air pressure management device 10 monitors the rate of air pressure drop of each tire 2, and when the rate of air pressure drop exceeds (is greater than) a threshold, notifies that the tire 2 has an abnormal air pressure.

[0031] like Figure 1 As shown, sensors 3 are installed in each of the multiple tires 2 of the vehicle 1, and these sensors 3 are connected to the air pressure management device 10 in a communicable manner. Furthermore, the vehicle 1 is equipped with an external temperature sensor 4 for measuring the outside temperature. This external temperature sensor 4 is installed in a location not easily affected by external interference such as direct sunlight or engine exhaust heat, and is connected to the air pressure management device 10 in a communicable manner. The vehicle 1 equipped with the air pressure management device 10 is preferably a truck or bus with relatively large tires 2 that operates over long distances, but is not limited to this.

[0032] Sensor 3 is a Tire Pressure Monitoring System (TPMS) sensor, configured to include a pressure sensor 3a for measuring the air pressure of tire 2 and a temperature sensor 3b for measuring the temperature of the air inside tire 2. Furthermore, sensor 3 may also be configured to include an acceleration sensor for measuring the centrifugal acceleration acting on tire 2. Sensor 3 is mounted, for example, on the air valve of each tire 2. Each sensor 3 is provided with a sensor ID (identification information), and the correspondence between the sensor ID of sensor 3, the tire ID (identification information) of the tire 2 with which the sensor 3 is located, and the wheel position on which the tire 2 is mounted (e.g., in a truck or bus, left front wheel, right front wheel, left inner rear wheel, left outer rear wheel, right inner rear wheel, or right outer rear wheel, etc.) is registered in the air pressure management device 10. The measurement data from each sensor 3 can be transmitted to the air pressure management device 10 at predetermined intervals using short-range wireless communication, such as radio frequency (RF) communication. It should be noted that, in this embodiment, air is used as an example of the gas filled in the tire 2, but the air contains a gas in which the nitrogen ratio is adjusted to be higher than usual (e.g., more than 98%).

[0033] The air pressure management device 10 is an on-board device mounted on the body of vehicle 1. For example... Figure 2 As shown, the barometric pressure management device 10 includes a sensor receiving unit 11, a storage unit 12, a communication unit 13, a display unit (notification unit) 14, a path guidance unit 15, a control unit 16, a temperature-to-pressure calculation unit 17, a pressure drop rate calculation unit 18, a thermal process quantity calculation unit (physical quantity acquisition unit) 19, a pressure drop rate threshold setting unit 20, a table updating unit 21, a first determination unit 22, and a second determination unit 23. Furthermore, the barometric pressure management device 10 is connected to a preset server device (external device) 30 via a communication network 40, such as an Internet connection, in a manner capable of communication. In this embodiment, the barometric pressure management device 10 is described as an in-vehicle device mounted on the vehicle 1, but it is not limited thereto. For example, it can be configured as a portable terminal such as a smartphone, and the portable terminal can be connected to the vehicle 1 as needed.

[0034] The sensor receiving unit 11 receives (acquires) data transmitted from each of the sensors 3 (pressure sensor 3a, temperature sensor 3b) on the multiple tires 2 and from the external temperature sensor 4. In this embodiment, the pressure management device 10 is configured to include the sensor receiving unit 11 as an integral part, but the sensor receiving unit 11 may also be mounted on the vehicle as a separate unit.

[0035] The storage unit 12 has a storage unit such as a volatile or non-volatile memory or a hard disk drive (HDD). Various programs or data implemented by the control unit 16 are stored in the storage unit 12. In this embodiment, the storage unit 12 stores information on the air pressure and temperature of each tire 2, as well as information on the external air temperature, received by the sensor receiving unit 11 at predetermined intervals. In this case, preferably, regarding the air pressure and temperature information of each tire 2, the corresponding tire ID and wheel position are determined from the sensor ID, and these are stored as corresponding historical information. Furthermore, in the vehicle 1, when the tires 2 are rotated, the correspondence between the tire ID (sensor ID) and the wheel position registered in the air pressure management device 10 is modified.

[0036] The communication unit 13 is configured to wirelessly communicate with the server device 30, which is an external device, via the communication network 40. In this embodiment, the communication unit 13 periodically sends the thermal process quantity (physical quantity) received by the tires 2 of the vehicle and the tire pressure drop rate of the tires 2 to the server device 30. These thermal process quantities and tire pressure drop rates of the tires 2 can be calculated separately based on the tire pressure and temperature of the tires 2. In the server device 30, a database is formed according to the tire specifications (model or size, etc.), and the thermal process quantities and tire pressure drop rates of tires sent from various vehicles available on the market are stored in each database. In this case, the communication unit 13 can also obtain relevant information on the thermal process quantities and tire pressure drop rates of tires with the same specifications as the tires 2 of the vehicle from the database of the server device 30 under the control of the control unit 16.

[0037] Display unit 14 is a display device installed on a vehicle dashboard or similar surface, providing various information to the user (driver). In this embodiment, it displays, for example, map information including the route to the set destination, and information such as the current tire pressure and temperature of each tire 2 mounted on the vehicle 1, as well as the outside air temperature. Furthermore, display unit 14 can display information such as temperature-to-pressure conversion or the rate of tire pressure drop calculated based on the tire pressure and temperature. Moreover, when the tire pressure of a tire 2 is determined to be abnormal based on the rate of tire pressure drop, display unit 14 can display information about the duration (distance) the vehicle 1 can travel with the tire 2 mounted. Therefore, in this embodiment, display unit 14 functions as a notification unit for abnormal tire pressure.

[0038] The route guidance unit 15 has a so-called navigation function and retrieves the route from the location of vehicle 1 to the destination to provide route guidance. For example, if it is determined that the tire 2 has abnormal air pressure, the route guidance unit 15 retrieves the route from the current location of vehicle 1 to the nearest maintenance service shop to provide route guidance.

[0039] The control unit 16 includes a central processing unit (CPU), read-only memory (ROM), random-access memory (RAM), etc., and controls the operation of the overall air pressure management device 10 according to the program stored in the storage unit 12. For example, if it is determined that the air pressure of tire 2 is abnormal, when tire 2 continues to be used at the calculated air pressure drop rate, the estimated time (air pressure drop estimate time) before the air pressure of tire 2 drops to the limit air pressure is estimated is displayed on the display unit 14.

[0040] Under the control of the control unit 16, the temperature-to-pressure calculation unit 17 calculates the temperature-to-pressure conversion of the tire pressure to a predetermined temperature based on the obtained temperature and pressure of each tire 2. Normally, the tire pressure of the tire 2 tends to change with air temperature, and therefore the pressure may differ between when the vehicle is running and when it is stationary, making it difficult to accurately manage pressure fluctuations. Therefore, the temperature-to-pressure calculation unit 17 converts the tire pressure of the tire 2 to the pressure at a specified temperature (e.g., 25°C) based on, for example, Boyle's law or Charles's law. This suppresses pressure fluctuations accompanying changes in tire temperature, enabling accurate management of pressure variations.

[0041] Under the control of the control unit 16, the tire pressure drop rate calculation unit 18 calculates the tire pressure drop rate based on the change in temperature-converted tire pressure over a predetermined period. The tire pressure drop rate is defined as the pressure drop per unit time (e.g., 1 minute) in kPa, representing the tendency of tire pressure to drop. Typically, tire pressure drops naturally over time due to leakage. The absolute value of this pressure drop depends on the tire pressure; therefore, in the case of tires used in trucks and buses, the pressure may drop by approximately 30 to 50 kPa within a month. In cases of tire blowouts, valve malfunctions, or wheel damage, the pressure drop rate becomes significantly greater than in cases of natural leakage. Therefore, by focusing on this pressure drop rate, tire problems can be detected early. It should be noted that, preferably, the tire pressure drop rate calculation unit 18 repeatedly calculates the tire pressure drop rate from the change in temperature-converted tire pressure over a predetermined period (e.g., 5 minutes). This allows for accurate and early determination of whether the tire pressure is abnormal.

[0042] Under the control of the control unit 16, the thermal process quantity calculation unit 19 calculates the amount of heat received by each tire 2 within a predetermined period, either periodically or in real time, based on the acquired temperature information of each tire 2. The thermal process quantity, also known as the Temperature Severity Number (TSN), is an indicator of the amount of heat received by the tire 2 within the predetermined period. A higher thermal process quantity indicates a greater tendency for oxidation and deterioration of the tire 2. This is because as the temperature of the tire 2 increases, the air permeability coefficient of the rubber components constituting the tire 2 also increases. Furthermore, the temperature of the tire 2 varies significantly, particularly depending on the heat generated by the tire itself during vehicle 1 operation and the external air temperature during vehicle 1 operation. Preferably, the predetermined period is set to at least one day.

[0043] Under the control of the control unit 16, the air pressure drop rate threshold setting unit 20 sets an air pressure drop rate threshold. Compared to the air pressure drop rate, the air pressure drop rate threshold is a threshold used to determine whether the tire pressure of the tire 2 is abnormal. Therefore, similar to the air pressure drop rate, the air pressure drop rate threshold is defined by the amount of air pressure drop (kPa) per unit time (e.g., 1 minute). In this determination, the air pressure drop rate threshold can be set to a fixed value, but since the air pressure drop rate varies significantly depending on the tire 2's specifications, air pressure, or temperature, setting a fixed threshold would make it difficult to accurately determine whether the tire 2's air pressure is abnormal.

[0044] Therefore, the air pressure drop rate threshold is set corresponding to the thermal process quantity of the tire 2 as a preset physical quantity, and varies according to this thermal process quantity. In this embodiment, the air pressure drop rate threshold setting unit 20 has a threshold table 20a that specifies air pressure drop rate thresholds corresponding to the thermal process quantity. By referring to the threshold table 20a, the air pressure drop rate threshold corresponding to the calculated thermal process quantity is set. According to this structure, the set air pressure drop rate threshold can be changed according to the thermal process quantity, thus enabling accurate determination of whether there is an abnormality in the air pressure of the tire 2.

[0045] Furthermore, the correspondence between the air pressure drop rate threshold and the thermal process quantity can be set, for example, through actual machine testing or simulation using tires 2 of the same specifications. It should be noted that, in this embodiment, the air pressure drop rate threshold setting unit 20 is configured to have a threshold table 20a that specifies air pressure drop rate thresholds corresponding to the thermal process quantity, but it may also be configured to have the threshold table 20a in the storage unit 12.

[0046] Under the control of the control unit 16, the table updating unit 21 updates the threshold table 20a of the air pressure drop rate threshold setting unit 20 periodically or at a preset time according to the obtained information on the thermal process quantity and air pressure drop rate. In this embodiment, the table updating unit 21 obtains information on the thermal process quantity and air pressure drop rate of tires of the same specifications (model or size) as the tires 2 of this vehicle from the database of the server device 30. The table updating unit 21 calculates an approximate formula representing the relationship between the thermal process quantity and the air pressure drop rate from the obtained information, generates a threshold table representing the relationship between the thermal process quantity and the air pressure drop rate threshold by adding a predetermined margin to the approximate formula, and updates it to a new threshold table 20a. This predetermined margin is, for example, set to a specified value, determined by experiment or empirical rules.

[0047] According to this structure, since the threshold table 20a is updated based on the information related to the amount of heat process and the rate of air pressure drop obtained from the database, the accuracy of determining whether the tire pressure of the tire 2 is abnormal can be improved, and the driver can be notified of the abnormal air pressure at an earlier time. It should be noted that in this embodiment, the structure of the table update unit 21 obtaining the information related to the amount of heat process and the rate of air pressure drop from the database of the server device 30 is described, but it is not limited to this. It is also possible to obtain the information related to the amount of heat process and the rate of air pressure drop of the tire 2 accumulated in the vehicle through continuous use, and update the threshold table 20a based on this information.

[0048] Under the control of the control unit 16, the first determination unit 22 determines whether the tire pressure of the tire 2 is abnormal. Specifically, the first determination unit 22 determines whether the tire pressure of the tire 2 is abnormal by comparing the tire pressure drop rate calculated by the tire pressure drop rate calculation unit 18 with the tire pressure drop rate threshold set by the tire pressure drop rate threshold setting unit 20. If the tire pressure drop rate is greater than the tire pressure drop rate threshold, the first determination unit 22 determines that the tire pressure of the tire 2 is abnormal; if the tire pressure drop rate is less than the tire pressure drop rate threshold, the first determination unit 2 determines that the tire pressure of the tire 2 is normal.

[0049] Under the control of the control unit 16, the second determination unit 23 determines whether the air pressure of the pre-paired set of tires 2 is abnormal. First, the air pressure drop rate calculation unit 18 calculates the air pressure drop rate of the pre-paired set of tires 2 based on the wheel positions of the vehicle 1. Generally, the temperature of the tires 2 tends to be higher at the inner wheel positions of the vehicle 1 than at the outer wheel positions, making it easier for the air pressure to drop. Therefore, pairing is set at opposing positions where the temperatures of the tires 2 are approximately equal (e.g., left front wheel and right front wheel, left inner rear wheel and right inner rear wheel, left outer rear wheel and right outer rear wheel). The second determination unit 23 determines whether the air pressure of the aforementioned set of tires is abnormal based on the deviation of the calculated air pressure drop rates. In this embodiment, since tires at positions where the temperatures of the tires 2 are approximately equal are paired, it can generally be assumed that the calculated air pressure drop rates are also approximately equal, with a deviation close to 0. However, if one tire 2 malfunctions and the air pressure drop rate increases, the deviation of each air pressure drop rate is larger than a preset threshold, and therefore, it can be determined that the air pressure of that tire 2 is abnormal. Therefore, in this structure, based on the deviation in the rate of decrease of tire pressure of the paired set of tires 2, it is determined whether the tire pressure of one of the tires 2 in the set is abnormal. Thus, for example, in the early stage of a fault, it is possible to determine with high accuracy whether the tire pressure of the tire 2 is abnormal. Therefore, by combining the determination of the second determination unit 23 with the determination of the first determination unit 22, it is possible to accurately and early determine whether the tire pressure of the tire 2 is abnormal.

[0050] On the other hand, the server device 30 is connected to the pressure management device 10 in a communicative manner, and while maintaining the information sent from the pressure management device 10, it sends the required information according to the needs of the pressure management device 10. For example... Figure 2 As shown, the server device 30 includes a communication unit 31, a storage unit 32, and a control unit 33.

[0051] The communication unit 31 is configured to wirelessly communicate with the tire pressure management device 10 via the communication network 40. The communication unit 31 receives information from each tire pressure management device 10 regarding the amount of heat transfer and the rate of tire pressure drop. Furthermore, the communication unit 31, according to the needs of the tire pressure management device 10, sends information to the tire pressure management device 10 regarding the amount of heat transfer and the rate of tire pressure drop for tires of the same specifications as the required tires.

[0052] The storage unit 32 stores information on the thermal process amount and pressure drop rate of each vehicle's tires, sent from each tire pressure management device 10. Specifically, the storage unit 32 constructs a database storing information on the thermal process amount and pressure drop rate for each tire specification. This database is updated periodically or in real-time based on the acquired information on the tire's thermal process amount and pressure drop rate.

[0053] The control unit 33 includes a CPU, ROM, RAM, etc., and controls the overall operation of the server device 30 based on information received from the air pressure management device 10 or a program stored in the storage unit 32.

[0054] Next, the operation of the air pressure management device 10 according to this embodiment will be described. Figure 3 A flowchart illustrating the operating sequence of the air pressure management device. Figure 4 A graph showing the relationship between the temperature detected and the detection frequency during a predetermined period. Figure 5 A graph showing the relationship between the temperature acceleration coefficient and temperature. Figure 6 A schematic diagram of a threshold table illustrating the relationship between thermal process quantities and pressure drop thresholds. Figure 7 A graph showing the estimated time for the pressure to drop before reaching the limit pressure.

[0055] Regularly repeat Figure 3 The working sequence of steps ST1 to ST10 is shown in the figure. Figure 3 As shown, firstly, the sensor receiving unit 11 acquires (receives) information on the temperature and air pressure of the tires 2 measured by the sensors 3 installed on each tire 2 of the vehicle 1 at predetermined intervals (e.g., 10 minutes) (step ST1). This acquired information is stored in the storage unit 12 as historical information associated with the time information of each tire 2 identified using the sensor ID.

[0056] Next, the thermal process quantity calculation unit 19 calculates the thermal process quantity of tire 2 during a predetermined period (step ST2). The thermal process quantity calculation unit 19 calculates the thermal process quantity of all six tires 2 separately, but for ease of description, it will focus on one tire 2. The thermal process quantity calculation unit 19 categorizes the temperature information of tire 2 obtained from the storage unit 12 for a predetermined period (e.g., the most recent month) into temperature ranges of 1°C from 0°C to 120°C. Figure 4 As shown, the detection degree is obtained for each temperature range. This detection degree represents the cumulative time when the temperature information measured within the predetermined period is divided into each temperature range. Generally, the temperature of tire 2 tends to be lower on the outer rear of the vehicle and higher on the inner rear wheels. Therefore, it is preferable to obtain the detection degree (cumulative time) according to the wheel position on which tire 2 is mounted.

[0057] The thermal process quantity during the predetermined period is calculated using the temperature acceleration factor (acceleration factor) related to the state change of the tire component, which is given in advance with temperature as a parameter, and the detection degree (cumulative time) when the multiple temperature information measured during the predetermined period is divided into predetermined temperature intervals, and is obtained by the following formula (1).

[0058] Thermal process quantity during the predetermined period = Σ(K(ti)×T(ti))…(1)

[0059] In equation (1), the amount of heat process within the predetermined period is the sum of the heat generated in all the temperature ranges mentioned above. Furthermore, ti is the temperature, K(ti) is the temperature acceleration coefficient at temperature ti, and T(ti) is the cumulative time at temperature ti. The temperature acceleration coefficient K(ti) is a contribution coefficient related to the state change of the tire component with temperature ti as a parameter; for example, according to the known Arrhenius reaction rate equation, it can be considered to be proportional to exp(α·ti). Figure 5 In this model, based on the assumption that tire deterioration doubles when the temperature *ti* rises by 10°C, α is set to 0.069. Furthermore, *ti* is the highest temperature within each temperature range, but is not limited to this; for example, it could also be the average temperature within each temperature range. Cumulative time refers to the cumulative time within the temperature range, including the specified temperature.

[0060] Next, the pressure drop rate threshold setting unit 20 sets the pressure drop rate threshold based on the calculated thermal process quantity (step ST3). In this embodiment, the pressure drop rate threshold setting unit 20 has a threshold table 20a that specifies pressure drop rate thresholds corresponding to thermal process quantities. Therefore, as Figure 6 As shown, the air pressure drop rate threshold setting unit 20 sets an air pressure drop rate threshold Q corresponding to the calculated thermal process quantity R, referring to the threshold table 20a. Based on this structure, the set air pressure drop rate threshold can be changed according to the current thermal process quantity, thus enabling accurate determination of whether the tire 2's air pressure is abnormal.

[0061] Next, the temperature-to-pressure calculation unit 17 calculates the temperature-to-pressure based on the obtained temperature and pressure of each tire 2 (step ST4). Specifically, the temperature-to-pressure calculation unit 17 converts the obtained tire 2 pressure to the pressure at a specified temperature (e.g., 25°C) at predetermined intervals. Thus, by suppressing the pressure fluctuations accompanying the temperature changes of the tire 2, pressure changes can be properly managed.

[0062] Next, the air pressure drop rate calculation unit 18 calculates the air pressure drop rate based on the calculated change in temperature-converted air pressure (step ST5). Specifically, by dividing the change in temperature-converted air pressure (kPa) before and after a predetermined time by the predetermined time, the air pressure drop amount (kPa) per unit time (e.g., 1 minute) can be calculated. In this embodiment, by focusing on the air pressure drop rate and determining whether there is an air pressure abnormality based on the air pressure drop rate, problems with the tire 2 can be detected accurately and at an early stage.

[0063] Next, the first determination unit 22 determines whether the pressure drop rate calculated by the pressure drop rate calculation unit 18 is greater than the pressure drop rate threshold (step ST6). In this determination, if the pressure drop rate is below the pressure drop rate threshold (step ST6; No), the first determination unit 22 displays on the display unit 14 that the tire pressure of 2 is normal (step ST7). After step ST7, the air pressure management device 10 temporarily stops processing, but periodically repeats the processing from step ST1. Furthermore, in the above determination, if the pressure drop rate is greater than the pressure drop rate threshold (step ST6; Yes), the first determination unit 22 displays on the display unit 14 that the tire pressure of 2 is abnormal (step ST8). According to this structure, the tire pressure is determined to be abnormal based on the pressure drop rate threshold and the pressure drop rate set according to the current thermal process quantity, thus enabling high-precision determination of whether the tire pressure of 2 is abnormal.

[0064] Next, if the control unit 16 determines that the tire 2 has abnormal air pressure, while continuing to use the tire 2 at the calculated rate of air pressure decrease, the display unit 14 displays the period until the tire 2 reaches its limit air pressure (step ST9). Specifically, as follows... Figure 7 As shown, when the control unit 16 determines that the tire 2 has abnormal air pressure, it estimates the time from the moment the abnormality was determined (ta) to the moment the tire 2's air pressure drops to its limit pressure (tb) while continuing to use the tire 2 at the aforementioned rate of air pressure drop. The control unit 16 then displays this estimated air pressure drop time on the display unit 14. The limit pressure refers to the air pressure at which the vehicle 1 cannot be driven, for example, set to 70% or less of the "maximum air pressure" specified by the Japan Automobile Tire Manufacturers Association (JATMA). This limit pressure can be based on the aforementioned temperature-converted air pressure reference or an absolute air pressure reference. Furthermore, when estimating the time until the air pressure drops to the limit pressure, temperature variations during tire use over a year, estimated based on ambient temperature, can also be considered.

[0065] According to this structure, since the time until the air pressure drops to the limit is displayed, the driver (user) can retreat to a safe place or move to a maintenance service shop within that time. It should be noted that in this embodiment, the control unit 16 is configured to estimate the time until the air pressure drops to the limit (estimated air pressure drop time), but it can also estimate the distance that the vehicle 1 can move within that time.

[0066] Next, the control unit 16 instructs the route guidance unit 15 to retrieve the route from the current location of vehicle 1 to the nearest maintenance service shop, and displays the retrieved maintenance service shop on the display unit 14 (step ST10). In this case, route guidance to the aforementioned maintenance service shop can be implemented. Furthermore, if the control unit 16 does not find the nearest maintenance service shop that can be reached within the time limit before the air pressure drops to the aforementioned limit, it can also display the contact information (telephone number) of that maintenance service shop. Thus, with vehicle 1 moved to a safe location, on-site service can be requested. After step ST10, the air pressure management device 10 temporarily terminates the process, but periodically repeats the process from step ST1.

[0067] It should be noted that in the above embodiment, the structure described is that the first determination unit 22 determines whether the air pressure drop rate calculated by the air pressure drop rate calculation unit 18 is greater than the air pressure drop rate threshold. After the determination by the first determination unit 22, the second determination unit 23 can also determine whether the air pressure of a pre-paired set of tires 2 is abnormal. According to this structure, since the air pressure of a set of tires 2 is determined based on the deviation of the air pressure drop rate of the paired set of tires 2, for example, even in the early stage of a failure, it is possible to determine whether the air pressure of the tires 2 is abnormal with high accuracy. Furthermore, by combining the determination of the second determination unit 23 with the determination of the first determination unit 22, it is possible to correctly and early determine whether the air pressure of the tires 2 is abnormal.

[0068] Next, the operation of the threshold table 20a of the updating air pressure drop rate threshold setting unit 20 will be described. Figure 8 A diagram illustrating the operation of generating a threshold table based on information related to thermal process quantity and air pressure drop rate is provided. Preferably, the threshold table 20a is updated periodically, for example, when the engine of vehicle 1 is operated. In this embodiment, the table updating unit 21 obtains information 25a related to the thermal process quantity and air pressure drop rate of tires of the same specifications (model or size) as the tires 2 of this vehicle from the database of the server device 30. Figure 8 As shown, the table updating unit 21 generates an approximate formula 25 representing the relationship between the thermal process quantity and the rate of pressure drop based on the acquired information 25a. This approximate formula... Figure 8 The example is a linear expression. Furthermore, this approximation can also be created using, for example, the least squares method. The table update unit 21 generates and updates the threshold table 20a, which represents the relationship between the thermal process quantity and the pressure drop rate threshold, by adding a predetermined margin α to the approximation 25. The predetermined margin α, relative to the approximation 25, is a predetermined value added along the axial direction of the pressure drop rate.

[0069] According to this structure, since the threshold table 20a is updated based on relevant information such as the amount of heat process and the rate of air pressure drop obtained from the database, the accuracy of determining whether the tire pressure of 2 is abnormal can be improved, and by displaying the abnormal air pressure on the display unit 14, the driver can be notified at an earlier time. Figure 8 In the process, relevant information 25a of thermal process quantity and air pressure drop rate is obtained from the database of server device 30 to make approximate formula 25, but relevant information of thermal process quantity and air pressure drop rate of tire 2 accumulated in the vehicle due to continued use can also be obtained, and threshold table 20a is updated based on this relevant information of thermal process quantity and air pressure drop rate.

[0070] In this embodiment, thermal process quantities are described as examples of tire-related preset physical quantities, but it is not limited to this. Tire pressure or temperature can also be used as tire-related preset physical quantities. Figure 9 This is a schematic diagram of a threshold table illustrating the relationship between air pressure and the air pressure drop threshold. In this structure, as shown... Figure 9 As shown, threshold tables are set for the types of gases (air, nitrogen) sealed in tire 2. Therefore, the threshold tables can be changed according to the type of gas sealed, and it is possible to accurately determine whether the tire 2 has abnormal pressure. Figure 9 The table shows a threshold table 20b1 for representing the relationship between the pressure of air of a typical composition and the pressure drop threshold, and a threshold table 20b2 for representing the relationship between the pressure of nitrogen and the pressure drop threshold, but is not limited thereto and may include other gases.

[0071] These threshold tables 20b1 and 20b2 specify the threshold values ​​for the rate of decrease in air pressure corresponding to the air pressure. In this case, the air pressure can be an instantaneous value, but it is preferable to use the average air pressure measured over a predetermined period (e.g., more than one day).

[0072] In this structure, by referring to threshold tables 20b1 and 20b2, the set air pressure drop rate threshold can be changed according to the average air pressure within a predetermined period, so that it can be correctly determined whether the air pressure of tire 2 is abnormal.

[0073] Furthermore, although the illustration is omitted, it can also be configured to have a threshold table to represent the relationship between tire temperature and pressure drop rate threshold, which are physical quantities. For this case, instantaneous temperatures can be used, but it is preferable to use the average tire temperature measured over a predetermined period (e.g., more than one day). In this configuration, by referring to the threshold table (not shown), since the set pressure drop rate threshold can be changed according to the measured temperature, it is possible to accurately determine whether the tire pressure of tire 2 is abnormal.

[0074] As described above, the tire pressure management device 10 according to this embodiment includes: a temperature-to-pressure calculation unit 17, which calculates the temperature-to-pressure of the tire 2 based on the obtained temperature and pressure of the tire 2; a pressure drop rate calculation unit 18, which calculates the pressure drop rate, representing the tendency of the tire 2 to drop in pressure, based on the change in temperature-to-pressure within a preset period; a pressure drop rate threshold setting unit 20, which sets a pressure drop rate threshold corresponding to the obtained thermal process quantity using a threshold table 20a that specifies a pressure drop rate threshold corresponding to the thermal process quantity related to the tire 2; and a first determination unit 22, which determines whether the tire 2's pressure is abnormal based on the calculated pressure drop rate and the set pressure drop rate threshold. Therefore, the first determination unit 22 determines whether the tire 2's pressure is abnormal based on the pressure drop rate threshold set according to the current thermal process quantity and the pressure drop rate, thereby enabling high-precision determination of whether the tire 2's pressure is abnormal.

[0075] Furthermore, according to this embodiment, as a physical quantity, any one of the thermal process quantity of the tire 2, temperature, or air pressure can be used, so that it can be accurately determined whether the air pressure of the tire 2 is abnormal.

[0076] Furthermore, according to this embodiment, the air pressure drop rate calculation unit 18 includes a second determination unit 23. This second determination unit 23 calculates the air pressure drop rate of a paired set of tires 2 based on the wheel positions of the vehicle on which the tires 2 are mounted. It determines whether the air pressure of one tire 2 in the set is abnormal based on the deviation of each air pressure drop rate. Therefore, for example, even in the initial stage of a malfunction, it is possible to determine with high accuracy whether the air pressure of the tire 2 is abnormal. Thus, by combining the determination of the second determination unit 23 and the determination of the first determination unit 22, it is possible to accurately and early determine whether the air pressure of the tire 2 is abnormal.

[0077] Furthermore, according to this embodiment, a table updating unit 21 is included. This table updating unit 21 obtains the thermal process amount and air pressure drop rate of the tire 2, and updates the threshold table 20a based on the obtained thermal process amount and air pressure drop rate. Therefore, the threshold table 20a can be updated to the latest threshold table 20a at any time, thereby enabling high-precision determination of whether the air pressure of the tire 2 is abnormal.

[0078] Furthermore, according to this embodiment, the table update unit 21 obtains the thermal process amount and air pressure drop rate of tires 2 of the same specifications as those stored in the database of the server device 30. Therefore, a large amount of data can be used to determine with high accuracy whether the air pressure of the tires 2 is abnormal.

[0079] Furthermore, according to this embodiment, a display unit 14 is included. When the first determination unit 22 determines that the tire pressure of the tire 2 is abnormal, the display unit 14 displays the time until the tire pressure drops to the limit pressure while the tire 2 continues to be used at the calculated rate of pressure drop. Therefore, the driver (user) can retreat to a safe place or move to a maintenance service shop within this time.

[0080] The tire pressure management method according to this embodiment includes: step ST4, calculating the tire temperature-converted pressure based on the obtained temperature and tire pressure of the tire 2; step ST5, calculating the tire pressure drop rate based on the change in temperature-converted pressure within a preset period; step ST3, setting a tire pressure drop rate threshold corresponding to the obtained thermal process quantity using a threshold table 20a that specifies a tire pressure drop rate threshold corresponding to the thermal process quantity related to the tire 2; and step ST6, determining whether the tire pressure of the tire 2 is abnormal based on the calculated tire pressure drop rate and the set tire pressure drop rate threshold. Therefore, it is possible to determine with high accuracy whether the tire pressure of the tire 2 is abnormal.

[0081] According to the air pressure management procedure of this embodiment, the air pressure management device 10 performs the following steps: Step ST4, calculating the temperature-converted air pressure of the tire 2 based on the obtained temperature and air pressure; Step ST5, calculating the air pressure drop rate based on the change in temperature-converted air pressure within a preset period; Step ST3, setting an air pressure drop rate threshold corresponding to the obtained thermal process quantity using a threshold table 20a that specifies a threshold for the air pressure drop rate corresponding to the thermal process quantity related to the tire 2; and Step ST6, determining whether the air pressure of the tire 2 is abnormal based on the calculated air pressure drop rate and the set air pressure drop rate threshold. Therefore, it is possible to determine with high accuracy whether the air pressure of the tire 2 is abnormal.

[0082] The embodiments of the present invention have been described above, but the present invention should not be limited to the embodiments described above.

[0083] Explanation of reference numerals in the attached figures

[0084] 1: Vehicle

[0085] 2: Tires

[0086] 3: Sensors

[0087] 3a: Barometric pressure sensor

[0088] 3b: Temperature sensor

[0089] 4: External temperature sensor

[0090] 10: Air pressure management device

[0091] 12: Storage Department

[0092] 14: Display Department (Notification Department)

[0093] 16: Control Department

[0094] 17: Temperature to Pressure Calculation Section

[0095] 18: Pressure Drop Rate Calculation Unit

[0096] 19: Thermal Process Quantity Calculation Department (Physical Quantity Acquisition Department)

[0097] 20: Barometric Pressure Drop Rate Threshold Setting Unit

[0098] 20a, 20b1, 20b2: Threshold Table

[0099] 21: Form Update Department

[0100] 22: First Judgment Department

[0101] 23: Second Judgment Department

[0102] 30: Server device (external equipment)

[0103] 32: Storage Department

Claims

1. A pneumatic pressure management device, wherein, include: The temperature-to-pressure calculation unit calculates the temperature-to-pressure of the tire based on the obtained tire temperature and pressure. The air pressure drop rate calculation unit calculates the air pressure drop rate, which represents the tendency of the tire air pressure to drop, based on the change in air pressure converted from temperature within a preset period. The thermal process quantity calculation unit calculates the thermal process quantity as an indicator representing the heat received by the tire during a preset period, based on the obtained temperature of the tire. The air pressure drop rate threshold setting unit uses a threshold table that specifies an air pressure drop rate threshold corresponding to the thermal process amount of the tire, and sets the air pressure drop rate threshold corresponding to the calculated thermal process amount. as well as The first determination unit determines whether the tire pressure is abnormal based on the calculated air pressure drop rate and the set air pressure drop rate threshold.

2. The air pressure management device according to claim 1, wherein, The tire pressure drop rate calculation unit calculates the tire pressure drop rate for a paired set of tires based on the wheel position of the vehicle on which the tires are mounted. The air pressure management device includes a second determination unit, which determines whether the air pressure of one of the tires in a group of tires is abnormal based on the deviation of the air pressure drop rate.

3. The air pressure management device according to claim 1, wherein, The air pressure management device includes a table updating unit, which is used to obtain the thermal process amount and the air pressure drop rate of the tire, and update the threshold table according to the obtained thermal process amount and air pressure drop rate.

4. The air pressure management device according to claim 3, wherein, The table updating unit obtains the thermal process amount and the air pressure drop rate of a tire of the same specification as the tire stored in the external device.

5. The air pressure management device according to any one of claims 1 to 4, wherein, The tire pressure management device includes a notification unit that, when the first determination unit determines that the tire pressure is abnormal, When the tire continues to be used at the calculated rate of pressure drop, the notification unit notifies the time until the tire pressure drops to the limit pressure.

6. A method for managing air pressure, wherein, include: The step of calculating the tire temperature-to-air-pressure conversion based on the obtained tire temperature and air pressure; The step of calculating the rate of air pressure drop based on the change in air pressure converted from the temperature during a preset period; The step of calculating the amount of heat process as an indicator of the heat received by the tire during a preset period, based on the obtained temperature of the tire. The step of setting the pressure drop rate threshold corresponding to the calculated thermal process quantity using a threshold table that specifies the pressure drop rate threshold corresponding to the thermal process quantity of the tire; as well as The step of determining whether the tire pressure is abnormal based on the calculated rate of pressure drop and the set threshold for the rate of pressure drop.

7. A pressure management program product, comprising a pressure management program, wherein, The pressure management procedure causes the pressure management device to perform the following steps: The step of calculating the tire temperature-to-air-pressure conversion based on the obtained tire temperature and air pressure; The step of calculating the rate of air pressure drop based on the change in air pressure converted from the temperature during a preset period; The step of calculating the amount of heat process as an indicator of the heat received by the tire during a preset period, based on the obtained temperature of the tire. The step of setting the pressure drop rate threshold corresponding to the calculated thermal process quantity using a threshold table that specifies the pressure drop rate threshold corresponding to the thermal process quantity of the tire; as well as The step of determining whether the tire pressure is abnormal based on the calculated rate of pressure drop and the set threshold for the rate of pressure drop.

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