Wheel state acquisition system

Abstract

The objective of this invention is to accurately determine whether a wheel is experiencing abnormal tire air pressure. In this wheel condition acquisition system, the air pressure (temperature-corrected air pressure) is obtained separately for each of the multiple wheels, assuming the internal temperature of the tire is a predetermined set temperature, based on the detected air pressure and temperature of each tire. Furthermore, if the decrease in the temperature-corrected air pressure (a positive value) of one wheel A is greater than the decrease in the temperature-corrected air pressure of each of the other wheels, then wheel A is considered to have abnormal tire air pressure. During vehicle operation, air pressure may decrease due to a drop in the internal temperature of the tire. Therefore, this wheel condition acquisition system, by basing its assessment on the decrease in temperature-corrected air pressure, can accurately determine whether a wheel is experiencing abnormal tire air pressure.

Description

Technical Field

[0001] This invention relates to a wheel state acquisition system for obtaining the state of a wheel. Background Technology

[0002] The wheel condition acquisition system described in Patent Document 1 includes: an air pressure sensor installed on each of a plurality of wheels to detect the air pressure of the tires of the wheels; and a slow leakage condition acquisition unit that acquires whether each of the plurality of wheels is in a slow leakage state based on the air pressure detected by the plurality of air pressure sensors for each of the plurality of wheels, i.e., the detected air pressure. In the slow leakage condition acquisition unit, if the difference between the average value of the detected air pressure of one of the plurality of wheels during a first period (i.e., the first average value) and the average value during a second period (i.e., the second average value) is greater than or equal to a first threshold, and the difference for each of the other wheels is less than the first threshold, then that wheel is acquired to be in a slow leakage state.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2022-090477 Summary of the Invention

[0004] The objective of this invention is to improve a wheel condition acquisition system, for example, to acquire with high precision whether the tire air pressure of a wheel is abnormal.

[0005] In the wheel condition acquisition system of this invention, the air pressure, i.e., the temperature-corrected air pressure, is obtained based on the detected air pressure and detected temperature of each tire of a plurality of wheels, assuming the internal temperature of the tire is a predetermined set temperature. Then, if the decrease in the temperature-corrected air pressure (a positive value) of one wheel A is greater than the decrease in the temperature-corrected air pressure of each of the other wheels, wheel A is identified as having abnormal tire air pressure. During vehicle operation, there are cases where air pressure decreases due to a decrease in the internal temperature of the tire. In contrast, in this wheel condition acquisition system, since the decrease is based on the temperature-corrected air pressure, it is unnecessary to consider the decrease in air pressure caused by a decrease in temperature. Therefore, it is possible to obtain with high accuracy whether a wheel is in a state of abnormal tire air pressure. Attached Figure Description

[0006] Figure 1 This is a perspective view schematically representing the overall wheel state acquisition system involved in an embodiment of the present invention.

[0007] Figure 2 This is a diagram schematically representing the main components of the aforementioned wheel state acquisition system.

[0008] Figure 3This is a flowchart showing the slow leakage status acquisition procedure stored in the storage section of the vehicle body side unit of the aforementioned wheel status acquisition system.

[0009] Figure 4 This is a flowchart illustrating the procedure for obtaining abnormal air pressure stored in the aforementioned storage unit.

[0010] Figure 5 This is a graph showing the changes in air pressure at the wheels of a vehicle equipped with the aforementioned wheel status acquisition system.

[0011] Figure 6 This is a graph showing the change in air pressure after subtracting the reference pressure from the temperature-corrected air pressure of the aforementioned wheel, i.e., the change in air pressure reduction.

[0012] Explanation of reference numerals in the attached figures

[0013] 12…Wheel-side unit; 16…Body-side unit; 20…Air pressure sensor; 22…Temperature sensor; 24…Wheel information creation unit; 26…Transmitter; 42…Receiver; 44…Display; 46…Vehicle status detection device; 48…TPMSECU. Detailed Implementation

[0014] Hereinafter, a wheel state acquisition system according to an embodiment of the present invention will be described in detail based on the accompanying drawings.

[0015]

Example

[0016] like Figure 1 As shown, the wheel status acquisition system includes: wheel side units 12FL, 12FR, 12RL, and 12RR, respectively disposed on each of the front, rear, left, and right wheels 10FL, 10FR, 10RL, and 10RR, which are multiple wheels disposed on the vehicle; and a body side unit 16 disposed on the body 14.

[0017] In the following, when it is necessary to distinguish wheel 10, wheel side unit 12, etc. by wheel position FL, FR, RL, RR, etc., the attached reference numerals indicating the wheel position will be used. However, when there is no need to distinguish them or when they are referred to collectively, the attached reference numerals indicating the wheel position will not be used.

[0018] like Figure 2 As shown, the wheel-side unit 12 includes an air pressure sensor 20, a temperature sensor 22, a wheel information creation unit 24 for creating wheel information, and a transmitter 26 for wirelessly transmitting wheel information.

[0019] Air pressure sensor 20 directly detects the air pressure in the tire of wheel 10, and temperature sensor 22 directly detects the internal temperature of the tire.

[0020] The wheel information creation unit 24, primarily computer-based, creates wheel information at predetermined intervals, including air pressure P detected by air pressure sensor 20, temperature T detected by temperature sensor 22, and identification information ID that identifies the wheel itself. The created wheel information is then supplied to transmitter 26, which transmits the supplied wheel information wirelessly.

[0021] In this embodiment, the air pressure detected by the air pressure sensor 20 and the air pressure contained in the wheel information will be referred to as the detected air pressure, and the temperature detected by the temperature sensor 22 and the temperature contained in the wheel information will be referred to as the detected temperature.

[0022] The vehicle side unit 16 includes a receiver 42, a display 44 serving as a reporting device, a vehicle status detection device 46 for detecting the vehicle's status, and a wheel status acquisition ECU 48, which is primarily a computer. Since the wheel status acquisition ECU 48 in this embodiment mainly acquires the tire air pressure status, it will be referred to below as a TPMS (Tire Pressure Monitoring System) ECU 48. The TPMS ECU 48 includes an execution unit, a storage unit, and an input / output unit, with the receiver 42, display 44, and vehicle status detection device 46 connected to the input / output unit.

[0023] Receiver 42 receives wheel information wirelessly transmitted from wheel-side unit 12. In this embodiment, one receiver is provided in vehicle-side unit 16, but for example, multiple receivers can be provided corresponding to the front, rear, left, and right wheels 10FL, 10FR, 10RL, and 10RR respectively, or multiple receivers can be provided in a shared manner for two or more of the front, rear, left, and right wheels 10FL, 10FR, 10RL, and 10RR.

[0024] The display 44 reports by showing the status of the wheels 10. The display 44 shows information such as air pressure received from the receiver 42 regarding the wheels; or, if the air pressure of one of the wheels 10 (front, rear, left, right) is abnormal, or if the wheel 10 is in a slow leaking state, it displays the slow leaking state and the position of that wheel 10. Furthermore, the status of the wheels 10 is not limited to the display 44; for example, a sound generating device can be installed to report the status via sound.

[0025] The vehicle state detection device 46 can detect whether the vehicle is in a stopped state or a moving state. For example, if the vehicle's speed is less than a set speed at which it can be inferred to be stopped, it can be detected as being in a stopped state; if it is above the set speed, it can be detected as being in a moving state. The vehicle state detection device 46 includes, for example, wheel speed sensors respectively provided for each wheel 10, and can detect the vehicle's speed based on the wheel speeds of each wheel 10 detected by these wheel speed sensors. In addition, the vehicle state detection device 46 may also include drive state detection devices, brake state detection devices, etc., that detect the operating state of the drive system and brake system provided on the vehicle. Based on both the vehicle's speed and the operating state of the vehicle's drive system or brake system, it is possible to determine with high accuracy whether the vehicle is in a stopped state or a moving state.

[0026] The operation of the wheel state acquisition system configured as described above will be explained.

[0027] In this embodiment, it is determined whether the air pressure of the tire of wheel 10 is abnormal.

[0028] It executes at predetermined set intervals. Figure 4 The flowchart illustrates the air pressure anomaly acquisition procedure. In this procedure, it is determined whether the tire of wheel 10 has blown out and whether the tire's air pressure is lower than a predetermined set pressure. Furthermore, the determination of whether the tire has blown out and whether it is in an abnormally low-pressure state (lower than the set pressure) is based on detected air pressure, rather than on temperature-corrected air pressure as described later.

[0029] In step 1 (hereinafter referred to as S1; the same applies to other steps), it is determined whether wheel information is received in receiver 42. If received, in S2, the identification information ID, detected air pressure P, and detected temperature T contained in the wheel information are read. In S3, the position of the wheel 10 that sent the wheel information is obtained based on the identification information ID and a predetermined table (not shown). In S4, it is determined whether the detected air pressure P is lower than a predetermined set pressure Pth. The set pressure Pth can be, for example, a pressure determined by regulations, and can be a value of 80% of the air pressure under predetermined conditions when the vehicle is traveling. In addition, the set pressure Pth can be a pressure lower than the so-called normal range. Hereinafter, there is a case where the set pressure Pth is referred to as the set pressure Pth specified by regulations.

[0030] If the determination in S4 is yes, then in S5 it is determined that the air pressure is abnormally low, and the situation is reported via the display 44. In this embodiment, the report is made by displaying the abnormally low air pressure and the position of the wheel on the display 44.

[0031] If the determination in S4 is negative, in S6 it is determined whether the decreasing gradient (which is a positive value and is the absolute value of the changing gradient) dP of the detected air pressure P is greater than the tire blowout determination threshold dPth. If the determination in S6 is positive, in S7 it is inferred that the tire of wheel 10 has blown out, and the situation is reported via display 44.

[0032] If both S4 and S6 are negative, the detected air pressure of the wheel 10 is displayed on the display 44 in S8. Additionally, the detected air pressure P, detected temperature T, wheel position, etc., obtained in S2 and S3 are stored.

[0033] It executes at predetermined set intervals. Figure 3 The flowchart shows the slow leakage state determination procedure. This slow leakage state determination procedure is executed for each of the front, rear, left, and right wheels 10 to determine whether it is a slow leakage state in which air is slowly leaking from the tire.

[0034] For example, there might be a situation where the tire is punctured by a nail, or where air is leaking from the tire even though it hasn't blown out. In this case, because the decrease gradient dP of the detected air pressure P is less than the blowout determination threshold dPth, the tire of wheel 10 is generally not considered to be in a blowout state (wheel 10 can also be described as being in a blowout state). Therefore, even if air leaks from the tire, until the detected air pressure P falls below the legally prescribed set pressure Pth, the situation of wheel 10 being in an abnormal air pressure state is not reported.

[0035] Therefore, it is desirable to detect that the wheel 10 is in a state of slow air leakage compared to a tire blowout, in other words, a slow leak state, before the detected air pressure P becomes lower than the set pressure Pth specified by regulations.

[0036] Furthermore, when the vehicle is in motion, if the temperature of the wheel 10 decreases, the air pressure decreases. Therefore, based on the detected air pressure P, it is difficult to determine whether the decrease in air pressure is due to a slow leak or a decrease in temperature. In view of this, in this embodiment, the presence or absence of a slow leak is determined based on the detected air pressure P, the detected temperature T, and Boyle-Charlie's law, i.e., the air pressure Pb when the internal temperature of the tire is a set temperature (e.g., a standard temperature).

[0037] Specifically, assuming that the volume of the tires of the four wheels 10 located at the front, rear, left, and right is constant, the Boyle-Charlie law expressed by the following equation (1) holds. The temperature-corrected air pressure Pb is obtained by substituting the measured air pressure P, the measured temperature T, and 25°C (standard temperature) into equation (1).

[0038] (Pb+101)=(P+101)(25℃+273℃) / (T+273℃)···(1)

[0039] In equation (1) above, 101 [kPa] is atmospheric pressure. The measured air pressure [kPa] is relative to atmospheric pressure, but in Boyle-Charles' law, since absolute pressure (pressure based on pressure under vacuum) is used, atmospheric pressure is added. In addition, since absolute temperature is used in Boyle-Charles' law, 273°C is added to the measured temperature.

[0040] Furthermore, when the temperature drops while the vehicle is in motion, the detected air pressure decreases for all four wheels 10 located at the front, rear, left, and right. In contrast, it is rare for two or more of the four wheels 10 located at the front, rear, left, and right to be in a state of slow leakage simultaneously; it can be assumed that in most cases, only one wheel 10 is in a state of slow leakage.

[0041] Therefore, in this embodiment, when the decrease (positive value) of the temperature-corrected air pressure Pb of a wheel 10 from the reference pressure is greater than or equal to the decrease of the temperature-corrected air pressure Pb of each of the other three wheels 10 after removing one of the four wheels 10 from the reference pressure, the wheel 10 is determined to be in a slow leakage state, which is a threshold for determining an abnormal air pressure.

[0042] The reference pressure is a value used as a reference when the air pressure of each of the four wheels 10's tires changes. In this embodiment, a reference pressure is set for each of the four wheels 10, and is expressed as the air pressure when the tire's internal temperature is at a standard temperature (temperature-corrected air pressure). The reference pressure can be the initial value of the tire's air pressure, but if the tire's air pressure has been adjusted, it is the adjusted air pressure.

[0043] In steps S21 to 29 of this slow leakage condition determination procedure, it is determined whether pressure adjustment has been performed while the vehicle is stationary. If pressure adjustment has been performed, the reference pressure is updated accordingly. If pressure adjustment has not been performed, the previous reference pressure (the initial value of the tire air pressure or the air pressure after the last pressure adjustment) is used as is.

[0044] The steps following S30 of the slow leakage condition determination procedure are performed while the vehicle is in motion. That is, while the vehicle is in motion, the wheel 10 is determined to be in a slow leakage condition based on the amount of decrease in temperature-corrected air pressure from the reference pressure.

[0045] The following describes the application of this slow leak condition determination procedure to the 10FL front left wheel.

[0046] In S21, the vehicle is determined to switch from a driving state to a stopped state based on whether it has stopped, or in other words, based on its speed. If the determination in S21 is yes, the detection air pressure P and detection temperature T before the vehicle stops are obtained in S22. In other words, the detection air pressure P and detection temperature T contained in the wheel information received in the last time wheel information was received are obtained. For example, the detection air pressure P and detection temperature T contained in the wheel information received in the last time were read from S8. In S23, the detection air pressure P and detection temperature T before the vehicle stops are substituted into equation (1) to obtain the temperature correction air pressure Pb1 before the vehicle stops.

[0047] Next, in S24, it is determined whether the vehicle has started driving. It is determined whether the vehicle has switched from a stopped state to a driving state. If the determination in S24 is yes, in S25, the detected air pressure P and detected temperature T are obtained from the wheel information initially received after driving starts. In S26, the detected air pressure P and detected temperature T (included in the wheel information initially received after driving starts) after driving starts are substituted into equation (1) to obtain the temperature-corrected air pressure Pb2 after driving starts.

[0048] Next, in S27, the change in air pressure ΔPbr is obtained by subtracting the temperature-corrected air pressure Pb1 before stopping from the temperature-corrected air pressure Pb2 after starting to drive. In S28, it is determined whether the change ΔPbr is greater than a predetermined pressure adjustment judgment threshold ΔPrth. In other words, it is determined whether the temperature-corrected air pressure Pb has increased above the pressure adjustment judgment threshold ΔPrth while the vehicle is stationary.

[0049] If the determination in S28 is yes, it is inferred that the air pressure of the left front wheel 10FL was adjusted while the vehicle was stationary. In S29, the adjusted air pressure, i.e., the temperature-corrected air pressure Pb2 immediately after starting to drive, is set as the new reference pressure PaFL for the left front wheel 10. The reference pressure PaFL is updated and changed. Conversely, if no air pressure adjustment was performed while the vehicle was stationary, the determination in S28 is no. The reference pressure Pa is not updated and remains unchanged from the previous reference pressure.

[0050] Next, in S30, it is determined whether the vehicle is in motion. If the determination is yes, in S31, the detected air pressure P and detected temperature T are obtained from the wheel information received from the receiver 42. In S32, the temperature-corrected air pressure Pb is obtained based on the detected air pressure P, detected temperature T, and equation (1). In S33, the value (Pb-Pa) obtained by subtracting the reference pressure Pa from the temperature-corrected air pressure Pb is obtained, which is the air pressure reduction value (negative value) ΔPb. The air pressure reduction value ΔPb is a negative value representing the amount by which the temperature-corrected air pressure Pb decreases relative to the reference pressure Pa at the current moment. Since this procedure is performed on the left front wheel 10FL, the air pressure reduction value ΔPb can be called ΔPbFL.

[0051] Then, in S34, the air pressure reduction values ​​(ΔPbFR, ΔPbRL, ΔPbRR) of the other wheels 10 (right front wheel 10FR, left rear wheel 10RL, right rear wheel 10RR) are obtained, and the differences between these values ​​and the air pressure reduction value ΔPbFL of the left front wheel 10FL are calculated. For example, the air pressure reduction value ΔPbFR of the right front wheel 10FR can be expressed as PbFR - PaFR, and the difference ΔPbFL1 between the air pressure reduction value ΔPbFR of the right front wheel 10FR and the air pressure reduction value ΔPbFL of the left front wheel 10FL can be expressed as ΔPbFR - ΔPbFL.

[0052] ΔPbFL1=ΔPbFR-ΔPbFL

[0053] ΔPbFR=PbFR-PaFR

[0054] ΔPbFL=PbFL-PaFL

[0055] Then, similarly, the differences ΔPbFL2 and ΔPbRR (the air pressure drop value ΔPbRL for the left rear wheel 10RL), and ΔPbFL3 (the air pressure drop value ΔPbRR for the right rear wheel 10RR) are calculated respectively, and it is determined in S35 whether they are greater than the leakage detection threshold ΔPLth. If at least one of the differences ΔPbFL1, ΔPbFL2, and ΔPbFL3 are less than the leakage detection threshold ΔPLth, the determination in S35 is negative. Subsequently, while the vehicle is in motion, S21, S24, and S30 to S36 are repeatedly executed. If all the differences ΔPbFL1, ΔPbFL2, and ΔPbFL3 are greater than the leakage detection threshold ΔPLth, the determination in S35 is positive. In S36, the display 44 reports that the left front wheel 10FL is in a slow leakage state.

[0056] In addition, the same slow leakage condition determination procedure is performed on the right front wheel 10FR, left rear wheel 10RL, and right rear wheel 10RR.

[0057] Figure 5 , 6 It is a graph showing the changes in air pressure. Figure 5 The vertical axis represents the decrease in air pressure. Figure 6 The vertical axis represents air pressure. For example... Figure 6 As shown, the reference pressures Pa (PaFL, PaFR, PaRL, PaRR) are generally different in each of the front, rear, left, and right wheels 10. Furthermore, for each of the front, rear, left, and right wheels 10, the air pressure reduction values ​​ΔPbFL, ΔPbFR, ΔPbRL, and ΔPbRR, obtained after subtracting the reference pressure Pa from the current temperature-corrected air pressure Pb, are respectively obtained. Moreover, as... Figure 5 As shown, if the absolute value of the air pressure reduction ΔPbFL for the left front wheel 10FL is greater than the absolute values ​​of the air pressure reduction ΔPbFR, ΔPbRL, and ΔPbRR for the other wheels 10FR, 10RL, and 10RR respectively, exceeding the leakage threshold ΔPLth, it is determined to be a slow leakage condition. Figure 5 , 6 In the case shown, the leakage is determined to be slow at time tb.

[0058] As described above, in this embodiment, since the air pressure Pb is corrected based on temperature, it is possible to obtain with high accuracy whether the wheel 10 is in a slow leakage state.

[0059] In addition, such as Figure 6 As shown, it is possible to detect a slow leak in wheel 10 as early as possible, before the air pressure P falls below the set pressure Pth specified by regulations.

[0060] Furthermore, since it is not necessary to obtain the average value of the first period, the second period, etc. for air pressure, it is easy to determine whether it is a slow leakage state.

[0061] In this embodiment, the portion of the TPMSECU48 that stores S23, S26, S32, etc., and the portion that executes them constitutes a temperature-corrected air pressure acquisition unit; the portion that stores S33 to S36 and the portion that executes them constitutes an air pressure anomaly acquisition unit; and the portion that stores S21 to S29 and the portion that executes them constitutes a reference pressure change unit. Furthermore, the portion that stores S2, S6, S7 and the portion that executes them constitutes a tire blowout acquisition unit, and the portion that stores S2, S4, S5 and the portion that executes them constitutes an abnormal low pressure acquisition unit.

[0062] Furthermore, the present invention can be implemented in various ways with different modifications and improvements based on the knowledge of those skilled in the art.

[0063] Inventions eligible for patent protection

[0064] (1) A wheel state acquisition system, comprising:

[0065] An air pressure sensor is installed on each of the multiple wheels of the vehicle and detects the air pressure in the tires of each wheel individually.

[0066] Temperature sensors are installed on each of the aforementioned multiple wheels to detect the internal temperature of the tires of each wheel.

[0067] The temperature-corrected air pressure acquisition unit acquires, based on the air pressure (detected air pressure) detected by each of the plurality of air pressure sensors and the temperature (detected temperature) detected by each of the plurality of temperature sensors, the tire air pressure (temperature-corrected air pressure) for each of the plurality of wheels when the internal temperature of the tire is a predetermined set temperature; and

[0068] The air pressure anomaly acquisition unit determines that the air pressure of the aforementioned wheel is abnormal if the decrease in temperature-corrected air pressure for one of the plurality of wheels, as obtained by the temperature-corrected air pressure acquisition unit, is greater than the decrease in temperature-corrected air pressure for each of the other wheels in the plurality of wheels.

[0069] In item (1), an abnormal state of air pressure in the tires of a wheel refers to a slow leakage state in which air is slowly leaking from the tires. In this sense, the part that obtains the abnormal air pressure can be called the part that obtains the slow leakage state of the wheel.

[0070] The case where the decrease in temperature-corrected air pressure (positive value) for one wheel is greater than the decrease in temperature-corrected air pressure for the other wheels means that it is greater than any one of the decreases in temperature-corrected air pressure for the other wheels. In other words, it means that the decrease in temperature-corrected air pressure for one wheel is greater than the maximum decrease in temperature-corrected air pressure for the other wheels.

[0071] (2) Obtain the system based on the wheel state described in item (1), wherein,

[0072] If the decrease in temperature-corrected air pressure for one wheel, as determined by the temperature-corrected air pressure acquisition unit, is greater than or equal to the decrease in temperature-corrected air pressure for each of the other wheels, the air pressure anomaly acquisition unit determines that the one wheel is in a state of abnormal tire air pressure.

[0073] (3) Obtain the system based on the wheel state described in item (1) or (2), wherein,

[0074] The aforementioned air pressure anomaly acquisition unit includes an air pressure reduction value acquisition unit. This air pressure reduction value acquisition unit acquires for each of the plurality of wheels the value obtained by subtracting the reference pressure from the temperature-corrected air pressure acquired by the temperature-corrected air pressure acquisition unit, which is the air pressure reduction value (negative value). If the absolute value of the air pressure reduction value acquired by the air pressure reduction value acquisition unit for one wheel is greater than or equal to the absolute value of the air pressure reduction value for each of the other wheels, the unit determines that the air pressure of the tire of that wheel is abnormal.

[0075] (4) Obtain the system based on the wheel state described in item (3), wherein,

[0076] The wheel status acquisition system includes:

[0077] The vehicle condition detection device detects the condition of the aforementioned vehicles; and

[0078] When the vehicle is in a stopped state as detected by the vehicle state detection device, the reference pressure changing unit determines whether the temperature correction air pressure obtained by the temperature correction air pressure acquisition unit for each of the plurality of wheels has increased by a predetermined pressure adjustment determination threshold. If it is determined that the temperature correction air pressure for at least one of the plurality of wheels has increased by the pressure adjustment determination threshold, the reference pressure is changed for each of the at least one wheel.

[0079] The change in temperature-corrected air pressure when the vehicle is stationary can be obtained as the difference between the temperature-corrected air pressure just before or immediately after stopping and the temperature-corrected air pressure just after or immediately before starting to move. The temperature-corrected air pressure just before stopping can be the last temperature-corrected air pressure obtained while the vehicle is in motion, and the temperature-corrected air pressure just before starting to move can be the last temperature-corrected air pressure obtained while the vehicle is stationary.

[0080] (5) Obtain the system based on the wheel state described in item (4), wherein,

[0081] The aforementioned reference pressure changing unit changes the reference pressure for at least one wheel to a pressure determined based on the temperature-corrected air pressure after the aforementioned pressure adjustment determination threshold has been increased.

[0082] The reference pressure can be changed to the temperature-corrected air pressure after the pressure adjustment judgment threshold has been increased.

[0083] (6) Obtain the system based on the wheel state recorded in any one of items (1) to (5), wherein,

[0084] The temperature-corrected air pressure acquisition unit obtains the temperature-corrected air pressure by substituting the detected temperature and the detected air pressure for each of the plurality of wheels into the formula representing Boyle-Charlie's law. This temperature-corrected air pressure is the air pressure at which the internal temperature of the tire is the standard temperature set as the temperature.

[0085] (7) Obtain the system based on the wheel state recorded in any one of items (1) to (6), wherein,

[0086] The wheel status acquisition system includes a reporting device that reports a situation when the air pressure anomaly acquisition unit determines that one of the wheels is in a state of abnormal air pressure in the tire.

[0087] (8) Obtain the system based on the wheel state recorded in any one of items (1) to (7), wherein,

[0088] The wheel status acquisition system includes:

[0089] The tire blowout acquisition unit determines whether the decrease gradient of the detected air pressure of each of the plurality of wheels, detected by the plurality of air pressure sensors, is above a predetermined set gradient. If it determines that the decrease gradient of the detected air pressure of at least one of the plurality of wheels is above the set gradient, it acquires information indicating that the tire of that at least one wheel has blown out.

[0090] The abnormal low pressure acquisition unit determines whether the air pressure of the tire of each of the plurality of wheels detected by the plurality of air pressure sensors, i.e., the detected air pressure, is lower than a predetermined set pressure. If it is determined that the detected air pressure of at least one of the plurality of wheels is lower than the set pressure, the unit acquires that the air pressure of the tire of at least one wheel is abnormally low.

[0091] (9) A wheel state acquisition system, comprising:

[0092] An air pressure sensor is installed on each of the multiple wheels of the vehicle and detects the air pressure of the tires of each wheel.

[0093] Temperature sensors are installed on each of the aforementioned multiple wheels to detect the internal temperature of the tires of each wheel.

[0094] The temperature-corrected air pressure acquisition unit acquires the air pressure of each of the multiple wheels' tires, i.e., the detected air pressure, based on the air pressure of each of the multiple air pressure sensors and the internal temperature of each of the multiple wheels' tires, i.e., the detected temperature, based on the internal temperature of each of the multiple temperature sensors. The unit acquires the air pressure of each of the multiple wheels' tires, i.e., the temperature-corrected air pressure, when the internal temperature of the tires is a predetermined set temperature.

[0095] The abnormal air pressure acquisition unit obtains whether the air pressure of each of the plurality of wheels is abnormal based on the decrease in the temperature-corrected air pressure of each of the plurality of wheels from the reference pressure obtained by the temperature-corrected air pressure acquisition unit.

[0096] The vehicle condition detection device detects the condition of the aforementioned vehicles; and

[0097] The reference pressure changing unit determines whether the temperature correction air pressure obtained by the temperature correction air pressure acquisition unit for each of the plurality of wheels has increased above a predetermined pressure adjustment determination threshold when the vehicle state detection device detects that the vehicle is in a stopped state. If it determines that the temperature correction air pressure for at least one of the plurality of wheels has increased above the pressure adjustment determination threshold, the reference pressure is changed for each wheel of the tire with the at least one temperature correction air pressure.

[0098] The wheel state acquisition system described in this section can adopt any of the technical features described in items (1) to (8).

[0099] (10) A wheel state acquisition system, wherein,

[0100] The aforementioned wheel status acquisition system includes a wheel-side unit disposed on each of the plurality of wheels of the vehicle, and a body-side unit disposed on the body of the vehicle.

[0101] The aforementioned wheel-side unit includes:

[0102] An air pressure sensor detects the air pressure in the tires of the aforementioned wheels;

[0103] Temperature sensors detect the internal temperature of the aforementioned tires;

[0104] The wheel information creation unit creates wheel information including the air pressure detected by the aforementioned air pressure sensor (i.e., the detected air pressure) and the temperature detected by the aforementioned temperature sensor (i.e., the detected temperature); and

[0105] The transmitter sends the wheel information created by the aforementioned wheel information creation unit.

[0106] The aforementioned vehicle body side unit includes:

[0107] One or more receivers receive wheel information transmitted from multiple of the aforementioned wheel-side units;

[0108] The temperature-corrected air pressure acquisition unit, based on the detected air pressure and detected temperature included in the wheel information transmitted from the plurality of wheel-side units and received in one or more receivers, acquires the tire air pressure, i.e., the temperature-corrected air pressure, for each of the plurality of wheels when the internal temperature of the tire is a predetermined set temperature; and

[0109] The air pressure anomaly acquisition unit determines that the air pressure of the aforementioned wheel is abnormal when the decrease in temperature-corrected air pressure for one of the plurality of wheels, as obtained by the temperature-corrected air pressure acquisition unit, is greater than the decrease in temperature-corrected air pressure for each of the other wheels after removing the aforementioned wheel from the plurality of wheels.

[0110] The wheel state acquisition system described in this section can adopt any of the technical features described in items (1) to (9).

[0111] (11) A wheel state acquisition system, comprising:

[0112] An air pressure sensor detects the air pressure in the tires of the aforementioned wheels of a vehicle.

[0113] A temperature sensor detects the internal temperature of the tire of the aforementioned wheel, which is installed on the aforementioned wheel.

[0114] The temperature-corrected air pressure acquisition unit obtains the air pressure when the internal temperature of the tire is a predetermined set temperature, based on the air pressure detected by the air pressure sensor (i.e., the detected air pressure) and the temperature detected by the temperature sensor (i.e., the detected temperature); and

[0115] The slow leakage condition acquisition unit determines whether the wheel is in a slow leakage condition based on the decrease in temperature correction air pressure obtained by the temperature correction air pressure acquisition unit.

[0116] The wheel state acquisition system described in this section can adopt any of the technical features described in items (1) to (10).

Claims

1. A wheel state acquisition system, wherein, include: An air pressure sensor is placed on each of the multiple wheels of the vehicle and detects the air pressure in the tires of each wheel individually. Temperature sensors are installed at each of the plurality of wheels and detect the internal temperature of the tire of each wheel. A vehicle status detection device detects the status of the vehicle; as well as Controller The controller is configured as follows: Based on the air pressure detected by each of the plurality of air pressure sensors (i.e., the detected air pressure) and the temperature detected by each of the plurality of temperature sensors (i.e., the detected temperature), the tire air pressure (i.e., the temperature-corrected air pressure) is obtained for each of the plurality of wheels, assuming the internal temperature of the tire is a predetermined set temperature. For each of the plurality of wheels, the value obtained is the air pressure reduction value obtained by subtracting the reference pressure from the obtained temperature-corrected air pressure. If the absolute value of the air pressure reduction for one of the plurality of wheels is greater than or equal to an anomaly determination threshold for the absolute value of the air pressure reduction for each of the other wheels in the plurality of wheels, the air pressure of that wheel is determined to be in an abnormal state. If the vehicle is in a stopped state as detected by the vehicle state detection device, it is determined whether the temperature-corrected air pressure for each of the plurality of wheels has increased by or equal to a predetermined pressure adjustment determination threshold. If it is determined that the temperature-corrected air pressure for at least one of the plurality of wheels has increased by or equal to the pressure adjustment determination threshold, the reference pressure is changed for each of the at least one wheel.

2. The wheel state acquisition system according to claim 1, wherein, The reference pressure is a value set separately for each of the plurality of wheels.

3. The wheel status acquisition system according to claim 1 or 2, wherein, The wheel status acquisition system includes: The tire blowout acquisition unit determines whether the decrease gradient of the detected air pressure of each of the plurality of wheels, detected by each of the plurality of air pressure sensors, is above a predetermined set gradient. If it determines that the decrease gradient of the detected air pressure of at least one of the plurality of wheels is above the set gradient, it acquires information indicating that the tire of that at least one wheel has blown out. The abnormal low pressure acquisition unit determines whether the air pressure detected by each of the plurality of air pressure sensors for each of the plurality of wheels, i.e., the detected air pressure, is lower than a predetermined set pressure. If it is determined that the detected air pressure of at least one of the plurality of wheels is lower than the set pressure, the unit acquires that the air pressure of the tire of the at least one wheel is abnormally low.

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