Wheel status acquisition system

Abstract

To accurately acquire whether an air pressure of a tire of a wheel is in an abnormal state.SOLUTION: A wheel condition acquisition system acquires a temperature corrected air pressure which is an air pressure when an internal temperature of a tire is a preset temperature set in advance on the basis of a detected air pressure of a tire and a detection temperature for each of a plurality of wheels. When one wheel A of the plurality of wheels has a larger drop amount (positive value) of the temperature corrected air pressure than a drop amount of the temperature corrected air pressure for each of other wheels, one wheel A is determined to be in an abnormal state of the tire air pressure. In a traveling state of a vehicle, the air pressure of a tire drops due to drop in the internal temperature of the tire, therefore, the wheel condition acquisition system can accurately acquire, on the basis of the drop amount of the temperature corrected air pressure whether the air pressure of a tire of a wheel is to be in an abnormal state or not.SELECTED DRAWING: Figure 5

Description

Technical Field

[0005]

[0001] The present invention relates to a wheel state acquisition system for acquiring the state of wheels.

Background Art

[0002] The wheel state acquisition system described in Patent Document 1 includes a pneumatic pressure sensor provided for each of a plurality of wheels to detect the pneumatic pressure of the tires of the wheels, and a slow leak state acquisition unit that acquires whether each of the plurality of wheels is in a slow leak state based on the detected pneumatic pressure, which is the pneumatic pressure of the tires of each of the plurality of wheels detected by the plurality of pneumatic pressure sensors. In the slow leak state acquisition unit, when the difference between the first average value, which is the average value in the first period of the detected pneumatic pressure of one of the plurality of wheels, and the second average value, which is the average value in the second period, is greater than or equal to the first threshold value, and the difference for each of the other wheels is less than the first threshold value, it is acquired that the one wheel is in the slow leak state.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The problem of the present invention is to improve the wheel state acquisition system, for example, to accurately acquire whether the pneumatic pressure of the tire of the wheel is abnormal.

Means for Solving the Problems

[0005] In the wheel condition acquisition system according to the present invention, a temperature-corrected air pressure, which is the air pressure when the internal temperature of the tire is at a predetermined set temperature, is acquired for each of the multiple wheels based on the detected air pressure and detected temperature of the tire. When the decrease in temperature-corrected air pressure (positive value) for one wheel A is greater than the decrease in temperature-corrected air pressure for each of the other wheels, it is determined that the air pressure of wheel A is abnormal. During vehicle operation, the air pressure may decrease due to a decrease in the internal temperature of the tire. However, in this wheel condition acquisition system, since it is based on the decrease in temperature-corrected air pressure, it is not necessary to consider the decrease in air pressure due to the decrease in temperature. Therefore, it is possible to accurately determine whether a wheel has abnormal air pressure or not. [Brief explanation of the drawing]

[0006] [Figure 1] This is a perspective view conceptually illustrating the entire wheel state acquisition system according to an embodiment of the present invention. [Figure 2] This diagram conceptually shows the main components of the wheel status acquisition system described above. [Figure 3] This is a flowchart showing the slow leak status acquisition program stored in the memory unit of the vehicle-side unit of the wheel status acquisition system described above. [Figure 4] This is a flowchart representing the pneumatic abnormality acquisition program stored in the memory unit mentioned above. [Figure 5] This figure shows the change in tire pressure in the wheels of a vehicle equipped with the above-mentioned wheel condition acquisition system. [Figure 6] This figure shows the change in the air pressure drop value, which is the value obtained by subtracting the reference pressure from the temperature-compensated air pressure of the above-mentioned wheel. Embodiment of the Invention

[0007] A wheel condition acquisition system according to one embodiment of the present invention will be described in detail below with reference to the drawings. [Examples]

[0008] As shown in Figure 1, the wheel status acquisition system includes wheel-side units 12FL, 12FR, 12RL, and 12RR, each provided on one of the front, rear, left, and right wheels 10FL, 10FR, 10RL, and 10RR of the vehicle, and a vehicle-side unit 16 provided on the vehicle body 14.

[0009] In the following, when it is necessary to distinguish between the wheel 10, wheel-side unit 12, etc., by wheel position FL, FR, RL, RR, etc., a code indicating the wheel position will be added. However, when it is not necessary to distinguish between them, or when they are referred to collectively, a code indicating the wheel position may not be added.

[0010] Each wheel-side unit 12 includes, as shown in Figure 2, an air pressure sensor 20, a temperature sensor 22, a wheel information creation unit 24 that creates wheel information, a transmitter 26 that wirelessly transmits wheel information, and the like. The air pressure sensor 20 directly detects the air pressure in the tire of the wheel 10, and the temperature sensor 22 directly detects the temperature inside the tire. The wheel information creation unit 24 is computer-based and, at predetermined set intervals, creates wheel information including the air pressure P detected by the air pressure sensor 20, the temperature T detected by the temperature sensor 22, and identification information ID that can identify itself. The created wheel information is supplied to the transmitter 26, which then transmits the supplied wheel information wirelessly. In this embodiment, the air pressure detected by the air pressure sensor 20 and the air pressure included 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 included in the wheel information will be referred to as the detected temperature.

[0011] The vehicle-side unit 16 includes a receiver 42, a display 44 as a notification device, a vehicle status detection device 46 for detecting the vehicle's status, and a computer-based wheel status acquisition ECU 48. In this embodiment, the wheel status acquisition ECU 48 primarily acquires the tire pressure status and will therefore be referred to as the TPMS (Tire Pressure Monitoring System) ECU 48. The TPMSECU 48 includes an execution unit, a storage unit, an input / output unit, etc., to which the receiver 42, the display 44, the vehicle status detection device 46, etc., are connected.

[0012] The receiver 42 receives wheel information transmitted wirelessly from the wheel-side unit 12. In this embodiment, one receiver is provided on the vehicle body-side unit 16, but for example, multiple receivers can be provided, each corresponding to one of the front, rear, left, and right wheels 10FL, 10FR, 10RL, and 10RR, or common to two or more of the front, rear, left, and right wheels 10FL, 10FR, 10RL, and 10RR.

[0013] The display 44 notifies by displaying the status of the wheels 10. The display 44 displays the air pressure and other information included in the wheel information received by the receiver 42, and if it is detected that the air pressure of one of the front, rear, left, or right wheels 10 is abnormal and the wheel 10 is in a slow leak state where air is leaking from the tire, it displays that the wheel 10 is in a slow leak state, its position, etc. Note that the status of the wheels 10 is not limited to the display 44; for example, an audio generator could be provided to notify by voice.

[0014] The vehicle state detection device 46 can, for example, detect whether the vehicle is stopped or in motion. For example, it can detect that the vehicle is stopped if its speed is less than a set speed at which it can be estimated that the vehicle is stopped, and detect that it is in motion if its speed is equal to or greater than the set speed. The vehicle state detection device 46 can, for example, include wheel speed sensors provided for each of the wheels 10, and detect the vehicle's speed based on the wheel speed of each wheel 10 detected by these wheel speed sensors. The vehicle state detection device 46 can also include a drive state detection device, a brake state detection device, etc., that detect the operating state of the drive system and brake system provided on the vehicle. By using both the vehicle's speed and the operating state of the vehicle's drive system and brake system, it becomes possible to accurately estimate whether the vehicle is stopped or in motion.

[0015] The operation of the wheel status acquisition system configured as described above will now be explained. In this embodiment, it is determined whether or not the air pressure in the tire of wheel 10 is in an abnormal state.

[0016] The air pressure anomaly acquisition program, as shown in the flowchart in Figure 4, is executed at predetermined set intervals. This air pressure anomaly acquisition program acquires whether the wheel 10 has a puncture and whether the tire pressure is lower than a predetermined set pressure. Furthermore, whether the tire has a puncture and whether the tire pressure is in an abnormally low-pressure state below the set pressure are determined based on the detected air pressure, not the temperature-compensated air pressure described later.

[0017] In step 1 (hereinafter abbreviated as S1; the same applies to other steps), it is determined whether wheel information has been received by the receiver 42. If received, in S2, the identification information ID, the detected air pressure P, and the detected temperature T included in the wheel information are read. In S3, based on the identification information ID and a predetermined table (not shown), the position of the wheel 10 that transmitted the wheel information is obtained. 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, the pressure defined by regulations, or can be a value of 80% of the air pressure in a state where the vehicle is traveling under predetermined conditions. Also, the set pressure Pth can be a pressure lower than the so-called normal range. Hereinafter, the set pressure Pth may be referred to as the regulatory set pressure Pth.

[0018] If the determination in S4 is YES, in S5, it is determined that the air pressure is abnormally low, and this is notified via the display 44. In this embodiment, it is notified by displaying on the display 44 that the air pressure is abnormally low, the position of the wheel, etc.

[0019] If the determination in S4 is NO, in S6, it is determined whether the decrease gradient (a positive value, which is the absolute value of the change gradient) dP of the detected air pressure P is greater than a puncture determination threshold value dPth. If the determination in S6 is YES, in S7, it is estimated that the tire of the wheel 10 has punctured, and this is notified via the display 44. If the determinations in S4 and S6 are both NO, in S8, the detected air pressure of the wheel 10 is displayed on the display 44. Also, the detected air pressure P, the detected temperature T, the wheel position, etc. obtained in S2 and S3 are stored.

[0020] The slow leak state determination program represented by the flowchart of FIG. 3 is executed every predetermined set time. This slow leak state determination program is executed for each of the front, rear, left, and right wheels 10, and it is determined whether each is in a slow leak state where air leaks out of the tire relatively slowly.

[0021] For example, when a nail pierces the tire, etc., it does not burst, but air may leak out of the tire. In this case, since the decrease gradient dP of the detected air pressure P is smaller than the puncture determination threshold dPth, it is normal that the tire of the wheel 10 is not acquired as being in a punctured state (the wheel 10 can also be referred to as being in a punctured state). Therefore, even if air is leaking from the tire, the wheel 10 will not be notified that the air pressure is abnormal until the detected air pressure P becomes lower than the set pressure Pth of the regulations. Therefore, it is desirable that it be detected that the wheel 10 is in a state where air leaks out more slowly compared to the case of a puncture, in other words, in a slow leak state, before the detected air pressure P becomes lower than the set pressure Pth of the regulations.

[0022] Also, in the driving state of the vehicle, when the temperature of the wheel 10 drops, the air pressure drops. Therefore, when based on the detected air pressure P, it is difficult to obtain whether the decrease in air pressure is due to being in a slow leak state or due to a decrease in temperature. Therefore, in this embodiment, based on the detected air pressure P, the detected temperature T, and Boyle's law, that is, based on the temperature-corrected air pressure Pb which is the air pressure when the temperature inside the tire is the set temperature (for example, when it is the standard temperature), it is determined whether it is in a slow leak state.

[0023] Specifically, for each of the four wheels 10 located at the front, rear, left, and right, when it is assumed that the volume of the tire is almost constant even if the temperature etc. changes, Boyle's law shown by the following formula holds. p / t = constant In other words, the following equation holds between the first state (p1, t1) and the second state (p2, t2). p1 / t1 = p2 / t2 Assuming the detected air pressure P, detected temperature T (25°C, standard temperature), and temperature-corrected air pressure Pb (the air pressure when the internal temperature of the tire is at the set temperature), substituting (P+101) for p1, (T+273°C) for t1, (Pb+101) for p2, and (25°C+273°C) for t2 in the above equation, the temperature-corrected air pressure Pb is obtained as shown in equation (1) below. (Pb+101)=(P+101)(25℃+273℃) / (T+273℃)...(1) In equation (1) above, 101 [kPa] is atmospheric pressure. The detected air pressure [kPa] is the pressure relative to atmospheric pressure, but since Boyle's Law and Charles's Law use absolute pressure (pressure based on the pressure in a vacuum), atmospheric pressure is added. Also, since Boyle's Law and Charles's Law use absolute temperature, 273°C is added to the detected temperature, etc.

[0024] Furthermore, if 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. However, it is rare for two or more of the four wheels 10 located at the front, rear, left, and right to simultaneously enter a slow leak state; in most cases, it is thought that only one wheel 10 will enter a slow leak state.

[0025] Therefore, in this embodiment, if the decrease (positive value) of the temperature-compensated air pressure Pb for one wheel 10 from the reference pressure is greater than or equal to the slow leak state determination threshold, which is the air pressure abnormality determination threshold, then that one wheel 10 is determined to be in a slow leak state.

[0026] The reference pressure is the baseline value when the air pressure of each of the four wheels 10 changes. In this embodiment, the reference pressure is set for each of the four wheels 10 and is expressed as the air pressure when the internal temperature of the tire is at a standard temperature (temperature-corrected air pressure). The reference pressure can be the initial value of the tire air pressure, but if the tire air pressure is adjusted, it will be the air pressure after the adjustment.

[0027] In steps S21-29 of this slow leak condition determination program, it is determined whether or not pressure adjustment has been performed while the vehicle is stopped. If pressure adjustment has been performed, the reference pressure is updated and changed. If pressure adjustment has not been performed, the previous reference pressure (the initial tire pressure or the pressure after the last pressure adjustment) is used. The slow leak condition determination program from S30 onward is executed while the vehicle is in motion. That is, while the vehicle is in motion, it is determined whether or not the wheel 10 is in a slow leak condition based on the amount of decrease in temperature-corrected air pressure from the reference pressure.

[0028] The following describes the case where this slow leak condition detection program is executed on the left front wheel 10FL. In S21, it is determined whether the vehicle has stopped, or in other words, whether the vehicle has switched from a running state to a stopped state, based on the vehicle's speed. If the determination in S21 is YES, in S22, the detected air pressure P and detected temperature T immediately before stopping are obtained, or in other words, the detected air pressure P and detected temperature T included in the wheel information when the wheel information was received last time. For example, the detected air pressure P, detected temperature T, etc. included in the wheel information received last time, which was stored in S8, are read. In S23, the detected air pressure P and detected temperature T immediately before stopping are substituted into equation (1) to obtain the temperature-corrected air pressure Pb1 immediately before stopping.

[0029] Next, in S24, it is determined whether or not the vehicle has started moving. It is determined whether or not the vehicle has switched from a stopped state to a moving 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 first received after the start of driving, and in S26, the temperature-corrected air pressure Pb2 immediately after the start of driving is obtained by substituting the detected air pressure P and detected temperature T immediately after the start of driving (included in the wheel information first received after the start of driving) into equation (1).

[0030] Next, in S27, the change in air pressure ΔPbr is obtained by subtracting the temperature-corrected air pressure Pb1 just before stopping from the temperature-corrected air pressure Pb2 immediately after starting to drive. In S28, it is determined whether the change in ΔPbr is greater than a predetermined pressure adjustment threshold ΔPrth. In other words, it is determined whether the temperature-corrected air pressure Pb has increased by more than or equal to the pressure adjustment threshold ΔPrth while the vehicle is stopped.

[0031] If the judgment in S28 is YES, it is presumed that pressure adjustment was performed on the left front wheel 10FL while the vehicle was stationary, and 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. On the other hand, if pressure adjustment was not performed while the vehicle was stationary, the judgment in S28 is NO. The reference pressure Pa is not updated and remains the same as the previous reference pressure.

[0032] 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 by 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), and in S33, the air pressure drop value (negative value) ΔPb is obtained, which is the value obtained by subtracting the reference pressure Pa from the temperature-corrected air pressure Pb (Pb-Pa). The air pressure drop value ΔPb represents the decrease in the current temperature-corrected air pressure Pb from the reference pressure Pa as a negative value. Since this program is executed on the left front wheel 10FL, the air pressure drop value ΔPb can be called ΔPbFL.

[0033] Then, in S34, the air pressure drop values ​​(ΔPbFR, ΔPbRL, ΔPbRR) for each of the other wheels 10 (right front wheel 10FR, left rear wheel 10RL, right rear wheel 10RR) are obtained, and the difference between these values ​​and the air pressure drop value ΔPbFL for the left front wheel 10FL is calculated. For example, the air pressure drop value ΔPbFR for the right front wheel 10FR can be expressed as PbFR-PaFR, and the difference ΔPbFL1 between the air pressure drop value ΔPbFR for the right front wheel 10FR and the air pressure drop value ΔPbFL for the left front wheel 10FL can be expressed as ΔPbFR-ΔPbFL. ΔPbFL1 = ΔPbFR - ΔPbFL ΔPbFR = PbFR - PaFR ΔPbFL = PbFL - PaFL

[0034] Then, similarly, the difference ΔPbFL2 (ΔPbFL2=ΔPbRL-ΔPbFL) between the left rear wheel 10RL and the air pressure drop value ΔPbRL, and the difference ΔPbFL3 (ΔPbFL3=ΔPbRR-ΔPbFL) between the right rear wheel 10RR and the air pressure drop value ΔPbRR are calculated. In S35, it is determined whether each of the differences ΔPbFL1, ΔPbFL2, and ΔPbFL3 is greater than or equal to the leak detection threshold ΔPLth. If at least one of the differences in air pressure drop values ​​ΔPbFL1, ΔPbFL2, and ΔPbFL3 is less than or equal to the leak detection threshold ΔPLth, the judgment in S35 is NO. Subsequently, while the vehicle is running, steps S21, 24, 30-36 are repeatedly executed. If all of the differences in air pressure drop values ​​ΔPbFL1, ΔPbFL2, and ΔPbFL3 are greater than the leak detection threshold ΔPLth, the judgment in S35 is YES. In S36, the display 44 informs the user that the left front wheel 10FL is experiencing a slow leak. Furthermore, this slow leak condition detection program is executed similarly for the right front wheel 10FR, left rear wheel 10RL, and right rear wheel 10RR.

[0035] Figures 5 and 6 show the changes in air pressure. In Figure 5, the vertical axis represents the air pressure drop, and in Figure 6, the vertical axis represents the air pressure. As shown in Figure 6, the reference pressure Pa (PaFL, PaFR, PaRL, PaRR) is usually different for each of the front, rear, left, and right wheels 10. For each of the front, rear, left, and right wheels 10, the air pressure drop values ​​ΔPbFL, ΔPbFR, ΔPbRL, and ΔPbRR are obtained by subtracting the reference pressure Pa from the current temperature-corrected air pressure Pb. As shown in Figure 5, if the absolute value of the air pressure drop value ΔPbFL for the left front wheel 10FL becomes greater than or equal to the leak detection threshold ΔPLth than the absolute values ​​of the air pressure drop values ​​ΔPbFR, ΔPbRL, and ΔPbRR for the other wheels 10FR, 10RL, and 10RR, respectively, it is determined that a slow leak is occurring. In the case shown in Figures 5 and 6, a slow leak is determined at time tb.

[0036] As described above, in this embodiment, since it is based on temperature-compensated air pressure Pb, it is possible to accurately determine whether or not the wheel 10 is in a slow leak state. Furthermore, as shown in Figure 6, the slow leak condition of the wheel 10 can be detected early, before the air pressure P falls below the legally set pressure Pth. Furthermore, since it becomes unnecessary to obtain average values ​​for air pressure over periods such as the first and second periods, it is possible to easily determine whether or not a slow leak is occurring.

[0037] In this embodiment, the temperature-compensated air pressure acquisition unit is configured by the parts of the TPMSECU48 that store and execute S23, 26, 32, etc., the air pressure abnormality acquisition unit is configured by the parts of the TPMSECU48 that store and execute S33-36, etc., and the reference pressure change unit is configured by the parts of the TPMSECU48 that store and execute S21-29, etc. Furthermore, the puncture acquisition unit is configured by the parts of the TPMSECU48 that store and execute S2, 6, 7, etc., and the abnormal low pressure acquisition unit is configured by the parts of the TPMSECU48 that store and execute S2, 4, 5, etc.

[0038] Furthermore, the present invention can be implemented in various forms with various modifications and improvements based on the knowledge of those skilled in the art. [Explanation of Symbols]

[0039] 12: Wheel-side unit 16: Vehicle-side unit 20: Air pressure sensor 22: Temperature sensor 24: Wheel information generation unit 26: Transmitter 42: Receiver 44: Display 46: Vehicle status detection device 48: TPMSECU Patentable invention

[0040] (1) Each of the multiple wheels of the vehicle is provided with an air pressure sensor that detects the air pressure of the tire of the wheel, Each of the aforementioned plurality of wheels is provided with a temperature sensor that detects the temperature inside the tire of the wheel, A temperature-corrected air pressure acquisition unit acquires a temperature-corrected air pressure, which is the air pressure of each of the multiple wheels when the internal temperature of the tire is a predetermined set temperature, based on the detected air pressure, which is the air pressure detected by each of the multiple air pressure sensors, and the detected temperature, which is the temperature detected by each of the multiple temperature sensors. An air pressure abnormality acquisition unit acquires that the air pressure of one wheel is in an abnormal state if the amount of decrease in the temperature-compensated air pressure for one of the plurality of wheels, acquired by the temperature-compensated air pressure acquisition unit, is greater than the amount of decrease in the temperature-compensated air pressure for each of the other wheels excluding the one wheel. A wheel status acquisition system including the wheel status acquisition system.

[0041] In paragraph (1), when we say that a wheel has abnormal tire pressure, it means, for example, that it is in a slow-leak state where air slowly leaks out of the tire. In that sense, the abnormal tire pressure acquisition unit can be called a slow-leak state acquisition unit that acquires that a wheel is in a slow-leak state.

[0042] A decrease in temperature-compensated air pressure (a positive value) for one of several wheels is greater than the decrease in temperature-compensated air pressure for the other wheels when it is greater than any of the decreases in temperature-compensated air pressure for the other wheels. In other words, it is when the decrease in temperature-compensated air pressure for one wheel is greater than the maximum decrease in temperature-compensated air pressure for the other wheels.

[0043] (2) The wheel condition acquisition system according to item (1), wherein the air pressure abnormality acquisition unit acquires that the air pressure of one wheel is in an abnormal state when the amount of decrease in the temperature-corrected air pressure for one wheel acquired by the temperature-corrected air pressure acquisition unit is greater than or equal to an abnormality determination threshold than the amount of decrease in the temperature-corrected air pressure for each of the other wheels.

[0044] (3) The wheel condition acquisition system according to item (1) or (2), wherein the air pressure abnormality acquisition unit includes an air pressure drop value acquisition unit that acquires for each of the plurality of wheels an air pressure drop value (negative value) which is the value obtained by subtracting the reference pressure from the temperature-corrected air pressure acquired by the temperature-corrected air pressure acquisition unit, and when the absolute value of the air pressure drop value for one wheel acquired by the air pressure drop value acquisition unit is greater than or equal to an abnormality determination threshold value than the absolute value of the air pressure drop value for each of the other wheels, the system acquires that the air pressure of the tire of one wheel is in an abnormal state.

[0045] (4) The wheel status acquisition system A vehicle status detection device for detecting the status of the vehicle, When the vehicle status detected by the vehicle status detection device is in a stopped state, the temperature-compensated air pressure acquisition unit determines whether the temperature-compensated air pressure for each of the plurality of wheels acquired has increased by a predetermined pressure adjustment determination threshold, and if it is determined that the temperature-compensated air pressure for at least one of the plurality of wheels has increased by the pressure adjustment determination threshold, the reference pressure changing unit changes the reference pressure for each of the at least one wheel. A wheel condition acquisition system as described in item (3), including the wheel condition acquisition system described in item (3).

[0046] When the vehicle is stationary, the change in temperature-compensated air pressure can be obtained as the difference between the temperature-compensated air pressure immediately before or after stopping and the temperature-compensated air pressure immediately before or after starting to drive. The temperature-compensated air pressure immediately before stopping can be the temperature-compensated air pressure last obtained during driving, and the temperature-compensated air pressure immediately before driving can be the temperature-compensated air pressure last obtained while stopped.

[0047] (5) The wheel condition acquisition system according to item (4), wherein the 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 it has increased by more than the pressure adjustment determination threshold.

[0048] The reference pressure can be changed to the temperature-compensated air pressure after it has increased above the pressure regulation threshold.

[0049] (6) The wheel condition acquisition system according to any one of items (1) to (5), wherein the temperature-corrected air pressure acquisition unit acquires the air pressure when the temperature inside the tire is the standard temperature set by substituting the detected temperature and the detected air pressure for each of the plurality of wheels into the formula representing Boyle's Law.

[0050] (7) The wheel condition acquisition system according to any one of items (1) to (6), which includes a notification device that notifies when the air pressure abnormality acquisition unit has determined that the air pressure of the tire of one wheel is in an abnormal state.

[0051] (8) The wheel status acquisition system A puncture detection unit determines whether the decrease in detected air pressure, which is the air pressure of the tires of each of the plurality of wheels detected by each of the plurality of air pressure sensors, is equal to or greater than a predetermined set gradient, and if it is determined that the decrease in detected air pressure of at least one of the plurality of wheels is equal to or greater than the set gradient, it acquires that each of the tires of that at least one wheel has been punctured. An abnormal low pressure acquisition unit determines whether the detected air pressure, which is the air pressure of the tire for each of the plurality of wheels detected by each of the plurality of air pressure sensors, is lower than a predetermined set pressure, and if it is determined that the detected air pressure of at least one of the plurality of wheels is lower than the set pressure, it acquires that the air pressure of the tire of at least one wheel is abnormally low. A wheel condition acquisition system as described in any one of items (1) through (7), including the above.

[0052] (9) Each of the multiple wheels of the vehicle is provided with an air pressure sensor that detects the air pressure of the tire of the wheel, Each of the aforementioned plurality of wheels is provided with a temperature sensor that detects the temperature inside the tire of the wheel, A temperature-corrected air pressure acquisition unit acquires a temperature-corrected air pressure for each of the multiple wheels, based on the detected air pressure, which is the air pressure of each of the multiple wheels' tires detected by each of the multiple air pressure sensors, and the detected temperature, which is the internal temperature of each of the multiple wheels' tires detected by each of the multiple temperature sensors, when the internal temperature of the tire is a predetermined set temperature. An air pressure abnormality acquisition unit acquires whether or not the air pressure is in an abnormal state for each of the plurality of wheels, based on the decrease in the temperature-compensated air pressure from the reference pressure for each of the plurality of wheels acquired by the temperature-compensated air pressure acquisition unit, A vehicle status detection device for detecting the status of the vehicle, When the vehicle status detected by the vehicle status detection device is in a stopped state, the temperature-compensated air pressure acquisition unit determines whether the temperature-compensated air pressure for each of the plurality of wheels acquired has increased by a predetermined pressure adjustment determination threshold, and if it is determined that the temperature-compensated air pressure for at least one of the plurality of wheels has increased by the pressure adjustment determination threshold, the reference pressure changing unit changes the reference pressure for each of the wheels of the at least one tire with temperature-compensated air pressure. A wheel status acquisition system including the wheel status acquisition system.

[0053] The wheel condition acquisition system described in this section may adopt any of the technical features described in (1) through (8).

[0054] (10) Provided on each of the multiple wheels of the vehicle, An air pressure sensor for detecting the air pressure of the tire of the wheel, A temperature sensor for detecting the internal temperature of the tire, A wheel information creation unit creates wheel information including detected air pressure, which is the air pressure detected by the air pressure sensor, and detected temperature, which is the temperature detected by the temperature sensor. A wheel-side unit including a transmitter that transmits the wheel information created by the wheel information creation unit, Provided on the vehicle body of the aforementioned vehicle, One or more receivers that receive wheel information transmitted from multiple wheel-side units, A temperature-corrected air pressure acquisition unit acquires, for each of the plurality of wheels, the temperature-corrected air pressure, which is the air pressure of the tire when the internal temperature of the tire is a predetermined set temperature, based on the detected air pressure and the detected temperature included in the wheel information transmitted from the plurality of wheel-side units received by one or more receivers, A vehicle body-side unit that includes an air pressure abnormality acquisition unit that acquires that the tire pressure of one wheel is abnormal when the amount of decrease in temperature-compensated air pressure for one of the plurality of wheels, acquired by the temperature-compensated air pressure acquisition unit, is greater than the amount of decrease in temperature-compensated air pressure for each of the other wheels excluding the one wheel, and acquires that the tire pressure of that one wheel is abnormal. A wheel status acquisition system including the wheel status acquisition system.

[0055] The wheel condition acquisition system described in this section may adopt any of the technical features described in (1) through (9).

[0056] (11) An air pressure sensor provided on the wheel of the vehicle for detecting the air pressure of the tire of the wheel, A temperature sensor provided on the wheel detects the temperature inside the tire of the wheel, A temperature-corrected air pressure acquisition unit acquires the air pressure when the internal temperature of the tire is a predetermined set temperature, based on the detected air pressure, which is the air pressure detected by the air pressure sensor, and the detected temperature, which is the temperature detected by the temperature sensor. A slow leak state acquisition unit acquires whether or not the wheel is in a slow leak state based on the decrease state of the temperature-corrected air pressure acquired by the temperature-corrected air pressure acquisition unit. A wheel status acquisition system including the wheel status acquisition system.

[0057] The wheel status acquisition system described in this section may adopt any of the technical features described in (1) through (10).

Claims

1. Each of the vehicle's multiple wheels is equipped with an air pressure sensor that detects the air pressure in the tire of that wheel, Each of the aforementioned plurality of wheels is provided with a temperature sensor that detects the temperature inside the tire of the wheel, A temperature-corrected air pressure acquisition unit acquires a temperature-corrected air pressure, which is the air pressure of each of the multiple wheels when the internal temperature of the tire is a predetermined set temperature, based on the detected air pressure, which is the air pressure detected by each of the multiple air pressure sensors, and the detected temperature, which is the temperature detected by each of the multiple temperature sensors. The system includes an air pressure abnormality acquisition unit that acquires that the air pressure of one wheel is in an abnormal state when the amount of decrease in the temperature-compensated air pressure for one of the plurality of wheels, acquired by the temperature-compensated air pressure acquisition unit, is greater than the amount of decrease in the temperature-compensated air pressure for each of the other wheels excluding the one wheel, The air pressure abnormality acquisition unit includes an air pressure drop value acquisition unit that acquires an air pressure drop value for each of the plurality of wheels, which is the value obtained by subtracting the reference pressure from the temperature-corrected air pressure acquired by the temperature-corrected air pressure acquisition unit, and acquires that the air pressure of one wheel is in an abnormal state if the absolute value of the air pressure drop value for one wheel acquired by the air pressure drop value acquisition unit is greater than or equal to an abnormality determination threshold value than the absolute value of the air pressure drop value for each of the other wheels. A wheel status acquisition system in which the reference pressure is a value set for each of the plurality of wheels.

2. The wheel status acquisition system, A vehicle status detection device for detecting the status of the vehicle, A wheel state acquisition system according to claim 1, which includes a reference pressure changing unit that, when the state of the vehicle detected by the vehicle state detection device is in a stopped state, determines whether the temperature-compensated air pressure for each of the plurality of wheels acquired by the temperature-compensated air pressure acquisition unit has increased by a predetermined pressure adjustment determination threshold, and when it is determined that the temperature-compensated air pressure for at least one of the plurality of wheels has increased by the pressure adjustment determination threshold, changes the reference pressure for each of the at least one wheel.

3. The wheel status acquisition system, A puncture detection unit determines whether the decrease gradient of the detected air pressure, which is the tire air pressure for each of the plurality of wheels detected by each of the plurality of air pressure sensors, is equal to or greater than a predetermined set gradient, and if it is determined that the decrease gradient of the detected air pressure for at least one of the plurality of wheels is equal to or greater than the set gradient, it acquires that each of the at least one wheels has a puncture. A wheel status acquisition system according to claim 1 or 2, further comprising: an abnormal low pressure acquisition unit that determines whether the detected air pressure, which is the tire pressure for each of the plurality of wheels detected by each of the plurality of air pressure sensors, is lower than a predetermined set pressure, and acquires that the tire pressure of at least one of the plurality of wheels is abnormally low when it is determined that the detected air pressure of at least one of the plurality of wheels is lower than the set pressure.

Images