tire pressure monitoring device

Abstract

To provide a tire air pressure monitoring device that can appropriately notify an occupant of the state of the air pressure of a tire while complying with regulations.SOLUTION: A tire air pressure monitoring device 10 includes: an air pressure sensor 14 which detects the air pressure of a tire 100 as detected air pressure Pd; a temperature sensor 20 which detects the outside air temperature as the detected temperature Td; a U / I device 22 which notifies the occupant of a warning when reduction in the air pressure occurs; and a controller 24. The controller 24 calculates corrected air pressure Pc obtained by correcting the detected air pressure Pd on the basis of the detected temperature Td. In a case where the corrected air pressure Pc is greater than or equal to a prescribed warning threshold Pthw and the detected air pressure Pd is less than the warning threshold Pthw, the occupant is notified of the auxiliary warning indicating the occurrence of reduction in the air pressure due to reduction in the outside air temperature via the U / I device 22.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] This specification discloses an air pressure monitoring device for monitoring air pressure in a tire. [Background technology]

[0002] Tire pressure monitoring devices that monitor tire pressure have been known for some time. These tire pressure monitoring devices detect tire pressure using a sensor and issue an alarm if the detected tire pressure is below a specified threshold.

[0003] Incidentally, tire pressure changes with temperature. Therefore, in winter or other times when the outside temperature drops, the alarm output state may become unstable, confusing the occupants. That is, in an environment with low outside temperature such as winter, the tire pressure may fall below a threshold immediately after the vehicle system is started, causing the alarm to be output. However, once the vehicle starts moving and the tire temperature rises, the tire pressure also rises above the threshold, causing the alarm to be canceled. That is, in an environment with low outside temperature such as winter, the alarm may come on and go off within a short period of time. In this case, the occupants may not be able to determine whether or not to replenish the tire with air, becoming confused and possibly mistaking the system for a malfunction.

[0004] Therefore, Patent Document 1 discloses a technology that corrects the threshold so that the lower the outside temperature, the lower the threshold, and does not output an alarm if the detected air pressure is equal to or higher than the corrected threshold, even if it is lower than the threshold before correction. This technology stabilizes the alarm output state even in an environment with low outside temperatures, such as winter, preventing confusion among occupants. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-086783 Summary of the Invention [Problem to be solved by the invention]

[0006] However, in some countries, regulations require that a warning be issued if the detected tire pressure is below the pre-correction threshold. The technology disclosed in Patent Document 1 cannot satisfy these regulations.

[0007] Therefore, this specification discloses a tire pressure monitoring device that can properly notify a vehicle occupant of the tire pressure state while complying with regulations. [Means for solving the problem]

[0008] The tire pressure monitoring device disclosed in this specification comprises an air pressure sensor that detects the air pressure of a tire as a detected air pressure, a temperature sensor that detects the outside air temperature or the temperature of the tire as a detected temperature, a user interface that notifies an occupant of an alarm if a drop in the air pressure occurs, and a controller, wherein the controller is configured to calculate a corrected air pressure by correcting the detected air pressure based on the detected temperature, and if the corrected air pressure is equal to or greater than a specified alarm threshold and the detected air pressure is less than the alarm threshold, notify the occupant of an auxiliary alarm via the user interface indicating that a drop in the air pressure has occurred due to a drop in outside air temperature.

[0009] With this configuration, if a drop in tire pressure occurs due to a drop in outside temperature, an alarm is output to indicate this, allowing the occupant to properly understand the tire pressure status. In addition, an alarm is always output when the detected tire pressure is below the alarm threshold, thereby complying with regulations.

[0010] In this case, the controller determines a correction amount based on the detected temperature and calculates the corrected air pressure by adding the correction amount to the detected air pressure, and the correction amount may increase as the detected temperature decreases.

[0011] With this configuration, the corrected air pressure can be calculated appropriately according to the detected temperature.

[0012] The controller may also be configured to notify an occupant via the user interface of a standard warning urging the occupant to replenish the air pressure if both the corrected air pressure and the detected air pressure are below the warning threshold.

[0013] With this configuration, when the corrected air pressure is below the warning threshold, a standard warning different from the auxiliary warning is issued, allowing the occupant to more appropriately grasp the state of the tire air pressure.

[0014] The controller may also be configured to, after starting to notify the auxiliary alarm, cancel the auxiliary alarm when the detected air pressure reaches or exceeds a cancellation threshold that is higher than the alarm threshold, and, after starting to notify the standard alarm, maintain the standard alarm until the vehicle system is turned off.

[0015] The auxiliary warnings with low priority can be quickly cancelled to effectively prevent confusion among the occupants, while the standard warnings with high priority continue until the vehicle system is turned off, so that the occupants do not forget to replenish the tire pressure as soon as possible.

[0016] The user interface may also include a multi-information display located in front of the driver's seat and displaying at least vehicle speed, and a multimedia display which is an additional display located inside the vehicle, and the controller may be configured to, as the auxiliary warning, display an alarm mark on the multi-information display indicating that there is a problem with the air pressure, and to display a message on the multimedia display indicating that a drop in the air pressure is occurring due to a drop in outside air temperature.

[0017] By displaying a warning symbol on the multi-information display, occupants can immediately recognize that a warning has been issued. In addition, by displaying a message on the multimedia display, occupants can more accurately understand the content of the warning. [Effects of the Invention]

[0018] The tire pressure monitoring device disclosed in this specification can appropriately notify the occupant of the tire pressure state while complying with regulations. [Brief explanation of the drawings]

[0019] [Figure 1] FIG. 1 is a diagram illustrating a configuration of a tire pressure monitoring device. [Figure 2] FIG. 10 is a diagram illustrating an example of a correction amount. [Figure 3] 10 is a table showing the relationship between the state of air pressure and the state of an alarm. [Figure 4] FIG. 4 is a diagram showing an example of changes over time in detected air pressure and corrected air pressure. [Figure 5] FIG. 10 is a diagram showing another example of changes over time in the detected air pressure and the corrected air pressure. DETAILED DESCRIPTION OF THE INVENTION

[0020] The configuration of a tire pressure monitoring device 10 (hereinafter referred to as "TPMS10") will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of the TPMS 10. The TPMS 10 is a device generally called a Tire Pressure Monitoring System. The TPMS 10 monitors the air pressure of a tire 100 of a vehicle, and issues an alarm to the occupant if there is a problem with the air pressure.

[0021] As shown in FIG. 1 , the TPMS 10 includes multiple tire units 12, a receiver 18, a temperature sensor 20, a U / I device 22, and a controller 24. A tire unit 12 is disposed on each of multiple tires 100. Each tire unit 12 includes an air pressure sensor 14 and a transmitter 16. The air pressure sensor 14 detects the air pressure of the corresponding tire 100. Hereinafter, the air pressure detected by the air pressure sensor 14 will be referred to as the "detected air pressure Pd." The transmitter 16 wirelessly transmits the detected air pressure Pd to the receiver 18. A battery (not shown) is also incorporated in the tire unit 12, and the air pressure sensor 14 and transmitter 16 are powered by power supplied from the battery.

[0022] The receiver 18 outputs the detected air pressure Pd output from the transmitter 16 to the controller 24. The temperature sensor 20 detects the outside air temperature. Hereinafter, the outside air temperature detected by the temperature sensor 20 will be referred to as the "detected temperature Td." The temperature sensor 20 may be provided exclusively for the TPMS 10, or a temperature sensor built into an air conditioner may be used for the TPMS 10.

[0023] The U / I device 22 is a device that receives instructions from occupants and notifies occupants of information. Such a U / I device 22 may include, for example, a speaker that outputs audio, a display that displays images, and a lamp that lights up to notify status. In this example, the U / I device 22 includes a multi-information display and a multimedia display (neither is shown). The multi-information display is a display located directly in front of the driver's seat that displays important information related to vehicle operation and safety (e.g., vehicle speed, fuel, alarms, etc.). The multimedia display is an additional display provided inside the vehicle that displays other information (e.g., map information, audio information, etc.).

[0024] The controller 24 is physically a computer having a processor and a memory, and may be a single computer or may be configured by combining multiple physically separated computers.

[0025] The controller 24 determines whether the air pressure in the tire 100 is appropriate based on the detection results of the air pressure sensor 14 and the temperature sensor 20, and outputs an alarm according to the determination result to the U / I device 22. The alarm output control by this controller 24 will be described below.

[0026] If the air pressure of the tire 100 is excessively low, the vehicle's driving performance may be degraded and fuel economy may deteriorate. Therefore, if the air pressure of the tire 100 is excessively low, it is necessary to output an alarm to the occupant informing him / her of the excessively low air pressure and to prompt him / her to replenish the air pressure. Therefore, when the detected air pressure Pd is less than a predetermined alarm threshold Pthw, the controller 24 causes the U / I device 22 to output an alarm indicating a drop in air pressure. Note that the alarm threshold Pthw is usually set based on the air pressure when the vehicle is running. For example, if the air pressure when the tire 100 reaches a predetermined HOT (warm) state after the tire 100 has been properly replenished with air or after a tire change is driven, and the set air pressure Phot is used, the alarm threshold Pthw is set as Pthw = Phot × K1. Note that K1 is a coefficient less than 1, for example, K1 = 0.8.

[0027] In conventional TPMS, only one type of alarm is output when the detected tire pressure Pd is less than the alarm threshold Pthw. In this case, the conventional TPMS may confuse the occupants. This will be briefly explained.

[0028] The air pressure of the tire 100 varies greatly depending on the temperature of the tire 100. That is, normally, the air pressure decreases as the temperature of the tire 100 decreases, and increases as the temperature of the tire 100 increases. Therefore, the magnitude relationship between the detected air pressure Pd and the warning threshold value Pthw may change depending on the running state of the tire 100 and changes in the outside air temperature.

[0029] For example, before the vehicle starts running, even if the detected air pressure Pd is less than the warning threshold value Pthw, when the vehicle starts running, the temperature of the tire 100 may rise due to running friction or the like, and the detected air pressure Pd may increase to be equal to or higher than the warning threshold value Pthw. In this case, since the detected air pressure Pd during vehicle running is equal to or higher than the warning threshold value Pthw, it can be said that air pressure replenishment is unnecessary. However, in the conventional TPMS, at the stage before starting running, when Pd < Pthw, an alarm prompting air pressure replenishment is always output. As a result, although air pressure replenishment is actually unnecessary, an alarm prompting air pressure replenishment is issued, causing confusion among passengers.

[0030] Also, at the turn of seasons, the outside air temperature fluctuates greatly. For example, consider a case where there are consecutive days with a low outside air temperature, a warm day, and then a low day. In this case, on the first day, since the outside air temperature is low, Pd < Pthw, and an alarm is output. On the second day, since the outside air temperature is high, Pd ≥ Pthw, and no alarm is issued. Then, on the third day, since the outside air temperature is low, Pd < Pthw, and an alarm is output. That is, in this case, the output state of the alarm changes depending on the day, so the passengers are confused as to whether they should replenish the air pressure.

[0031] Patent Document 1 discloses that in order to avoid such problems, the warning threshold value Pthw is corrected according to the temperature, and based on the corrected warning threshold value Pthw, it is determined whether an alarm is necessary. According to such a technique, even when the outside air temperature changes, it is possible to appropriately determine whether air pressure replenishment is necessary to some extent. However, currently, in the regulations, it is stipulated that when the detected air pressure Pd is less than the warning threshold value Pthw before correction, some kind of alarm must be output. Therefore, the technique of Patent Document 1 cannot meet the requirements stipulated by the regulations.

[0032] Therefore, the TPMS 10 disclosed herein calculates a corrected air pressure Pc by correcting the detected air pressure Pd according to the detected temperature Td. Then, the corrected air pressure Pc and the detected air pressure Pd are compared with an alarm threshold Pthw, and the output alarm changes depending on the comparison result. Specifically, the TPMS 10 of this example provides at least two types of air pressure alarms: a standard alarm and an auxiliary alarm. The standard alarm indicates that tire pressure needs to be replenished. The auxiliary alarm indicates that tire pressure has dropped, but that this drop is likely due to a drop in outside temperature. The controller 24 outputs the standard alarm when both the detected air pressure Pd and the corrected air pressure Pc are below the alarm threshold Pthw. However, if the detected air pressure Pd is below the alarm threshold Pthw but the corrected air pressure Pc is equal to or greater than the alarm threshold Pthw, the controller 24 outputs the auxiliary alarm. The operation of the controller 24 is described below.

[0033] First, the calculation of the corrected air pressure Pc will be described. The controller 24 constantly calculates the corrected air pressure Pc by correcting the detected air pressure Pd based on the detected temperature Td. The corrected air pressure Pc is calculated so that it is higher than the detected air pressure Pd as the detected temperature Td decreases. For example, the corrected air pressure Pc may be calculated by adding a correction amount α to the detected air pressure Pd. In this case, the correction amount α increases as the detected temperature Td decreases. For example, as shown in FIG. 2, the correction amount α may be proportional to the value obtained by subtracting the detected temperature Td from a predetermined reference temperature T0. That is, α may be expressed as α=(T0-Td)×K2 (note that K2 is a constant greater than 0).

[0034] Once the corrected air pressure Pc is calculated, the controller 24 compares the corrected air pressure Pc with the alarm threshold Pthw, and also compares the detected air pressure Pd with the alarm threshold Pthw. Based on the comparison results, the controller 24 determines whether an alarm should be issued and, if an alarm should be issued, the type of alarm.

[0035] Figure 3 is a table showing the relationship between the pneumatic state and the warning state. As in Case 1 of Figure 3, when both the detected pneumatic pressure Pd and the corrected pneumatic pressure Pc are not less than the warning threshold value Pthw, the controller 24 does not output a warning. Also, as in Case 2, even when the corrected pneumatic pressure Pc is less than the warning threshold value Pthw, and when the detected pneumatic pressure Pd is not less than the warning threshold value Pthw, the controller 24 does not output a warning.

[0036] When the detected pneumatic pressure Pd is less than the warning threshold value Pthw, as in Case 3 or Case 4, a warning is output. However, even when Pd < Pthw, when the corrected pneumatic pressure Pc is not less than the warning threshold value Pthw (in the case of Case 3), a supplementary warning is output. In the supplementary warning, for example, a warning mark indicating that there is an abnormality in the pneumatic pressure is displayed in yellow, and a message "Pneumatic pressure drop (warning due to outside air temperature drop). If the warning continues for consecutive days, replenish the pneumatic pressure." is displayed in yellow. Here, the warning mark and the message may be displayed together on one display, or may be displayed separately on two displays. In this example, the warning mark is displayed on the multi-information display so that the occupant can notice the warning immediately. However, since the displayable range of the multi-information display is limited, the message is displayed on the multimedia display.

[0037] This supplementary warning is cancelled at the timing when the detected pneumatic pressure Pd becomes not less than the cancellation threshold value Pthe. The cancellation threshold value Pthe is not particularly limited as long as it is higher than the warning threshold value Pthw.

[0038] When both the detected pneumatic pressure Pd and the corrected pneumatic pressure Pc are not more than the warning threshold value Pthw (in the case of Case 4), a standard warning is output. In the standard warning, for example, a warning mark indicating that there is an abnormality in the pneumatic pressure is displayed in the same color as the supplementary warning (i.e., yellow), and a message "Pneumatic pressure drop. Affects driving performance and fuel consumption. Replenish the pneumatic pressure." is displayed in the same color as the supplementary warning. Also in this case, the warning mark is displayed on the multi-information display, and the message is displayed on the multimedia display.

[0039] When the standard warning is output, it is highly likely that the air pressure in the tire 100 has definitely dropped and that the tire really needs to be replenished with air. Therefore, this standard warning continues to be output until the vehicle system is turned off.

[0040] Furthermore, the controller 24 also outputs an alarm when the detected air pressure Pd drops suddenly (case 5). Specifically, the controller 24 constantly calculates the amount of decrease ΔP in the detected air pressure Pd over a predetermined unit time (e.g., several seconds) and compares this amount of decrease ΔP with a specified reference amount of decrease ΔPth. If the comparison result is ΔP≧ΔPth, it is determined that the detected air pressure Pd has dropped suddenly, and an emergency alarm is output. In the emergency alarm, a warning symbol indicating a sudden drop in air pressure is displayed in a color (e.g., red) different from that of the auxiliary alarm, and a message stating, "Air pressure has dropped suddenly. Immediately stop the vehicle in a safe place and have the tire changed or the puncture repaired" is displayed in a color different from that of the auxiliary alarm. In this case, the warning symbol is also displayed on the multi-information display, and the message is also displayed on the multimedia display. The emergency alarm is an important alarm with a high degree of urgency. Therefore, the emergency alarm is continuously output until the vehicle system is turned off. Furthermore, even when another alarm (that is, an auxiliary alarm or a special alarm) is being output, if it is necessary to output a special alarm, the special alarm may be output with priority.

[0041] 4 is a diagram showing an example of changes over time in the detected air pressure Pd and the corrected air pressure Pc. In the example of FIG. 4, the vehicle system is started at time t0. When the vehicle system is started, the controller 24 periodically acquires the detected air pressure Pd and the detected temperature Td and calculates the corrected air pressure Pc.

[0042] In the example of FIG. 4, since the outside air temperature is low, immediately after the vehicle system is started, the detected air pressure Pd is less than the warning threshold value Pthw, but the corrected air pressure Pc is not less than the warning threshold value Pthw. Therefore, after time t0, the controller 24 causes the U / I device 22 to output an auxiliary warning. By seeing this auxiliary warning, the occupant can understand that although the air pressure is decreasing, the decrease is due to the decrease in the outside air temperature, so air pressure replenishment is not necessarily required. Also, in the case where Pd < Pthw, since a warning is being output, the requirements defined by the regulations can be met.

[0043] Thereafter, at time t1, when the vehicle starts to run, due to running friction and the like, the temperature of the tire 100 gradually increases. And thereby, the detected air pressure Pd also gradually increases, and at time t2, the detected air pressure Pd becomes not less than the release threshold value Pthe. In this case, at time t2, the output of the auxiliary warning is released. Thereby, the occupant can more surely recognize that air pressure replenishment is unnecessary.

[0044] Next, another example of change over time will be described with reference to FIG. 5. In the example of FIG. 5, since the air pressure is low, at time t0, both the detected air pressure Pd and the corrected air pressure Pc are less than the warning threshold value Pthw. Therefore, after time t0, the controller 24 causes the U / I device 22 to output a standard warning. Thereby, the occupant can recognize that the air pressure is decreasing and air pressure replenishment is necessary. Note that once the standard warning is output, it is continuously output without being released until the vehicle system is turned off. Therefore, as shown in FIG. 5, even when the corrected air pressure Pc becomes not less than the warning threshold value Pthw at time t2, the output of the standard warning continues.

[0045] As is clear from the above description, according to the TPMS 10 of this example, when the detected air pressure Pd is less than the warning threshold value Pthw, some kind of warning is always output. Therefore, the requirements stipulated by the regulations can be satisfied. On the other hand, even if Pd < Pthw, if the corrected air pressure Pc is equal to or greater than the warning threshold value Pthw, an auxiliary warning indicating that the warning is due to a decrease in the outside air temperature is output. With such a configuration, the occupant can recognize that this warning is due to a decrease in the outside air temperature, that there is no major problem with the air pressure, and that air pressure replenishment is unnecessary. As a result, according to the TPMS 10 of this example, confusion of the occupant can be prevented.

[0046] Note that if the TPMS 10 has the configuration described in claim 1, other configurations may be changed. For example, in the previous description, the outside air temperature has been detected as the detected temperature Td, but the temperature of the tire 100 may be detected. In this case, for example, the temperature sensor 20 may be incorporated into the tire unit 12. Also, in the above description, the release threshold value Pthe is set to a value different from the warning threshold value Pthw, but the two may be the same value as each other. Also, like the standard warning, the auxiliary warning may be continuously output until the vehicle system is turned off.

Description of Reference Numerals

[0047] 10 Tire pressure monitoring device, 12 Tire unit, 14 Air pressure sensor, 16 Transmitter, 18 Receiver, 20 Temperature sensor, 22 U / I device, 24 Controller, 100 Tire.

Claims

1. an air pressure sensor that detects the air pressure of a tire as a detected air pressure; a temperature sensor that detects an outside air temperature or a temperature of the tire as a detected temperature; a user interface that notifies an occupant of an alarm when the tire pressure drops; A controller; Equipped with The controller calculating a corrected air pressure by correcting the detected air pressure based on the detected temperature; If the corrected air pressure is equal to or greater than a predetermined warning threshold and the detected air pressure is less than the warning threshold, an auxiliary warning indicating that a drop in air pressure has occurred due to a drop in outside air temperature is issued to an occupant via the user interface. A tire pressure monitoring device characterized by being configured as follows.

2. 2. The tire pressure monitoring device according to claim 1, the controller determines a correction amount based on the detected temperature, and calculates the corrected air pressure by adding the correction amount to the detected air pressure, The correction amount increases as the detected temperature decreases. A tire pressure monitoring device.

3. 2. The tire pressure monitoring device according to claim 1, The controller is configured to notify a passenger via the user interface of a standard warning urging the passenger to replenish the air pressure when both the corrected air pressure and the detected air pressure are below the warning threshold.

4. 4. The tire pressure monitoring device according to claim 3, the controller is configured to cancel the auxiliary warning when the detected air pressure reaches or exceeds a cancellation threshold that is higher than the warning threshold after starting to notify the auxiliary warning, and to maintain the standard warning after starting to notify the standard warning until the vehicle system is turned off.

5. 2. The tire pressure monitoring device according to claim 1, the user interface includes a multi-information display disposed in front of the driver's seat and displaying at least vehicle speed, and a multimedia display which is an additional display disposed inside the vehicle; The controller is configured to display, as the auxiliary warning, a warning mark indicating that there is a problem with the tire air pressure on the multi-information display, and to display, on the multimedia display, a message indicating that the tire air pressure has decreased due to a drop in outside air temperature. A tire pressure monitoring device.

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