JP2012206681A - Receiver of tire air pressure monitoring system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically execute initialization in a receiver of a tire air pressure monitoring system.SOLUTION: A rapid pressure reduction detection threshold value Th1 is automatically updated from an initial value in accordance with the rise in an air pressure. When adjustment of the tire air pressure is performed, the rapid pressure reduction detection threshold value Th1 is made to be the initial value equal to a low air pressure detection threshold value Th2, and is initialized. Thus, initialization is executed for each of the prescribed cycles, and the rapid pressure reduction detection threshold value Th1 in accordance with the temperature change can be automatically set. Accordingly, regardless of the change in an outside air temperature, an alarm is reliably given in rapid pressure reduction of a tire. Through the low air pressure detection threshold value Th2, an alarm is given in pressure reduction accompanied by natural leakage of air which is not detected by the rapid pressure reduction detection threshold value Th1.

Description

  The present invention relates to a receiver for a tire pressure monitoring system.

  Conventionally, a tire pressure monitoring system (TPMS: Tire Pressure Monitoring System) that monitors tire pressure is known. Each tire of a vehicle on which TPMS is mounted is provided with a sensor unit that detects tire air pressure. Each sensor unit transmits an information signal including a tire air pressure detection result to the vehicle-mounted device. When the tire pressure falls below a threshold value based on the received information signal, the in-vehicle device warns the user through an indicator.

  For example, in Patent Document 1, the initialization switch is operated when the tire air pressure is adjusted to the manufacturer's recommended air pressure. Thereby, the vehicle-mounted device shifts to the initialization mode. When the in-vehicle device receives an information signal from each sensor unit in the initialization mode, the in-vehicle device sets a value that is decreased by a certain ratio (for example, 20%) of the tire air pressure included in the signal as a threshold value.

Japanese Patent Laid-Open No. 2003-211925

  In the configuration described in Patent Document 1, the threshold is set by the user operating the initialization switch. Here, it is known that the tire air pressure increases as the temperature rises (Boyle Charles' law). Therefore, the air pressure of the tire varies according to the change in the outside air temperature accompanying the change in season. For example, it is assumed that the threshold is set through the operation of the initialization switch when the outside air temperature is high. Thereafter, when the outside air temperature decreases, the tire air pressure decreases according to the above rule even if there is no leakage of the tire air pressure. In this case, before the tire air pressure decreases by a certain percentage, there is a risk that the air pressure falls below the threshold value and a warning of a decrease in air pressure is issued.

  On the other hand, when the outside air temperature rises, there is a possibility that a warning about a decrease in air pressure will not be given even if the tire air pressure decreases beyond a certain rate. Although the above problem is solved by the user operating the initialization switch at regular intervals, it is not preferable to force the user to perform such an operation on a regular basis.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a receiver for a tire pressure monitoring system that is automatically initialized.

Hereinafter, means for achieving the above-described object and its operation and effects will be described.
The invention according to claim 1 is a new receiver for a tire pressure monitoring system that issues a warning when the tire air pressure included in the information signal from the sensor unit attached to each tire falls below a first threshold value. The second threshold value is set as a fixed value, and the first threshold value is updated from the initial value in accordance with a change in air pressure due to a change in tire temperature, and the first threshold value is set as the initial value at a specific timing. When the air pressure is suddenly reduced, a warning is given when the air pressure falls below the first threshold, and a warning is also given when the tire air pressure falls below the second threshold except when the air pressure is suddenly reduced. The gist is to do.

  According to this configuration, the first threshold value is automatically updated from the initial value as the air pressure varies. Then, the first threshold is initialized at a specific timing to be an initial value. Thereby, the 1st threshold value according to the change of the temperature of a tire and external temperature can be set up automatically. Therefore, an appropriate warning can be given when the tire suddenly depressurizes regardless of changes in the outside air temperature. Further, through the second threshold, a warning can be given at the time of decompression other than the sudden decompression, for example, due to natural air leakage.

  According to a second aspect of the present invention, in the receiver of the tire air pressure monitoring system according to the first aspect, the specific timing is a time when the tire air pressure fluctuates by a certain value or more within a certain time as the air pressure is adjusted. It is the gist of that.

  According to this configuration, when the adjustment of the tire air pressure is executed, the first threshold value is set to an initial value. Thereby, the 1st threshold value according to the change of the temperature of a tire and external temperature can be set up automatically.

  According to a third aspect of the present invention, in the receiver of the tire air pressure monitoring system according to the first aspect, the specific timing is the temperature of the tire that has risen as the vehicle travels since the vehicle has stopped. The gist is that it is when the cooling time expected to reach the outside temperature has passed.

  According to Boyle Charles's law, the tire pressure increases as the tire temperature rises. According to the above configuration, the first threshold value is initialized after the temperature of the tire becomes substantially the same as the outside air temperature due to heat radiation. Therefore, it is possible to prevent the first threshold value from being initialized while the air pressure is high.

  According to the present invention, initialization can be automatically performed in the receiver of the tire pressure monitoring system.

The lineblock diagram of the tire pressure monitoring system in a 1st embodiment. The graph which shows the fluctuation | variation of the air pressure in 1st Embodiment. The enlarged view of the range A of FIG. 2 in 1st Embodiment. 5A is a flowchart showing a processing procedure related to updating a sudden pressure reduction detection threshold, and FIG. 5B is a flowchart showing a processing procedure related to initialization of a sudden pressure reduction detection threshold in the CPU of the vehicle according to the first embodiment. The graph which shows the fluctuation | variation of the air pressure in 2nd Embodiment. The flowchart which shows the process sequence which concerns on initialization of the sudden pressure reduction detection threshold value in CPU of the vehicle in 2nd Embodiment.

(First embodiment)
Hereinafter, a first embodiment in which a receiver of a tire pressure monitoring system (TPMS) according to the present invention is embodied will be described with reference to FIGS.

  As shown in FIG. 1, a sensor unit 30 is provided in the valve portion of each tire of the vehicle 1. The sensor unit 30 includes a pressure sensor 33, a CPU (Central Processing Unit) 31, a transmission circuit 32, and a transmission antenna 32a as shown in an enlarged view on the lower side of FIG.

  The pressure sensor 33 detects the tire air pressure and outputs the detection result to the CPU 31. The CPU 31 recognizes the tire air pressure based on the detection result from the pressure sensor 33. Then, the CPU 31 generates an information signal including tire air pressure information at regular intervals, and outputs the information signal to the transmission circuit 32. The transmission circuit 32 modulates the information signal and transmits the signal as a radio signal via the transmission antenna 32a.

  In addition, based on the detection result from the pressure sensor 33, the CPU 31 includes a sudden decompression bit in the information signal when a certain pressure or more is reduced in a certain time, and the information signal is transmitted to the transmission circuit 32 and the transmission antenna Wirelessly transmit via 32a. The constant time and the constant pressure are determined based on the manner in which the air pressure decreases when the tire is punctured.

  The receiver 10 mounted on the vehicle 1 includes a CPU 11, a receiving circuit 12, a receiving antenna 12 a, and a memory 13. An indicator 15 is electrically connected to the CPU 11.

  The receiving circuit 12 receives an information signal via the receiving antenna 12a. Then, the receiving circuit 12 demodulates the received information signal and outputs the demodulated information signal to the CPU 11. The CPU 11 recognizes the tire air pressure based on the demodulated information signal.

  The memory 13 stores a threshold value related to a tire pressure drop warning and a maximum tire pressure value after initialization. In this example, as shown in FIG. 2, a sudden pressure reduction detection threshold Th1 and a low air pressure detection threshold Th2 are set as thresholds. The low air pressure detection threshold Th2 is set as a fixed value based on the manufacturer's recommended air pressure. For example, the low air pressure detection threshold Th2 is set to a value obtained by decreasing the manufacturer's recommended air pressure by a certain percentage (20%). This low air pressure detection threshold Th2 is used not for puncture but for a low air pressure alarm when air naturally leaks from the tire.

When the tire air pressure falls below the low air pressure detection threshold Th2 stored in the memory 13, the CPU 11 warns the user that the air pressure has decreased through the indicator 15.
The initial value of the sudden pressure reduction detection threshold Th1 is set to the same value as the low air pressure detection threshold Th2. Then, the sudden pressure reduction detection threshold Th1 is updated as the tire air pressure increases.

  Specifically, the tire air pressure increases according to the temperature of the tire according to Boyle Charles' law. For this reason, when the vehicle travels, the tire air pressure increases as the tire temperature rises due to frictional heat with the road. Therefore, when the vehicle starts running, the tire air pressure gradually increases, and after the vehicle stops, the increased air pressure decreases.

  When the CPU 11 receives the information signal, the CPU 11 determines whether or not the tire air pressure included in the signal exceeds the maximum value of the tire air pressure stored in the memory 13. From the above situation, it is considered that the tire air pressure exceeds the maximum value while the vehicle is running. When the CPU 11 determines that the tire air pressure included in the information signal exceeds the maximum value, the CPU 11 updates the sudden pressure reduction detection threshold Th1 to a value decreased by a certain ratio (for example, 20%) with respect to the air pressure. At this time, the CPU 11 updates the maximum value stored in the memory 13 to the tire air pressure included in the information signal received this time.

  Therefore, as indicated by the triangular mark in FIG. 2, the sudden pressure reduction detection threshold Th1 is updated when the tire air pressure reaches the maximum value as the vehicle travels. This sudden pressure reduction threshold value Th1 is used for an alarm when the tire is punctured.

  The CPU 11 recognizes that the sudden decompression bit is included in the information signal, and warns that the tire is punctured through the indicator 15 when the tire air pressure included in the signal is equal to or less than the sudden decompression detection threshold Th1. On the other hand, even if the tire air pressure included in the information signal is equal to or less than the sudden pressure reduction detection threshold Th1, the CPU 11 does not issue a warning unless the signal is included in the low pressure detection threshold Th2 unless the rapid pressure reduction bit is included in the signal. . In this example, the rapid pressure reduction detection threshold Th1 is set for each tire.

  Here, as described in the above “problem to be solved by the invention”, for example, the threshold value may not be an appropriate value due to a change in outside air temperature. Therefore, the sudden pressure reduction detection threshold Th1 is automatically initialized every time the air pressure adjustment is executed.

  Specifically, as shown in FIG. 3, when the air pressure change ΔP within the predetermined time T1 becomes equal to or higher than the predetermined pressure P1, the CPU 11 sets the sudden pressure reduction detection threshold Th1 as the low air pressure detection threshold Th2 as the air pressure adjustment is executed. The initial value is the same value as. Then, the maximum value of the air pressure stored in the memory 13 is reset. This completes the initialization process.

  Here, since it is expected that the air pressure adjustment is performed every one to two months, it is possible to set the sudden pressure reduction detection threshold Th1 corresponding to at least the season (exactly the outside air temperature). Thereby, the precision concerning the warning of sudden pressure reduction can be improved. Moreover, since the sudden pressure reduction detection threshold Th1 is automatically initialized when the air pressure is adjusted, the operation of the initialization switch is not necessary, and convenience is improved. Further, since the initialization switch can be omitted, the TPMS can be configured more easily.

  Further, the low air pressure detection threshold Th2 is a fixed value that does not depend on the air pressure adjusted by the user. Therefore, the low air pressure detection threshold Th2 is prevented from being set outside the proper range, and a warning can be reliably issued when the tire air pressure falls below a certain level.

The first threshold corresponds to the sudden pressure reduction detection threshold Th1, and the second threshold corresponds to the low air pressure detection threshold Th2.
Hereinafter, the processing procedure of the CPU 11 at the time of updating the sudden pressure reduction detection threshold Th1 will be described with reference to the flowchart of FIG. The flowchart is repeatedly executed at a predetermined control cycle.

  First, an information signal is received (S101), and the tire air pressure included in the signal is recognized (S102). Then, it is determined whether or not the air pressure exceeds the maximum value of the tire air pressure stored in the memory 13 (S103). When it is determined that the maximum value is not exceeded (NO in S103), the process is terminated. That is, unless the tire air pressure exceeds the maximum value, the sudden pressure reduction detection threshold Th1 is not updated.

  On the other hand, when it is determined that the tire air pressure exceeds the maximum value (YES in S103), the rapid pressure reduction detection threshold Th1 is updated based on the air pressure (S104). The maximum value stored in the memory 13 is updated to the air pressure value of the information signal received this time (S105). The process is thus completed.

  Next, the procedure of the initialization process of the sudden pressure reduction detection threshold Th1 in the CPU 11 will be described with reference to FIG. The flowchart is repeatedly executed at a predetermined control cycle.

  First, it is determined whether or not air pressure adjustment has been performed (S201). When it is determined that the air pressure adjustment is not performed (NO in S201), the process is terminated. That is, the presence or absence of execution of air pressure adjustment is monitored every predetermined control cycle. When it is determined that the air pressure adjustment has been executed (YES in S201), the sudden pressure reduction detection threshold Th1 stored in the memory 13 is set as an initial value, and the maximum value of the tire air pressure is reset (S202). The process is thus completed.

As described above, according to the embodiment described above, the following effects can be obtained.
(1) The sudden pressure reduction threshold value Th1 is automatically updated from the initial value as the air pressure increases. When the tire air pressure adjustment is executed, the sudden pressure reduction detection threshold Th1 is initialized to the same initial value as the low air pressure detection threshold Th2. Thereby, initialization is performed for every predetermined period, and the sudden pressure reduction threshold value Th1 according to the temperature change can be automatically set. Therefore, an appropriate warning can be given when the tire suddenly depressurizes regardless of changes in the outside air temperature. Further, a warning can be given at the time of pressure reduction due to natural air leakage that is not detected by the sudden pressure reduction detection threshold Th1 through the low air pressure detection threshold Th2.

  (2) Two threshold values are properly used as necessary. For example, when the tire is punctured, a warning is issued when the air pressure of the tire suddenly depressurizes and falls below the sudden depressurization detection threshold Th1. Therefore, a warning related to tire puncture can be reliably performed.

  Further, the low air pressure detection threshold Th2 is a fixed value. Therefore, it is not necessary to set the low air pressure detection threshold Th2 through the operation of the initialization switch after adjusting the air pressure to an appropriate value as in the prior art. Therefore, convenience is improved.

  Further, since the low air pressure detection threshold Th2 does not depend on the air pressure adjusted by the user, the low air pressure detection threshold Th2 is prevented from being set outside the appropriate range. Thereby, when the tire air pressure naturally leaks, a warning can be given at an appropriate timing.

  (3) When the tire air pressure exceeds the maximum value stored in the memory 13, the sudden pressure reduction detection threshold Th <b> 1 is updated to a value that is reduced by a certain percentage with respect to the air pressure. Thus, even when the air pressure increases due to the temperature rise of the tire, a warning can be reliably issued when the tire air pressure decreases by a certain rate.

  In particular, European legislation requires that a warning be issued when the air pressure of a tire is increased by 20% after the tire has been increased by running the vehicle for 20 minutes. According to the above configuration, a system suitable for this European law can be constructed.

(4) As described above, regardless of the air pressure after the air pressure adjustment, the sudden pressure reduction detection threshold Th1 is set to an initial value. Therefore, the initialization process can be executed without waiting for the completion of the air pressure adjustment.
(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to FIGS. 5 and 6. The TPMS of this embodiment is different from the first embodiment in the initialization timing of the sudden pressure reduction detection threshold Th1. Hereinafter, a description will be given focusing on differences from the first embodiment.

As shown by a one-dot chain line in FIG. 1, a timer 14 and an ignition switch 16 are electrically connected to the CPU 11.
The CPU 11 determines whether or not the ignition of the vehicle is in an on state through the ignition switch 16. If the ignition is off, the vehicle is not allowed to travel because the engine is stopped. Further, the CPU 11 measures the time during which the vehicle ignition is off through the timer 14 until a cooling time T2, which will be described later.

  In the present embodiment, the sudden pressure reduction detection threshold Th1 is initialized when a certain period of time has elapsed since the ignition was turned off. Specifically, as shown in FIG. 5, when the CPU 11 recognizes that the ignition is switched to the off state, the CPU 11 starts measuring the time T <b> 3 when the ignition is in the off state through the timer 14. When the time T3 reaches the cooling time T2, the CPU 11 sets the sudden pressure reduction detection threshold Th1 to an initial value that is the same value as the low air pressure detection threshold Th2. The maximum value of the air pressure stored in the memory 13 is reset (more precisely, the low air pressure detection threshold Th2). Therefore, the rapid pressure reduction detection threshold Th1 is updated based on the information signal received first after initialization.

  Here, the cooling time T2 is set to a time required for the temperature of the tire, which has risen as a result of traveling, to reach almost the same temperature as the outside air temperature by dissipating heat while the vehicle is stopped. The cooling time T2 is set to about 1 to 2 hours, for example. Since the vehicle is stopped for 1 to 2 hours every day, the initialization process is performed every day. Therefore, even if the outside air temperature changes as described in the above “problem to be solved by the invention”, it is possible to set the sudden pressure reduction detection threshold Th1 corresponding to the outside air temperature. Thereby, the precision concerning a warning can be improved.

  The initialization process is performed after the cooling time T2 has elapsed after the vehicle stops. Therefore, during the initialization process, it is possible to prevent the tire from being sufficiently cooled and the tire pressure from being high. Thereby, it is suppressed that the high sudden pressure reduction detection threshold Th1 is set immediately after the start of traveling. In addition, by performing the initialization process after the elapse of the cooling time T2, the number of processes can be minimized.

  Next, the procedure of the initialization process of the rapid pressure reduction detection threshold Th1 in the CPU 11 in the present embodiment will be described with reference to FIG. The flowchart is repeatedly executed at a predetermined control cycle.

  First, it is determined whether or not the ignition is off through the ignition switch 16 (S301). When it is determined that the ignition is not off (NO in S301), the process is terminated. That is, it is monitored whether or not the ignition is in an off state, that is, whether or not the vehicle is stopped, every predetermined control cycle.

  When it is determined that the ignition is off (YES in S301), measurement of time T3 during which the ignition is off is started through the timer 14 (S302). Then, it is determined whether or not the time T3 has passed the cooling time T2 (S303). When time T3 does not elapse cooling time T2 (NO in S303), the process is terminated. That is, as long as the ignition is kept off, the above process is repeated until the time T3 has passed the cooling time T2. When the time T3 has passed the cooling time T2 (YES in S303), the rapid pressure reduction detection threshold Th1 is set to the initial value, and the maximum value stored in the memory 13 is reset (S304). Thus, the processing of the CPU 11 is finished. Further, before the cooling time T2 elapses (NO in S303), when the ignition is switched on (NO in S301), after the time T3 measured through the timer 14 is cleared (S305), the CPU 11 The process ends.

As mentioned above, according to embodiment described, in addition to the effect of (1)-(4) of 1st Embodiment, there can exist the following effects.
(5) The rapid pressure reduction detection threshold Th1 is initialized after the temperature of the tire becomes substantially the same as the outside air temperature due to heat radiation. Thus, it is possible to prevent the sudden pressure reduction detection threshold Th1 from being initialized while the air pressure is high.

In addition, the said embodiment can be implemented with the following forms which changed this suitably.
In both the above embodiments, when the tire air pressure included in the information signal exceeds the maximum value stored in the memory 13, the sudden pressure reduction detection threshold Th1 is updated. However, the update timing of the sudden pressure reduction detection threshold Th1 is not limited to this, and may be updated when, for example, the average air pressure during a certain period becomes maximum.

  In the first embodiment, it is determined that the air pressure adjustment has been performed when the change ΔP in the air pressure within the certain time T1 becomes equal to or greater than the certain pressure P1. However, when the air pressure change ΔP approximates zero after the air pressure change ΔP within the predetermined time T1 becomes equal to or greater than the constant pressure P1, the sudden pressure reduction detection threshold Th1 may be set as the initial value, assuming that the air pressure adjustment is completed. This makes it more accurate to determine whether or not air pressure adjustment has been performed.

  In both the above embodiments, when it is recognized that the sudden decompression bit is added to the information signal, sudden decompression occurs when the tire air pressure included in the signal is equal to or less than the sudden decompression detection threshold Th1. As a warning is made. However, the CPU 11 of the vehicle 1 may determine whether or not sudden decompression has occurred based on the tire air pressure included in the information signal without relying on the sudden decompression bit. In this case, the CPU 11 determines that sudden pressure reduction has occurred when there is a decrease in the constant pressure over a certain period of time based on the tire air pressure included in the continuously received information signal. Thereby, even if the sensor unit 30 is a structure which does not transmit the information signal to which the rapid decompression bit was added, each said embodiment is applicable.

  In both the above embodiments, the information signal is transmitted from the sensor unit 30 at regular intervals regardless of whether the vehicle is traveling. However, the sensor unit 30 may transmit the information signal to the receiver 10 only when the vehicle is traveling. In this case, for example, the sensor unit 30 includes an acceleration sensor that detects the presence or absence of rotation of the tire as an acceleration. Based on the detection result of the acceleration sensor, the CPU 31 transmits an information signal at regular intervals through the transmission circuit 32 and the like only when the tire is rotating. Further, the sensor unit 30 may transmit an information signal in response to a request signal transmitted from the vehicle.

  In the second embodiment, the cooling time T2 is constant, but may be variable. For example, an outside air temperature sensor is provided in the vehicle, and the cooling time T2 is set shorter as the outside air temperature acquired through the sensor becomes higher. This is because if the outside air temperature is high, it takes time for the tire temperature to reach the same temperature as the outside air temperature. Further, in the configuration in which the sensor unit 30 is provided with a temperature sensor and the detection result of the sensor is added to the information signal, the cooling time T2 may be set longer as the difference between the tire temperature and the outside air temperature increases. Good. Thereby, the cooling time T2 can be set to a more accurate time.

-It is not restricted to the initialization timing in both said embodiment, You may initialize automatically every progress of a fixed period.
In the second embodiment, the sudden pressure reduction detection threshold Th1 is automatically initialized when the period during which the ignition is off has passed the cooling time T2. However, if it can be recognized that the vehicle is stopped, the period is not limited to a period in which the ignition is off, for example, a period in which the shift lever is in the parking position or a period in which the vehicle speed is maintained at zero. It may be.

Next, the technical idea that can be grasped from the embodiment will be described together with the effects.
(A) The receiver of the tire pressure monitoring system according to any one of claims 1 to 3, wherein the second threshold value is set to the same value as the initial value.

According to this configuration, the second threshold value is the same value as the initial value of the first threshold value. Therefore, when initializing, the first threshold value may be the same value as the second threshold value.
(B) The receiver for the tire pressure monitoring system according to (a), wherein the initial value and the second threshold value are set based on a manufacturer recommended pressure.

  According to this configuration, the initial value and the second threshold value are set based on the manufacturer recommended pressure. Therefore, the initial value of the first threshold value, that is, the lower limit value thereof can be set to an appropriate value. Further, through the second threshold value, a warning can be reliably issued when the tire air pressure falls below a certain level in cases other than sudden pressure reduction.

  (C) In the receiver of the tire pressure monitoring system according to any one of claims 1 to 3, and (a) and (b) above, the tire air pressure included in the information signal is When the threshold value of 1 is the maximum value in the period from when the initial value is set to the present value to the present time, the tire pressure monitoring system updates the first threshold value to a value decreased by a certain rate with respect to the air pressure. Receiving machine.

  According to this configuration, when the tire air pressure reaches the maximum value, the first threshold value is updated to a value that is decreased by a certain percentage with respect to the air pressure. Thereby, even when the air pressure increases due to the temperature rise of the tire, a warning can be reliably issued when the tire air pressure decreases (rapid pressure reduction) by a certain rate.

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 10 ... Receiver, 30 ... Sensor unit, 33 ... Pressure sensor.

Claims (3)

In the receiver of the tire pressure monitoring system that issues a warning when the tire air pressure included in the information signal from the sensor unit attached to each tire falls below the first threshold,
Newly set the second threshold as a fixed value,
The first threshold value is updated from the initial value according to the change in air pressure due to the temperature change of the tire, and the first threshold value is set as the initial value at a specific timing,
When the air pressure suddenly decreases, a warning is given when the air pressure falls below the first threshold,
A receiver for a tire pressure monitoring system that issues a warning even when the tire pressure falls below the second threshold except when the pressure is suddenly reduced. In the receiver of the tire pressure monitoring system according to claim 1,
The specific timing is a receiver of the tire pressure monitoring system when the tire pressure changes by a certain value or more within a certain time as the air pressure is adjusted. In the receiver of the tire pressure monitoring system according to claim 1,
The specific timing is a receiver of a tire air pressure monitoring system, which is a time when a cooling time when the temperature of a tire that has risen with traveling is expected to become an outside air temperature has elapsed since the vehicle has stopped.

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