JP6342884B2 - Tire pressure monitoring system receiver - Google Patents

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 in-vehicle device (TPMS receiver) shifts to the threshold setting mode. When the in-vehicle device receives an information signal including a tire temperature detection result in addition to the tire pressure from each sensor unit in the threshold setting mode, the in-vehicle device uses the tire pressure (pressure value) and the tire temperature (temperature value) included in the signal. In addition, a low air pressure alarm threshold straight line is calculated using Boyle Charles' law. As a result, a low air pressure alarm that follows a change in pressure inside the tire due to a change in temperature inside the tire while the vehicle is running becomes possible.

JP 2010-254018 A

  If the ambient temperature (temperature value received from the sensor unit in the threshold setting mode) when the low air pressure alarm threshold straight line is calculated does not change, the optimum low air pressure alarm threshold can be provided. The ambient temperature changes due to a change or the like. For this reason, for example, when summer just reaches the low air pressure alarm threshold line set in winter, it cannot be said to be the optimum low air pressure alarm threshold value. In the above technique, re-threshold setting by the initialization switch is expected, but this is a troublesome operation for the user.

  The present invention has been made paying attention to such problems, and its object is to provide a tire pressure monitoring system capable of providing an optimal low air pressure alarm threshold value even in an environment where the ambient temperature has changed. Is to provide a receiver.

A receiver for a tire pressure monitoring system that solves the above problems receives an information signal including information related to tire pressure and tire temperature from a sensor unit mounted on each tire, and includes the tire pressure included in the information signal. In the receiver of the tire pressure monitoring system that issues a warning when the air pressure falls below the low air pressure alarm threshold, the tire air pressure is the low air pressure alarm threshold in the relationship between the tire temperature and the tire air pressure, and the tire Set a reference point that is the temperature of the tire included in the information signal, passed the reference point, and obeyed Boyle Charles' law derived from the tire temperature and tire pressure included in the information signal comprising a threshold setting means for setting a low pressure warning threshold straight line with a slope, the threshold setting means, Lee First determine the ambient temperature from the temperature of the tire included in the information signal received after the ignition ON after the tire temperature has exceeded the time down to ambient temperature after Nisshon OFF, based on the ambient temperature as the determined, the low The gist is to reset the air pressure alarm threshold line.

  According to this configuration, the low air pressure alarm threshold straight line is reset based on the information signal that is not affected by the tire temperature during traveling. As a result, a low air pressure alarm threshold straight line that follows the ambient temperature is set. Therefore, an optimal low air pressure alarm threshold value can be provided even in an environment where the ambient temperature has changed.

The receiver of the upper Symbol tire pressure monitoring system, the threshold value setting means, the individual ambient temperature a minimum value of the temperature of the tire included after the ignition ON from the sensor unit of each tire on the information signal first received respectively It may be determined.

According to this configuration, the low air pressure alarm threshold straight line can be reset based on an information signal that is not affected by sunlight, residual heat of the engine, or the like .

For upper Symbol tire pressure monitoring system receiver, said threshold setting means, said the low pressure warning threshold linearly, in a temperature region lower than the reference point may be set to the low pressure warning threshold.

  According to this configuration, the low air pressure alarm threshold value is set as the lower limit value in the low air pressure alarm threshold line. For this reason, even if it is a case where the temperature of a tire becomes lower than the temperature in a reference point, it can suppress that a low air pressure warning threshold value is set too low.

  According to the present invention, an optimal low air pressure alarm threshold value can be provided even in an environment where the ambient temperature has changed.

The block diagram which shows the structure of a tire pressure monitoring system. The graph which shows a low air pressure alarm line.

Hereinafter, an embodiment of a tire pressure monitoring system will be described.
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 temperature sensor 34, 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.

  The temperature sensor 34 detects the temperature of the tire and outputs the detection result to the CPU 31. The CPU 31 recognizes the tire temperature based on the detection result from the temperature sensor 34.

  Then, for example, the CPU 31 generates an information signal including tire air pressure and temperature information at regular intervals, and outputs the information signal to the transmission circuit 32. The transmission circuit 32 modulates the information signal and wirelessly transmits the signal via the transmission antenna 32a.

  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 and a vehicle speed sensor 16 are electrically connected to the CPU 11.

The memory 13 stores a low air pressure warning threshold Th. The low air pressure warning threshold Th is set to a value obtained by, for example, reducing the manufacturer's recommended tire pressure Prec by 20%.
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 and temperature based on the demodulated information signal.

  The CPU 11 determines that the vehicle 1 has started traveling when the vehicle 1 reaches a certain speed or higher through the vehicle speed sensor 16. Further, the CPU 11 determines that the vehicle 1 has stopped when the vehicle 1 becomes less than a certain speed through the vehicle speed sensor 16.

  As shown in FIG. 2, when the period from the stop to the start of travel reaches a certain period (for example, 1 hour), the CPU 11 detects the tire temperature “T winter” (here) included in the information signal received after the start of travel. In this example, winter is assumed) and a reference point K1 at which the low air pressure warning threshold Th intersects is set. At this time, the CPU 11 sets the lowest temperature among the temperatures of the individual tires included in the information signal first received from the sensor unit 30 of each tire as the tire temperature “T winter”, and the temperature of the tire “T winter”. Is determined as the ambient temperature. Then, the CPU 11 sets a low air pressure alarm threshold straight line L1 (a thin two-dot chain line) that passes through the reference point K1. The inclination of the low air pressure warning threshold line L1 is determined according to Boyle's law derived from the tire temperature and tire air pressure included in the information signal. Further, the low air pressure warning threshold line L1 is set to the low air pressure warning threshold Th in a temperature region lower than the reference point K1. As a result, a “winter low air pressure alarm line” indicated by a thick solid line in FIG. 2 is set. Thereafter, when the tire air pressure included in the information signal is equal to or lower than the line, the CPU 11 gives a low air pressure warning through the indicator 15. Do.

  Here, assuming the summer, the CPU 11 determines that the tire temperature “T summer” included in the information signal received after the start of travel when the period from the stop to the start of travel has reached the certain period (for example, 1 hour). ”And the low air pressure warning threshold Th are set. At this time, the CPU 11 sets the lowest temperature among the temperatures of the individual tires included in the information signal first received from the sensor unit 30 of each tire as the tire temperature “T summer”, and the temperature of the tire “T summer”. Is determined as the ambient temperature. Then, the CPU 11 sets a low air pressure warning threshold straight line L2 (thin alternate long and short dash line) that passes through the reference point K2. The inclination of the low air pressure warning threshold line L2 is determined according to Boyle's law derived from the tire temperature and the tire air pressure included in the information signal. Further, the low air pressure warning threshold line L2 is set to the low air pressure warning threshold Th in a temperature region lower than the reference point K2. As a result, the “summer low air pressure alarm line” indicated by a thick chain line in FIG. 2 is set. Thereafter, when the tire air pressure included in the information signal is equal to or lower than the line, the CPU 11 issues a low air pressure warning through the indicator 15. Do.

  As described above, the CPU 11 determines the ambient temperature for each initial start of travel when the period from the stop to the start of travel reaches a certain period (for example, 1 hour), and based on the determined ambient temperature, the tire Reset the low air pressure warning threshold line common to all four wheels. The CPU 11 corresponds to threshold setting means. And the said fixed period (1 hour as an example) is prescribed | regulated as a period when the temperature of a tire falls to ambient temperature after stopping after driving | running | working. In other words, even if the temperature of the tire rises due to frictional heat with the road during driving, the temperature of the tire turns down as the vehicle stops, and if one hour elapses while the vehicle is stopped, the temperature of the tire is approximately the same as the ambient temperature. It stabilizes at. Therefore, the information signal received after the first start of travel when the period from the stop to the start of travel reaches a certain period (one hour as an example) is an information signal that is not affected by the tire temperature during travel. .

Next, the operation of the tire pressure monitoring system will be described.
Referring to FIG. 2, it is assumed that a low air pressure alarm threshold line L1 (thin two-dot chain line) is set in winter and a “winter low air pressure alarm line” indicated by a thick solid line is set. In this case, if the tire air pressure included in the winter information signal is higher than the “winter low air pressure alarm line”, the low air pressure alarm is not performed. This can be said in common to the examples and comparative examples.

  In the comparative example that does not follow the ambient temperature, the “winter low air pressure warning line” is used as it is even in summer. Therefore, when the tire air pressure included in the summer information signal is the air pressure P that is equal to or lower than the line, Even if the air pressure P is at the same level as the tire recommended air pressure Prec, there is a possibility that a low air pressure alarm is performed (false alarm).

  In contrast, in the embodiment that follows the ambient temperature, the low air pressure alarm threshold line L2 (thin alternate long and short dash line) is reset in summer, and the “summer low air pressure alarm line” indicated by the thick chain line is reset. . For this reason, if the tire air pressure included in the summer information signal is larger than the air pressure P, the low air pressure alarm is not performed. That is, in the embodiment, the false alarm due to the comparative example is prevented.

As described above, according to the present embodiment, the following effects can be obtained.
(1) The CPU 11 resets the low air pressure warning threshold line based on the information signal received after the start of travel when the period from the stop to the start of travel reaches a certain period (for example, 1 hour). According to this configuration, the low air pressure alarm threshold straight line is reset based on the information signal that is not affected by the tire temperature during traveling. As a result, a low air pressure alarm threshold straight line that follows the ambient temperature is set. Therefore, an optimal low air pressure alarm threshold value can be provided even in an environment where the ambient temperature has changed.

  (2) The CPU 11 determines the ambient temperature from the temperature of the tire included in the information signal received after the start of traveling, and resets the low air pressure alarm threshold line based on the determined ambient temperature. According to this configuration, it is possible to set a low air pressure warning threshold line that follows changes in ambient temperature.

  (3) The CPU 11 determines the lowest value among the temperatures of the individual tires included in the information signals received from the sensor units 30 of the respective tires after the start of traveling as the ambient temperature. According to this configuration, the low air pressure alarm threshold straight line can be reset based on an information signal that is not affected by sunlight, residual heat of the engine, or the like.

  (4) The predetermined period (one hour as an example) is defined as a period in which the temperature of the tire decreases to the ambient temperature after stopping after traveling. According to this configuration, the low air pressure alarm threshold straight line can be reset based on the information signal that is not affected by the tire temperature during traveling.

  (5) The CPU 11 sets the low air pressure alarm threshold straight line to the low air pressure alarm threshold Th in a temperature region lower than the reference point. According to this configuration, the low air pressure warning threshold Th is set as the lower limit value in the low air pressure warning threshold line. For this reason, even if it is a case where the temperature of a tire becomes lower than the temperature in a reference point, it can suppress that a low air pressure warning threshold value is set too low.

(6) A low air pressure alarm threshold line can be automatically set without depending on the operation of the initialization switch.
In addition, the said embodiment can also be changed and actualized as follows.
Instead of the configuration in which the stop and the start of travel are determined through the vehicle speed sensor 16, it may be determined that the vehicle is stopped when the ignition is OFF, and the start of travel is determined when the ignition is detected. In this case, the CPU 11 determines a period from the ignition OFF to the ignition ON as a period from the stop to the start of traveling, and determines whether or not the period has reached the predetermined period (one hour as an example). According to this configuration, it is possible to easily specify stopping and starting of traveling.

  Alternatively, it may be determined that the vehicle is stopped when the shift position is set to the parking position or the neutral position, and may be determined to start running when the shift position is set to the drive position or the reverse position.

  -The fixed period prescribed | regulated as the period when the temperature of a tire falls to ambient temperature after stopping after driving | running | working is not limited to 1 hour by the said embodiment. If the fixed period is shortened, the low air pressure alarm threshold straight line that follows the ambient temperature can be reset even in the vehicle 1 in a usage pattern in which traveling immediately after stopping is repeated. On the other hand, if the predetermined period is lengthened, the low air pressure alarm threshold straight line is reset based on the information signal that is not reliably affected by the tire temperature during traveling, so that it is possible to reliably follow changes in the ambient temperature.

  ・ Instead of the configuration in which the minimum value of the temperature of each tire is determined as the ambient temperature, the average value of the four tires, the second lowest value, the remaining average value except the highest and lowest, fixed A temperature value of a tire (for example, the right rear wheel) or the like may be determined as the ambient temperature.

  In place of the configuration in which the low air pressure alarm threshold Th is set as the lower limit value in the low air pressure alarm threshold line, the inclination according to Boyle's law may be maintained even in a temperature region lower than the reference point.

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 10 ... Receiver (receiver of tire pressure monitoring system), 11 ... CPU (threshold setting means), 12 ... Reception circuit, 12a ... Reception antenna, 13 ... Memory, 15 ... Indicator, 16 ... Vehicle speed sensor, DESCRIPTION OF SYMBOLS 30 ... Sensor unit, 31 ... CPU, 32 ... Transmission circuit, 32a ... Transmission antenna, 33 ... Pressure sensor, 34 ... Temperature sensor.

Claims (3)

A tire that receives an information signal including information on tire air pressure and tire temperature from a sensor unit attached to each tire, and issues a warning when the tire air pressure included in the information signal falls below a low air pressure alarm threshold value. In the receiver of the air pressure monitoring system,
In the relationship between the tire temperature and the tire air pressure, a reference point is set in which the tire air pressure is the low air pressure alarm threshold, and the tire temperature is the tire temperature included in the information signal. A threshold setting means for setting a low air pressure alarm threshold straight line that passes through a point and has a slope according to Boyle's law derived from the tire temperature and tire pressure included in the information signal;
It said threshold setting means, near the temperature of the tire after the ignition OFF determines the ambient temperature from the temperature of the tire included in said information signal received first after the ignition ON after a lapse of time down to ambient temperature and the determined A receiver for a tire air pressure monitoring system, wherein the low air pressure alarm threshold straight line is reset based on temperature. Said threshold setting means, tire pressure according to claim 1 for determining the ambient temperature a minimum value of the temperatures of the individual tires contained in said information signal received first from each sensor unit of each tire after the ignition ON Surveillance system receiver. The receiver of a tire pressure monitoring system according to claim 1 or 2, wherein the threshold setting means sets the low air pressure warning threshold line to the low air pressure warning threshold in a temperature region lower than the reference point.

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