JP2007045202A - Tire air pressure monitoring system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire air pressure monitoring system capable of determining the mounting position of the tire in a short determination time while keeping correctness of the determination. <P>SOLUTION: The radio wave intensity average value of reception of a first predetermined reception number of times N<SB>1</SB>is obtained for each tire sensor when the first predetermined reception number of times is N<SB>1</SB>. If the absolute value of the difference of the average value in each tire sensor is not less than a first determination value D<SB>1</SB>, the determination of front or rear wheel is performed from the result. When it is less than the first determination value D<SB>1</SB>, the radio wave intensity average value of reception of a second predetermined reception number of times N<SB>2</SB>is obtained for each tire sensor when the second predetermined reception number of times N<SB>2</SB>is larger than the first predetermined reception number of times N<SB>1</SB>. If the absolute value of the difference of the average value in each tire sensor is not less than the second predetermined determination value D<SB>2</SB>smaller than the first determination value D<SB>1</SB>, the determination of front or rear wheel is performed from the result. The state of each tire is monitored by the state signal for the determined tire. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a tire air pressure monitoring system for monitoring the air pressure of a tire of a vehicle or the like.

  The tire pressure monitoring system is a receiver (ECU) installed on a vehicle body that receives air pressure data periodically transmitted by radio (radio waves) from a tire pressure sensor (hereinafter abbreviated as a tire sensor) installed in a tire. ), And if the received air pressure value is lower than the predetermined value, the warning light installed in the instrument panel (hereinafter abbreviated as instrument panel) is turned on to warn the driver. . Each tire sensor has a unique ID number, and automatically recognizes the relationship between the ID number of each tire sensor and the position of the attached tire from the radio wave intensity of the radio wave intensity sensor attached to the vehicle body. . In addition, even if the set air pressure differs between the front and rear wheels, and the prescribed air pressure value to be warned differs between the front and rear wheels, the receiver will issue a warning that the air pressure has fallen correctly by recognizing whether it is the front wheel or the rear wheel. be able to.

JP 2004-291951 A

  Since the radio wave intensity from the tire sensor fluctuates due to the influence of the traveling environment, the position of the mounted tire may be erroneously determined. In order to avoid misjudgment and increase accuracy, it is sufficient to acquire a large amount of radio wave intensity data. However, if a large amount of radio wave intensity data is acquired, the determination takes time.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a tire air pressure monitoring system capable of determining a tire mounting position in a short determination time while maintaining accuracy of determination.

A tire pressure monitoring system according to a first invention for solving the above-mentioned problem is as follows.
Transmitting means that is provided in each tire of the vehicle and transmits an identification signal that can individually identify each tire, and a state signal that indicates the state of each tire including air pressure;
One or a plurality of receiving means provided in a vehicle, for receiving a signal from the transmitting means, detecting the identification signal and the state signal, and detecting a signal strength of the signal;
Signal processing means for inputting the identification signal, the state signal and the signal strength detected by the receiving means;
The signal processing means includes
When the receiving means receives a signal from each transmitting means for a first predetermined number of times, the signal intensity of a signal from any transmitting means and the signal strength of a signal from another transmitting means is a first predetermined value at the receiving means. Find the average value for each number of times,
When the absolute value of the difference between the average values is equal to or greater than the first determination value, the magnitude of the average value of the signal strength of the other transmitting means relative to the position of the receiving means and the average value of the signal strength of any transmitting means Based on the above, the position of the tire on which any transmission means is mounted is specified,
When the absolute value of the difference between the average values is less than the first determination value, when the receiving unit receives a signal from each transmitting unit for a second predetermined number of times greater than the first predetermined number of times, any transmission is performed. For each of the signal strength of the signal from the means and the signal strength of the signal from the other transmission means, obtain an average value for the second predetermined number of times at the receiving means,
When the absolute value of the difference between the average values is equal to or greater than a second determination value smaller than the first determination value, the position of the reception unit and the other transmission units with respect to the average value of the signal strength for any transmission unit Based on the magnitude of the average value of the signal strength, specify the position of the tire where any transmission means is mounted,
The condition of each tire is monitored by the condition signal for the identified tire.

A tire pressure monitoring system according to a second invention for solving the above-described problems is as follows.
In the tire pressure monitoring system according to the first invention,
The receiving means is provided on the front or rear side of the vehicle,
The transmission means transmits rotation direction information indicating the rotation direction of each tire as a state signal of each tire,
The signal processing means includes
Based on the rotation direction information and the traveling direction information indicating the traveling direction of the vehicle, specify whether the transmission means is mounted on the left side or the right side,
When the reception means receives a signal from each transmission means mounted on the same side for the first predetermined number of times, the signal strength of the signal from one transmission means on the same side is the signal strength from the other transmission means on the same side. For the signal strength, an average value for the first predetermined number of times in the receiving means is obtained,
When the absolute value of the difference between the average values is greater than or equal to the first determination value, if the average value of the signal strength for the other transmission means is smaller than the average value of the signal strength for one transmission means, It is determined that the transmission means is attached to a tire in front of or behind the vehicle,
When the absolute value of the difference between the average values is less than the first determination value, the receiving unit receives a signal from each transmitting unit on the same side for a second predetermined number of times greater than the first predetermined number of times. , For the signal strength of the signal from the other transmitting means on the same side as the signal strength of the signal from one transmitting means on the same side, respectively, obtain an average value for the second predetermined number of times in the receiving means,
When the absolute value of the difference between the average values is equal to or greater than a second determination value that is smaller than the first determination value, the average of the signal strength for the other transmission means with respect to the average value of the signal strength for one transmission means If the value is small, it is determined that one of the transmission means is attached to a tire in front of or behind the vehicle.

A tire pressure monitoring system according to a third aspect of the present invention for solving the above problem is as follows.
Transmitting means that is provided in each tire of the vehicle and transmits an identification signal that can individually identify each tire, and a state signal that indicates the state of each tire including air pressure;
A first receiving means provided on a vehicle for receiving a signal from the transmitting means, detecting the identification signal and the state signal, and detecting a signal intensity of the signal;
The first receiving means is installed away from the vehicle in the front-rear direction, and the second receiving means detects the signal strength of the signal from the transmitting means,
The signal intensity detected by the first receiving means, the signal intensity detected by the second receiving means, the identification signal and the status signal detected by the first receiving means are inputted, and the first receiving means And signal processing means configured integrally with
The transmission means transmits rotation direction information indicating the rotation direction of each tire as a state signal of each tire,
The signal processing means includes
Based on the rotation direction information and the traveling direction information indicating the traveling direction of the vehicle, specify whether the transmission means is mounted on the left side or the right side,
When the first receiving means and the second receiving means receive a signal from each transmitting means for a first predetermined number of times, the first receiving means and the second receiving means with respect to the signal strength of the signal from each transmitting means. Each average value for the first predetermined number of times at
Arbitrary one of the first predetermined number of times at the first receiving means for the transmitting means on the same side and the first predetermined number of times at the second receiving means for the other one transmitting means on the same side The sum of the average values of the minutes, the average value for the first predetermined number of times at the first receiving means of the other one transmitting means, and the first predetermined value at the second receiving means of the arbitrary one transmitting means When the absolute value of the difference between the sums of the average values for the number of times is equal to or greater than the first determination value, the transmission unit that has the radio field intensity at the first reception unit out of the combination with the larger sum of the average values is the above The first receiving means side determines that the transmitting means having the radio wave intensity at the second receiving means is disposed on the second receiving means side,
When the absolute value of the difference between the sums of the two sets of average values is less than the first determination value, the first receiving means and the second receiving means send the signals from the transmitting means to the first When receiving a second predetermined number of times greater than one predetermined number of times, an average value for the second predetermined number of times at the first receiving means and the second receiving means is obtained for the signal strength of the signal from each transmitting means,
Arbitrary one of the second predetermined number of times at the first receiving means for the transmitting means on the same side and the second predetermined number of times at the second receiving means for the other one transmitting means on the same side A sum of average values of minutes, an average value of a second predetermined number of times at the first receiving means of the other one transmission means, and a second predetermined value at the second receiving means of any one of the transmission means When the absolute value of the difference between the sums of the average values for the number of times is equal to or greater than the second determination value, the transmission unit that is the radio wave intensity at the first reception unit out of the combination with the larger sum of the average values is the above The first receiving means side determines that the transmitting means having the radio wave intensity at the second receiving means is disposed on the second receiving means side,
The condition of each tire is monitored by the condition signal for the identified tire.

A tire pressure monitoring system according to a fourth invention for solving the above-described problem is
Transmitting means that is provided in each tire of the vehicle and transmits an identification signal that can individually identify each tire, and a state signal that indicates the state of each tire including air pressure;
A plurality of receiving means provided near each wheel of the vehicle, receiving a signal from the transmitting means, detecting the identification signal and the status signal, and detecting the signal strength of the signal;
Signal strength detected by the plurality of receiving means, signal processing means to which the identification signal and the status signal are input,
The signal processing means includes
When one arbitrary receiving unit receives a signal from each transmitting unit for a first predetermined number of times, the signal intensity of the signal from each transmitting unit is averaged for the first predetermined number of times by the arbitrary receiving unit. Seeking each
The transmission means that has transmitted the signal that is the maximum average value when the absolute value of the difference between the maximum average value and the other average values is equal to or greater than the first determination value among all the average values that are obtained, It is determined that it is attached to a tire near the position of the receiving means,
When the absolute value of the difference between the maximum average value and the other average value is less than the first determination value, the arbitrary reception unit outputs a signal from each transmission unit more than the first predetermined number of times. When the second predetermined number of times is received, the average value for the second predetermined number of times at the arbitrary receiving means is obtained for the signal strength of the signal from each transmitting means,
Among all the obtained average values, when the absolute value of the difference between the maximum average value and other average values is equal to or larger than the second determination value smaller than the first determination value, a signal that becomes the maximum average value is transmitted. Determining that the transmission means is attached to a tire near the position of the arbitrary reception means,
The state of each tire is monitored by the state signal for the determined tire.

A tire pressure monitoring system according to a fifth aspect of the present invention for solving the above problem is as follows.
Transmitting means that is provided in each tire of the vehicle and transmits an identification signal that can individually identify each tire, and a state signal that indicates the state of each tire including air pressure;
A plurality of receiving means provided near each wheel of the vehicle, receiving a signal from the transmitting means, detecting the identification signal and the status signal, and detecting the signal strength of the signal;
Signal strength detected by the plurality of reception means, signal processing means to which the identification signal and the status signal are input,
The signal processing means includes
When each receiving means receives a signal from one arbitrary transmitting means for the first predetermined number of times, the average value for the first predetermined number of times at each receiving means is obtained for the signal strength of the signal from the arbitrary transmitting means. Seeking each
Among all the obtained average values, when the absolute value of the difference between the maximum average value and other average values is equal to or greater than the first determination value, the arbitrary transmission means receives a signal that has the maximum average value. It is determined that the tire is mounted on a tire near the position of the receiving means.
When the absolute value of the difference between the maximum average value and the other average value is less than the first determination value, each reception unit outputs a signal from the arbitrary transmission unit more than the first predetermined number of times. When the second predetermined number of times is received, the average value for the second predetermined number of times at each receiving means is obtained for the signal strength of the signal from the arbitrary transmitting means,
Among all the obtained average values, when the absolute value of the difference between the maximum average value and other average values is equal to or larger than the second determination value smaller than the first determination value, the arbitrary transmission means is set to the maximum It is determined that the tire is mounted in the vicinity of the position of the receiving means that has received the average signal.
The state of each tire is monitored by the state signal for the determined tire.

  According to the present invention, it is possible to determine the mounting position of a tire as early as possible while maintaining the accuracy of the determination, and quickly and reliably monitor the state of each tire based on the state signal for the determined tire. can do.

  In the tire pressure monitoring system, the radio wave intensity from the tire sensor fluctuates due to the influence of the traveling environment or the like, and therefore the influence of fluctuation can be mitigated by using the average value of the radio wave intensities of a plurality of reception times. If the average value of the radio field intensity of a larger number of receptions is used, the fluctuation range can be reduced. However, if this is done, a long determination time is required because the average value of the radio field intensity of many receptions is used. In the tire pressure monitoring system, for example, it is desirable to detect an abnormality in tire air pressure early during traveling, and for this purpose, it is desirable to be able to make a determination with the radio wave intensity with as few receptions as possible.

  Therefore, in the tire pressure monitoring system according to the present invention, the number of radio wave intensity data to be acquired and the determination value are set in stages, and the determination process is performed, thereby maintaining the accuracy of the determination and mounting the tire as early as possible. The position is determined. Some of the specific embodiments are shown in FIGS. 1 to 5 and will be described in detail below.

  FIG. 1 is a schematic configuration diagram showing an example of an embodiment of a tire pressure monitoring system according to the present invention, and FIG. 1 (a) shows a main receiver including a radio wave intensity sensor and an arrangement of tire sensors. (B) shows the configuration of the main receiver.

  As shown in FIG. 1, the tire pressure monitoring system of the present embodiment is installed in the front wheel T1 and the rear wheel T2, and each tire has an identification signal such as an ID number and an air pressure value that can individually identify each tire. Tire sensors S1 and S2 that periodically transmit signals including these, such as state signals indicating the state, and the vehicle body 10, and detect intensity values of radio waves from the tire sensors S1 and S2. One main unit that has a single radio field intensity sensor, receives a radio field intensity value from the radio field intensity sensor, receives a signal including an air pressure value and an ID number from the tire sensors S1 and S2, and performs a predetermined calculation process A receiver 1 is provided.

  The main receiver 1 includes an antenna 3 that receives a signal including an air pressure value and an ID number from the tire sensors S1 and S2, and a signal receiving unit 4 that processes the signal from the antenna 3 and detects the air pressure value and the ID number. , An intensity detector 5 that detects the radio field intensity of the signal at the antenna 3 and transmits the detected radio field intensity value; the radio field intensity value transmitted from the intensity detector 5; and the air pressure value recognized by the signal receiver 4 And an arithmetic unit 6 that performs a predetermined arithmetic process using the ID number. As described above, the main receiver 1 is configured such that the signal receiver 4 and the intensity detector 5 share the antenna 3, and the antenna 3 and the intensity detector 5 are connected to the inside of the main receiver 1. 1 has one radio wave intensity sensor. Hereinafter, the radio wave intensity sensor including the antenna 3 and the intensity detector 5 is referred to as a radio wave intensity sensor D1 for convenience.

The calculation unit 6 recognizes the position of the tire on which the tire sensors S1 and S2 are mounted from the comparison of the radio wave intensity values at the radio wave intensity sensor D1 when signals are received from the tire sensors S1 and S2. For example, when the main receiver 1 (the radio wave intensity sensor D1) is arranged on the front side of the vehicle, the radio wave transmitted by the tire sensor S1 attached to the front wheel T1 is relatively strong (the radio wave intensity value in FIG. 1A). R _{1f, N} ), on the contrary, the radio wave transmitted by the tire sensor S2 attached to the rear wheel T2 is relatively weak (the radio wave intensity value R _{2f, N in} FIG. 1A). From the comparison of the radio field intensities, it can be recognized that the tire sensor S1 is attached to the front wheel and the tire sensor 2 is attached to the rear wheel. When the received air pressure value is lower than a predetermined value, a calculation process is performed in which a warning lamp 7 installed in the instrument panel is turned on to warn the driver of the corresponding tire.

The left and right wheels of the tire can be identified by, for example, a configuration in which tire sensors S1 and S2 are provided with a tire rotation direction sensor that detects a tire rotation direction in addition to a tire sensor that detects tire air pressure. It becomes. In this case, the tire sensors S1 and S2 transmit the rotational direction information together with the air pressure value and the ID number. In the main receiver 1, the left wheel is determined from the rotational direction information from the tire sensors S1 and S2 and the traveling direction information of the vehicle 10. Recognize the right wheel. For example, as shown in FIG. 2, when the vehicle 10 is moving forward, since the front and tire sensors S1 _L of the left wheel T1 _L, the direction of rotation of the tire sensors S1 _R of the front right wheel T1 _R different tire Whether the front wheel is the front left wheel T1 _L or the front right wheel T1 _R can be recognized by the rotation direction information from the sensors S1 _L and S1 _R. Similarly, the left rear wheel T2 _L tire sensor S2 of _L, also different for the rotating direction of the tire sensor S2 _R of the rear right wheel T2 _R, the rotation direction information from the tire sensor S2 _L, S2 _R, left rear wheel T2 _L Or the rear right wheel T2 _R. That is, it becomes possible to recognize the front and rear wheels of the vehicle 10 by comparing the radio field intensity in the main receiver 1, and the left wheel of the vehicle 10 is determined by the rotation direction information transmitted from the tire sensors S1 _L , S1 _R , S2 _L , S2 _R. The right wheel can be recognized.

  Next, the details of the predetermined calculation process performed by the calculation unit 6 of the main receiver 1 of the present embodiment will be described with reference to FIG. FIG. 3 shows a tire when the main receiver 1 having the radio wave intensity sensor D1 is arranged at one place in front of the vehicle body, in other words, when the radio wave intensity sensor D1 is arranged at only one place in front of the vehicle body. It is a flowchart which shows the position recognition procedure of.

<Step S1>
The tire position recognition procedure starts when the ignition (IG) is turned on.

<Step S2>
It is determined whether the signal of the ID number registered in the own vehicle has been received. If the signal is the ID number registered in the own vehicle, the process proceeds to step S3. Otherwise, the process returns to step S1. This has the purpose of eliminating signals from tire sensors of other vehicles.

<Step S3>
It is determined whether or not the air pressure value included in the received signal is equal to or lower than the warning threshold value. If the air pressure value is equal to or lower than the warning threshold value, an air pressure warning is issued (step S4), and the process proceeds to step S5. Proceed to step S5.

<Step S4>
From the record of the arrangement position of the tire sensors S1, S2 with respect to the tire position (see steps S13, S14 described later), the warning light 7 on the instrument panel is turned on for the tire at the corresponding position to display a pneumatic warning. At this time, if the set air pressure is different between the front wheel T1 and the rear wheel T2, it is recognized from the record of the arrangement positions of the tire sensors S1, S2 with respect to the tire position whether the warning object is the front wheel T1 or the rear wheel T2. If it is the front wheel T1, it is compared with the set air pressure value of the front wheel T1 that should be warned, and if it is the rear wheel T2, it is compared with the set air pressure value of the rear wheel that should be warned. ing.

<Step S5>
The left and right wheel information included in the signal is confirmed. If it is the left wheel, the process proceeds to step S6, and the processes from step S6 to S16 are performed. If it is the right wheel, the process proceeds to step S17. Note that, in step S17, processing exactly the same as that in steps S6 to S16 is performed, so the detailed procedure is omitted in FIG.

<Step S6>
For the received ID number of the left wheel, the radio field intensity values R _{1f, N} and R _{2f, N} are stored, and the process proceeds to step S7. Here, R _{1f, N} is the radio field intensity value at the radio field intensity sensor D1 from the first tire sensor S1, and R _{2f, N} is the radio field intensity at the radio field intensity sensor D1 from the second tire sensor S2. Value. N is a reception number assigned consecutively in the order of reception.

<Step S7>
For the ID number included in the signal, one counter N _i is added (N _i = N _i +1), and the process proceeds to step S8. Incidentally, i is, either S1 or S2, a counter N _S1 for the first tire sensor S1, a configuration having a counter N _S2 for the second tire sensor S2.

<Step S8>
It is confirmed whether the smaller one of N _s1 and N _s2 is the first predetermined number of times N ₁ or more. If the first predetermined number N ₁ or more, the process proceeds to step S9, if the first less than the predetermined number N _1, the flow returns to step S1, until the number of receptions reaches the first predetermined number N ₁ or more, the radio wave strength value R Repeat reception and storage of _{1f, N} and _{R2f, N.}

<Step S9>
It calculates the following equation (1), checks whether it is the calculation result is judged value D ₁ or more. If the judgment value D ₁ or more, the process proceeds to step S12, if less than the determination value D _1, the process proceeds to step S10.

ここで、「Ａｖｅ（）」を、括弧内の数値の平均値を求める関数と規定する。

Here, “Ave ()” is defined as a function for obtaining an average value of numerical values in parentheses.

<Step S10>
It is confirmed whether the smaller one of N _s1 and N _s2 is _{equal to} or greater than the second predetermined number of times N ₂ (> N ₁ ). If the second predetermined number N ₂ or more, the process proceeds to step S11, if it is smaller than the second predetermined number N _2, the flow returns to step S1, and repeats until the second predetermined number N ₂ or more. That is, here, when the calculation result of the above formula (1) is less than the determination value D _1, the second predetermined number of times N that is larger than the first predetermined number N ₁ in order to ensure the accuracy of the received radio wave intensity. The reception and storage of the radio field intensity values R _{1f, N} and R _{2f, N} are repeated until ₂ .

<Step S11>
The following equation (2) is calculated, and it is confirmed whether the calculation result is equal to or greater than the determination value D ₂ (<D ₁ ). If the judgment value D ₂ or more, the process proceeds to step S12, if less than the determination value D _2, the flow advances to step S16.

<Step S12>
When the process proceeds from step S9 to this step, the following expression (3) is calculated. If expression (3) is satisfied, the process proceeds to step S13. If expression (3) is not satisfied, the process proceeds to step S14.
If the process proceeds from step S11 to this step, the following expression (4) is calculated. If the expression (4) is satisfied, the process proceeds to step S13. If the expression (4) is not satisfied, the process proceeds to step S14.

Ave ( _{R1f, N-N1 + 1 to R1f, N} )> Ave ( _{R2f, N-N1 + 1 to R2f, N} ) (3)
Ave ( _{R1f, N-N2 + 1 to R1f, N} )> Ave ( _{R2f, N-N2 + 1 to R2f, N} ) (4)

<Step S13>
The first tire sensor S1 is determined to be the left tire of the axle (front wheel T1) close to the electric field strength sensor D1, stored, and the process proceeds to step S15.

<Step S14>
The second tire sensor S2 is determined to be the left tire of the axle (front wheel T1) close to the electric field strength sensor D1, stored, and the process proceeds to step S15.

<Step S15>
The counter N _i is reset to 0, the flow ends.

<Step S16>
In step S11, when the calculation result of formula (2) is less than the determination value D _2, since the error warning, and outputs the determination unrecoverable error, the process proceeds to step S15.

That is, in summary, in the present embodiment, as a method for determining the position of the mounted tire, when the first predetermined number of reception times N ₁ , for each of the tire sensors S1 and S2, the reception intensity average of N ₁ receptions by the radio field intensity sensor. If the difference in values (see equation (1)) is greater than or equal to the first determination value D ₁ , the determination of the front and rear wheels is made from this result, and if it is less than D ₁ , the determination is suspended, and then from N ₁ When the second predetermined number of times of reception N ₂ is large, the difference in the radio field intensity average value of N ₂ receptions by the radio field intensity sensor (see formula (2)) is smaller than D _{1 for} each of the tire sensors S1 and S2. if the second judgment value D ₂ or more, and to perform the determination of the front wheel-rear wheel from the results. Thus, in the present embodiment, the determination as two steps, is performed judged up determination value D ₂ of the difference between the radio wave intensity average value of N ₂ times of reception when the second predetermined number of times of receiving N _2. Therefore, it is possible to determine the mounting position of the tire as early as possible while maintaining the accuracy of the determination.

Here, a specific process of the procedure shown in FIG. 3 will be described with reference to FIG.
As shown in FIG. 1, a main receiver 1 (radio wave intensity sensor D1) is disposed in front of the vehicle body. For example, as a standard value, the radio wave intensity average value Ave (R _{1f, N} ) is set to 30 dB, and the radio field intensity average value Ave (R _{2f, N} ) from the tire sensor S2 of the rear wheel T2 is set to 25 dB. Further, it is assumed that the first predetermined reception number N ₁ is 10 times and the second predetermined reception number N ₂ is 20 times.

The fluctuation range of the first predetermined reception number N ₁ = 10 reception radio wave intensity average values is empirically about ± 4 dB, and the second predetermined reception number N ₂ = 20 reception radio wave average values The fluctuation range of was empirically about ± 2 dB.

In this case, 10 times of the radio wave intensity average value at the time of receiving N ₁ = 10 times, radio intensity average value Ave (R _{1f, N)} from the tire sensor S1 of the front wheel T1 is, 26~34dB (= 30 ± 4 dB), and the radio field intensity average value Ave (R _{2f, N} ) from the tire sensor S2 of the rear wheel T2 is 21 to 29 dB (= 25 ± 4 dB). Therefore, even if the worst case is taken into consideration, if the first determination value D ₁ = 3 dB (= 29−26 dB) or more is set, no erroneous determination will occur. Further, the first determination value D ₁ = 3 dB is smaller than the standard value difference of 5 dB (= 30−25 dB), and in many cases, the tire position is recognized when the first predetermined reception number N ₁ = 10 times is received. Can be determined.

If the determination is put on hold when N ₁ = 10 times of reception, the average value of the radio field intensity for 20 times at the time of reception of N ₂ = 20 times is the average value Ave of the radio field intensity from the tire sensor S1 of the front wheel T1. R _{1f, N} ) is 28 to 32 dB (= 30 ± 2 dB), and the radio field intensity average value Ave (R _{2f, N} ) from the tire sensor S2 of the rear wheel T2 is 23 to 27 dB (= 25 ± 2 dB). . In this case, since the radio wave intensity average value Ave (R _{1f, N} ) and the radio wave intensity average value Ave (R _{2f, N} ) always have a significant difference, the second determination value D ₂ = 0 dB is set. It is always possible to determine. From the above determination, it is possible to recognize that the detected field intensity value is relatively strong from the front wheel T1, and the relatively weak field intensity value from the rear wheel T2.

  FIG. 4 is a schematic configuration diagram showing another example of the embodiment of the tire pressure monitoring system according to the present invention. FIG. 4A shows the arrangement of the radio wave intensity sensor, the main receiver, and the tire sensor. 4 (b) and FIG. 4 (c) show configuration examples of the main receiver. In FIG. 4, the same components as those shown in FIG. 1 of the first embodiment are denoted by the same reference numerals, and redundant description is omitted.

  As shown in FIG. 4 (a), the tire pressure monitoring system of the present embodiment is also equipped with tire sensors S1, S2 installed in the front wheels T1 and rear wheels T2, a vehicle body 10 and a radio wave intensity sensor inside. It has one main receiver 1A (1B) having D1, and further has one radio wave intensity sensor D2 installed in a position different from the main receiver 1A (1B) in the vehicle body 10.

  FIGS. 4B and 4C show configuration examples of the main receiver 1A (1B) and the radio wave intensity sensor D2.

  For example, in FIG. 4B, the main receiver 1A includes the antenna 3, the signal receiving unit 4, the intensity detecting unit 5, and the calculating unit 6, like the main receiver 1 in the first embodiment. The antenna 8 is installed at a position different from the main receiver 1A (rear side of the vehicle) and receives signals from the tire sensors S1 and S2, and the radio wave intensity at the antenna 8 is provided inside the main receiver 1A. And an intensity detector 9 for detecting and transmitting the detected radio field intensity value. The main receiver 1 </ b> A has a configuration in which one radio wave intensity sensor D <b> 1 is provided inside the main receiver 1 by the intensity detector 5 and the antenna 3 shared with the signal receiver 4, and the intensity detector 9 And an antenna 8 disposed on the rear side of the vehicle. Hereinafter, the radio wave intensity sensor including the antenna 8 and the intensity detector 9 is referred to as a radio wave intensity sensor D2 for convenience.

  In FIG. 4C, the main receiver 1B includes the antenna 3, the signal receiving unit 4, the intensity detecting unit 5, and the calculating unit 6 like the main receiver 1 in the first embodiment. 3 and the intensity detection unit 5 have one radio wave intensity sensor D1 inside the main receiver 1, and another radio wave intensity sensor D2 at a position (rear side of the vehicle) different from the main receiver 1B. Is a configuration in which is installed. The radio field intensity sensor D2 detects the radio field intensity at the antenna 8 that receives signals from the tire sensors S1 and S2, and transmits the detected radio field intensity value to the arithmetic unit 6 of the main receiver 1B. Part 9.

  As described above, in this embodiment, the system has a plurality of (two in FIGS. 4B and 4C) radio wave intensity sensors D1 and D2.

In this embodiment, the main receiver 13 including the radio wave intensity sensor D1 is arranged on the front wheel T1 side, the radio wave intensity sensor D2 is arranged on the rear wheel T2 side, and the radio wave intensity values detected by the radio wave intensity sensors D1 and D2 are the main. By transmitting to the receiver 1A (1B) and performing predetermined calculation processing, it is difficult to be affected by noise, and the front and rear wheels can be reliably recognized. As shown in FIG. 2, if the tire sensors S1 _L , S1 _R , S2 _L , S2 _R have a tire rotation direction sensor, the left and right wheels of the vehicle 10 are also changed according to the transmitted rotation direction information. It becomes possible to recognize.

The calculation unit 6 recognizes the position of the tire on which the tire sensors S1 and S2 are mounted from the comparison of the radio wave intensity values at the radio wave intensity sensors D1 and D2 when signals are received from the tire sensors S1 and S2. For example, in the main receiver 1 (radio wave intensity sensor D1) disposed on the front side of the vehicle, the radio wave transmitted by the tire sensor S1 attached to the front wheel T1 is relatively strong (the radio wave intensity value in FIG. 4A). R _{1f, N} ), on the contrary, the radio wave transmitted by the tire sensor S2 mounted on the rear wheel T2 is relatively weak (the radio wave intensity value R _{1r, N in} FIG. 1A). Further, in the radio wave intensity sensor D2 disposed on the rear side of the vehicle, the radio wave transmitted from the tire sensor S1 mounted on the front wheel T1 is relatively weak (the radio wave intensity value R _{2f, N in} FIG. 4A). Conversely, the radio wave transmitted by the tire sensor S2 attached to the rear wheel T2 is relatively strong (the radio wave intensity value R _{2r, N in} FIG. 1A). From the comparison of the radio field intensities, it can be recognized that the tire sensor S1 is attached to the front wheel and the tire sensor 2 is attached to the rear wheel. When the received air pressure value is lower than a predetermined value, a calculation process is performed in which a warning lamp 7 installed in the instrument panel is turned on to warn the driver of the corresponding tire.

  Next, details of a predetermined calculation process performed by the calculation unit 6 of the main receiver 1A (1B) of the present embodiment will be described with reference to FIG. FIG. 5 shows the position of the tire when the main receiver 1A (1B) having the radio wave intensity sensor D1 is arranged at one place in front of the vehicle body and the other radio wave intensity sensor D2 is arranged at one place behind the vehicle body. It is a flowchart which shows a recognition procedure.

<Step S21>
The tire position recognition procedure starts when the ignition (IG) is turned on.

<Step S22>
It is determined whether the signal of the ID number registered in the own vehicle has been received. If the signal is the ID number registered in the own vehicle, the process proceeds to step S23, and if not, the process returns to step S21. This has the purpose of eliminating signals from tire sensors of other vehicles.

<Step S23>
It is determined whether or not the air pressure value included in the received signal is equal to or lower than the warning threshold value. If the air pressure value is equal to or lower than the warning threshold value, an air pressure warning is issued (step S24), and the process proceeds to step S25. Proceed to step S25.

<Step S24>
From the record of the arrangement positions of the tire sensors S1 and S2 with respect to the tire position (see steps S32 and S33 described later), the warning light 7 on the instrument panel is turned on for the tire at the corresponding position, and an air pressure warning is displayed. At this time, if the set air pressure is different between the front wheel T1 and the rear wheel T2, it is recognized from the record of the arrangement positions of the tire sensors S1, S2 with respect to the tire position whether the warning object is the front wheel T1 or the rear wheel T2. If it is the front wheel T1, it is compared with the set air pressure value of the front wheel T1 that should be warned, and if it is the rear wheel T2, it is compared with the set air pressure value of the rear wheel that should be warned. ing.

<Step S25>
For the received tire ID number, the radio field intensity values R _{1f, N} , R _{1r, N} , R _{2f, N} , R _{2r, N} are stored, and the process proceeds to step S26. Here, R _{1f, N} is a radio field intensity value at the front side radio wave intensity sensor D1 from the first tire sensor S1, and R _{1r, N} is a rear side radio wave from the first tire sensor S1. It is a radio wave intensity value at the intensity sensor D2. R _{2f, N} is a radio field intensity value at the front side radio field intensity sensor D1 from the second tire sensor S2, and R _{2r, N} is a rear side radio field intensity sensor from the second tire sensor S2. It is a field intensity value at D2. N is a reception number assigned consecutively in the order of reception.

<Step S26>
With respect to the ID number included in the signal, one counter N _i is added (N _i = N _i +1), and the process proceeds to step S27. Incidentally, i is, either S1 or S2, a counter N _S1 for the first tire sensor S1, a configuration having a counter N _S2 for the second tire sensor S2.

<Step S27>
It is confirmed whether the smaller one of N _s1 and N _s2 is the first predetermined number of times N ₁ or more. If the first predetermined number N ₁ or more, the process proceeds to step S28, if the first less than the predetermined number N _1, the flow returns to step S21, until the first predetermined number N ₁ or more, the radio wave strength value R _{1f, N} , R _{1r, N} , R _{2f, N} and R _{2r, N} are repeatedly received and stored.

<Step S28>
It calculates the following equation (5), checks whether it is the calculation result is judged value D ₁ or more. If the judgment value D ₁ or more, the process proceeds to step S31, if less than the determination value D _1, the process proceeds to step S29.

<Step S29>
It is confirmed whether the smaller one of N _s1 and N _s2 is _{equal to} or greater than the second predetermined number of times N ₂ (> N ₁ ). If the second predetermined number N ₂ or more, the process proceeds to step S30, if it is smaller than the second predetermined number N _2, the flow returns to step S21, and repeats until the second predetermined number N ₂ or more. That is, here, when the calculation result of the above formula (3) is less than the determination value D _1, the second predetermined number N of times that the number of receptions is larger than the first predetermined number N ₁ in order to ensure the accuracy of the received radio wave intensity. The reception and storage of the radio field intensity values R _{1f, N} , R _{1r, N} , R _{2f, N} , R _{2r, N} are repeated until ₂ .

<Step S30>
The following equation (6) is calculated, and it is confirmed whether the calculation result is equal to or greater than the determination value D ₂ (<D ₁ ). If the judgment value D ₂ or more, the process proceeds to step S31, if less than the determination value D _2, the flow advances to step S35.

<Step S31>
When the process proceeds from step S28 to this step, the following expression (7) is calculated. If the expression (7) is satisfied, the process proceeds to step S32. If the expression (7) is not satisfied, the process proceeds to step S33.
If the process proceeds from step S30 to this step, the following expression (8) is calculated. If expression (8) is satisfied, the process proceeds to step S32. If expression (8) is not satisfied, the process proceeds to step S33.

Ave ( _{R1f, N-N1 + 1 to R1f, N} ) + Ave ( _{R2r, N-N1 + 1 to R2r, N} )> Ave ( _{R2f, N-N1 + 1 to R2f, N} ) + Ave ( _{R1r, N-N1 + 1 to R1r, N} ) (7)
Ave ( _{R1f, N-N2 + 1 to R1f, N} ) + Ave ( _{R2r, N-N2 + 1 to R2r, N} )> Ave ( _{R2f, N-N2 + 1 to R2f, N} ) + Ave ( _{R1r, N-N2 + 1 to R1r, N} ) (8)

<Step S32>
The first tire sensor S1 is determined to be the front wheel T1 side, and the second tire sensor S2 is determined to be the rear wheel T2 side, stored, and the process proceeds to step S34.

<Step S33>
The second tire sensor S2 is determined to be the front wheel T1 side, and the first tire sensor S1 is determined to be the rear wheel T2 side, stored, and the process proceeds to step S34.

<Step S34>
The counter N _i is reset to 0, the flow ends.

<Step S35>
In step S30, when the calculation result of formula (6) is less than the determination value D _2, and outputs the determination unrecoverable error, the process proceeds to step S34.

That is, in summary, in the present embodiment, two radio wave intensity sensors D1 and D2 are used as a method for determining the position of the mounted tire, and the sum of the average values of strong (maximum) radio wave intensity at each of the radio wave intensity sensors D1 and D2 { By comparing Ave (R _{1f, N} ) + Ave (R _{2r, N} )} with the sum of the average values of other radio wave strengths {Ave (R _{1r, N} ) + Ave (R _{2f, N} )} The wheel is being judged. Specifically, when the first predetermined number of receptions N ₁ , the difference (see equation (5)) is compared with the N ₁ reception radio field intensity average values, and if the difference is equal to or greater than the first determination value D _1. if, as a result makes a determination of the front wheel-rear wheel from pending determination is less than D _1, then when N ₁ is greater than a second predetermined number of times of receiving N _2, radio intensity average value of N ₂ times of reception Thus, the difference between them (see equation (6)) is compared, and if it is equal to or larger than the second determination value D ₂ which is smaller than D _1, the determination of the front and rear wheels is performed from this result. Thus, also in the present embodiment, the determination is made in two stages, and the determination is made up to the determination value D ₂ of the difference in the received radio field intensity average value for N ₂ times at the second predetermined number of reception times N ₂ . Therefore, it is possible to determine the mounting position of the tire as early as possible while maintaining the accuracy of the determination.

In the first and second embodiments described above, the determination stage is set to two stages and the determination of the front and rear wheels is performed. However, in the present invention, the determination stage may be further divided into three or more stages. Assuming that the third predetermined number of receptions in the third stage is N ₃ , and the _third determination value that is the determination value of the difference in radio field intensity average value for N ₃ receptions is D ₃ , for example, the first predetermined number of receptions N ₁ is 10 times, the first determination value D ₁ is 3 dB, the second predetermined reception number N ₂ is 15, the second determination value D ₂ is 2 dB, the third predetermined reception number N ₃ is 20, and the third determination value D ₃ is It may be set to 0 dB.

In the present embodiment, the radio wave intensity sensors D2 shown in FIG. 4 of the second embodiment are further increased, and the respective radio wave intensity sensors are provided in the vicinity of the respective wheels. For example, referring to FIG. 2, in the case of a four-wheel vehicle, in the vicinity of the front wheels T1 _L , T1 _R , front wheels T2 _L , T2 _R , that is, tire sensors S1 _L , S1 _R , S2 _L , S2 _R. Is a configuration in which four radio wave intensity sensors are provided in the vicinity of. In the case of this embodiment, it is desirable that each radio wave intensity sensor detects the radio wave intensity of the signal from the tire sensor and also detects a status signal such as an ID number and an air pressure value from the signal. With this configuration, in this embodiment, in one radio wave intensity sensor, a tire sensor received at the maximum radio wave intensity is detected, and the detected tire sensor is in the vicinity of the arrangement position of the radio wave intensity sensor. It is determined that the tire is attached to the tire.

  Here, a specific determination procedure in the present embodiment will be described. Also in the present embodiment, as in the first to third embodiments, the determination process is performed by providing stages to the number of radio wave intensity data to be acquired and the determination value, thereby maintaining the determination accuracy as early as possible. The tire mounting position is determined.

Specifically, when one arbitrary radio wave intensity sensor receives a signal from each tire sensor for the first predetermined number N ₁ times, the signal intensity of the signal from each tire sensor is each the average value of the first predetermined number N ₁ times, among all the average values obtained, when the absolute value of the difference between the maximum mean value and the other average value of the first determination value D ₁ or more, It is determined that the tire sensor that has transmitted the signal having the maximum average value is attached to the tire in the vicinity of the position of the arbitrary radio wave intensity sensor.

If the difference between the maximum average value and the other average value is less than the first determination value D ₁ , the arbitrary radio wave intensity sensor outputs the signal from each tire sensor to the second greater than the first predetermined number N ₁ . When receiving a predetermined number N ₂ times, the signal intensity of the signal from each tire sensor is determined for an average value of the second predetermined number of times N ₂ at any radio wave intensity sensor, and among all the obtained average values, If the absolute value of the difference between the maximum average value and the other average values is equal to or greater than the second determination value D _{2 that is} smaller than the first determination value D _1, the tire sensor that has transmitted the signal that is the maximum average value is arbitrarily selected It is determined that the tire is mounted on a tire near the position of the radio wave intensity sensor. The state of each tire is monitored by a state signal such as an air pressure value for the determined tire.

  Also in the present embodiment, similarly to the fourth embodiment, the number of radio wave intensity sensors D2 is further increased, and each radio wave intensity sensor is provided in the vicinity of each wheel. Also in the present embodiment, it is desirable that each radio wave intensity sensor detects the radio wave intensity of the signal from the tire sensor and the status signal such as the ID number and the air pressure value from the signal. Using this configuration, in this embodiment, a plurality of radio wave intensity sensors detect a radio wave intensity sensor that maximizes the signal intensity of a signal transmitted from one tire sensor, and the tire sensor detects It is determined that the tire is mounted on a tire near the position where the radio wave intensity sensor is arranged.

  As in the first to third embodiments, the specific determination procedure in the present embodiment is also performed by determining the number of radio wave intensity data to be acquired and the determination value while performing the determination process, while maintaining the accuracy of the determination, The tire mounting position is determined as early as possible.

Specifically, when each radio wave intensity sensor receives a signal from one arbitrary tire sensor for the first predetermined number N ₁ times, the signal intensity of the signal from the arbitrary tire sensor is each the average value of the first predetermined number N ₁ times, among all the average values obtained, when the absolute value of the difference between the maximum mean value and the other average value of the first determination value D ₁ or more, It is determined that an arbitrary tire sensor is attached to a tire in the vicinity of the position of the radio wave intensity sensor that has received the signal having the maximum average value.

When the difference between the maximum average value and the other average value is less than the first determination value D ₁ , each radio wave intensity sensor outputs a signal from an arbitrary tire sensor that is greater than the first predetermined number N ₁ . When receiving a predetermined number N ₂ times, for each signal intensity of the signal from any tire sensor, an average value for the second predetermined number N ₂ of each radio wave intensity sensor is obtained, and among all the obtained average values, When the absolute value of the difference between the maximum average value and the other average values is equal to or greater than the second determination value D _{2 that is} smaller than the first determination value D ₁ , any tire sensor receives a signal that is the maximum average value It is determined that the tire is mounted on a tire near the position of the radio field intensity sensor. And the state of each tire is monitored by the state signal with respect to the determined tire.

  The present invention is applied to a tire air pressure monitoring system that monitors the tire air pressure of a vehicle. However, the present invention is applicable to any object that wirelessly monitors an object in a severe noise environment. Is possible.

It is a schematic block diagram which shows an example of embodiment of the tire pressure monitoring system which concerns on this invention, (a) shows arrangement | positioning of a main receiver and a tire sensor, (b) shows the structure of a main receiver. It is. It is a figure explaining the advancing direction of a vehicle and the rotation direction of a tire sensor. It is a flowchart which shows the position recognition procedure of the tire when a field intensity sensor is arrange | positioned in one place ahead of a vehicle body. It is a schematic block diagram which shows another example of embodiment of the tire pressure monitoring system which concerns on this invention, (a) shows arrangement | positioning of a main receiver, a tire sensor, and a field intensity sensor, (b) is main reception. (C) shows still another configuration example of the main receiver. It is a flowchart which shows the position recognition procedure of the tire when a field intensity sensor is arrange | positioned in two places.

Explanation of symbols

1, 1A, 1B main receiver (receiving means, first receiving means)
D2 radio wave intensity sensor (second receiving means)
3, 8 Antenna 4 Signal receiving unit 5, 9 Strength detection unit 6 Calculation unit (signal processing means)
7 Warning light 10 Vehicle S1, S2 Tire sensor (transmission means)
T1 front wheel T2 rear wheel

Claims (5)

Transmitting means that is provided in each tire of the vehicle and transmits an identification signal that can individually identify each tire, and a state signal that indicates the state of each tire including air pressure;
One or a plurality of receiving means provided in a vehicle, for receiving a signal from the transmitting means, detecting the identification signal and the state signal, and detecting a signal strength of the signal;
Signal processing means for inputting the identification signal, the state signal and the signal strength detected by the receiving means;
The signal processing means includes
When the receiving means receives a signal from each transmitting means for a first predetermined number of times, the signal intensity of a signal from any transmitting means and the signal strength of a signal from another transmitting means is a first predetermined value at the receiving means. Find the average value for each number of times,
When the absolute value of the difference between the average values is equal to or greater than the first determination value, the position of the receiving unit and the average value of the signal strengths of other transmitting units relative to the average value of the signal strength of any transmitting unit Based on the size, identify the position of the tire with any transmission means,
When the absolute value of the difference between the average values is less than the first determination value, when the receiving unit receives a signal from each transmitting unit for a second predetermined number of times greater than the first predetermined number of times, any transmission is performed. For each of the signal strength of the signal from the means and the signal strength of the signal from the other transmission means, obtain an average value for the second predetermined number of times at the receiving means,
When the absolute value of the difference between the average values is equal to or greater than a second determination value smaller than the first determination value, the position of the reception unit and the other transmission units with respect to the average value of the signal strength for any transmission unit Based on the magnitude of the average value of the signal strength, specify the position of the tire where any transmission means is mounted,
A tire pressure monitoring system for monitoring the state of each tire based on the state signal for the identified tire. In the tire pressure monitoring system according to claim 1,
The receiving means is provided on the front or rear side of the vehicle,
The transmission means transmits rotation direction information indicating the rotation direction of each tire as a state signal of each tire,
The signal processing means includes
Based on the rotation direction information and the traveling direction information indicating the traveling direction of the vehicle, specify whether the transmission means is mounted on the left side or the right side,
When the reception means receives a signal from each transmission means mounted on the same side for the first predetermined number of times, the signal strength of the signal from one transmission means on the same side is the signal strength from the other transmission means on the same side. For the signal strength, an average value for the first predetermined number of times in the receiving means is obtained,
When the absolute value of the difference between the average values is greater than or equal to the first determination value, if the average value of the signal strength for the other transmission means is smaller than the average value of the signal strength for one transmission means, It is determined that the transmission means is attached to a tire in front of or behind the vehicle,
When the absolute value of the difference between the average values is less than the first determination value, the receiving unit receives a signal from each transmitting unit on the same side for a second predetermined number of times greater than the first predetermined number of times. , For the signal strength of the signal from the other transmitting means on the same side as the signal strength of the signal from one transmitting means on the same side, respectively, obtain an average value for the second predetermined number of times in the receiving means,
When the absolute value of the difference between the average values is equal to or greater than a second determination value that is smaller than the first determination value, the average of the signal strength for the other transmission means with respect to the average value of the signal strength for one transmission means If the value is small, it is determined that one of the transmission means is attached to a tire in front of or behind the vehicle. Transmitting means that is provided in each tire of the vehicle and transmits an identification signal that can individually identify each tire, and a state signal that indicates the state of each tire including air pressure;
A first receiving means provided on a vehicle for receiving a signal from the transmitting means, detecting the identification signal and the state signal, and detecting a signal intensity of the signal;
The first receiving means is installed away from the vehicle in the front-rear direction, and the second receiving means detects the signal strength of the signal from the transmitting means,
The signal intensity detected by the first receiving means, the signal intensity detected by the second receiving means, the identification signal and the status signal detected by the first receiving means are inputted, and the first receiving means And signal processing means configured integrally with
The transmission means transmits rotation direction information indicating the rotation direction of each tire as a state signal of each tire,
The signal processing means includes
Based on the rotation direction information and the traveling direction information indicating the traveling direction of the vehicle, specify whether the transmission means is mounted on the left side or the right side,
When the first receiving means and the second receiving means receive a signal from each transmitting means for a first predetermined number of times, the first receiving means and the second receiving means with respect to the signal strength of the signal from each transmitting means. Each average value for the first predetermined number of times at
Arbitrary one of the first predetermined number of times at the first receiving means for the transmitting means on the same side and the first predetermined number of times at the second receiving means for the other one transmitting means on the same side The sum of the average values of the minutes, the average value for the first predetermined number of times at the first receiving means of the other one transmitting means, and the first predetermined value at the second receiving means of the arbitrary one transmitting means When the absolute value of the difference between the sums of the average values for the number of times is equal to or greater than the first determination value, the transmission unit that has the radio field intensity at the first reception unit out of the combination with the larger sum of the average values is the above The first receiving means side determines that the transmitting means having the radio wave intensity at the second receiving means is disposed on the second receiving means side,
When the absolute value of the difference between the sums of the two sets of average values is less than the first determination value, the first receiving means and the second receiving means send the signals from the transmitting means to the first When receiving a second predetermined number of times greater than one predetermined number of times, an average value for the second predetermined number of times at the first receiving means and the second receiving means is obtained for the signal strength of the signal from each transmitting means,
Arbitrary one of the second predetermined number of times at the first receiving means for the transmitting means on the same side and the second predetermined number of times at the second receiving means for the other one transmitting means on the same side A sum of average values of minutes, an average value of a second predetermined number of times at the first receiving means of the other one transmission means, and a second predetermined value at the second receiving means of any one of the transmission means When the absolute value of the difference between the sums of the average values for the number of times is equal to or greater than the second determination value, the transmission unit that is the radio wave intensity at the first reception unit out of the combination with the larger sum of the average values is the above The first receiving means side determines that the transmitting means having the radio wave intensity at the second receiving means is disposed on the second receiving means side,
A tire pressure monitoring system for monitoring the state of each tire based on the state signal for the identified tire. Transmitting means that is provided in each tire of the vehicle and transmits an identification signal that can individually identify each tire, and a state signal that indicates the state of each tire including air pressure;
A plurality of receiving means provided near each wheel of the vehicle, receiving a signal from the transmitting means, detecting the identification signal and the status signal, and detecting the signal strength of the signal;
Signal strength detected by the plurality of receiving means, signal processing means to which the identification signal and the status signal are input,
The signal processing means includes
When one arbitrary receiving unit receives a signal from each transmitting unit for a first predetermined number of times, the signal intensity of the signal from each transmitting unit is averaged for the first predetermined number of times by the arbitrary receiving unit. Seeking each
The transmission means that has transmitted the signal that is the maximum average value when the absolute value of the difference between the maximum average value and the other average values is equal to or greater than the first determination value among all the average values that are obtained, It is determined that it is attached to a tire near the position of the receiving means,
When the absolute value of the difference between the maximum average value and the other average value is less than the first determination value, the arbitrary reception unit outputs a signal from each transmission unit more than the first predetermined number of times. When the second predetermined number of times is received, the average value for the second predetermined number of times at the arbitrary receiving means is obtained for the signal strength of the signal from each transmitting means,
Among all the obtained average values, when the absolute value of the difference between the maximum average value and other average values is equal to or larger than the second determination value smaller than the first determination value, a signal that becomes the maximum average value is transmitted. Determining that the transmission means is attached to a tire near the position of the arbitrary reception means,
A tire pressure monitoring system for monitoring the state of each tire based on the state signal for the determined tire. Transmitting means that is provided in each tire of the vehicle and transmits an identification signal that can individually identify each tire, and a state signal that indicates the state of each tire including air pressure;
A plurality of receiving means provided near each wheel of the vehicle, receiving a signal from the transmitting means, detecting the identification signal and the status signal, and detecting the signal strength of the signal;
Signal strength detected by the plurality of receiving means, signal processing means to which the identification signal and the status signal are input,
The signal processing means includes
When each receiving means receives a signal from one arbitrary transmitting means for the first predetermined number of times, the average value for the first predetermined number of times at each receiving means is obtained for the signal strength of the signal from the arbitrary transmitting means. Seeking each
Among all the obtained average values, when the absolute value of the difference between the maximum average value and other average values is equal to or greater than the first determination value, the arbitrary transmission means receives a signal that has the maximum average value. It is determined that the tire is mounted on a tire near the position of the receiving means.
When the absolute value of the difference between the maximum average value and the other average value is less than the first determination value, each reception unit outputs a signal from the arbitrary transmission unit more than the first predetermined number of times. When the second predetermined number of times is received, the average value for the second predetermined number of times at each receiving means is obtained for the signal strength of the signal from the arbitrary transmitting means,
Among all the obtained average values, when the absolute value of the difference between the maximum average value and other average values is equal to or larger than the second determination value smaller than the first determination value, the arbitrary transmission means is set to the maximum It is determined that the tire is mounted in the vicinity of the position of the receiving means that has received the average signal.
A tire pressure monitoring system for monitoring the state of each tire based on the state signal for the determined tire.

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