JP2015074387A - Tire position determination system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire position determination system that can complete the determination of tire positions in a short time.SOLUTION: A tire air pressure detector 4 enables electric wave transmission at a transmission timing of electric waves which arrive periodically, makes a plurality of transmissions of electric waves for auto location every time to take a specified detector angle in this time zone, and uses this plurality of transmissions as one set to repeat this set by a plurality of times. A TPMS (Tire Pressure Monitoring System) receiver 12 reads the number of pulses of an axle rotation detection part 21 every time to receive electric waves for auto location to calculate pulse mean values of axle rotation amounts every time one set is transmitted by a plurality of times. Further, the electric waves for auto location are linked with axles 18a-18d by comparing forward and backward pulse mean values, thereby specifying tire positions.

Description

  The present invention relates to a tire position determination system that determines the position of each tire in a vehicle.

  Conventionally, as disclosed in Patent Document 1, a tire position determination system (auto-location function) that automatically determines a tire position necessary for air pressure monitoring of each tire is well known. The system of Patent Document 1 includes a first sensor (4a to 4d) provided on a wheel (2a to 2d) and four second sensors (5a to 5d) associated with specific positions in the vehicle. And a measurement system (3) for locating the wheel. The first sensor transmits signals (S4a to S4d) indicating the wheel position to the measurement system. The second sensor measures the angular position of the wheel and outputs the measured values (S5a to S5d). The measurement system determines the phase position (W1a to W3a, W1b to W3b) of the signal of the first sensor related to the measurement value, and the phase position stays within the predetermined allowable range (WTa, WTb) in the predetermined monitoring period. The wheel position is determined by checking whether or not.

Special table 2011-527971 gazette

  By the way, in the case of Patent Document 1, since the tolerance is inevitably generated in the second sensor, it is necessary to increase WTa and WTb according to the tolerance. As a result, there is a problem that the position determination cannot be completed in a short time.

  The objective of this invention is providing the tire position determination system which can complete determination of a tire position in a short time.

  A tire position determination system for solving the above problems includes a tire pressure detector attached to each tire, and a receiver that receives a tire pressure signal transmitted from the tire pressure detector and monitors the tire pressure. The tire pressure detector includes a detector angle monitoring unit for monitoring that the tire pressure detector takes a specific detector angle, and the specific detector angle. An operation of transmitting a radio wave a plurality of times, and a radio wave transmission control unit that repeats the operation a plurality of times with a specific time interval as a set, and the receiver receives an axle each time the radio wave is received. An axle rotation amount reading unit that reads an axle rotation amount from an axle rotation detection unit that can detect the rotation amount of the vehicle, and a plurality of the axle rotation amounts for each set are averaged, and based on these average values And a position determination unit determines the ear position.

  According to this configuration, when the tire rotates, the tire air pressure detector transmits a radio wave (ID radio wave) every time a specific detector angle is taken at a certain timing, thereby transmitting the radio wave transmission a plurality of times. The operation is repeatedly executed at specific time intervals. Each time the receiver receives a radio wave from the tire pressure detector, the receiver reads the axle rotation amount of the axle rotation detection unit and calculates the average value of the axle rotation amount for each set of transmissions. Then, by comparing the average values before and after, the radio wave ID and the axle are linked to identify the tire position. By the way, when the tire pressure detector transmits a radio wave at a specific detector angle, there is a possibility that the transmission timing varies due to a tolerance or the like. This leads to variations in the amount of axle rotation detected on the receiver side, and as a result, the tire position cannot be completed early. However, if the determination is made by calculating the average value of the axle rotation amount as in this configuration, the variation in the transmission timing of the tire air pressure detector is mitigated, and the possibility that the axle rotation amount converges to a valid value is high. Become. Therefore, it is advantageous to complete the determination of the tire position in a short time.

  In the tire position determination system, the radio wave transmission control unit performs radio wave transmission operation with a minute time as a time zone in which radio wave transmission is possible, and when the minute time has passed, the radio wave transmission control unit performs radio wave transmission for a time longer than the minute time. It is preferable that the radio wave transmission necessary for the tire position determination is performed by repeating the above operation of performing the radio wave transmission operation in the minute time again after the waiting time has elapsed. According to this configuration, the time period during which the tire pressure detector must transmit radio waves can be shortened, which contributes to power saving of the power source of the tire pressure detector.

  In the tire position determination system, the average value calculation of the axle rotation amount is performed by uniformly adding an offset value to each of the first calculation for calculating the average value of the plurality of axle rotation amounts and the plurality of axle rotation amounts. Then, the axle rotation amount to which the offset value is added is modulo calculated so as to form a modulus with a counter value for counting the axle rotation amount, and an average of a plurality of calculated modulo values is obtained, and the offset is calculated from the result. A second calculation for subtracting a value, and the position determination unit includes a first calculation when a difference between a minimum and a maximum among a plurality of the modulo values obtained in the calculation process of the second calculation is larger than the offset value. The calculation result of the calculation is an average value, and when the difference between the minimum and maximum is less than or equal to the offset value, the calculation result of the second calculation is preferably an average value. According to this configuration, it is possible to calculate the average value with high accuracy, which is advantageous for ensuring the accuracy of tire position determination.

  In the tire position determination system, it is preferable that the offset value is half of the modulus of the counter for counting the axle rotation amount or a value close to the half. According to this configuration, it is possible to accurately calculate the average value of the axle rotation amount by using a half value of the counter or a value close to half.

  In the tire position determination system, the specific detector rotation angle is preferably an angle when the tire air pressure detector takes a pole position in the tire rotation direction. According to this configuration, the position of the pole of the tire air pressure detector is easily detected by, for example, the gravity detector, which is advantageous for easily detecting a specific detector angle.

  According to the present invention, in the tire position determination system, the determination of the tire position can be completed in a short time.

The block diagram of the tire position determination system of one Embodiment. Explanatory drawing which shows the component of gravity component force detected with a tire air pressure detector. The communication sequence diagram of a tire pressure detector. The plot figure which shows the pulse number change of two axles when a certain ID is received with the receiver. Explanatory drawing which shows the electromagnetic wave transmission timing of a tire pressure detector. Explanatory drawing of how to obtain | require a pulse average value. Explanatory drawing which shows the example of calculation of a pulse average value. The plot figure which shows the pulse number change of each axle when ID1-ID4 is received with the receiver.

Hereinafter, an embodiment of a tire position determination system will be described with reference to FIGS.
As shown in FIG. 1, the vehicle 1 includes a tire pressure monitoring system (TPMS: Tire Pressure Monitoring System) 3 that monitors tire pressures and the like of the tires 2 (2a to 2d). The tire pressure monitoring system 3 has a tire pressure detector 4 (4a to 4d: also referred to as a tire valve) attached to each tire 2a to 2d, and the tire pressure detected by the tire pressure detectors 4a to 4d is converted into the tire pressure. By transmitting the air pressure signal Stp to the vehicle body 5, the air pressure of the tires 2 a to 2 d in the vehicle body 5 is directly monitored.

  The tire pressure detector 4 is generated in the controller 6 that controls the operation of the tire pressure detector 4, the pressure detector 7 that detects the tire pressure, the temperature detector 8 that detects the tire temperature, and the tire pressure detector 4. A gravity detector 9 that detects the gravity to be transmitted, and a transmission antenna 10 that enables radio transmission from the tire pressure detector 4. In the memory 11 of the controller 6, a tire ID (valve ID) is written and stored as a unique ID of each tire pressure detector 4. The pressure detector 7 is preferably a pressure sensor, for example. The temperature detector 8 is preferably a temperature sensor, for example. The gravity detector 9 is preferably an acceleration sensor (G sensor), for example. The transmitting antenna 10 preferably transmits, for example, a radio wave in the UHF (Ultra High Frequency) band.

  The vehicle body 5 includes a receiver (hereinafter referred to as a TPMS receiver) 12 that monitors the air pressure of the tires 2a to 2d by receiving the tire pressure signals Stp transmitted from the tire pressure detectors 4a to 4d. The TPMS receiver 12 includes a tire pressure monitoring ECU (Electronic Control Unit) 13 that controls the operation of the TPMS receiver 12 and a receiving antenna 14 that enables the TPMS receiver 12 to receive radio waves. In the memory 15 of the tire pressure monitoring ECU 13, the IDs of the tire pressure detectors 4a to 4d are written and stored in a state where the tire positions are associated with each other. For example, the right front tire pressure detector 4a is ID1, the left front tire pressure detector 4b is ID3, the right rear tire pressure detector 4c is ID4, and the left rear tire pressure detector 4d is ID2. For example, a display unit 16 installed on an in-vehicle instrument panel or the like is connected to the TPMS receiver 12.

  The tire pressure detector 4 confirms that the tire 2 has entered the rotation state based on the detection signal from the gravity detection unit 9, or at regular or irregular intervals with a predetermined time interval. Is transmitted from the transmitting antenna 10 to the vehicle body 5. The tire pressure signal Stp is preferably a signal including, for example, a tire ID, pressure data, temperature data, and the like. Whether or not the tire 2 has entered the rotating state is determined by confirming whether or not the output of the gravity detection unit 9 has changed. Further, even when it is determined that the tire 2 is not rotating, the tire air pressure signal Stp is transmitted at the same or longer interval than that at the time of rotation.

  When the tire pressure signal Stp transmitted from the tire pressure detectors 4a to 4d is received by the receiving antenna 14, the TPMS receiver 12 checks the tire ID in the tire pressure signal Stp, and if this tire ID check is established, Check the pressure data in the tire pressure signal Stp. If the pressure value is equal to or lower than the low pressure threshold, the TPMS receiver 12 displays the low pressure tire on the display unit 16 in association with the tire position. The TPMS receiver 12 performs the tire pressure determination for each tire pressure signal Stp received, and monitors the tire pressures of the tires 2a to 2d.

  The tire pressure monitoring system 3 includes a tire position determination function (tire position determination system 17) that performs so-called auto-location that automatically determines at which position in the front, rear, left and right the tires 2a to 2d are attached. The tire position determination system 17 transmits radio waves from the tire pressure detectors 4a to 4d when the tire pressure detectors 4a to 4d take a specific position in the tire rotation direction, and the TPMS receiver 12 receives the radio waves. The position of the tires 2a to 2d is determined using the principle of confirming the rotation amount of the axle 18 (18a to 18d).

  FIG. 2 illustrates a gravity component detected by the gravity detection unit 9. The gravity detector 9 detects a gravity force Gr in the axle direction (tire radial direction) with respect to the gravity G as the gravity applied to the tire air pressure detector 4. When the tire air pressure detector 4 is located at the peak (position “12 o'clock” or “6 o'clock” on the paper surface) in the rotation trajectory of the tire 2, the gravitational component force Gr is “−1G unless the centrifugal force is taken into consideration. "Or" + 1G ". Incidentally, when the tire air pressure detector 4 is positioned at “3 o'clock” and “9 o'clock” on the paper surface in the rotation locus of the tire 2, the gravitational component force Gr is “0 G” unless centrifugal force is taken into consideration.

  FIG. 3 shows an outline of a communication sequence of radio wave transmission in the tire pressure detector 4. The tire pressure detector 4 takes a transmission pattern in which a transmission timing t at which radio wave transmission is possible repeatedly appears at a certain period. “T1”, which is a minute time after the transmission timing t arrives, is set to a time zone in which radio wave transmission is possible. The time width T1 is preferably “1 second”, for example. Radio wave transmission is repeated at “T2”, which is a cycle in which the transmission timing t appears. This time interval T2 is a time zone in which radio wave transmission is on standby, and for example, “30 seconds” is preferable. As described above, the tire pressure detector 4 repeatedly performs an operation of transmitting radio waves for 1 second with an interval of 30 seconds.

  As shown in FIG. 1, the tire air pressure detector 4 includes a detector angle monitoring unit 19 that monitors that the tire air pressure detector 4 takes a specific detector angle, and a specific detection at a radio wave transmission timing t. An operation of transmitting a radio wave from the tire pressure detector 4 at a unit angle is performed a plurality of times, and the radio wave transmission control unit 20 is configured to repeat this operation a plurality of times with a specific time interval as one set. These are preferably provided in the controller 6, for example.

  The specific detector angle is preferably an angle at which the tire air pressure detector 4 takes a pole position in the tire rotation direction, for example. The positions of the poles are, for example, “12 o'clock” position, “3 o'clock” position, “6 o'clock” position, and “9 o'clock” position. The specific detector angle is preferably an angle at which the tire pressure detector 4 takes a peak position in the tire rotation direction, for example. The peak position refers to, for example, a “12 o'clock” position and a “6 o'clock” position.

  The radio wave transmission control unit 20 performs a radio wave transmission operation using a minute time T1 (about 1 second) as a time zone in which radio wave transmission is possible, and after the time zone T1, a time T2 (about about 2 hours) that is sufficiently longer than the minute time. For 30 seconds), radio wave transmission is not executed, and after the elapse of this waiting time, the radio wave transmission for auto-location is executed by repeating the above-described operation of executing the radio wave transmission operation again. Specifically, the radio wave transmission control unit 20 causes radio waves to be transmitted from the transmission antenna 10 every time the gravitational component force Gr takes a peak within the time width T1 at the transmission timing t at which radio wave transmission is possible. The radio wave transmission control unit 20 repeatedly executes this operation as one set at a time interval T2. The radio wave for auto-location may be a signal including at least the tire ID, and may be the above-described tire pressure signal Stp or any other radio wave.

  The TPMS receiver 12 rotates the axle from the axle rotation detector 21 (21a to 21d) that can detect the amount of rotation of the axle 18 (18a to 18d) every time it receives a radio wave for autolocation from the tire pressure detector 4. An axle rotation amount reading unit 22 that reads the amount, and a position determination unit 23 that averages a plurality of read axle rotation amounts for each set of radio wave transmission and determines the tire position based on these average values Pave. The axle rotation amount reading unit 22 and the position determination unit 23 are preferably provided, for example, in the tire air pressure monitoring ECU 13.

  The axle rotation detection units 21a to 21d are provided on the axles 18a to 18d, and for example, an ABS (Antilock Brake System) sensor may be used. In this case, the axle rotation amount is preferably the number of pulses Px, for example. The axle rotation detection units 21a to 21d detect, for example, a plurality of (for example, 48) teeth provided on the axles 18a to 18d by the sensing unit on the vehicle body 5 side, thereby generating a rectangular wave-shaped pulse signal Spl as the axle rotation amount. The data is output to the reading unit 22. The axle rotation amount reading unit 22 detects 96 pulses (count value: 0 to 95) per tire rotation if both the rising edge and the falling edge of the pulse signal Spl are detected.

  When the position determination unit 23 receives a radio wave transmitted a plurality of times at the peak position from the tire pressure detector 4 within the time width T1, the position determination unit 23 averages a plurality of pulse numbers Px obtained by the plurality of receptions. The average value (pulse average value) Pave of the number of pulses is calculated. The position determination unit 23 calculates the pulse average value Pave for each set of transmission of radio waves by the tire air pressure detector 4 and compares the pulse average values Pave to thereby determine the positions of the tires 2a to 2d. Determine.

  Next, operation | movement of the tire position determination system 17 is demonstrated using FIGS. The TPMS receiver 12 switches to the auto location mode in accordance with a predetermined cycle, and executes tire position determination.

  First, FIG. 4 illustrates the tire position determination principle of this example. Each of the tires 2a to 2d (axles 18a to 18d) has a structure in which the tires 2a to 2d rotate independently to allow turning such as a curve. As a result, before and after turning, the timing at which the tire pressure detectors 4a to 4d reach the peak position changes, so the radio wave transmission timing of the tire pressure detectors 4a to 4d also changes. That is, when an axle 18 corresponding to the same ID is seen before and after turning, the measured pulse number Px converges to a predetermined value, whereas the axle 18 does not correspond to the ID. For example, the measured pulse number Px changes to another value. Based on this principle, this example determines the tire position.

  As shown in FIG. 5, the tire pressure detector 4 can transmit a radio wave for a time width T1 (for example, 1 second) when a radio wave transmission timing t1 arrives. At this time, the radio wave transmission control unit 20 transmits a radio wave from the transmission antenna 10 every time it is detected that the tire air pressure detector 4 is positioned at the peak position in the tire rotation direction. Here, at the transmission timing t1, the radio wave is transmitted three times during the time width T1. Each tire pressure detector 4 performs a plurality of radio wave transmissions during a transmittable time zone when its own transmission timing t1 arrives.

  By the way, even if the vehicle 1 travels at a low speed of about 10 km / h, the tire 2 rotates about three times in one second. Therefore, if the time width T1 capable of radio wave transmission in the tire pressure detector 4 is set to “1 second”, even if the vehicle 1 travels at a low speed, the tire air pressure detector 4 transmits radio waves at least three times. It is possible. Of course, as the vehicle speed increases, the radio wave transmitted from the tire pressure detector 4 inevitably increases.

  When the time period T1 has elapsed, the tire pressure detector 4 enters a standby state for radio wave transmission again, and does not perform radio wave transmission for a time interval T2 (for example, 30 seconds) until the next radio wave transmission. When the transmission timing t2 of the radio wave arrives, the tire pressure detector 4 can transmit the radio wave again for a time width T1 (for example, 1 second). Also at this time, the radio wave transmission control unit 20 transmits radio waves from the transmission antenna 10 every time it is detected that the tire air pressure detector 4 is located at the peak position in the tire rotation direction. In the figure, the radio wave is transmitted three times during the time interval T1 even at the transmission timing t2.

  As shown in FIG. 6, if the TPMS receiver 12 is in the auto location mode, the axle rotation amount reading unit 22 receives the radio wave transmitted from the tire pressure detector 4 at the transmission timing t1, t2. Each time it is received by the machine 12, the number of pulses Px of each axle rotation detection unit 21a to 21d is read. In the case of the figure, at a predetermined ID at the transmission timing t1, the number of pulses Px of a certain axle rotation detection unit 21 is illustrated, Pa1 at the first reception, Pa2 at the second reception, and at the third reception. Shown as Pa3. These Pa1 to Pa3 vary somewhat due to, for example, an error in radio wave transmission timing caused by the tolerance of the tire pressure detector 4.

  When receiving ID1 at the transmission timing t1, the axle rotation amount reading unit 22 reads the pulse number Px of each axle rotation detection unit 21a to 21d every time ID1 is received. Similarly, the axle rotation amount reading unit 22 reads the pulse number Px of each axle rotation detection unit 21a to 21d every time ID2 to ID4 are received at the transmission timing t1.

  The position determination unit 23 calculates an average value (pulse average value) for each of the axle rotation detection units 21a to 21d in the plurality of pulse numbers Px read from each of the axle rotation detection units 21a to 21d when receiving ID1 at the transmission timing t1. Pave-A is calculated. That is, as the pulse average value Pave-A when ID1 is received at the transmission timing t1, a total of four average values are calculated for each of the right front axle 18a, the left front axle 18b, the right rear axle 18c, and the left rear axle 18d. . Similarly, the position determination unit 23 calculates a pulse average value Pave-A at the transmission timing t1 for each of the axle rotation detection units 21a to 21d for ID2 to ID4. A total of 16 pulse average values Pave-A at the transmission timing t1 are calculated for each of ID1 to ID4. The position determination unit 23 holds the calculated pulse average value Pave-A of each ID1 to ID4 in the memory 15 as the pulse average of each axle 18a to 18d at the transmission timing t1.

  By the way, the pulse number Px is a number that modulo the count value from 0 to 95. Therefore, if the count value varies in the vicinity of, for example, 0 and 95, for example, “0”, “95”, “1”, “94”, “0”,..., And the pulse average value Pave is obtained by a simple arithmetic average. If -A is calculated, it converges to about "48". That is, actually, although the pulse average value Pave-A has to take a numerical value such as “0.5” or “94.8”, it takes a completely different value.

  Therefore, the position determination unit 23 performs the following two types of calculations, the first calculation and the second calculation, and determines the pulse average value Pave-A based on the results. In the present example, the first calculation is a calculation in which the number of pulses Px (count value) to be calculated is arithmetically calculated as it is to obtain an average. In the second calculation, all the pulse numbers Px (count value) are once added with an offset value to calculate each modulo value, an arithmetic average of these modulo values is calculated, and the offset value is subtracted from the result. It is. The offset value is preferably, for example, half of the modulus of the counter that counts the axle rotation amount (here, “48”). Then, in the plurality of modulo values calculated in the calculation process of the second calculation, if the difference between the minimum and maximum is larger than the offset value (“48” half of the modulus), the calculation result of the first calculation is adopted, and the offset value If it is less than (“48” half of the modulo), the calculation result of the second calculation result is adopted.

  FIG. 7 shows specific processing for calculating the pulse average value Pave. Assume that the count value of the pulse number Px is, for example, “3”, “44”, “6”, “89”, “56”, “91”. In this case, the calculation result of the first calculation is “289/6 = 48.17”. Further, the modulo value of “3” is “51 (≡3 + 48)”, the modulo value of “44” is “92 (≡44 + 48)”, the modulo value of “6” is “54 (≡6 + 48)”, “89” The modulo value of “41” (≡89 + 48), the modulo value of “56” is “8≡ (56 + 48)”, and the modulo value of “91” is “43 (≡91 + 48)”. In this case, since the difference between the minimum and maximum among the plurality of calculated modulo values, here, the difference between “92” and “8” is greater than “48”, the first calculation is adopted as the pulse average calculation. That is, “289/6 = 48.17”, which is the calculation result of the first calculation, is set as the pulse average value Pave-A.

  Further, it is assumed that the count value of the pulse number Px is, for example, “2”, “1”, “3”, “95”, “2”, “3”. At this time, when the first calculation is performed, the calculation result is “106/6 = 17.67”. In the second calculation, first, the modulo value of each count value is calculated. That is, the modulo value of “2” is “50 (≡2 + 48)”, the modulo value of “1” is “49 (≡1 + 48)”, the modulo value of “3” is “51 (≡3 + 48)”, “95”. The modulo value of “47” (≡95 + 48), the modulo value of “2” is “50 (≡2 + 48)”, and the modulo value of “3” is “51 (≡3 + 48)”. Since the difference between the minimum and maximum modulo values, here, the difference between “51” and “47” is “48” or less, the second calculation is adopted as the pulse average calculation. Subsequently, an arithmetic average of a plurality of calculated modulo values is taken, and the calculation result is “298/6 = 49.67”. Then, the calculation result “1.67 (= 49.67-48)” obtained by subtracting “48” from the calculated average is set as the pulse average value Pave-A.

  Incidentally, when the count value of the pulse number Px is, for example, “24”, “20”, “15”, “44”, “35”, “29”, the second calculation is adopted, and the pulse average value Pave− “27.83” is calculated as A. When the count value of the pulse number Px is, for example, “1”, “92”, “3”, “1”, “88”, “94”, the second calculation is adopted, and the pulse average value Pave− “94.67” is calculated as A.

  The axle rotation amount reading unit 22 also calculates the number of pulses Px of each axle rotation detection unit 21a to 21d every time the radio wave transmitted from the tire pressure detector 4 is received by the TPMS receiver 12 at the next transmission timing t2. Read. In the case of the figure, the traveling speed of the vehicle 1 is slightly increased, and there are four receptions. In the predetermined ID at the transmission timing t2, the number of pulses Px at the first reception is Pb1, and the pulses at the second reception. The number Px is Pb2, the number of pulses at the third reception is Pb3, and the number of pulses at the fourth reception is Pb4. These Pb1 to Pb4 also vary somewhat due to, for example, an error in radio wave transmission timing caused by the tolerance of the tire pressure detector 4.

  When receiving ID1 at transmission timing t2, the axle rotation amount reading unit 22 reads the number of pulses Px of each axle rotation detection unit 21a to 21d every time ID1 is received. Similarly, the axle rotation amount reading unit 22 reads the pulse number Px of each axle rotation detection unit 21a to 21d every time ID2 to ID4 are received at the transmission timing t2.

  The position determination unit 23 calculates an average value (pulse average value) for each of the axle rotation detection units 21a to 21d in the plurality of pulse numbers Px read from the axle rotation detection units 21a to 21d at the time of reception of ID1 at the transmission timing t2. Pave-B is calculated. That is, as the pulse average value Pave-B when ID1 is received at the transmission timing t2, four average values are calculated for each of the right front axle 18a, the left front axle 18b, the right rear axle 18c, and the left rear axle 18d. . Similarly, the position determination unit 23 calculates the pulse average value Pave-B at the transmission timing t2 for each of the axle rotation detection units 21a to 21d for ID2 to ID4.

  The position determination unit 23 determines the tire position by comparing the previous pulse average value Pave-A held in the memory 15 with the pulse average value Pave-B calculated later. That is, the position determination unit 23 confirms which axle rotation detection unit 21a to 21d outputs Pave-A and Pave-B coincide with each other in ID1 to ID4 or equal to or less than a certain allowable width. Identify the tire position.

  FIG. 7 illustrates a specific example of tire position determination. First, look at ID1. In ID1, the pulse average values Pave-A and Pave-B match or approximate at the transmission timings t1 and t2 is the output of the right front axle rotation detection unit 21a. Therefore, the position determination part 23 specifies ID1 as tire ID of the right front tire 2a. By the same determination, it is determined that ID2 is the left front tire 2b, ID3 is the left rear tire 2d, and ID4 is the right rear tire 2c. When the position determination unit 23 can confirm the positions of all the four tires 2 a to 2 d, the position determination unit 23 updates the tire position by overwriting this position information in the memory 15.

  In addition, the position determination part 23 will retry the same process, if a tire position determination cannot be completed by one determination. That is, the tire position is determined by recalculating the pulse average value Pave at the next transmission timing t and comparing it with the previous (for example, the previous) pulse average value Pave. And the position determination part 23 continues a determination process until it can determine the tire position of all the four wheels, and completes an auto location. The above autolocation is repeatedly executed according to a predetermined cycle.

According to the configuration of the present embodiment, the following effects can be obtained.
(1) The tire pressure detector 4 can transmit a radio wave at a transmission time t of a minute time that periodically arrives, and at this time zone, a radio wave for autolocation is obtained every time a specific detector angle is taken. A plurality of transmissions are performed, and the plurality of transmissions are set as one set and this is repeated a plurality of times. The TPMS receiver 12 reads the axle rotation amount (number of pulses Px) every time it receives a radio wave from the tire pressure detector 4, and calculates an average value Pave of the axle rotation amount for each set of transmissions. Then, by comparing the average value Pave before and after, the radio wave for autolocation (ID1 to ID4) and the axles 18a to 18d are linked to specify the tire position. By the way, when the tire pressure detector 4 transmits a radio wave at a specific detector angle, there is a possibility that the transmission timing varies due to a tolerance or the like. This leads to variations in the axle rotation amount detected on the TPMS receiver 12 side, and as a result, the tire position cannot be completed early. However, if the average value of the axle rotation amount is calculated and determined as in this example, the variation in the transmission timing of the tire air pressure detector 4 is mitigated, and the possibility that the axle rotation amount converges to a valid value is high. Become. Therefore, the determination of the tire position can be completed in a short time.

  (2) The tire air pressure detector 4 has a minute time zone ("T1" time zone) in which radio waves can be transmitted, but a time zone in which radio waves cannot be transmitted ("T2" time zone). Then, a communication sequence that repeatedly appears is taken. Therefore, the time period during which the tire pressure detector 4 must transmit radio waves can be shortened, which contributes to power saving of the power source of the tire pressure detector 4.

  (3) The position determination unit 23 can execute a first calculation that simply averages the count value of the number of pulses Px and a second calculation using modulo calculation, and is calculated in the calculation process of the second calculation. Depending on the difference between the minimum value and the maximum value, the calculation used for calculating the average value is appropriately switched. Therefore, even when the counter value of the number of pulses Px crosses the modulo value, the pulse average value Pave can be calculated with high accuracy. Therefore, it is advantageous for determining the tire position quickly and accurately.

  (4) The offset value may be set to a value half the modulus of the counter value of the axle rotation amount. Therefore, the average value of the axle rotation amount (pulse average value Pave) can be calculated with high accuracy using a fixed value that is half of the modulus of the counter value.

  (5) The specific detector angle may be a pole position in the tire rotation direction of the tire pressure detector 4. By the way, the pole position of the tire air pressure detector 4 can be easily detected by the gravity detection unit 9, so that a specific detector angle can be easily detected.

  (6) In the tire pressure detector 4, T1 of a time zone in which radio wave transmission is possible is set to “1 second”, and T2 of a time zone waiting for radio wave transmission is set to “30 seconds”. Therefore, it is easy to satisfy the laws and regulations of the Radio Law of each country.

  (7) When the tire positions of all the wheels cannot be determined by one determination, the new average value Pave is calculated again at the next transmission timing t, and the newly calculated average value Pave and the past value are calculated. The determination is retried by comparing. This process is repeated until the tire positions of all the wheels can be determined. Therefore, the position determination for all wheels can be completed.

Note that the embodiment is not limited to the configuration described so far, and may be modified as follows.
-The number of transmissions of the radio wave for auto-location that is transmitted in the time zone of the time width T1 is not limited to being transmitted every time the peak position is taken during T1, but is set to a constant value such as 3 times or 4 times. It may be fixed.

A time limit may be provided for the auto location determination process, and if the position determination is not completed after the time limit, the process may be forcibly terminated and re-executed next time.
The time width T1 may be a value different between the tire air pressure monitoring and the auto location. This also applies to T2.

The time width T1 and the time interval T2 can be appropriately set to various time widths.
The time width T1 and the time interval T2 may be variable, for example, by switching to another value according to the vehicle speed, travel time, or the like.

  The offset value is not limited to a half value of the counter method for counting the axle rotation amount, and may be a value sufficiently close to a half value of the method, for example. Further, the offset value can be appropriately changed to a value other than half of the modulus.

The gravity component detected by the tire pressure detector 4 may be, for example, gravity in a direction orthogonal to the axle direction.
The axle rotation detection unit 21 can be changed to various detection members (sensors, switches, communication devices, etc.) as long as the rotation of the axle 18 can be detected.

Next, technical ideas that can be grasped from the above-described embodiment and other examples will be described below together with their effects.
(A) In the tire position determination system, the position determination is a process for determining a position by calculating a new average value and comparing it with a past value when the specification of the tire positions of all the wheels is not completed in one process. Is repeated, and the determination is repeated until the determination of the tire positions of all the wheels is completed. According to this configuration, it is possible to reliably complete the determination of the tire position.

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 2 (2a-2d) ... Tire, 3 Tire pressure monitoring system, 4 (4a-4d) ... Tire pressure detector, 12 ... Receiver (TPMS receiver), 17 ... Tire position determination system, 18 ( 18a-18d) ... axle, 19 ... detector angle monitoring unit, 20 ... radio wave transmission control unit, 21 (21a-21d), ... axle rotation detection unit, 22 ... axle rotation amount reading unit, 23 ... position determination unit, Stp Tire pressure signal, T1: Minute time width in which radio wave transmission is possible, T2: Time interval in which radio wave transmission is not executed, Px: Number of pulses as an example of axle rotation amount, Pave (Pave-A, Pave-B) ... Average value (pulse average value).

Claims (5)

Tire position determination comprising: a tire pressure detector attached to each tire; and a receiver that receives a tire pressure signal transmitted from the tire pressure detector and monitors the tire pressure. In the system,
The tire pressure detector is
A detector angle monitoring unit for monitoring that the tire pressure detector takes a specific detector angle;
An operation for transmitting radio waves at the specific detector angle is executed a plurality of times, the operation is set as a set, and a radio wave transmission control unit that repeats a plurality of times at specific time intervals,
The receiver
An axle rotation amount reading unit that reads an axle rotation amount from an axle rotation detection unit capable of detecting the rotation amount of the axle each time the radio wave is received;
A tire position determination system comprising: a position determination unit that averages a plurality of axle rotation amounts for each set and determines a tire position based on the average value. The radio wave transmission control unit performs radio wave transmission operation with a minute time as a time zone in which radio wave transmission is possible, and when the minute time has passed, the radio wave transmission control unit does not execute radio wave transmission for a time longer than the minute time, and this waiting time. 2. The tire position according to claim 1, wherein the radio wave transmission necessary for tire position determination is performed by repeating the above-described operation of performing the radio wave transmission operation again in a minute time after the elapse of time. Judgment system. In calculating the average value of the axle rotation amount, the first calculation for calculating the average value of the plurality of axle rotation amounts and the offset value are uniformly added to all of the plurality of axle rotation amounts, and the offset value is added. A second calculation of subtracting the offset value from the result of calculating the average of the plurality of modulo values, modulo calculating the axle rotation amount so as to form a modulus with a counter value for counting the axle rotation amount; With
When the difference between the minimum and maximum among the plurality of modulo values obtained in the calculation process of the second calculation is larger than the offset value, the position determination unit sets the calculation result of the first calculation as an average value, and sets the minimum The tire position determination system according to claim 1 or 2, wherein when the difference between the maximum value and the maximum value is equal to or less than the offset value, the calculation result of the second calculation is an average value. 4. The tire position determination system according to claim 3, wherein the offset value is a half of a modulus of a counter for counting the axle rotation amount or a value close to the half. The tire position according to any one of claims 1 to 4, wherein the specific detector rotation angle is an angle at which the tire air pressure detector takes a pole position in a tire rotation direction. Judgment system.