JP2012040940A - Failure discrimination device and failure discrimination method for tire pneumatic pressure monitor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately discriminate between electronic jamming and a receiver failure.SOLUTION: This failure discrimination device for a tire pneumatic pressure monitor includes a transmitter installed in a tire and the receiver for receiving the radio wave including the information on tire pneumatic pressure transmitted from the transmitter. The failure discrimination device detects the intensity of the radio wave received by the receiver, detects the traveling conditions of a vehicle including the steering state and the traveling speed of the vehicle (S320, S330), and based on the traveling conditions, calculates three or more positions of the vehicle varying with the elapse of time (S342). The distance from the position of the vehicle to a radio wave transmission source which is in inverse proportion to a radio wave intensity detected by a radio wave intensity detection means is obtained at each of the three or more positions of the vehicle. An equal intensity area in which estimated distances from the positions of the vehicle to the radio wave transmission source are equal to each other is obtained at each position of the vehicle. When the equal intensity area at each position of the vehicle is brought into a predetermined matched state, the equal intensity area in the matched state is specified as a radio wave transmission source (S363). When the equal intensity area in matched state is absent and the radio wave transmission source cannot be specified, the receiver 3 is determined to be failed (S390).

Description

  The present invention relates to a tire pressure monitor failure determination device and a failure determination method thereof.

  2. Description of the Related Art Conventionally, an in-vehicle radar device disclosed in Patent Document 1 is known as a countermeasure against an obstacle caused by external radio waves. In Patent Document 1, first, after a radar observation period in which a reception signal reflected from an object to be detected is detected by a beam receiving unit to detect a relative distance and a relative speed, a beam transmission unit transmits a next transmission signal. The period outside the radar observation period is defined as the radio wave interference determination period.

  If a frequency component exceeding the threshold is observed during this radio disturbance determination period, the continuity of the noise component is verified retroactively from the present. Judging by the obstacles.

  In addition to monitoring the distance traveled by the vehicle, the signal from the counter monitors the continuity of the radio disturbance. Deciding.

JP 2008-111173 A

  Therefore, it is possible to determine whether the circuit system is abnormal (failure) or radio wave interference, but because the determination is based only on time and distance regardless of the running state of the vehicle, the accuracy of the failure determination is not necessarily high enough. I can't say that.

  The present invention has been made in view of such conventional problems, and an object of the present invention is to provide a tire pressure monitor failure determination device and failure determination method capable of accurately determining radio wave interference and receiver failure. It is to be.

  A feature of the present invention is a failure determination device for a tire pressure monitor including a transmitter provided in a tire and a receiver that receives a radio wave including tire pressure information emitted from the transmitter. This failure determination device detects the radio field intensity received by the receiver, detects a driving situation including a steering state and a driving speed of the vehicle, and calculates three or more positions of the vehicle over time based on the driving situation. . Then, at three or more vehicle positions, an estimated distance from the vehicle position to the radio wave transmission source that is inversely proportional to the radio wave intensity detected by the radio wave intensity detecting means is obtained at each vehicle position, and an equal intensity range in which the assumed distance is equal is obtained. When the equal intensity range at each vehicle position is in a predetermined coincidence state, the equal intensity range in the coincidence state is specified as a radio wave transmission source. When the radio wave source cannot be specified, it is determined that the receiver is out of order.

  According to the failure determination device and the failure determination method of the tire pressure monitor according to the present invention, the radio wave generation source is predicted with high accuracy based on the driving situation including the steering state and the driving speed of the vehicle, and the radio wave interference and the receiver. Can be determined with high accuracy.

1 is a block diagram illustrating a configuration of an entire system including a tire air pressure monitor failure determination apparatus according to an embodiment of the present invention. It is a block diagram which shows the detailed structure of the receiver 3 of FIG. 3 is a graph for explaining the operation of the signal output circuit 16 of FIG. 2. It is a block diagram which shows the detailed structure of the control part 6 of FIG. 3 is a flowchart showing an example of a processing procedure for the tire pressure monitor of FIG. 7 is a flowchart illustrating an example of a processing procedure in which a failure determination device of a tire pressure monitor predicts a radio wave generation source and determines a radio wave interference and a failure of the receiver 3. FIG. 7A is a graph showing an example of the time change of the electric field intensity of the received radio wave, and FIG. 7B is a graph showing an example of the time change of the steering angle plotted in step S320. FIG.7 (c) is a graph which shows an example of the time change of the behavior (direction) of a vehicle. FIG. 7D is a graph showing an example of the vehicle travel locus TG on the xy coordinates. FIG. 7E is a diagram illustrating an example of radius circles Cb to Cd drawn in an overlapping manner on the travel locus TG. It is a figure which shows an example when the intersection of circle | round | yen Ca-Cc exists in the intersection area | region (alpha). FIG. 9A is a graph showing an example of a case where the change in the radio wave intensity is equal to or less than a predetermined value despite the change in the steering state being equal to or greater than the predetermined value, and FIG. In this example, the example of (a) is drawn, and the intersections of the circles Ca to Cc do not fall within the intersection region α. It is a graph which shows an example of the electric wave radiation characteristic of vehicles. It is a graph which shows the inversely proportional relationship of the electric field strength detected by the electric field strength detection circuit 15, and the assumed distance to a radio wave transmission source.

  Embodiments of the present invention will be described below with reference to the drawings. In the description of the drawings, the same parts are denoted by the same reference numerals.

(First embodiment)
With reference to FIG. 1, the configuration of the entire system including a tire pressure monitor and a failure determination device according to an embodiment of the present invention will be described. This system is a tire pressure monitoring system (TPMS) that constantly monitors the tire pressure of an automobile. This TPMS first mounts a sensor (transmitter 2) inside each tire 5 and wheel, detects the air pressure and temperature of the tire 5, and transmits air pressure information and a status code to the receiver 3 mounted on the vehicle body 1 by radio waves. Etc. And it is what is called direct TPMS which issues an alarm when the air pressure is out of the standard.

  The transmitter 2 detects information such as the air pressure in the tire 5 and transmits it by radio waves in the UHF band. The receiver 3 is connected to the control unit 6 by a harness or the like. Air pressure information, a status code, and the like received by the receiver 3 are transmitted to the control unit 6 via this harness. The control unit 6 is also connected to the display 4 and determines the state of air pressure of the tire 5. When it is determined that the air pressure is out of the reference, the control unit 6 issues an alarm to the driver through the display 4. The control unit 6 is also connected to a steering angle sensor 8 that detects the steering state of the vehicle and a vehicle speed sensor 9 that detects the speed of the vehicle.

  The steering angle sensor 8 and the vehicle speed sensor 9 correspond to an example of “traveling state detection means” that detects a traveling state including the steering state of the vehicle and the traveling speed.

The detailed configuration of the receiver 3 will be described with reference to FIG. The receiver 3 includes an antenna 10 that receives a UHF band radio wave, a filter 11 that extracts a predetermined frequency component from the radio wave received by the antenna 10, an amplifier 12 that amplifies the absolute value of the amplitude of the extracted radio wave, A detection / oscillation circuit 13 for adjusting the waveform of the amplified radio wave, an electric field strength detection circuit 15 for detecting the electric field strength of the shaped radio wave (an example of the radio wave strength), and an electric field when an electric field strength equal to or higher than a recognition threshold flows. A signal output circuit 16 for converting the intensity into a signal and a power supply circuit 14 for supplying power to the detection / oscillation circuit 13 are provided.

  The electric field intensity detected by the electric field intensity detection circuit 15 and the electric field intensity signal converted by the signal output circuit 16 are transmitted to the control unit 6.

  The electric field intensity detection circuit 15 corresponds to an example of “radio wave intensity detection means” that detects the radio wave intensity received by the receiver 3.

  As shown in FIG. 3, the signal output circuit 16 converts the electric field intensity data into a signal and outputs it to the control unit 6 when the electric field intensity equal to or higher than the recognition threshold is detected by the electric field intensity detection circuit 15.

  A detailed configuration of the control unit 6 in FIG. 1 will be described with reference to FIG. As the control unit 6, a data processing device, a register or memory device that temporarily stores data, and a microprocessing unit (MPU) including an input / output device that interfaces with peripheral devices can be used. When the control unit 6 grasps this functionally, the signal reading unit 25 that reads the electric field strength signal converted by the signal output circuit 16 and the data processing unit 26 that converts the read signal into data such as pressure. And an electric field strength reading unit 18 for reading the electric field strength detected by the electric field strength detection circuit 15 and a traveling position prediction for predicting the traveling position of the vehicle based on the read electric field strength, steering angle information 27 and vehicle speed information 28. Unit 19, radio wave source identifying unit 20 that identifies the source of the jamming radio wave based on the electric field strength and the predicted traveling position of the vehicle, and radio wave jamming and receiver 3 based on whether or not the radio wave source is identified. An interference radio wave / fault determination unit 21 that determines a failure, a display command unit 22 that outputs a display command of a determination result by the interference radio wave / fault determination unit 21 to the display 4, and a device that is determined to be a disturbance radio wave And a failure detection time extension unit 24 for extending the detection time for detecting the fault.

  The travel position prediction unit 19 corresponds to an example of “vehicle position calculation means” that calculates three or more positions of the vehicle over time based on a travel situation including the steering state and travel speed of the vehicle.

  In addition, the radio wave source specifying unit 20 is based on the electric field strength detected by the electric field strength detection circuit 15 at three or more vehicle positions according to a relationship in which the electric field strength is inversely proportional to the distance from the vehicle position to the radio wave source. Then, an assumed distance from the vehicle position to the radio wave transmission source is obtained at each vehicle position, and an equal intensity range (equal intensity range) with the assumed distance as a radius and at the vehicle position is obtained at each vehicle position. Corresponding to “radio wave source specifying means” for specifying the equal intensity range in the coincidence state as a radio wave source when the region where the equal intensity ranges intersect is in a coincidence state, that is, when the cross region is within a predetermined region. .

  FIG. 11 shows the relationship between the electric field strength detected by the electric field strength detection circuit 15 and the estimated distance from the electric field strength to the radio wave transmission source. The relationship between the electric field strength and the assumed distance to the radio wave transmission source is an inversely proportional relationship in which the assumed distance to the radio wave transmission source becomes shorter as the electric field strength increases.

  When the radio wave source is specified by the radio wave source specifying unit 20, the jamming radio wave / fault determination unit 21 determines that the radio wave source is a jamming radio wave, and determines that the receiver 3 is faulty when the radio wave source cannot be specified. According to this determination result, it corresponds to “receiver failure determination means” that instructs the display instruction unit 22 to issue a display instruction to the display 4 if a failure occurs.

  Next, an example of a processing procedure in which the TPMS in FIG. 1 determines the air pressure state of the tire 5 will be described with reference to FIG.

  (A) First, in step S10, the receiver 3 waits for reception of radio waves in the UHF band. When the receiver 3 receives a UHF band radio wave (YES in S10), the process proceeds to step S20, and the field intensity of the UHF band radio wave received by the receiver 3 is detected.

  (B) Proceeding to step S30, the radio field strength data is transmitted to the control unit 6. In step S40, it is determined whether or not the initial value of the electric field strength data is equal to or greater than a recognition threshold value. If it is less than the recognition threshold (NO in S40), the process returns to S10. On the other hand, if it is equal to or greater than the recognition threshold (YES in S40), the process proceeds to step S50, where the electric field strength data is converted into a signal (digital data) and transmitted to the control unit 6.

  (C) Proceeding to step S60, the digital data of the electric field strength is converted into data such as the air pressure of each tire 5, and information such as the tire air pressure is displayed on the display 4 (S70). By repeatedly performing the above procedure, the TPMS in FIG. 1 can constantly monitor the air pressure state of the tire 5.

  Next, with reference to FIG. 6, an example of a processing procedure in which the failure determination device of the tire pressure monitor predicts the equi-intensity range to determine the radio wave interference and the failure of the receiver 3 will be described. The flowchart shown in FIG. 6 is started after receiving the electric field strength data of radio waves (after step S30 in FIG. 5).

  (I) First, in step S310, it is determined whether or not the electric field strength of the received radio wave exceeds a threshold value (interference radio wave detection threshold value Va). If the jamming radio wave detection threshold value Va is exceeded (YES in S310), the radio wave jamming duration timer t is started using the timer function provided in the control unit 6 (step S315).

  (B) Proceeding to step S320, the vehicle orientation at the time of exceeding the jamming wave detection threshold Va is set to 0 °, and the steering angle is plotted from the steering state of the vehicle detected by the steering angle sensor 8. Thereafter, the process proceeds to step S330. FIG. 7A is a graph showing an example of the time change of the electric field intensity of the received radio wave, and FIG. 7B is a graph showing an example of the time change of the steering angle plotted in step S320.

  On the other hand, if the electric field strength of the radio wave does not exceed the jamming radio wave detection threshold Va (NO in S310), the process proceeds to step S317, and it is determined whether the radio wave jamming duration timer t is already counting. . If the timer t is counting (YES in S317), the timer t is reset (S318), and the process returns to step S310. If the timer t is not counting (NO in S317), the process directly returns to S310.

  (Ii) In step S330, the steering angle is integrated and the vehicle behavior is plotted on the zy coordinates. FIG.7 (c) is a graph which shows an example of the time change of the behavior (direction) of a vehicle. In addition, as shown in FIG. 7D, the vehicle travel locus TG on the xy coordinates is plotted from the vehicle behavior (direction) and the vehicle speed information 28. Thereafter, the process proceeds to step S341, and it is determined whether or not the timer t has counted 10 minutes. If the timer t has counted 10 minutes (YES in S431), the process proceeds to step S342, and if the timer t has not reached 10 minutes (NO in S431), the process returns to step S310.

(E) In step S342, the A position to the C position are set as the vehicle position in the traveling locus TG of the vehicle on the xy coordinates as follows. The A position is a vehicle position when the electric field intensity exceeds a jamming radio wave detection threshold (a lower limit value for detecting jamming radio waves) Va. The position C is the vehicle position farthest from the position A during the period (10 minutes) in which the electric field intensity equal to or greater than the jamming wave detection threshold value Va continues. The B position is a vehicle position where the electric field strength is strongest between the A position and the C position. The electric field strengths at positions A to C are Va (interference wave detection threshold), Vb, and Vc, respectively. FIG. 7D is a graph showing an example of the vehicle travel locus TG on the xy coordinates.

  Thus, the time when the radio wave intensity received by the receiver 3 is equal to or greater than a predetermined value (interference radio wave detection threshold Va) is set as the specific start time of the radio wave source, and the vehicle position at the specific start time is set to the A position (first Position). Thereafter, the position farthest from the A position is the C position (second position) during a period in which the radio field intensity of a predetermined value or more continues, and the radio field intensity is the highest in the period in which the radio field intensity of the jamming radio wave detection threshold Va or more continues. The vehicle position when it becomes stronger is defined as a B position (third position).

  (F) In step S350, the circles Ca to Cc having radii obtained from the relationship between the radio wave intensities Va to Vc and the distance, each centered on the A position to the C position, are superimposed on the travel locus TG. FIG. 7E is a diagram illustrating an example of circles Ca to Cc having a radius drawn to overlap the travel locus TG. Referring to FIG. 11, the radii Ra to Rc of the circles Ca to Cc are assumed distances from the vehicle position to the radio wave source determined by the relationship inversely proportional to the electric field strengths Va to Vc. Here, the electric field intensity Va is an interference radio wave detection threshold value, and the radius Ra calculated based on the threshold value indicates the maximum distance from the radio wave source.

  (And) In step S361, it is determined whether or not the set of intersections of the circles Ca to Cc is within the intersection area α as a predetermined area. Specifically, as shown in FIG. 7E, attention is paid to one of the maximum two intersections created when the circles Ca and Cb intersect, and the intersection of the circles Cb and Cc, the circle Cc. Similarly, attention is paid to one intersection at the intersection of Ca and Ca, and it is determined whether or not these three intersections are gathered in an intersection region α having a circle with a predetermined radius as an outer edge. FIG. 8 is a diagram illustrating an example when the set of intersections of the circles Ca to Cc is within the intersection region α. If each intersection is within the intersection area α (YES in S361), the process proceeds to step S363, where it is determined that there is radio interference, and the timer t is set to 10 minutes. Thereafter, the process returns to step S310. On the other hand, if each intersection is not within the intersection region α (NO in S361), the process proceeds to step S390, where it is determined that the receiver 3 is out of order, and that effect is displayed on the display 4. As described above, based on the respective radio wave intensities at the A position to the C position, the estimated distances Ra to Rc from the respective vehicle positions to the radio wave transmission sources that are inversely proportional to the radio wave intensity are obtained, respectively. The circles Ca to Cc having a radius with which the assumed distance to the radio wave transmission source is in the equiintensity range are obtained, and the intersection set of the circles in the equiintensity range is within the intersection region α. The central part of is identified as a radio wave source.

  (C) The jamming radio wave / fault determination unit 21 determines that the jamming radio wave / fault determination unit 21 is a jamming radio wave if the radio wave transmission source PE can be identified in order to identify the jamming radio wave (YES in S361). The failure detection time extension unit 24 extends the detection time for detecting a failure of the receiver 3 by a predetermined time, for example, 10 minutes. If a user is informed that the correct signal cannot be received by the jamming radio wave, there is a user who mistakenly considers it as a failure, so that the user's anxiety can be resolved. On the other hand, if the condition of S361 cannot be satisfied (NO in S361), the process proceeds to step S390, where it is determined that the receiver 3 is out of order, and that fact is displayed on the display 4.

With reference to FIG. 9A and FIG. 9B, an example in which it is determined that the receiver 3 is not an interference but a failure of the receiver 3 will be described. In some cases, the change in radio field intensity is less than or equal to a predetermined value despite the change in the steering state exceeding a predetermined value. For example, as shown in FIG. 9 (a), if the electric field strength does not change according to time even though the vehicle is traveling, the voltmeter of the receiver 3 is abnormal. Judgment is made and the failure of the receiver 3 is displayed on the display 4. In this case, as shown in FIG. 9B, the set of intersections of the circles Ca to Cc does not enter the intersection region α.

  As described above, according to the embodiment of the present invention, the following effects can be obtained.

  Based on the traveling state including the steering state and traveling speed of the vehicle, the A to C positions over time of the vehicle are calculated. The assumed distances (Ra to Rc) from each vehicle position to the radio wave source that are inversely proportional to the electric field strengths Va to Vc at the three vehicle positions (A to C) are obtained. Further, with the vehicle position (A to C) as the center, The equal intensity range of the radio wave source PE having the same assumed distance to the radio wave source is calculated as a circle. When a set of intersections of circles having an equal intensity range centered on the vehicle position (A to C) is within the intersection area α as a predetermined area, the central portion of the intersection set is specified as a radio wave transmission source. As a result, the radio wave generation source PE can be specified by combining the detected electric field strength and the driving situation including the steering state and the driving speed of the vehicle, so that the radio wave interference and the failure of the receiver 3 can be determined with high accuracy. Can do.

  The assumed distances Ra to Rc of the radio wave source PE calculated according to the relationship inversely proportional to the electric field strengths Va to Vc at the three vehicle positions A to C are circles Ca having radii Ra to Rc with the vehicle positions A to C as centers. Calculated as ˜Cc, and an intersection region of these circles Ca to Cc is detected. Thereby, the radio wave generation source PE can be obtained with high accuracy based on the relationship of the distance from the vehicle position that is inversely proportional to the radio wave intensity.

  The time when the electric field intensity received by the receiver 3 is equal to or greater than a predetermined value (jamming wave detection threshold Va) is set as the specific start time of the radio wave source, and the vehicle position at this specific start time is set as the A position (first position). After that, when the electric field strength of the predetermined value or more continues, the position farthest from the A position is the C position (second position), and when the electric field strength of the predetermined value or more continues, the electric field strength becomes strongest The vehicle position is defined as B position (third position). The circles Ca to Cc having radii Ra to Rc determined from the relationship between the electric field strengths Va to Vc and the distance centered on the A position to the C position are set as the equiintensity range of the radio wave transmission source PE. When the intersection of the equal intensity range is in a predetermined coincidence state, that is, within the intersection area α as the predetermined area, the equal intensity range is determined as the radio wave generation source PE. Thereby, since the radio wave generation source PE is assumed from the intersecting region of three or more circles, the radio wave generation source PE can be specified with high accuracy even if the electric field intensity changes.

  If the steering state has a change greater than or equal to a predetermined value and the change in radio field intensity is less than or equal to the predetermined value, it is determined that the tire pressure monitor is out of order. If the received electric field strength is high despite the vehicle being steered, it can be determined that the receiver 3 is not obstructed by radio waves and can be regarded as a failure. Thereby, it is possible to accurately discriminate between radio wave interference and failure of the receiver 3.

(Other embodiments)
As described above, the present invention has been described by way of one embodiment, but it should not be understood that the discussion and drawings that form part of this disclosure limit the present invention. From this disclosure, various alternative embodiments, examples and operational techniques will be apparent to those skilled in the art. That is, it should be understood that the present invention includes various embodiments and the like not described herein.

  For example, the B position may be set based on a reference other than the reference shown in step S342 in FIG. For example, it may be half of the A position to the C position. Alternatively, the B position may be an arbitrary position between the A position and the C position. Even in these cases, the vehicle position at the specific start time when the radio wave intensity received by the receiver 3 is equal to or higher than a predetermined value (interference radio wave detection threshold Va) is defined as the A position (first position), and then the predetermined value. The position farthest from the A position in the period in which the above radio wave intensity continues is defined as the C position (second position).

  In FIG. 4, the travel position prediction unit 19 instead of predicting the travel position of the vehicle based on the steering angle information 27 detected by the steering angle sensor 8 and the vehicle speed information 28 detected by the vehicle speed sensor 9, A steering torque sensor and a wheel speed sensor may be used.

  Further, when the radio wave characteristics of the vehicle are biased, the radio wave generation source PE can be predicted with higher accuracy by preparing in advance the radio wave radiation characteristics of the vehicle as shown in FIG. 10, for example.

  Furthermore, although the case where the predicted position of the radio wave generation source PE based on the electric field strengths Va to Vc at three vehicle positions (A to C) has been described, the number of vehicle positions is not limited to three. You may obtain | require the predicted position of the electromagnetic wave generation source PE based on the electric field strength in four or more vehicle positions. For example, by newly setting the D position arbitrarily between B and C or between A and B, it is possible to specify a radio wave source with higher accuracy. Further, the distance from the vehicle position that is inversely proportional to the radio wave intensity is obtained, and the equal intensity range having the same radio wave intensity centered on the vehicle position may be not only a circle but also a part of the circle (arc).

2: Transmitter 3: Receiver 4: Indicator 5: Tire 6: Control unit 8: Steering angle sensor (traveling condition detection means)
9: Vehicle speed sensor (traveling condition detection means)
15: Electric field intensity detection circuit (radio wave intensity detection means)
19: Travel position prediction unit (vehicle position calculation means)
20: Radio wave source specifying unit (Radio wave source specifying means)
21: Interference / failure determination unit (receiver failure determination means)

Claims (4)

A transmitter provided in the tire of the vehicle;
A failure determination device for a tire pressure monitor, including a receiver for receiving radio waves including tire pressure information emitted by the transmitter,
Radio wave intensity detecting means for detecting radio wave intensity received by the receiver;
A traveling state detecting means for detecting a traveling state including a steering state and a traveling speed of the vehicle;
Vehicle position calculating means for calculating three or more positions of the vehicle over time based on the traveling situation;
At each of the three or more vehicle positions, an assumed distance from the vehicle position to the radio wave transmission source that is inversely proportional to the radio wave intensity detected by the radio wave intensity detection means is obtained at each vehicle position, and an equal intensity range in which the assumed distances are equal. A radio wave generation source specifying means for specifying the equal intensity range in the coincidence state as a radio wave generation source when the equal intensity range at the vehicle position is in a predetermined coincidence state at each vehicle position;
A failure of the tire pressure monitor, comprising: a receiver failure determination unit that determines that the receiver is failed based on whether or not the radio wave source is specified by the radio wave source specifying unit. Discriminator.   The radio wave generation source specifying means represents the equi-intensity range as a circle whose radius is the distance from the vehicle position, and the intersection area of the circles calculated at the three or more vehicle positions has a predetermined match. 2. The tire pressure monitor failure determination device according to claim 1, wherein a radio wave transmission source is identified by detecting a state. 3.   The radio wave generation source specifying means sets the time when the radio wave intensity received by the receiver is equal to or higher than a predetermined value as a specific start time, sets the vehicle position at the specific start time as a first position, and then exceeds a predetermined value. The position farthest from the first position during the period when the radio field intensity continues is the second position, and the vehicle position when the radio field intensity is the strongest during the period when the radio field intensity equal to or greater than the predetermined value is the third position And the radio wave generation source is identified by detecting that a region where circles having a radius from the vehicle position and having a radius from the vehicle position intersect each other is in a predetermined coincidence state. The failure determination device for a tire pressure monitor according to claim 2. A transmitter provided in the tire;
A failure determination method for a tire pressure monitor, including a receiver that receives a radio wave including tire pressure information emitted by the transmitter,
Detecting the radio field intensity received by the receiver;
Detects the driving situation including the steering state and driving speed of the vehicle,
Based on the running situation, calculate three or more positions of the vehicle over time,
Obtaining an assumed distance from the vehicle position that is inversely proportional to the radio wave intensity at the three or more vehicle positions to the radio wave transmission source at each vehicle position, and obtaining an equal intensity range equal to the distance from the vehicle position at each vehicle position;
When the equal intensity range at each vehicle position is in a predetermined coincidence state, the equal intensity range in the coincidence state is specified as a radio wave generation source,
A failure determination method for a tire air pressure monitor, wherein the failure of the receiver is determined when there is no equal intensity range in the coincidence state and a radio wave transmission source cannot be specified.

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