JP2014114007A - Tire position determination device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire position determination device that can specify a tire position with a low calculation load using an array antenna.SOLUTION: A TPMS receiver comprises an array antenna 14 that receives radio wave (a tire pressure signal) transmitted from tire pressure detectors attached to tires. In a memory 15 of the TPMS receiver are previously registered antenna complex weight coefficients Ka and Kb by which null beam is directed against one specific tire pressure detector of the plurality of tire pressure detectors and beam is directed against the other. The TPMS receiver, when null beam is directed against a front right tire pressure detector and beam is directed against the other, cannot receive radio wave from a front right tire detector but can receive radio wave from the other, while when null beam is directed against a front left tire pressure detector and beam is directed against the other, cannot receive radio wave from the front left tire detector but can receive radio wave from the other. Therefore, confirmation before and after switching directionality allows a tire ID to be determined, based on which tire positions of all four wheels are specified.

Description

  The present invention relates to a tire position determination device that determines a mounting position of a tire.

  In recent years, vehicles tend to be equipped with a tire pressure monitoring system that monitors tire pressure during traveling for the purpose of ensuring safety during traveling. The tire pressure monitoring system attaches a tire pressure detector to each tire and wirelessly transmits a tire pressure signal wirelessly transmitted from each tire pressure detector to the vehicle body. When the vehicle receives the tire pressure signal at the receiver, it compares the tire pressure in the tire pressure signal with the low pressure threshold, and if the tire pressure is below the low pressure threshold, the low pressure tire is associated with the tire position. Displayed on the instrument panel of the driver's seat.

  In the case of displaying a tire pressure monitoring result, that is, a notification of whether the tire pressure is normal or abnormal, together with the tire position, it is necessary to know which mounting position each tire is in front, back, left, and right. As a method of grasping the tire position, for example, a method is known in which an initiator is arranged in each tire house, and a tire position is recognized by causing a corresponding tire pressure detector to respond by a radio wave transmitted from the initiator (patent) Reference 1 etc.).

JP 2008-168826 A

  However, since Patent Document 1 requires an initiator for each tire house, there is a problem that the configuration of the entire system becomes complicated. In addition, the cost is increased as the initiator is required. Here, as an example of determining the tire position without using the initiator, for example, it is assumed that the tire position is specified by estimating the arrival direction of the air pressure of the tire pressure detector by using the receiving antenna of the vehicle body as an array antenna. The However, in the case of an array antenna, for example, a complicated operation such as eigenvalue expansion is required, which causes a problem that the circuit scale increases.

  An object of the present invention is to provide a tire position determination device that uses an array antenna and can specify a tire position by calculation with a low load.

  A tire position determination device that solves the above problem transmits an air pressure detected by a tire air pressure detector attached to each tire to a vehicle body as a tire air pressure signal, and a receiver of the vehicle body receives the tire air pressure signal. Thus, the tire pressure monitoring system for monitoring the tire pressure in the vehicle body is used, and the position of the tire pressure detector is specified based on the radio wave transmitted from the tire pressure detector, and the tire mounting position is determined. And an antenna complex weighting factor that directs a null of the array antenna to only one specific one of the plurality of tire pressure detectors. The tire pressure detector is registered in advance for each direction of the tire pressure detector, and the antenna complex weight coefficient is used. , Said array null direction switching unit capable of switching the directivity of the antenna, based on the electric waves received at each directivity, and a determining tire position determination unit of the tire position.

  According to this configuration, if the directivity is formed so that the null is directed to a specific one of the plurality of tire pressure detectors and the beam is directed to the other, radio waves from the tire pressure detector in the null direction cannot be received. However, radio waves from other tire pressure detectors can be received. When the null direction is changed by switching the antenna complex weight coefficient, a combination of a plurality of tire pressure detectors that can receive radio waves and a combination that cannot receive radio waves is changed. Therefore, if the association of the reception combination is confirmed, it is possible to determine the mounting position of each tire. That is, it is possible to determine the mounting position of each tire by switching the directivity pattern of the array antenna.

  For this reason, if the tire position is determined using an array antenna as in this configuration, it is possible to determine the tire position without providing an initiator in each tire house. The tire position can be specified with a simple configuration that does not. Even if the tire position is specified using an array antenna, in the case of this configuration, only the antenna complex weight coefficient necessary for position determination is registered in the memory in advance, and it is selectively assigned to the array antenna. Thus, since the position is specified, the calculation is simpler than the normal processing. Therefore, it is possible to specify the tire position by calculation with a low load using an array antenna.

  The tire position determination device includes an array gain calculation unit that calculates an array gain of each ID received from the tire air pressure detector based on the input / output of the array antenna, and the tire position determination unit is configured to calculate the array gain from the array gain value. It is preferable to determine the ID in the direction in which the null is directed. According to this configuration, it is possible to accurately determine the ID of the tire pressure detector with the beam direction directed even if it is affected by the reception intensity.

  In the tire position determination device, it is preferable that the determination of the tire position is executed at a specific timing, and all four tire positions are specified in a single process. According to this configuration, all the tire positions of the four wheels are confirmed by a single process, so that the tire positions can be identified efficiently.

  In the tire position determining device, the radio wave used for determining the tire position is preferably the tire pressure signal transmitted as tire pressure information. According to this configuration, the tire pressure detector only needs to perform the operation of transmitting the tire pressure signal in both the tire pressure monitoring and the tire position determination. Therefore, it is not necessary to cause the tire pressure detector to take a special action when determining the tire position.

  In the tire position determination device, the tire pressure detector rotates based on a signal output from a gravitational component force detector of the tire pressure detector to obtain a rotation angle around the tire center formed by the tire pressure detector. It is preferable to include an angle determination unit and a radio wave transmission control unit that executes radio wave transmission only when the rotation angle calculated by the rotation angle determination unit forms a specific angle or angle range. According to this configuration, in the array antenna, a situation where a null or beam is not directed to the tire even though a directional null or a directional beam should have been directed to the tire is avoided. Therefore, it is advantageous for accurately determining the tire position.

  In the tire position determination device, the rotation angle determination unit confirms whether the change in the gravitational force increases or decreases, so that the tire pressure detector detects a vertical line passing through the tire center. It is preferable to identify the left or right side. According to this configuration, it is possible to determine whether the tire air pressure detector is located on the left or right with respect to a vertical line passing through the tire center, which further contributes to improvement in the determination accuracy of the tire position.

  In the tire position determination device, the tire air pressure detector is configured to detect a gravitational component force caused by a centrifugal force generated in the tire air pressure detector during tire rotation based on a signal output from the gravitational component force detecting unit. It is preferable that an offset value calculation unit for calculating an offset value is provided, and the rotation angle determination unit calculates the rotation angle from the gravity component force after reflecting the offset value in the actual value of the gravity component force. According to this configuration, since the rotation angle of the tire air pressure detector is calculated by the gravitational force without the offset value, the rotation angle can be calculated with high accuracy.

  In the tire position determination device, the tire air pressure detector includes a constant speed traveling determination unit that determines whether the vehicle is traveling at a constant speed based on a signal output from the gravity force detection unit, It is preferable that the radio wave transmission control unit also sets a condition for executing radio wave transmission that the vehicle is traveling at a constant speed. According to this configuration, for example, when the vehicle travels at a constant speed, if it is permitted to transmit a radio wave for tire position determination from the tire air pressure detector, the tire is derived from a stable offset value. In accordance with the rotation angle, it is possible to transmit a radio wave for tire position determination from the tire air pressure detector. Therefore, this further contributes to the improvement of the tire position determination accuracy.

  In the tire position determination device, a statistical processing unit that performs a process of receiving the ID of the tire pressure detector by directing a beam toward each of the tire pressure detectors a plurality of times, and calculating a statistics of the number of received IDs It is preferable that the tire position determination unit determines the tire position based on a statistical result by the statistical processing unit. According to this configuration, since the tire position is determined by taking the statistics of the received tire ID, it further contributes to accurately determining the tire position.

  In the tire position determination device, the statistical processing unit counts the ID that maximizes the array gain in each directivity, and the tire position determination unit determines the tire position based on the count result. Is preferred. According to this configuration, since the ID that maximizes the array gain in each directivity (each null) is counted and the tire position is specified from the counting result, that is, the majority method is used, the tire position is accurately determined. Is advantageous.

  In the tire position determination device, the statistical processing unit calculates an average value of an array gain for each ID in each of the beams, and the tire position determination unit determines the tire position based on the average value of the array gain. It is preferable to do. According to this configuration, the average value of the array gain is calculated for each ID in each directivity (each null), and the tire position is determined from the average value, that is, the averaging method is used, so the tire position is accurately determined. It is advantageous to do.

  In the tire position determination device, the tire pressure detector determines whether or not the vehicle has shifted from parking to driving based on a signal output from a gravity force detection unit of the tire pressure detector. It is preferable to include a determination unit and a mode switching unit that switches the operation mode of the tire pressure detector from the normal mode to the tire position determination mode when it is determined that the vehicle has shifted from parking to running. According to this configuration, for example, when it is determined that the vehicle has changed from parking to running, the operation mode of the tire air pressure detector is switched to the tire position determination mode, which is a dedicated mode for tire position determination. In the tire position determination mode, for example, it is advantageous to determine the tire position in a short time if radio waves are continuously transmitted from the tire air pressure detector in a short cycle. In addition, even if radio waves are transmitted continuously in a short time, it is only during the tire position determination mode. In normal mode, if radio waves are transmitted in a long cycle, the power consumed by the tire pressure detector Can be kept small. In this way, it is possible to achieve both the shortening of the tire position determination and the suppression of the power consumption of the tire pressure detector.

  The tire position determination device preferably includes a reception system switching unit that narrows down a reception system by connecting only necessary antenna elements of the array antenna after the tire position determination is completed. According to this configuration, after the tire position determination is completed, only the necessary reception system of the array antenna is connected, so that it is possible to stop the operation of the unnecessary reception system during normal operation. Therefore, it is possible to reduce the power consumed by the receiver.

  In the tire position determination device, the array antenna includes a circuit group of a phase shifter group, an amplifier group, and an adder for each tire pressure detector, and can always receive radio waves transmitted from each tire pressure detector. It is preferable to adopt a possible parallel processing method. According to this configuration, any time a radio wave is transmitted from the tire pressure detector, it is possible to receive the radio wave and determine the tire position, which is advantageous for determining the tire position in a short time. is there.

  According to the present invention, in a tire position determination device using an array antenna, a tire position can be specified by calculation with a low load.

The lineblock diagram of the tire pressure monitoring system of a 1st embodiment. The block diagram of the array antenna of a TPMS receiver. State diagram of directivity when null is directed to right front tire. Explanatory drawing which shows the sequence of tire position determination. State diagram of directivity when null is directed to left front tire. State diagram of directivity when null is directed to right rear tire. State diagram of directivity when null is directed to the left rear tire. The block diagram of the array antenna of 2nd Embodiment. The communication conceptual diagram of the state which does not receive tire ID of a null direction as normal. The communication conceptual diagram of the state which will receive tire ID of a null direction. The conceptual diagram explaining the tire rotation angle of 3rd Embodiment. The wave form diagram which shows the change of the array gain with respect to a tire rotation angle. The conceptual diagram explaining gravity force. The wave form diagram which shows the time change of the gravity component at the time of driving | running | working. The block diagram of a tire pressure monitoring system. (A), (b) is explanatory drawing which shows the example of a tire rotation angle. The wave form diagram which shows the change of the gravity component until the vehicle of 4th Embodiment starts driving | running | working and stops. The block diagram of a tire pressure detector. The wave form diagram which shows the change of the offset value after a vehicle starts driving | running | working and stops. The block diagram of the TPMS receiver of 5th Embodiment. A table that summarizes specific examples of the majority method. A table summarizing specific examples of the averaging method. The block diagram of a tire pressure monitoring system. The flowchart performed at the time of mode switching of a tire pressure detector. The block diagram of the array antenna at the time of normal operation | movement of 6th Embodiment. The block diagram of the array antenna of the state which narrowed down the receiving system. The block diagram of the array antenna of another example.

(First embodiment)
Hereinafter, 1st Embodiment of a tire position determination apparatus is described according to FIGS.
As shown in FIG. 1, the vehicle 1 is provided with a tire pressure monitoring system (TPMS: Tire Pressure Monitoring System) 3 that monitors the tire air pressure and the like of each tire 2 (2a to 2d). The tire pressure monitoring system 3 of this example is provided with a tire pressure detector 4 (also referred to as a tire valve: 4a to 4d) for each tire 2a to 2d, and the tire pressure detected by these tire pressure detectors 4a to 4d By directly transmitting the tire pressure signal Stp to the vehicle body 5, the tire pressure of each tire 2 a to 2 d in the vehicle body 5 is directly monitored.

  The tire pressure detector 4 is provided with a controller 6 that controls the operation of the tire pressure detector 4. A tire ID (also referred to as a valve ID) is written and stored in the memory 7 of each controller 6 as a unique ID of each tire 2. The tire pressure detector 4 is provided with a pressure sensor 8 that detects tire pressure, a temperature sensor 9 that detects tire temperature, and an acceleration sensor 10 that detects acceleration (rotation) of the tire 2, and these are the controller 6. It is connected to the. The controller 6 is connected to a transmission antenna 11 capable of transmitting a radio wave in the UHF (Ultra High Frequency) band.

The vehicle body 5 is provided with a receiver (hereinafter referred to as a TPMS receiver) 12 that receives the tire pressure signals Stp transmitted from the tire pressure detectors 4a to 4d and monitors the tire pressure. The TPMS receiver 12 is provided with a tire air pressure monitoring ECU (Electronic Control Unit) 13 that controls the operation of the TPMS receiver 12 and an array antenna 14 as a receiving antenna capable of receiving UHF radio waves. In the tire 15 of the tire pressure monitoring ECU 13, tire IDs of the respective tires 2a to 2d are written and stored in association with tire positions (right front, left front, right rear, and left rear). The TPMS receiver 12 is disposed, for example, at the center position of the vehicle body 5 so as to take the same distance from the tire pressure detectors 4a to 4d. 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 detectors 4a to 4d transmit the tire pressure signal Stp by UHF at the time of tire rotation detection based on the sensor output of the acceleration sensor 10 or at a predetermined timing (regular or irregular). The tire pressure signal Stp includes a tire ID, pressure data of the tires 2a to 2d, temperature data of the tires 2a to 2d, and the like. The tire pressure detectors 4a to 4d transmit radio waves with a predetermined time difference so that radio waves do not overlap with the other tire pressure detectors 4a to 4d.

  When the tire pressure signals Stp of the tire pressure detectors 4a to 4d are received by the array antenna 14, the TPMS receiver 12 checks the tire ID in the tire pressure signal Stp, and if the ID verification is established, the same tire pressure signal Stp Check the pressure data inside. At this time, 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 to monitor the tire pressures of the tires 2a to 2d.

  The tire pressure monitoring ECU 13 is provided with an auto-location function for determining the front / rear / left / right mounting positions of the tires 2 a to 2 d as one function of the tire pressure monitoring system 3. The auto-location function allows the tires 2a to 2d to be registered again in the tire pressure monitoring ECU 13 even when the tires 2a to 2d are rotated or replaced with new tires, for example. This is a function for periodically checking the mounting position of 2d.

  As shown in FIG. 2, the array antenna 14 includes a plurality (two in this example) of antenna elements 17 (17a, 17b) arranged at a predetermined interval and shape. Connected to each antenna element 17a, 17b is an antenna circuit 18 (18a, 18b) that applies various processes to the output of the antenna elements 17a, 17b. Each antenna circuit 18a, 18b comprises a phase shifter 19 that rotates the phase of the received radio wave and an amplifier 20 that amplifies the received radio wave. The array antenna 14 adds the antenna outputs obtained by multiplying the array input signals by complex values (complex weights) by the antenna circuits 18a and 18b, respectively, by the adder 21 to obtain an array output. This process is performed by sequentially changing the complex value, and the array output of each directivity condition obtained thereby is acquired as a received radio wave.

  Further, the array antenna 14 of this example is an order processing system in which the antenna circuits 18a and 18b are viewed as one group and are shared by the tire pressure detectors 4a to 4d. The sequential processing method is a method in which one group of antenna circuits 18a and 18b is sequentially switched to the directivity of each of the tires 2a to 2d and this is repeated.

  In the memory 15 of the tire pressure monitoring ECU 13, a plurality (two in this example) of antenna complex weight coefficients ka and kb are registered in advance as coefficients of a complex value group input to the antenna circuits 18a and 18b. In the array antenna 14, the beam and null directions are determined by the antenna complex weight coefficients ka and kb. The antenna complex weight coefficients ka and kb have a plurality (two in this example) of complex values “x + jy” input to the antenna circuits 18a and 18b. As the antenna complex weight coefficients ka and kb, for example, values obtained in the development stage are registered in the memory 15 in advance. The antenna complex weight coefficients ka and kb have different required values for each vehicle type, for example.

The first antenna complex weight coefficient ka is constructed from four terms “x _a1 + jy _a1 ”, “x _a2 + jy _a2 ”, “x _a3 + jy _a3 ”, and “x _a4 + jy _a4 ” input to the antenna circuit 18 a. . The second antenna complex weight coefficient kb is constructed from four terms “x _b1 + jy _b1 ”, “x _b2 + jy _b2 ”, “x _b3 + jy _b3 ”, and “x _b4 + jy _b4 ” input to the antenna circuit 18 b. . The antenna complex weight coefficients ka and kb are ka (x _a1 + jy _a1 , x _a2 + jy _a2 , x _a3 + jy _a3 , x _a4 + jy _a4 ) and kb (x _b1 + jy _b1 , x _b2 + jy _b2 , x _b3 + jy _b3 , x _b4 + jy _b4 ), the first terms are paired, the second terms are paired, the third terms are paired, and the fourth terms are paired, and each antenna circuit 18a, 18b. Is input.

The set of complex values “x _a1 + jy _a1 ” and “x _b1 + jy _b1 ” sets the directivity of the array antenna 14 so that the null is directed to the right front tire pressure detector 4 a and the beam is directed to the other. A set of complex values “x _a2 + jy _a2 ” and “x _b2 + jy _b2 ” sets the directivity of the array antenna 14 so that the null is directed to the left front tire pressure detector 4 b and the beam is directed to the other. The set of complex values “x _a3 + jy _a3 ” and “x _b3 + jy _b3 ” sets the directivity of the array antenna 14 so that the null is directed to the right rear tire pressure detector 4 c and the beam is directed to the other. The set of complex values “x _a4 + jy _a4 ” and “x _b4 + jy _b4 ” sets the directivity of the array antenna 14 so that the null is directed to the left rear tire pressure detector 4d and the beam is directed to the other.

  The tire pressure monitoring ECU 13 includes an antenna complex weight coefficient switching unit 22 that switches the directivity of the array antenna 14 using the two antenna complex weight coefficients ka and kb registered in the memory 15, and an array antenna for each switched directivity. A tire position determination unit 23 that determines front / rear / left / right positions of the tires 2a to 2d based on an array output input from the tire 14 is provided. The antenna complex weight coefficient switching unit 22 is an example of a null direction switching unit.

  Next, the operation of the auto location function will be described with reference to FIGS. Note that the auto-location function is executed periodically or irregularly during, for example, traveling. Further, the tire pressure detectors 4a to 4d take an operation of transmitting the tire pressure signal Stp regularly or irregularly.

As shown in FIG. 3, during the auto-location operation, the antenna complex weight coefficient switching unit 22 inputs one item of the complex value “x _a1 + jy _a1 ” of the first antenna complex weight coefficient ka to the first antenna circuit 18a. By inputting a complex value “x _b1 + jy _b1 ” of one item of the second antenna complex weight coefficient kb to the second antenna circuit 18b, the null of the array antenna 14 is directed to the right front tire pressure detector 4a, and otherwise. Set the beam to face. That is, in the antenna complex weight coefficients ka and kb stored in the memory 15, one item of the complex value “x _a1 + jy _a1 ” of the first antenna complex weight factor ka and one item of the complex weight factor kb of the second antenna complex weight factor kb. The value “x _b1 + jy _b1 ” is used to form a directivity according to these complex values.

  As shown in FIG. 4, the TPMS receiver 12 at this time cannot receive radio waves from the right front tire pressure detector 4a, and can receive radio waves from the other three tire pressure detectors 4b to 4d. . Therefore, since the tire position determination unit 23 cannot receive the tire pressure signal Stp from the right front tire pressure detector 4a, it cannot obtain the ID1 of the tire pressure detector 4a, but the tire pressure of the tire pressure detectors 4b to 4d. By receiving the signal Stp, ID2 to ID4 of the tire pressure detectors 4b to 4d are acquired.

As shown in FIG. 5, the antenna complex weight coefficient switching unit 22 inputs the two complex values “x _a2 + jy _a2 ” of the first antenna complex weight coefficient ka to the first antenna circuit 18 a and inputs the second antenna complex weight. By inputting the complex value “x _b2 + jy _b2 ” of the two items of the coefficient kb to the second antenna circuit 18b, the null of the array antenna 14 is directed to the left front tire pressure detector 4b, and other than that, the beam is directed. Set. That is, in the antenna complex weight coefficients ka and kb stored in the memory 15, the two complex values “x _a2 + jy _a2 ” of the first antenna complex weight coefficient ka and the two complex values of the second antenna complex weight coefficient kb are used. The value “x _b2 + jy _b2 ” is used to form a directivity according to these complex values.

  As shown in FIG. 4, the TPMS receiver 12 at this time cannot receive radio waves from the left front tire pressure detector 4b and can receive radio waves from the other three tire pressure detectors 4a, 4c, and 4d. Take. That is, the tire position determination unit 23 cannot receive the tire ID 2 of the left front tire pressure detector 4b, but receives the tire pressure signal Stp of the tire pressure detectors 4a, 4c, and 4d, thereby detecting the tire pressure detector. ID1, ID3, and ID4 of 4a, 4c, and 4d are acquired.

  When the null of the array antenna 14 is switched from the right front tire pressure detector 4a to the left front tire pressure detector 4b, the tire position determination unit 23 sets “ID1” as the tire ID that could not be obtained with the previous directivity pattern. Will receive. Therefore, the tire position determination unit 23 identifies ID1 that could not be received when the null of the array antenna 14 was directed to the right front tire pressure detector 4a as the right front tire.

As shown in FIG. 6, the antenna complex weight coefficient switching unit 22 inputs the complex values “x _a3 + jy _a3 ” of the three items of the first antenna complex weight coefficient ka to the first antenna circuit 18a, and the second antenna complex weight By inputting the complex value “x _b3 + jy _b3 ” of the three items of the coefficient kb to the second antenna circuit 18b, the null of the array antenna 14 is directed to the right rear tire pressure detector 4c, and other than that, the beam is directed. Set to. That is, in the antenna complex weight coefficients ka and kb stored in the memory 15, three items of complex values “x _a3 + jy _a3 ” of the first antenna complex weight factor ka and three items of complex of the second antenna complex weight factor kb are used. The value “x _b3 + jy _b3 ” is used to form a directivity according to these complex values.

  As shown in FIG. 4, the TPMS receiver 12 at this time cannot receive radio waves from the right rear tire pressure detector 4c, but can receive radio waves from the other three tire pressure detectors 4a, 4b, and 4d. Take a state. That is, the tire position determination unit 23 cannot receive the tire ID 3 of the right rear tire pressure detector 4c, but can detect the tire pressure by receiving the tire pressure signals Stp of the tire pressure detectors 4a, 4b, and 4d. ID1, ID2, and ID4 of the devices 4a, 4b, and 4d are acquired.

  When the null of the array antenna 14 is switched from the left front tire pressure detector 4b to the right rear tire pressure detector 4c, the tire position determination unit 23 sets “ID2” as the tire ID that could not be obtained with the previous directivity pattern. Will be received. Therefore, the tire position determination unit 23 identifies ID2 that could not be received when the null of the array antenna 14 was directed to the left front tire pressure detector 4b as the left front tire.

As shown in FIG. 7, the antenna complex weight coefficient switching unit 22 inputs four items of complex values “x _a4 + jy _a4 ” of the first antenna complex weight coefficient ka to the first antenna circuit 18a, and the second antenna complex weights. By inputting the complex value “x _b4 + jy _b4 ” of the four items of the coefficient kb to the second antenna circuit 18b, the null of the array antenna 14 is directed to the left rear tire pressure detector 4d, and other than that, the beam is directed. Set to. That is, in the antenna complex weight coefficients ka and kb stored in the memory 15, the four complex values “x _a4 + jy _a4 ” of the first antenna complex weight coefficient ka and the four complex values of the second antenna complex weight coefficient kb are used. The value “x _b4 + jy _b4 ” is used to form a directivity according to these complex values.

  As shown in FIG. 4, the TPMS receiver 12 at this time cannot receive radio waves from the left rear tire pressure detector 4d and can receive radio waves from the other three tire pressure detectors 4a to 4c. Take. In other words, the tire position determination unit 23 cannot receive the tire ID 4 of the left rear tire pressure detector 4d, but receives the tire pressure signal Stp of the tire pressure detectors 4a to 4c, whereby the tire pressure detector 4a. ID1 to ID3 of ˜4c are acquired.

  When the null of the array antenna 14 is switched from the right rear tire pressure detector 4c to the left rear tire pressure detector 4d, the tire position determination unit 23 sets “ID3 as a tire ID that could not be obtained with the previous directivity pattern. "Will be received. Therefore, the tire position determination unit 23 identifies ID3 that could not be received when the null of the array antenna 14 was directed to the right rear tire pressure detector 4c as the right rear tire. And the tire position determination part 23 specifies ID4 in which position specification is not completed among ID1-ID4 as the remaining left rear tires.

  The tire pressure monitoring ECU 13 updates the tire positions registered in the memory 15 when the mounting positions of all the tires 2a to 2d can be specified. Thereby, even if the mounting positions of the tires 2a to 2d are rotated or replaced with new tires and the mounting positions of the tires 2a to 2d are changed, the tire mounting positions registered in the memory 15 are updated to the correct positions. Is done. Then, the tire air pressure monitoring ECU 13 repeatedly performs this auto location in a predetermined cycle, and updates the accurate mounting positions of the tires 2a to 2d as appropriate.

According to the configuration of the present embodiment, the following effects can be obtained.
(1) The antenna complex weight coefficients ka and kb such that the null is directed to a specific one of the four tire pressure detectors 4a to 4d and the beam is directed to the other one are previously stored in the memory 15 at the stage of development of the array antenna 14. Register. When the antenna complex weight coefficients ka and kb are set, for example, when the directivity is formed so that the null is directed to the right front tire pressure detector 4a and the beam is directed to the other, the transmission radio wave from the right front tire pressure detector 4a is transmitted. Can't receive, but can receive radio waves from other sources. Subsequently, when the directivity is set so that the null is directed to the left front tire pressure detector 4b and the beam is directed to the other, the transmission radio wave from the left front tire pressure detector 4b cannot be received, but the radio wave from the other is received. it can. By the way, it can be understood that the radio wave newly received at this time is the radio wave from the direction in which the null was directed in the previous directivity pattern. That is, the tire ID 1 of the right front tire 2a can be specified. And if the same process is performed by each tire 2b-2d, the attachment position of all four wheels can be specified.

  For this reason, if the tire position is determined using the array antenna 14 as in this example, the tire position can be determined without providing an initiator in each tire house. The tire position can be specified with a simple configuration that is not used. Further, even if the tire position is specified using the array antenna 14, in this example, the antenna complex weight coefficients ka and kb necessary for position determination are registered in the memory 15 in advance, and are then stored in the array antenna 14. Since the position is specified by selectively substituting for the calculation, the calculation is simpler than normal processing (for example, calculation with high load such as eigenvalue expansion). Therefore, the tire position can be specified by using the array antenna 14 by calculation with a low load.

  (2) In the case of the array antenna 14, the number of nulls that can be formed has a relationship of “the number of antennas −1”. In the case of the system, normally, “4” antenna elements 17 are required according to the above formula. However, in this example, the number of antenna elements 17 and circuit devices can be reduced because only two antenna elements 17 are required.

  (3) When the auto-location function enters the execution state, the directivity of the array antenna 14 is changed in order, and the positions of all four wheels are confirmed. Therefore, since the tire positions of all four wheels are confirmed by a single process, the tire positions can be identified efficiently.

  (4) The radio waves transmitted from the tire pressure detectors 4a to 4d at the time of tire position determination are tire pressure signals Stp that are constantly transmitted. Therefore, in both the tire pressure monitoring and the tire position determination, the tire pressure detectors 4a to 4d have only to perform the operation of transmitting the tire pressure signal Stp, and therefore it is sufficient to always perform the same transmission operation. Therefore, the tire pressure detectors 4a to 4d do not have to take any special action when determining the tire position.

(Second Embodiment)
Next, a second embodiment will be described with reference to FIGS. In addition, 2nd Embodiment is an Example for determining accurately which ID is tire ID of the direction which faced directivity (null). Therefore, the same parts as those in the first embodiment are denoted by the same reference numerals, detailed description thereof is omitted, and only different parts are described in detail.

As shown in FIG. 8, the tire air pressure monitoring ECU 13 receives the array gain of each tire ID based on the array input vector X that is directly input from the antenna elements 17a to 17d and the array output Y that is the output after the array processing. and Aregein calculator 24 for G _ar calculated, data information (tire ID, pressure data, etc.) contained in the array output Y and a demodulator 25 to demodulate the provided. The array gain calculation unit 24 calculates the array gain G _ar of each tire ID in the directivity every time the null is directed toward each of the tires 2a to 2d. The demodulator 25 demodulates the received radio wave every time the tire pressure signal Stp is received in each null direction. Tire position determination unit 23, based on the Aregein G _ar calculated by Aregein calculator 24, and a tire ID demodulated determines tire position.

Next, the operation of the auto location function will be described with reference to FIGS.
As shown in FIG. 8, the input of the first antenna element 17a when null is directed to a certain tire 2 is the array input “a ₁ + jb ₁ ”, and the input of the second antenna element 17b is the array input “a ₂ + jb ₂ ”, the input of the third antenna element 17 c is the array input“ a ₃ + jb ₃ ”, and the input of the fourth antenna element 17 d is the array input“ a ₄ + jb ₄ ”. The array input vector X is input from the antenna elements 17a to 17d, and the array output Y is input from the adder 21.

The array input vector X is calculated by the following equation (1). In the following equation (1), [*] ^T represents a transposed matrix of “*”.

The array output Y is “a _out + jb _out ”, which is the result of combining the array inputs of the antenna elements 17 a to 17 d by array processing. The array output Y output from the adder 21 is input to the demodulator 25 in addition to the array gain calculator 24.

The array gain G _ar is calculated by the following equations (2) to (4). In the following formula (2), [*] ^H represents a complex conjugate transpose of “*”.

The array gain calculation unit 24 uses the array input vector X and the array output Y that are input when a beam is directed toward another tire 2 and a beam ID is received when the null is directed toward a certain tire 2. The array gain G _ar is calculated and output to the tire position determination unit 23. The demodulator 25 demodulates the array output Y input at this time, that is, the received tire ID and pressure data, and outputs the demodulated data to the tire position determination unit 23. Of the received tire IDs, the tire position determination unit 23 determines that the tire ID at which the array gain G _ar has the minimum value is the tire ID in the direction in which the null is directed. The above processing is executed in each null direction, and the four tire IDs are specified.

  FIG. 9 shows an example in which, for example, when a null (for example, “−50 dB”) is directed to the tire ID1 and a beam (for example, “0” dB) is directed to the tire ID2, the tire ID1 to which the null is directed is not normally received. . The input of the array antenna 14 takes a value closer to “0” as the radio wave is stronger. In the same figure, when the array input of the tire ID 1 is “−10 dB”, for example, the directivity in the direction of the tire ID 1 is “−50 dB”, so the input is attenuated and output, and the array output is “−60 dB”. Become. Further, when the array input of the tire ID 2 is “−5 dB”, for example, the directivity in the direction of the tire ID 2 is “0 dB”, so the input is output as it is, and the array output is “−5 dB”.

At this time, Aregein G _ar tire ID1 takes the output ratio based on the array input "-10dB" and the array output "-60dB". Further, Aregein G _ar tire ID2 takes the output ratio based on the array input "-5dB" and the array output "-5dB". Thus, in a typical communication environment without receiving radio waves from a directed null side, Aregein G _ar tire ID1 is calculated results to be lower than Aregein G _ar tire ID2. That is, under normal communication environment, the tire ID in the direction in which the null is directed can be identified as ID1 as expected.

  FIG. 10 shows an example in which, for example, when a null (for example, “−50 dB”) is directed to the tire ID1 and a beam (for example, “0” dB) is directed to the tire ID2, the tire ID1 with the null directed is received. . By the way, as can be seen from the figure, when determining the tire ID in the null direction, the array of the tire ID 1 is used only when the array output is compared, even though the null is directed toward the tire ID 1. The input becomes higher than the tire ID2, and the tire ID1 cannot be identified from the ID in the null direction.

In the case of FIG. 10, the array gain G _{ar of the} tire ID 1 takes an input / output ratio based on the array input “0 dB” and the array output “−50 dB”. Further, Aregein G _ar tire ID2 takes the output ratio based on the array input "-60dB" and the array output "-60dB". Therefore, even in a communication environment where thus receives radio waves from the tire 2 supposed toward null, Aregein G _ar is the calculation result lower than Aregein G _ar tire ID2 tire ID1 is obtained. That is, even in this communication environment, the tire ID in the direction in which the null is directed can be identified as ID1 as in the normal case.

  When the tire position determination unit 23 finishes determining the tire ID in one direction facing the null, the tire position determination unit 23 switches the null direction to another and specifies the tire ID by the same procedure. And the tire position of four wheels is determined by specifying tire ID of each null direction in all four wheels.

According to the configuration of this embodiment, in addition to (1) to (4) described in the first embodiment, the following effects can be obtained.
(5) At the time of tire position determination, even if the beam is directed to the other tire 2 while directing the null to a certain arbitrary tire 2, the radio wave from the tire 2 facing the null may be received. . This is because, for example, a change in the propagation environment caused by the rotational position of the tire 2 or a variety of actual environments during traveling are cited. Therefore, in this embodiment, it obtains the Aregein G _ar from the input and output of the array antenna 14, determines the tire position based on Aregein G _ar. Therefore, even if it is affected by the reception intensity, the tire ID with the null direction can be determined with high accuracy.

(Third embodiment)
Next, a third embodiment will be described with reference to FIGS. In addition, 3rd Embodiment is an Example which ensures the precision of tire position determination by controlling the electromagnetic wave transmission timing of the tire pressure detector 4 (4a-4d). In this example, only different portions will be described in detail.

  As shown in FIG. 11, each tire air pressure detector 4 takes a movement that rotates around the center of the tire 2 according to the rotation of the tire 2. For example, assuming that the angle formed by the tire air pressure detector 4 with respect to the vertical line Lk passing through the tire center is the tire rotation angle θ, the tire air pressure detector 4 is rotated at the tire rotation angle θ during tire rotation. Will rotate in the range of 0 ° to 360 °.

  FIG. 12 shows an output change of the gain (input / output ratio) [dB] of the array antenna 14 with respect to the tire rotation angle θ [deg]. As shown in the figure, when the tire rotation angle θ of the right rear tire 2c is “0 °”, the right rear tire 2c rotates even if the directivity null is directed to the right rear tire 2c. It can be seen that when the rotation angle θ changes, the null does not turn to the right rear tire 2c. This is mainly because the electrically formed directivity null point is very sharp and the tire air pressure detector 4 (acceleration sensor 10) cannot be allowed to rotate slightly. Therefore, this leads to deterioration in the accuracy of tire position determination, and some measures are required.

As shown in FIG. 13, the acceleration sensor (G sensor) 10 of this example detects a gravitational force component 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. If the gravitational force Gr is known, the rotation angle around the center of the tire 2 (axle 31) formed by the tire air pressure detector 4 can be known. The rotation angle can be calculated by, for example, the expression cos ⁻¹ (Gr / G), and is obtained as an angle with the vertical line Lk passing through the tire center as a reference “0 °”. The acceleration sensor 10 repeatedly detects the gravitational force Gr at a predetermined detection interval.

  Further, as shown in FIG. 14, the gravitational component force Gr during vehicle travel (during tire rotation) is dominated by the component force due to the centrifugal force rather than the component force in the axle direction. In particular, if the tire rotation speed increases, the gravitational component force Gr resulting from centrifugal force increases significantly. Therefore, when calculating the tire rotation angle θ from the gravitational component force Gr, in order to accurately calculate the angle, the component force resulting from the centrifugal force, that is, the gravity component force Gr, is obtained from the actual value of the signal output from the acceleration sensor 10. It is necessary to subtract the offset value.

  As shown in FIG. 15, the controller 6 calculates an offset value for calculating the offset value of the gravity force Gr generated due to the centrifugal force when the tire rotates based on the detection signal (gravity component force Gr) of the acceleration sensor 10. A rotation angle determination unit 33 that corrects the gravity component force Gr by subtracting the offset value from the actual value of the output signal of the acceleration sensor 10 and the value calculation unit 32 and determines the tire rotation angle θ from the corrected gravity component force Gr. And a radio wave transmission control unit 34 that causes the tire air pressure detector 4 to perform radio wave transmission when the tire rotation angle θ takes an arbitrary rotation angle. The acceleration sensor 10 is an example of a gravitational component force detection unit.

  The offset value calculation unit 32 calculates the offset value by taking a sample of the gravitational force Gr from the acceleration sensor 10 for a certain period of time (see FIG. 14) and obtaining an average value thereof. The rotation angle determination unit 33 corrects the actual value by subtracting the offset value from the actual value of the output signal of the acceleration sensor 10 at a predetermined calculation timing, and calculates the tire rotation angle θ based on the correction value. When the tire rotation angle θ obtained by the rotation angle determination unit 33 becomes an arbitrary rotation angle (angle or angle range), the radio wave transmission control unit 34 receives a radio wave (tire pressure) from the transmission antenna 11 for tire position determination. Signal Stp).

  Now, as shown in FIGS. 16A and 16B, when the tire 2 rotates, the acceleration sensor 10 detects a gravitational force component Gr corresponding to the tire rotation angle θ. At this time, the offset value calculation unit 32 samples the gravitational force Gr output from the acceleration sensor 10 for a certain period of time, and calculates an offset value by obtaining an average value thereof. The rotation angle determination unit 33 corrects the actual value by subtracting the offset value from the actual value of the output signal of the acceleration sensor 10, and calculates the tire rotation angle θ based on the correction value. For example, when the gravity component Gr is “0.984 G”, the tire rotation angle θ is calculated as “350 °”, and when the gravity component Gr is “0.174 G”, the tire rotation angle θ is calculated as “80 °”. Is done. The above angle calculation is repeatedly executed by a predetermined calculation cycle.

  Incidentally, the acceleration sensor 10 repeatedly detects the gravitational force Gr with a high frequency in a short cycle, and the offset value calculation unit 32 reads the gravitational force Gr periodically at a certain timing. The component force Gr is acquired and the offset value is calculated. When the offset value is calculated, the rotation angle determination unit 33 subtracts the previously obtained offset value from the actual value of the gravitational component force Gr to be acquired next, and calculates the tire rotation angle θ using this correction value. To do. The above processing is repeatedly executed during tire rotation.

  Here, in this type of acceleration sensor 10, since one cycle of angle calculation is 180 °, the gravitational component force Gr is obtained when the tire rotation angle θ is “0 ° to 180 °” and “180 ° to 360 °”. Takes the same value. That is, it cannot be distinguished whether the tire pressure detector 4 is located on the left or right side with respect to the vertical line Lk. Therefore, the rotation angle determination unit 33 of this example identifies whether the tire air pressure detector 4 is present on the left or right of the vertical line Lk by checking whether the change in the calculated gravitational force Gr increases or decreases. To do.

  When the tire rotation angle θ calculated by the rotation angle determination unit 33 becomes an arbitrary rotation angle (angle or angle range), the radio wave transmission control unit 34 receives a radio wave (tire pressure) from the transmission antenna 11 for tire position determination. Signal Stp). The arbitrary tire rotation angle θ mentioned here refers to a value of a rotation angle at which the desired directivity of the array antenna 14 can be maintained, or an angle range thereof. Further, the radio wave for tire position determination may be the tire pressure signal Stp described above or a simple signal that only notifies the tire ID. Therefore, at the time of tire position determination, the radio wave transmitted from the tire pressure detector 4 can be received with a desired array gain, and the tire position determination can be executed with high accuracy.

According to the configuration of the present embodiment, in addition to (1) to (5) described in the first and second embodiments, the following effects can be obtained.
(6) The tire air pressure detector 4 calculates the rotation angle of the tire 2 based on the gravitational component force Gr detected by the acceleration sensor 10 of the tire air pressure detector 4, and the tire air pressure detector 4 takes an arbitrary angle. Transmit radio waves for tire position determination. For this reason, although the directivity null of the array antenna 14 is directed to the predetermined tire 2, a situation in which the null is not directed to the tire 2 is avoided. Therefore, it is advantageous for accurately determining the tire position.

  (7) Although the signal of the acceleration sensor 10 itself cannot distinguish between “0 ° to 180 °” and “180 ° to 360 °” per tire rotation, the gravity component Gr increases or decreases. It is determined whether the tire air pressure detector 4 is located on the left or right of the vertical line Lk. Therefore, it further contributes to the improvement of the tire position determination accuracy.

  (8) The offset value is calculated by taking a sample of the gravitational component force Gr for a fixed time, and the offset value is removed from the actual value of the gravitational component force Gr to correct the gravitational component force Gr. Calculate tire rotation angle. Therefore, since the tire rotation angle can be obtained with high accuracy, the tire position determination accuracy can be further improved.

(Fourth embodiment)
Next, a fourth embodiment will be described with reference to FIGS. In addition, 4th Embodiment is an Example which changed a part of 3rd Embodiment, Comprising: Only a different part is explained in full detail also in this example.

  As shown in FIG. 17, when the vehicle 1 travels, there is a situation in which the rotational speed of the tire 2 changes depending on the vehicle speed situation (for example, when the vehicle is stopped, accelerating, traveling at a constant speed, decelerating, etc.). For this reason, for example, if the offset value is calculated when the vehicle 1 is accelerating or decelerating, the offset value is obtained by the gravity component Gr which is unstable due to a change that increases or decreases. The offset value cannot be determined, and the tire rotation angle θ cannot be accurately determined.

  Therefore, as shown in FIG. 18, the controller 6 of this example has a constant speed traveling determination that determines whether or not the vehicle 1 is traveling at a constant speed based on the offset value calculated by the offset value calculating unit 32. A portion 35 is provided. If there is no increase / decrease change in the offset value, the constant speed traveling determination unit 35 determines that the vehicle 1 is traveling at a constant speed. When it is determined that the vehicle 1 is traveling at a constant speed, the radio wave transmission control unit 34 is permitted to transmit a radio wave for tire position determination from the transmission antenna 11.

  Now, as shown in FIG. 19, it is assumed that the stopped vehicle 1 starts traveling and takes a motion of stopping, accelerating, driving at a constant speed, decelerating, and stopping. The constant speed traveling determination unit 35 sequentially monitors whether or not the vehicle 1 is traveling at a constant speed by confirming a change in the offset value. When there is no increase / decrease change in the offset value, the vehicle 1 Recognize that it is running. The radio wave transmission control unit 34 causes the transmission antenna 11 to transmit a radio wave for tire position determination when the tire rotation angle θ is an arbitrary rotation angle (angle or angle range) and the vehicle 1 is traveling at a constant speed. Therefore, radio wave transmission is permitted when the tire rotation angle θ calculated by an accurate offset value is calculated, which is advantageous for accurately determining the tire position.

According to the configuration of the present embodiment, the following effects can be obtained in addition to (1) to (8) described in the first to third embodiments.
(9) When the vehicle 1 travels at a constant speed, if radio wave transmission for tire position determination is permitted from the tire pressure detector 4, the value is in accordance with the tire rotation angle derived from the stable offset value, Radio waves for tire position determination can be transmitted from the tire pressure detector 4. Therefore, this further contributes to improving the accuracy of determining the tire position.

(Fifth embodiment)
Next, a fifth embodiment will be described with reference to FIGS. In addition, 5th Embodiment is a modification of 1st-4th embodiment, Comprising: Only a part from which this example differs is explained in full detail.

  As shown in FIG. 20, the tire pressure monitoring ECU 13 directs the tire pressure detectors 4a to 4d to direct nulls (otherwise beams) to receive each tire ID and to perform directivity switching repeated multiple times. A return unit 36 and a reception tire ID statistics unit 37 that takes statistics of reception tendency when a plurality of tire IDs are received are provided. In the case of the sequential processing method, the directivity switching repeater 36 switches nulls continuously and quickly so as to acquire the tire ID reception tendency in a short time, and executes this multiple times (multiple rounds). The reception tire ID statistics unit 37 determines the tire position by, for example, a majority method or an averaging method. The directivity switching repeater 36 and the received tire ID statistical unit 37 are examples of a statistical processing unit.

  FIG. 21 shows a table summarizing an operation example of the majority voting method. The majority decision method is a method of counting tire IDs having the smallest array gain in each null and determining the tire ID having the smallest total number as the tire ID in the null direction. For example, when null is directed to the right front tire 2a, for example, the ID1 reception count is “0”, the ID2 reception count is “12”, the ID3 reception count is “10”, and the ID4 reception count is “13”. "Time", ID1 with the smallest number of receptions is recognized as the ID of the right front tire 2a. The tire positions of ID2 to ID4 are also specified by the same method.

  FIG. 22 shows a table summarizing operation examples of the averaging method. The averaging method is a method of calculating the average value (average absolute value) of the array gain for each tire ID in each null, and determining the tire ID having the smallest average value as the tire ID in the null direction. For example, when null is directed to the right front tire 2a, for example, the array gain average value of ID1 is “low value”, the array gain average value of ID2 is “high value”, the array gain average value of ID3 is “high value”, and the array gain average of ID4 If the value is “high value”, ID1 having the lowest average value is recognized as the ID of the right front tire 2a. The tire positions of ID2 to ID4 are also specified by the same method.

  By the way, in both the majority method and the averaging method, the tire position is determined by intermittently transmitting a radio wave from the tire pressure detector 4. It depends on the radio wave transmission interval. In order to shorten the determination time, for example, the radio wave transmission period of each tire pressure detector 4a to 4d may be shortened. In this case, the radio wave transmission is repeated many times. The power consumed in ˜4d increases, which is not realistic.

  Therefore, as shown in FIG. 23, a mode switching function may be provided that allows the operation mode of the tire pressure detector 4 to be switched separately to a dedicated mode for specifying the tire position. In this case, the controller 6 of each tire pressure detector 4 is provided with a traveling state determination unit 38 that determines the traveling state of the vehicle 1 based on the gravitational force Gr detected by the acceleration sensor 10. For example, when the traveling state determination unit 38 detects that there is no change in the gravity component Gr, the traveling state determination unit 38 determines that the state of the vehicle 1 is stopped. Moreover, the driving | running | working state determination part 38 will determine the state of the vehicle 1 as parking, if it confirms that the state of a stop passes predetermined time.

  The controller 6 is provided with a mode switching unit 39 that switches the operation mode of the tire air pressure detector 4 based on the determination result of the traveling state determination unit 38. When it is determined that the vehicle 1 is in the parking state, the mode switching unit 39 switches the operation mode of the tire air pressure detector 4 from the normal mode to the tire position determination mode. The tire position determination mode is a mode in which radio waves (tire IDs) are repeatedly transmitted at a shorter cycle (shorter time interval) than in the normal mode. When the radio wave is transmitted a predetermined number of times in the tire position determination mode, the mode switching unit 39 returns the tire pressure detector 4 to the normal mode.

Next, the mode switching operation of the tire pressure detector 4 will be described with reference to FIG.
In step 101, the traveling state determination unit 38 recognizes the stop based on the gravitational force Gr detected by the acceleration sensor 10, and whether the stop time at that time has become a predetermined time (for example, 10 minutes) or more. Judge whether or not. If the stop time is equal to or longer than the predetermined time, it is determined that the vehicle is parked, and the process proceeds to step 102. When parking, there is a high possibility that the tire 2 will be replaced or rotated. On the other hand, if the stop time is less than the predetermined time, it is determined that the vehicle is stopped and the process proceeds to step 103.

  In step 102, the mode switching unit 39 switches the operation mode of the tire air pressure detector 4 from the normal mode to the tire position determination mode. The tire pressure detector 4 repeatedly transmits radio waves (tire IDs) in the tire position determination mode with a shorter cycle than in the normal mode. Thereby, the TPMS receiver 12 can receive the tire ID necessary for the tire position determination a plurality of times in a short time. Note that the radio wave transmitted from the tire pressure detector 4 in the tire position determination mode may be the tire pressure signal Stp or simply a signal for notifying the tire ID. When the radio wave is transmitted a predetermined number of times in the tire position determination mode, the process proceeds to step 103.

  In step 103, the mode switching unit 39 returns the operation mode of the tire pressure detector 4 from the tire position determination mode to the normal mode. As a result, the tire pressure detector 4 returns to a state in which, for example, a radio wave is transmitted at a long cycle, and the power consumed for the radio wave transmission is kept small.

According to the configuration of the present embodiment, in addition to (1) to (9) described in the first to fourth embodiments, the following effects can be obtained.
(10) The process of acquiring the tire ID by directing the beam toward each of the tires 2a to 2d is executed a plurality of times, the statistics of the reception tendency of the tire ID acquired at this time are calculated, and the tire position is determined based on the statistical result judge. Therefore, the tire position can be determined with high accuracy.

  (11) For example, when the reception count is “1”, the determination probability is “80%”, when the reception count is “3”, the determination probability is “94%”, and when the reception count is “5” When the determination probability is “97%” and the number of receptions is “7”, the determination probability is “99%”. As the number of receptions is increased, the determination probability tends to be improved accordingly. Therefore, if the number of times of acquiring the tire ID by directing the null toward each of the tires 2a to 2d is increased, the determination accuracy of the tire position can be increased accordingly.

(12) When the statistical processing method is the majority method, the tire position can be determined by a simple process of taking the majority of the number of received tire IDs.
(13) When the statistical processing method is an averaging method, the tire position can be determined by a simple process of averaging the array gains of the received tire IDs. Further, as a result of actual measurement, the averaging method is more advantageous than the majority method because the tire position determination accuracy tends to be higher.

  (14) When it is determined that the vehicle 1 has changed from parking to running, the operation mode of the tire air pressure detector 4 is switched from the normal mode to the tire position determination mode. In the tire position determination mode, radio waves are continuously transmitted from the tire pressure detector 4 at short intervals (short cycles), so that the tire position can be determined in a short time. Further, even if radio waves are transmitted from the tire pressure detector 4 at short intervals, it is only during the tire position determination mode, and radio waves are transmitted at long intervals in the normal mode. Power to be kept small. In this way, it is possible to achieve both shortening of the tire position determination and suppression of power consumption of the tire pressure detector 4.

(Sixth embodiment)
Next, a sixth embodiment will be described with reference to FIGS. In addition, 6th Embodiment is a modification of 1st-5th Embodiment, Comprising: Only a part from which this example differs is explained in full detail.

  As shown in FIG. 25, each antenna element 17a-17d is connected to each antenna circuit 18a-18d through A / D converters 40a-40d, respectively. The A / D converters 40a to 40d perform A / D conversion on the received radio waves, and output digital signals to the antenna circuits 18a to 18d. The antenna circuits 18a to 18d perform array signal processing on the input digital signals to obtain an array output necessary for determining the tire position.

  The tire pressure monitoring ECU 13 is provided with a reception system switching unit 41 capable of switching the number of reception systems of the array antenna 14. The reception system switching unit 41 switches the number of systems of the reception system by switching on / off of the switch 43 disposed in the middle of the branch line 42 and switching the antenna complex weight applied to the antenna circuits 18a to 18d, for example. . For example, when the tire position determination is completed, the reception system switching unit 41 restricts the reception system to one system and stops the operation of the other reception systems.

  Now, as shown in FIG. 25, when the reception system switching unit 41 determines that the vehicle 1 has started running from parking, for example, when an ignition switch (not shown) of the vehicle 1 is switched from OFF to ON, the tire position Is determined, the array antenna 14 is operated in a plurality of systems. At this time, the reception system switching unit 41 turns off the switch 43 to disable the branch line 42 and adds a predetermined antenna complex weight to the antenna circuits 18a to 18d to enable the antenna circuits 18a to 18d. Thereby, the array signal processing in the array antenna 14 becomes possible, and the tire position can be specified by the processing. The tire position determination unit 23 determines the attachment positions of the tires 2a to 2d through a process of acquiring a tire ID by directing each tire 2a to 2d with a null.

  As illustrated in FIG. 26, when the determination of the tire position is completed, the reception system switching unit 41 turns on the switch 43 to enable the branch line 42 and, for example, the antenna complex weight “0 + j0” to each antenna circuit 18a to 18d. ”To invalidate the antenna circuits 18a to 18d, thereby reducing the reception system of the array antenna 14 to one system. That is, the antenna element 17a is directly connected to the control circuit of the tire pressure monitoring ECU 13 through the branch line 42, and the operations of the antenna circuits 18a to 18d are stopped. The TPMS receiver 12 receives the tire air pressure signal Stp transmitted from the tire air pressure detectors 4a to 4d at a predetermined timing by the array antenna 14 having only one receiving system, whereby each tire 2a to 2d. Monitor tire pressure.

According to the configuration of the present embodiment, the following effects can be obtained in addition to (1) to (14) described in the first to fifth embodiments.
(15) Since the reception system of the array antenna 14 is reduced to one after the tire position determination is completed, the power consumption applied to the TPMS receiver 12 can be reduced.

Note that the embodiment is not limited to the configuration described so far, and may be modified as follows.
-In each embodiment, each communication which directs a beam to a predetermined one of the tire pressure detectors 4a to 4d and directs the beam to the other is performed first, and after collecting all the tire ID1 to ID4, in which direction The tire positions of all four wheels can also be specified by checking which tire ID has not been acquired when the null is facing.

In each embodiment, the switching order of nulls is not limited to right front → left front → right rear → left rear, and can be appropriately changed to other orders.
In each embodiment, various methods such as the MUSIC method, the beamformer method, and the Capon method can be adopted as a method for estimating the radio wave arrival direction of the array antenna 14.

  In each embodiment, the tire air pressure detector 4 is an operation for transmitting radio waves irregularly, for example, when parking and stopping, if the tire 2 is not rotating, from one transmission to the next transmission over time. The time interval may be gradually increased. In this case, the power supply of the tire pressure detector 4 can be saved.

In each embodiment, the tire air pressure detector 4 may take a system that does not transmit radio waves when the tire 2 is not rotating.
In each embodiment, a time limit may be set for the execution time of auto location, and if all four wheels cannot be located even if the time limit is exceeded, the processing may be forcibly terminated and the subsequent steps may be performed subsequently.

  In each embodiment, the radio wave used for determining the tire position may be a radio wave dedicated to position determination, for example. As an example of this, for example, in addition to the tire pressure signal Stp, for example, the tire pressure detectors 4a to 4d periodically transmit radio waves including only the tire ID, and the tire position is specified based on this ID. It may be.

  In each embodiment, the development stage refers to, for example, design and simulation work before manufacturing the TPMS receiver 12, the tire pressure monitoring ECU 13, and the array antenna 14.

In each embodiment, the target of tire position determination is not limited to the front and rear, left and right tires 2a to 2d, and may include, for example, spare tires.
In each embodiment, as shown in FIG. 27, the array antenna 14 is provided with a plurality of antenna circuit units 50a to 50d for each of the four tire pressure detectors 4a to 4d, and these are operated at the same time. A parallel processing method in which the tire position is determined by receiving radio waves transmitted from the tire pressure detectors 4a to 4d may be used. Each antenna circuit unit 50a-50d is connected to each antenna element 17a, 17b via a corresponding A / D converter 40a, 40b. In the case of the parallel processing method, any time a radio wave is transmitted from each of the tire pressure detectors 4a to 4d, the radio wave can be received, so that the tire position determination can be completed in a short time. In the case of this method, it is not necessary to switch the antenna complex weights of the antenna circuit units 50a to 50d, and they may be given to the phase shifters 19 and the amplifiers 20 as constants.

  -In 3rd and 4th embodiment, you may synchronize the calculation of an offset value, and the calculation of a tire rotation angle. That is, by simultaneously performing the sampling timing of the gravitational component force Gr and the tire rotation angle calculation timing, the gravity component force Gr is simultaneously sampled while calculating the tire rotation angle. The offset value may be updated and this process may be repeated.

In the third and fourth embodiments, the sampling period of the offset value and the calculation period of the tire rotation angle can be freely changed.
In the fifth embodiment, when the tire position is determined by statistical processing, it is not necessary to receive a predetermined number of tire IDs. For example, in the case of the majority method, when the tire ID is satisfied a predetermined number of times or continues a predetermined number of times, the processing may be terminated at that time. In the case of the averaging method, the process may be terminated when the average value satisfies a predetermined value.

In the sixth embodiment, the method of switching the reception system is not limited to the configuration using the switch 43, and may be realized by, for example, switching on / off the power supply of the element itself.
In each embodiment, the gravitational component force may be a component force in a direction orthogonal to the component force in the axle direction.

-In each embodiment, a gravity detection part is not limited to the acceleration sensor 10, A various sensor is applicable.
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 device, the tire position determination unit is configured to detect a tire pressure that is a transmission source of a newly received radio wave when the null is directed in another direction by switching the antenna complex weight coefficient. The tire position is determined by determining that the tire is in the direction in which the null was directed before the coefficient switching, and the position of the four wheels is specified by sequentially performing this process on each tire. According to this structure, it becomes possible to specify the attachment position of a tire smoothly in order.

  (B) In the tire position determination device, the receiver is disposed at a central position in a horizontal direction of the vehicle body (a plane direction along a road surface). According to this configuration, the radio wave transmitted from each tire pressure detector can be efficiently received by the receiver.

  (C) In the tire position determination device, the tire pressure detector is a type that repeatedly transmits the tire pressure signal by itself at a specific interval. According to this configuration, the entire system may be a simple configuration.

DESCRIPTION OF SYMBOLS 1 ... Vehicle, 2 (2a-2d) ... Tire, 3 ... Tire pressure monitoring system, 4 (4a-4d) ... Tire pressure detector, 5 ... Vehicle body, 10 ... Acceleration sensor as gravity force detection part, 12 ... TPMS receiver, 14 ... array antenna, 15 ... memory, 17 (17a to 17d) ... antenna element, 19 ... phase shifter, 20 ... amplifier, 21 ... adder, 22 ... antenna complex weight switching as null direction switching unit 23: Tire position determination unit, 24 ... Array gain calculation unit, 32 ... Offset value calculation unit, 33 ... Rotation angle determination unit, 34 ... Radio wave transmission control unit, 35 ... Constant speed travel determination unit, 36 ... Statistical processing unit Configuring directivity switching repeating unit, 37... Receiving tire ID statistical unit configuring statistical processing unit, 38... Traveling state determining unit, 39... Mode switching unit, 41 .. receiving system switching unit, Stp. Tire pressure signal, which is an example of a, ka, kb ... antenna complex weight coefficient, G _ar ... Aregein, theta ... tire rotation angle, Lk ... vertical line, Gr ... gravitational component force.

Claims (14)

Tire air pressure is transmitted to the vehicle body as a tire air pressure signal detected by a tire air pressure detector attached to each tire, and the tire air pressure is monitored by the receiver of the vehicle body by receiving the tire air pressure signal. In a tire position determination device that is used in a monitoring system, identifies the position of the tire pressure detector based on radio waves transmitted from the tire pressure detector, and determines the mounting position of the tire.
An array antenna capable of receiving radio waves transmitted from the tire pressure detector;
An antenna complex weight coefficient for directing the array antenna null to only one specific one of the plurality of tire pressure detectors is previously registered in the memory for each direction of the tire pressure detector, and the antenna complex weight A null direction switching unit capable of switching the directivity of the array antenna using a coefficient;
A tire position determination device, comprising: a tire position determination unit that determines the tire position based on radio waves received at each directivity. An array gain calculation unit for calculating an array gain of each ID received from the tire pressure detector based on the input and output of the array antenna;
The tire position determination device according to claim 1, wherein the tire position determination unit determines an ID in a direction in which a null is directed from the value of the array gain. The tire position determination apparatus according to claim 1 or 2, wherein the tire position determination is executed at a specific timing, and all four wheels are specified in a single process. The tire position determination device according to any one of claims 1 to 3, wherein the radio wave used for the determination of the tire position is the tire pressure signal transmitted as tire pressure information. The tire pressure detector is
Based on a signal output from the gravitational component force detection unit of the tire pressure detector, a rotation angle determination unit for obtaining a rotation angle around the tire center made by the tire pressure detector;
5. A radio wave transmission control unit that executes radio wave transmission only when the rotation angle calculated by the rotation angle determination unit forms a specific angle or angle range. The tire position determination device according to claim 1. The rotation angle determination unit determines whether the change in the gravitational force is increased or decreased, thereby determining whether the tire pressure detector is located on the left or right with respect to a vertical line passing through the tire center. The tire position determination device according to claim 5, wherein the tire position determination device is identified. The tire pressure detector is
Based on a signal output from the gravitational force detector, an offset value calculator that calculates an offset value of the gravitational force due to the centrifugal force generated in the tire pressure detector during tire rotation,
The tire position determination according to claim 5 or 6, wherein the rotation angle determination unit calculates the rotation angle from the gravity component force after reflecting the offset value in the actual value of the gravity component force. apparatus. The tire pressure detector is
Based on a signal output from the gravitational component force detection unit, a constant speed traveling determination unit that determines whether or not the vehicle is traveling at a constant speed,
The tire position determination device according to any one of claims 5 to 7, wherein the radio wave transmission control unit also sets a condition for executing radio wave transmission that the vehicle is traveling at a constant speed. A process for receiving the ID of the tire pressure detector by directing a null toward each of the tire pressure detectors is executed a plurality of times, and includes a statistical processing unit that calculates statistics of the number of received IDs.
The tire position determination unit according to any one of claims 1 to 8, wherein the tire position determination unit determines the tire position based on a statistical result by the statistical processing unit. The statistical processing unit counts the ID having the maximum array gain in each of the directivities, and the tire position determination unit determines the tire position based on the counting result. The tire position determination device according to 1. The statistical processing unit calculates an average value of an array gain for each ID in each directivity, and the tire position determination unit determines the tire position based on the average value of the array gain. The tire position determination device according to claim 9. The tire pressure detector is
Based on a signal output from the gravitational component force detection unit of the tire pressure detector, a traveling state determination unit that determines whether the vehicle has shifted from parking to traveling;
A mode switching unit that switches an operation mode of the tire air pressure detector from a normal mode to a tire position determination mode when it is determined that the vehicle has shifted from parking to running. 11. The tire position determination device according to claim 11. 13. A reception system switching unit that narrows down the reception system by connecting only necessary ones of the plurality of antenna elements of the array antenna after the tire position determination is provided. The tire position determination device according to any one of the above. The array antenna includes a circuit group of a phase shifter group, an amplifier group, and an adder for each tire pressure detector, and adopts a parallel processing system that can always receive radio waves transmitted from each tire pressure detector. The tire position determination device according to any one of claims 1 to 13, wherein