JP2014226941A - Wheel position determination device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wheel position determination device in which a state that wheel position determination is disabled due to the null point can be avoided.SOLUTION: In a tire sensor unit 3, an acceleration sensor 13 measures a gravity acceleration with a constant measuring interval plural times. And, the tire sensor unit 3 adds the measuring result of the gravity acceleration together with the measuring interval into a data signal and sends the data signal to a receiver unit 4. A receiver unit controller 33 of the receiver unit 4 determines, based on the measuring interval, how long before the timing of receiving the data signal by the receiver unit 4 a feature measuring point (lower peak) included in the measuring result is. The receiver unit controller 33 acquires, from a rotation sensor unit 24, a pulse signal when the lower peak appears, and determines that a tire sensor unit 3 of which wheel has transmitted the data signal by using the acquired pulse signal.

Description

  The present invention relates to a wheel position determination device.

  As a device for enabling a driver to check the state of a plurality of tires provided in a vehicle in a passenger compartment, a wireless tire state monitoring device has been proposed. The tire condition monitoring device includes a plurality of wheel side units that are respectively mounted on the wheels of the vehicle, and a receiver unit that is mounted on the vehicle body of the vehicle. Each wheel unit detects a corresponding tire state, that is, a pressure in the tire, and wirelessly transmits a data signal including data indicating the detected tire state.

  On the other hand, the receiver unit receives the data signal transmitted from each transmitter unit, and displays information on the tire pressure on a display provided in the passenger compartment as necessary. Further, in the tire condition monitoring device, it is related to the received data signal that the received data signal is transmitted from a transmitter unit provided in which tire among the plurality of tires. The position of the wheel is determined by the receiver unit.

  As a method of determining the position of the wheel, for example, there is a method disclosed in Patent Document 1. The TPMS sensor (wheel side unit) provided on the wheel has a transmitter and transmits the tire air pressure and rotation angle. The receiver (receiver unit) receives the data signal transmitted from the TPMS sensor and outputs the received data signal to the TPMS ECU. The vehicle body is provided with a wheel speed sensor corresponding to each wheel.

  When the TPMS sensor outputs a signal indicating a predetermined rotation angle, the wheel position determination unit included in the TPMS ECU monitors a change in the relative angle between the rotation angle and the rotation angle output from each wheel speed sensor. And a wheel position judgment part judges the wheel position of the wheel speed sensor which output the rotation angle with the smallest relative angle change after driving | running | working predetermined distance as the position of the TPMS sensor which transmitted the data signal.

JP 2010-1222023 A

  However, as the wheels rotate, the wheel-side units provided on each wheel also rotate, so the position and angle of the wheel-side units always change, and the receiver unit has a data signal reception strength from the wheel-side units. Change. And while the wheel side unit rotates with the wheel, there may be a range (so-called null point) where the reception intensity of the receiver unit is significantly reduced with respect to the data signal from the wheel side unit. If the wheel side unit is located within a certain range, the receiver unit cannot receive the data signal, and the wheel position cannot be determined.

  The objective of this invention is providing the wheel position determination apparatus which can avoid that wheel position determination becomes impossible by a null point.

  In order to solve the above-described problem, the wheel position determination device according to claim 1 includes a rotation position detection unit that detects rotation position information of the wheel corresponding to each of a plurality of wheels included in the vehicle, and each wheel. A wheel-side unit that is provided and has a position sensor that rotates together with the wheel, and that wirelessly transmits a data signal including position data detected by the position sensor; and data that is installed in the vehicle body of the vehicle and transmitted from the wheel-side unit And a receiver unit having a wheel position determination unit, and the wheel position determination unit determines which wheel the data signal is a data signal transmitted from a wheel side unit of which wheel. A position determination device, wherein the position sensor measures position data a plurality of times at a fixed measurement interval, and the wheel side unit has a plurality of measurement results. It is included in the data signal together with the measurement interval and transmitted to the receiver unit, and the wheel position determination unit determines how far the characteristic measurement point included in the measurement result is from the timing at which the receiver unit receives the data signal. Is determined based on the measurement interval, rotational position information at characteristic measurement points is acquired from the rotational position detector, and a data signal is transmitted from the wheel side unit of any wheel using the acquired rotational position information. The gist of this is to determine whether the data signal is correct.

  According to this, when determining the position of the wheel side unit, if a data signal is transmitted from the wheel side unit to the receiver unit, the wheel position determination unit of the receiver unit is extracted from a plurality of changes in position data. Understand the characteristic measurement points. The wheel-side position determination unit can grasp how long the characteristic measurement point appears from the reception timing of the data signal by using the number of times position data is measured and the measurement interval. And a wheel position determination part can determine the position of the wheel side unit which transmitted the data signal by acquiring the rotation position information at the grasped characteristic measurement point and using the acquired rotation position information.

  Therefore, even if the position data measurement result and the measurement interval are transmitted from the wheel side unit to the receiver unit at the null point, the tire rotation position becomes random after that, and the position data measurement result and the measurement interval. Will not continue to be transmitted at the null point. As a result, at a timing when the wheel side position determination unit acquires the position data after a certain time, the position data measurement result and the measurement interval are transmitted from a position other than the null point, and the wheel position determination unit uses the data signal. The position of the wheel side unit can be determined.

Moreover, it is preferable to change the said measurement interval according to the rotational speed of a wheel.
According to this, it is possible to always maintain the number of times of position data measurement during one rotation of the wheel regardless of the rotation speed of the wheel. Therefore, the position determination of a wheel side unit can be performed appropriately using a plurality of measured position data and characteristic measurement points. Further, when the rotational speed of the wheel is slow, the power consumption can be suppressed as much as possible by lengthening the measurement interval of the value related to the rotational speed.

The position sensor is an acceleration sensor, and the characteristic measurement point is preferably a point at which the acceleration sensor measures a maximum value or a minimum value of acceleration.
According to this, the judgment basis of the characteristic measurement point can be clarified.

  According to the present invention, it is possible to prevent the wheel position from being disabled due to the null point.

(A) is a schematic block diagram which shows the vehicle by which the tire condition monitoring apparatus is mounted, (b) is a figure which shows a wheel, a tire sensor unit, and an acceleration sensor. The schematic block diagram which shows a rotation sensor unit. The block diagram which shows the circuit structure of a tire sensor unit. (A)-(c) is a figure which shows the measurement result and measurement interval of a gravity acceleration value. The table | surface which shows the relationship between a measurement result, a measurement interval, and a peak.

Hereinafter, an embodiment in which the wheel position determination device is applied to a tire condition monitoring device will be described with reference to FIGS.
As shown in FIG. 1A, the vehicle 1 is equipped with an ABS (anti-lock / brake system) 10 and a tire condition monitoring device 20. The ABS 10 as a rotational position detection unit includes an ABS controller 23 and rotation sensor units 24 respectively corresponding to the four wheels 2 of the vehicle 1. Each wheel 2 includes a wheel portion 5 and a tire 6 attached to the wheel portion 5. In the following description, the front left wheel 2 is indicated by “FL”, the front right wheel 2 is indicated by “FR”, the rear left wheel 2 is indicated by “RL”, and the rear right wheel is appropriately indicated. The wheel 2 is indicated by the symbol “RR”.

The ABS controller 23 comprises a microcomputer or the like, and obtains the rotational speed (rotational position) of each wheel 2 based on a signal output from the rotation sensor unit 24.
As shown in FIG. 2, each rotation sensor unit 24 is provided in the vicinity of the wheel 2 and under the spring, and is disposed so as to face the gear 24a that rotates integrally with the wheel 2 and the outer peripheral surface of the gear 24a. Detector 24b. A plurality of teeth (48 in this embodiment) are provided at equal angular intervals on the outer peripheral surface of the gear 24a. And the detector 24b produces | generates a pulse signal as rotation position information of the wheel 2 from the position of a tooth | gear from the ignition-on state of the vehicle 1. FIG. The ABS controller 23 is wired to each detector 24b.

Next, the tire condition monitoring device 20 will be described.
As shown in FIG. 1A, the tire condition monitoring device 20 includes a tire sensor unit 3 as four wheel side units attached to four wheels 2, and a receiver unit 4 installed on the vehicle body of the vehicle 1. And. Each tire sensor unit 3 is attached to the wheel portion 5 to which the tire 6 is mounted so as to be disposed in the internal space of the tire 6. Each tire sensor unit 3 detects the state of the corresponding tire 6 (in-tire pressure, in-tire temperature), and wirelessly transmits a data signal including data indicating the detected tire state.

  As shown in FIG. 3, each tire sensor unit 3 includes a pressure sensor 11, a temperature sensor 12, an acceleration sensor 13, a sensor unit controller 14, and an RF transmission circuit 16. For example, the tire sensor unit 3 operates with power supplied from a battery (not shown). To do. The pressure sensor 11 detects the pressure (internal air pressure) in the corresponding tire 6 and outputs tire pressure data obtained by the detection to the sensor unit controller 14. The temperature sensor 12 detects the temperature (internal air temperature) in the corresponding tire 6 and outputs tire temperature data obtained by the detection to the sensor unit controller 14.

  The acceleration sensor 13 detects gravitational acceleration acting on itself, and outputs acceleration data obtained by the detection to the sensor unit controller 14. The sensor unit controller 14 includes a microcomputer including a CPU and a storage unit 14a (RAM, ROM, etc.), and an ID code that is identification information unique to each tire sensor unit 3 is registered in the storage unit 14a. This ID code is information used to identify each tire sensor unit 3 in the receiver unit 4. The sensor unit controller 14 outputs data including tire pressure data, tire temperature data, acceleration data, and an ID code to the RF transmission circuit 16. The RF transmission circuit 16 modulates data from the sensor unit controller 14 to generate a data signal, and wirelessly transmits the data signal from the antenna 19. Each tire sensor unit 3 periodically performs a tire state measurement operation at predetermined time intervals, and performs a data signal transmission operation toward the receiver unit 4.

  As shown in FIG. 1A, the receiver unit 4 is installed at a predetermined location of the vehicle body, and operates by power supplied from a battery (not shown) of the vehicle 1, for example. The receiver unit 4 includes a receiving antenna 32 arranged at an arbitrary position on the vehicle body, and receives and receives the data signal transmitted from the antenna 19 of each tire sensor unit 3 through the receiving antenna 32. Process the data signal.

  The receiver unit 4 includes a receiver unit controller 33 and an RF receiving circuit 35. The receiver unit controller 33 is composed of a microcomputer including a CPU and a storage unit (ROM, RAM, etc.), and comprehensively controls the operation of the receiver unit 4. The RF receiving circuit 35 demodulates the data signal received from each tire sensor unit 3 through the receiving antenna 32 and sends it to the receiver unit controller 33.

  The receiver unit controller 33 grasps the internal air pressure and the internal air temperature of the tire 6 corresponding to the transmitting tire sensor unit 3 based on the data signal from the RF receiving circuit 35. Further, the receiver unit controller 33 causes the display 38 to display information on the internal air pressure and the internal air temperature. The indicator 38 is arranged in the visible range of the passenger of the vehicle 1 such as the passenger compartment. The receiver unit controller 33 further informs an alarm (notifier) 37 of an abnormality in internal air pressure or internal air temperature. As the alarm device 37, for example, a device for notifying abnormality by lighting or blinking of light or a device for notifying abnormality by sound is applied.

  The receiver unit controller 33 is connected to the ABS controller 23 and receives the pulse signals generated by the rotation sensor units 24 through the ABS controller 23 at regular time intervals.

  As shown in FIG. 3, the uniaxial acceleration sensor 13 provided in the tire sensor unit 3 is well known as, for example, a piezoresistive type or a capacitance type acceleration sensor, and a data signal corresponding to the acceleration is provided. Generate and output.

  As shown in FIG. 1B, the acceleration sensor 13 is an acceleration sensor that can detect an acceleration component in a direction along one detection axis 7. The acceleration sensor 13 is arranged with respect to the wheel 2 so that the acceleration detection axis 7 extends in the vertical direction, and the acceleration sensor 13 detects the gravitational acceleration. The angular position of the tire sensor unit 3 changes with the rotation of the wheel 2 when the vehicle 1 moves forward.

  As shown in FIG. 4A, when the tire sensor unit 3 moves to the lowest position of the wheel 2 during the rotation of the wheel 2, the acceleration sensor 13 outputs 1G of gravitational acceleration to the sensor unit controller 14. When the tire sensor unit 3 moves to the lowest position of the wheel 2, the gravitational acceleration becomes a maximum value on the plus side, and this time is defined as an upper peak. When the tire sensor unit 3 moves to the uppermost position of the wheel 2, the acceleration sensor 13 outputs −1 G gravity acceleration to the sensor unit controller 14. When the tire sensor unit 3 moves to the uppermost position of the wheel 2, the gravitational acceleration has a maximum value on the minus side, and this time is defined as a lower peak.

  Therefore, the position of the tire sensor unit 3 can be detected based on the gravitational acceleration detected by the acceleration sensor 13, and the acceleration sensor 13 rotates with the wheel 2 to detect the gravitational acceleration as position data. It is.

  Next, the position determination operation of the tire sensor unit 3 in the tire condition monitoring device 20 will be described with reference to FIGS. 4 and 5 together with the operation. Since the position determination operations of the four wheels 2 are all the same, the position determination operation of one of the four wheels 2 will be described, and the description of the position determination operations of the remaining three wheels 2 will be omitted. .

  Further, the graph of FIG. 4A shows a case where the gravitational acceleration value is measured with a measurement interval of 10 ms. The graph of FIG. 4B shows the case where the vehicle speed is faster than the case shown in FIG. 4A, and shows the case where the gravitational acceleration value is measured with a measurement interval of 8 ms. The graph of FIG. 4C shows the case where the vehicle speed is faster than the case shown in FIGS. 4A and 4B, and the case where the gravitational acceleration value is measured with a measurement interval of 6 ms. Show. That is, the measurement interval of the gravitational acceleration is set according to the vehicle speed, and the measurement interval becomes shorter as the vehicle speed becomes faster.

  The sensor unit controller 14 of the tire sensor unit 3 performs a position determination operation every time a predetermined time is available. In each position determination operation, the sensor unit controller 14 causes the acceleration sensor 13 to measure the gravitational acceleration over a plurality of times (in this embodiment, 10 times) with a predetermined measurement interval from the start of the position determination. . In FIG. 4A, the position determination operation is performed at 10 measurement points surrounded by a black circle.

  When the acceleration sensor 13 detects the gravitational acceleration, the sensor unit controller 14 determines whether the gravitational acceleration is larger (increased) or smaller (decreased) than the previous measurement result. In the present embodiment, the sensor unit controller 14 encodes “0” when the gravitational acceleration decreases with respect to the previous measurement result, and encodes “1” when the gravitational acceleration increases. When the gravitational acceleration is measured 10 times, the sensor unit controller 14 outputs data including the encoded measurement result and the measurement interval to the RF transmission circuit 16. The RF transmission circuit 16 generates a data signal obtained by modulating data from the sensor unit controller 14 and wirelessly transmits the data signal from the antenna 19. In addition, since the gravity acceleration is measured 10 times, nine data are obtained from the encoded data.

  As shown in the table of FIG. 5, in the case of FIG. 4A, the gravitational acceleration measured at the second time is smaller than the gravitational acceleration measured at the first time, so the sign is “0”. Since the gravitational acceleration measured at the third time is smaller than the gravitational acceleration measured at the second time, the sign is “0”. Hereinafter, similarly, the gravity acceleration measured at the 10th time is encoded. As a result, in the case of FIG. 4A, “00000111” is obtained as a code.

  In the receiver unit 4, when the receiver unit controller 33 receives the data signal, the gravitational acceleration detected a lower peak from the encoded data after “0” or “1” continued several times. Extract points (characteristic measurement points). The lower peak is when the sign changes from “0” to “1” in the order from the first measurement to the tenth measurement. Although not shown, the upper peak is when the sign changes from “1” to “0”.

  In the case shown in FIG. 4A, the lower peak exists four times before the tenth measurement. At this time, since the measurement interval is 10 ms, the lower peak appears 40 ms before the tenth measurement time point (the time when the receiver unit controller 33 receives the signal).

  Next, the receiver unit controller 33 acquires each pulse signal generated 40 ms before of the pulse signals generated by the four rotation sensor units 24, and grasps the pulse signal at the time of the lower peak. Then, the position determination operation is repeated at predetermined time intervals, and the rotation sensor unit 24 that generates one pulse signal with a small change in value among the acquired pulse signals is specified. The receiver unit controller 33 determines that the tire sensor unit 3 associated with the one rotation sensor unit 24 is the tire sensor unit 3 that has transmitted the data signal.

  In the case shown in FIG. 4B, the lower peak exists seven times before the tenth measurement. At this time, since the measurement interval is 8 ms, the lower peak is measured 56 ms before the tenth measurement time (the time when the receiver unit controller 33 receives the signal).

  In the case shown in FIG. 4C, the lower peak exists 9 times before the 10th measurement. At this time, since the measurement interval is 6 ms, the lower peak is measured 54 ms before the tenth measurement time (the time when the receiver unit controller 33 receives the signal). 4B and 4C, the lower peak is grasped by the same method as described above, and the position of the tire sensor unit 3 that has transmitted the data signal is determined.

According to the above embodiment, the following effects can be obtained.
(1) The sensor unit controller 14 of the tire sensor unit 3 transmits a plurality of gravitational accelerations measured by the acceleration sensor 13 and measurement intervals to the receiver unit 4 at predetermined time intervals. For this reason, the receiver unit controller 33 of the receiver unit 4 can grasp from the measurement result and the measurement interval how long the lower peak has appeared from the timing of receiving the data signal. The receiver unit controller 33 acquires the pulse signal assumed at the lower peak from the rotation sensor unit 24, and synchronizes with the pulse signal to transmit the data signal, that is, the position of the wheel 2 Can be determined.

  Therefore, even if the data signal is transmitted at the null point, the rotational position of the tire 6 becomes random thereafter, and the data signal is not continuously transmitted at the null point. As a result, at a timing when the receiver unit controller 33 receives the data signal after a certain time, the data signal is transmitted from a position other than the null point, and the receiver unit controller 33 can determine the position of the tire sensor unit 3. It can be avoided that the position determination of the wheel 2 becomes impossible due to the null point.

  (2) The gravitational acceleration can be measured a plurality of times by the acceleration sensor 13 and the measurement result can be acquired by the receiver unit 4. Then, when the wheel 2 rides on an obstacle or the like, the receiver unit 4 can acquire road surface information from the change in gravitational acceleration at that time, and an appropriate vibration characteristic from the receiver unit 4 to the suspension of the vehicle 1 can be obtained. It is also possible to inform.

  (3) The gravitational acceleration measurement interval was shortened as the vehicle speed increased. For this reason, it becomes possible to always maintain the number of measurements during one rotation of the wheel 2 at an appropriate number regardless of the rotation speed of the wheel 2. Therefore, the position determination of the tire sensor unit 3 can be appropriately performed using a plurality of gravitational accelerations. Further, when the rotational speed of the wheel 2 is slow, the power consumption of the battery in the tire sensor unit 3 can be suppressed as much as possible by increasing the measurement interval of the gravitational acceleration.

  (4) The receiver unit controller 33 grasps the timing for detecting the gravitational acceleration peak as a characteristic measurement point. For this reason, the judgment basis of the characteristic measurement point can be clarified.

In addition, you may change this embodiment as follows.
In the embodiment, the lower peak is set as the characteristic measurement point, but it may be set at the upper peak.

  ○ In the embodiment, when grasping the lower peak, if the upper peak is close at the time of the tenth measurement, add half the total number of generated pulse signals to the pulse signal assumed for the upper peak. A peak pulse signal may be acquired.

  The characteristic measurement point may not be a point where the sign is switched from “0” to “1” or “1” to “0”, and may be set as appropriate. For example, the point “0” or “1” may be a predetermined number of consecutive points.

In the embodiment, the characteristic measurement point is set to only the lower peak, but the upper peak may be set at the same time.
In the embodiment, the magnitude of the gravitational acceleration is encoded by the sensor unit controller 14 of the tire sensor unit 3. However, the encoding of the magnitude of the gravitational acceleration may be performed by the receiver unit controller 33 of the receiver unit 4.

In the embodiment, the magnitude of the gravitational acceleration is encoded, but the characteristic measurement point may be extracted by comparing the gravitational acceleration itself without encoding.
In the embodiment, the acceleration sensor 13 is a uniaxial acceleration sensor, but may be a biaxial or triaxial acceleration sensor.

In the embodiment, in the position determination operation, the gravitational acceleration is measured 10 times, but the number of times of measurement is not limited to 10 and may be changed as appropriate.
As a position sensor, a magnetic sensor may be used instead of the acceleration sensor 13.

(Circle) this invention is not limited to application to a tire condition monitoring apparatus, It can apply to the various apparatuses which monitor the state of the wheel 2. FIG.
Next, the technical idea that can be grasped from the above embodiment and other examples will be described below.

  (A) The wheel side determination device is a wheel position determination device that is a tire sensor unit that wirelessly transmits a data signal including data indicating the detected tire state while detecting the state of the tire in the wheel.

  (B) The wheel position determination unit is a wheel position determination device that encodes the position data.

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 2 ... Wheel, 3 ... Tire sensor unit as wheel side unit, 4 ... Receiver unit, 13 ... Acceleration sensor as position sensor, 24 ... Rotation sensor unit as rotational position detection part, 33 ... Wheel position Receiver unit controller as a determination unit.

Claims (3)

A rotational position detector that detects rotational position information of the wheels corresponding to each of a plurality of wheels provided in the vehicle;
A wheel-side unit that is provided on each wheel and has a position sensor that rotates together with the wheel, and that wirelessly transmits a data signal including position data detected by the position sensor;
A receiver unit that is installed in the vehicle body of the vehicle, receives a data signal transmitted from the wheel side unit, and has a wheel position determination unit, and
The wheel position determination unit is a wheel position determination device that determines which data signal is a data signal transmitted from a wheel side unit of any wheel,
The position sensor measures position data a plurality of times at a fixed measurement interval, and the wheel side unit includes a plurality of measurement results together with the measurement interval in a data signal and transmits to the receiver unit,
The wheel position determination unit determines, based on the measurement interval, how far the characteristic measurement point included in the measurement result is from the timing at which the receiver unit receives the data signal, and at the characteristic measurement point. Wheel position characterized in that rotational position information is acquired from the rotational position detector, and using the acquired rotational position information, it is determined which data signal is a data signal transmitted from a wheel side unit of which wheel. Judgment device.   The wheel position determination device according to claim 1, wherein the measurement interval is changed according to a rotation speed of the wheel.   The wheel position determination device according to claim 1 or 2, wherein the position sensor is an acceleration sensor, and the characteristic measurement point is a point at which the acceleration sensor measures a maximum value or a minimum value of acceleration.