JP4450193B2 - Tire pressure detector - Google Patents

Description

  The present invention relates to a tire air pressure detecting device for detecting tire air pressure.

  Studies have been made on a battery-less drive type that performs charging by a transponder method known in the field of IC tags or the like for wireless communication between a vehicle body side and a wheel side in a tire pressure detection device.

  In the transponder method, the wheel side sensor device is charged with radio waves from the vehicle body side antenna, and when the power charge is completed, the sensor device is operated with the charge power, and data such as tire pressure is returned to the vehicle side. It is a method to do. This method does not require a battery as a power source for the sensor device, but requires a high antenna gain.

Therefore, in order to obtain a high antenna gain, a loop antenna in which an antenna coil is wound around the entire circumference of a tire wheel has been proposed as a wheel-side antenna (see Non-Patent Document 1).
SAE TECHNICICAL PAPER SERIES 2003-01-1279

  However, in the configuration of Non-Patent Document 1, it is necessary to form a loop around the entire circumference of the tire wheel. In consideration of the reliability of the fixing method, the number of man-hours for mounting work, etc., the receiving antenna on the wheel side is mounted on the tire wheel. It is desirable that the antenna be a small antenna that fits within the air injection valve.

  If the transmission antenna mounted on the vehicle body is set to an output level within the regulations of the Radio Law of each country and the reception antenna on the wheel side is configured to fit within the air injection valve attached to the tire wheel, the gain will be low, The range in which power can be charged is limited to a narrow range. As a result, communication is established only when the vehicle body side antenna and the tire side antenna are close to each other, the communication interval becomes long when traveling at a low speed, and communication may not be established depending on the wheel angle when the vehicle is stopped. is there.

  SUMMARY OF THE INVENTION In view of the above, the present invention has an object of expanding a communicable range in a transponder type tire air pressure detecting device.

In order to achieve the above object, according to the first aspect of the present invention, each of the plurality of wheels (6a to 6d) is provided to each of the plurality of wheels (6a to 6d) according to the air pressure of the tire. A sensing unit (21) that outputs a detection signal, a control unit (23a) that performs signal processing on the detection signal of the sensing unit (21), and a detection signal that is signal-processed by the control unit (23a), and power A sensor device (2) having a transmission / reception unit (23b) for receiving radio waves for charging and a charging unit (22) for charging power by radio waves for power charging, and provided on the vehicle body (7) side, Transmitting means (3) having a transmitting antenna (32) for transmitting radio waves for charging, receiving means (3) for receiving a detection signal, and control for determining tire air pressure based on the detection signal A vehicle body side device (3, 4) provided with a device (4), and the transmitting antenna (32) is shifted in the rotation direction of the wheel (6) in the vicinity of the wheel (6) in the vehicle body (7). A plurality of transmission antennas (32) are arranged such that the longitudinal direction thereof is parallel to the rotation direction of the wheel (6), and the transmission antenna (32) has a conductive coil (32b) in a loop shape. The loop type antenna is configured such that the normal direction of the loop surface of the conductor coil (32b) substantially coincides with the rotational direction of the wheel (6) .

  As described above, by arranging the plurality of transmission antennas (32) so as to be shifted in the wheel rotation direction, the drop in electric field strength that occurs when the transmission / reception antenna is used alone can be complemented with each other, and the communicable range is expanded. It becomes possible.

Further , the transmission antenna (32) can be arranged so that the longitudinal direction is parallel to the rotation direction of the wheel (6), so that the electric field strength can be increased, and the plurality of transmission antennas (32) can be rotated by the wheel. It is possible to more effectively obtain the effect obtained by shifting the arrangement in the direction.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

  An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an overall configuration of a tire air pressure detecting device according to an embodiment of the present invention. The upper direction in the drawing of FIG. 1 corresponds to the front of the vehicle 1, and the lower direction of the drawing corresponds to the rear of the vehicle 1. With reference to this figure, the tire pressure detecting device in the present embodiment will be described.

  As shown in FIG. 1, the tire air pressure detection device is attached to the vehicle 1 and includes a sensor device 2, a transceiver 3, a control device 4, and an alarm device 5.

  As shown in FIG. 1, the sensor device 2 is attached to each wheel 6 a to 6 d in the vehicle 1, detects the air pressure of the tire attached to the wheels 6 a to 6 d, and detects a detection signal indicating the detection result. Data is stored in a transmission frame and transmitted. The transmitter / receiver 3 is attached to the vehicle body 7 side of the vehicle 1, and charges the power to the sensor device 2 and receives a transmission frame transmitted from the sensor device 2. The control device 4 obtains the tire pressure by performing various processes and calculations based on the detection signal stored in the transmission frame received via the transceiver 3. The transceiver 3 and the control device 4 correspond to the vehicle body side device of the present invention.

  FIG. 2 shows a block configuration of the sensor device 2. The sensor device 2 is configured to be charged with a radio wave for charging the power transmitted from the transceiver 3 and driven based on the charged power.

  As shown in FIG. 2, the sensor device 2 has a configuration including a sensing unit 21, a charging unit 22, a microcomputer 23, and an antenna 24, and transmits radio waves for power charging from the transceiver 3 through the antenna 24. It operates by receiving and converting the radio wave into electric power energy and storing it in the charging unit 22. The power charging by the transponder method is well known in the field of battery-less ID tag recognition and the like, and will not be described here.

  The sensing unit 21 includes, for example, a diaphragm type pressure sensor and a temperature sensor, and outputs a detection signal corresponding to the tire pressure and a detection signal corresponding to the temperature. The charging unit 22 charges the radio wave received from the antenna 24 and supplies power to the sensing unit 21 and the microcomputer 23.

  The microcomputer 23 includes a CPU, a ROM, a RAM, an I / O, and the like. The microcomputer 23 includes a control unit 23a, a transmission / reception unit 23b, and the like, and executes predetermined processing according to a program stored in the ROM. It has become.

  The control unit 23a receives the detection signal from the sensing unit 21, performs signal processing on the signal as necessary, and uses this as data indicating the detection result as the sensor device 2 attached to any of the wheels 6a to 6d. It is stored in the transmission frame together with the ID information indicating that. Thereafter, the control unit 23a transmits the transmission frame to the transceiver 3 through the transmission / reception unit 23b. The process of sending a transmission frame to the transceiver 3 is executed according to the program when a radio wave transmission for performing the power charging is turned off. For example, the control unit 23a monitors ON / OFF of radio wave transmission from the transceiver 3, and executes a process of sending a transmission frame based on a falling signal when the radio wave transmission is turned off.

  The transmission / reception unit 23b functions as an input unit that receives a radio wave for power charging through the antenna 24 and sends it to the charging unit 22 and the control unit 23a, and transmits a transmission frame sent from the control unit 23a to the transceiver 3. It functions as an output unit for transmission.

  3A is a cross-sectional view of the air injection valve 8 incorporating the sensor device 2 as viewed from the front, and FIG. 3B is a cross-sectional view taken along line AA of FIG. As shown in FIGS. 3A and 3B, the sensor device 2 is integrally formed with the air injection valve 8 by a resin mold or the like. The air injection valve 8 is attached to the tire wheel so that the sensor device 2 is located inside the tire wheel and the air injection port is located outside the tire wheel. Thus, the corresponding tire air pressure is detected, and the transmission frame is transmitted at a predetermined transmission timing every predetermined cycle (for example, every minute) through the antenna 24 provided in each sensor device 2.

  Returning to FIG. 1, the transmitter / receiver 3 outputs a power charging radio wave at a predetermined communication timing every predetermined cycle (for example, every minute) to charge the power of the sensor device 2. After completion, the electric wave for power charging is turned on and off at a predetermined timing synchronized with the rotation of the wheels 6a to 6d. And the transmission frame sent from the sensor apparatus 2 at that time is received.

  FIG. 4A shows a block configuration of the transceiver 3, and FIG. 4B shows a cross-sectional configuration of the antenna 32 of the transceiver 3.

  As shown in FIG. 4A, the transceiver 3 includes a transmission / reception unit 31 and a transmission / reception antenna 32. The transmission / reception unit 31 inputs a function as an output unit that outputs a radio wave for power charging to the sensor device 2 through the antenna 32 and the received transmission frame from each sensor device 2 and receives the transmission frame. Thus, it functions as an input unit to be sent to the control device 4. As described above, the transmitter / receiver 3 according to the present embodiment has a configuration that serves as both a transmission unit that transmits a radio wave for power charging and a reception unit that receives a transmission frame. However, these may be configured separately. It is. The antenna 32 is used for both transmission and reception, but is hereinafter referred to as a “transmission antenna”.

  As shown in FIG. 4B, the transmission antenna 32 of this embodiment is a solenoid-type magnetic field antenna, and is configured by winding a conductive coil 32b around a magnetic core 32a.

  FIG. 5 shows an arrangement relationship between the sensor device 2 and the transceiver 3. Each transmitter / receiver 3 is installed at a location corresponding to the position of each sensor device 2 in the vehicle body 7, and is fixed to the vehicle body 7 at a position spaced apart from each sensor device 2 as shown in FIG. ing. As will be described later, two transceivers 3 according to the present embodiment are provided for each sensor device 2.

  Returning to FIG. 1, the control device 4 is a known device including a CPU, a ROM, a RAM, an I / O, a counter, and the like, and executes a predetermined process in accordance with a program stored in the ROM. .

  The control device 4 receives vehicle speed data obtained by another ECU (for example, a meter ECU) through an in-vehicle LAN (CAN) or the like, detects the rotational state of each wheel 6a to 6d based on the vehicle speed data, A radio wave for power charging is output to each sensor device 2 according to the detected rotation state. Further, the control device 4 receives the transmission frame sent from the transceiver 3, and based on the ID information indicating the wheel to which each sensor device 2 is stored, the transmission frame sent is the wheel 6a. -6d is specified.

  Further, the control device 4 obtains the tire pressure of each of the wheels 6a to 6d by performing various signal processing and calculation based on the data indicating the detection result stored in the received transmission frame, and the obtained tire pressure. An electrical signal corresponding to the above is output to the alarm device 5. Specifically, the control device 4 determines whether or not the tire air pressure is below a predetermined threshold value, and outputs a signal indicating that the tire air pressure has decreased to the alarm device 5 based on the determination result. It has become.

  The alarm device 5 is disposed at a place where the driver can visually recognize, and is configured by, for example, an alarm lamp, an alarm indicator (display), or an alarm buzzer installed in an instrument panel in the vehicle 1. For example, when a signal indicating a decrease in tire air pressure is sent from the control device 4, the alarm device 5 notifies the driver of the decrease in tire air pressure by issuing an alarm indicating that fact. The tire air pressure detection device is configured as described above.

  Next, the arrangement of the transmission antenna 32 will be described with reference to FIGS.

  FIG. 6 is a side view showing the positional relationship between the sensor device 2 and the transmission antenna 32. As shown in FIG. 6, the transmission antenna 32 is disposed in the tire house in the vehicle body 7. At this time, the transmission antenna 32 is arranged so that the longitudinal direction is parallel to the tire rotation direction. Furthermore, the antenna in the sensor device 2 is also arranged so that the longitudinal direction is parallel to the tire rotation direction. By arranging the transmission antenna 32 in such a manner, the peak of the electric field strength of the charge radio wave from the transceiver 3 in the sensor device 2 can be increased, and the reception gain of the sensor device 2 can be increased.

  As described above, two transceivers 3 are provided for each sensor device 2. These transmission antennas 32 are arranged so as to be shifted in the wheel rotation direction. The two transmission antennas 32 of the present embodiment have wheel rotation angles of 60 ° and 320 ° when the vertical direction passing through the center of the wheel 6 is 0 ° and the wheel rotation direction is clockwise in FIG. Is provided.

  FIG. 7 shows the electric field strength [dBμV / m] of the charge radio wave from the transmitter / receiver 3 in the sensor device 2, where the horizontal axis represents the wheel rotation angle and the vertical axis represents the electric field strength. 7 (a) and 7 (b) show the electric field strength of the charge radio wave from one transceiver 3, and in FIG. 7 (a), the transmission antenna 32 is provided at a wheel rotation angle of 320 °, and FIG. ), The transmitting antenna 32 is provided at a wheel rotation angle of 60 °. FIG. 7C shows the electric field strength of the charge radio waves from the two transceivers 3 provided at the wheel rotation angle of 60 ° and the wheel rotation angle of 320 °.

  In FIG. 7, it can be determined that communication is secured when the electric field strength of the charge radio wave from the transceiver 3 exceeds a predetermined value necessary for establishment of communication. In the present embodiment, the predetermined value is set to 170 dBμV / m.

  As shown in FIGS. 7A and 7B, the electric field strength at the mounting angle (320 °, 60 °) of the transmission antenna 32 is the maximum value, and is around 30 ° before and after the mounting angle of the transmission antenna 32. There is a sharp drop in the electric field strength, which is the minimum value. As a result, the communicable range centered on the mounting angle of the transmission antenna 32 is a range of about 25 ° (= 50 °) around the mounting angle of the transmission antenna 32. Furthermore, when the distance from the mounting angle of the transmission antenna 32 is increased, the distance tends to gradually decrease to 180 ° opposite to the mounting angle of the transmission antenna 32 due to distance attenuation. Thus, the electric field strength falls below a predetermined value in the vicinity of 30 ° before and after the mounting angle of the transmitting antenna 32 and about 45 ° before and after the mounting angle of 180 ° opposite to the mounting angle of the transmitting antenna 32, and communication is not established. It becomes.

  The decrease in the electric field strength around 30 ° before and after the mounting angle of the transmitting antenna 32 is because the magnetic field vector generated by the transmitting antenna 32 on the antenna 24 of the sensor device 2 is orthogonal to the mounting direction of the antenna 24 in the sensor device 2. . Further, the decrease in the electric field strength in the range of about 45 ° in the front and rear direction centering on the opposite side of the mounting angle of the transmission antenna 32 by 180 ° is because the propagation distance between the transmission antenna 32 and the antenna of the sensor device 2 becomes longer.

  Next, when the two transceivers 3 shown in FIG. 7 (c) are provided, the electric field strength shown in FIG. 7 (a) and the electric field strength shown in FIG. The maximum value of the electric field strength is set to an output level within the regulation. As a result, the drop in the electric field strength of one transmission antenna 32 can be complemented by the other transmission antenna 32, and in the example shown in FIG. 7C, the electric field strength has a predetermined value in the entire range of the wheel rotation angle. Over. Thereby, communication failure in the vicinity of 30 ° before and after the mounting angle of the transmission antenna 32 can be avoided. In addition, by disposing the two transmitting antennas 32 at a position away from each other, the propagation distance can be shortened, and communication within a range of about 45 ° before and after the mounting angle of the transmitting antenna 32 about 180 ° opposite side is the center. Failure can also be avoided.

  By arranging the two transmitting antennas 32 so as to be shifted in the wheel rotation direction in this way, the drop in electric field strength that occurs when the transmitting antenna 32 is used alone can be complemented with each other. Compared to the case of using the communication range, the communication range can be expanded. Thereby, the low gain of the small antenna 24 that can be built in the air injection valve 8 can be covered, and the communicable range can be expanded.

  Further, in the case of the configuration in which the longitudinal direction of the transmission antenna 32 is arranged in parallel to the wheel rotation direction, the electric field strength can be increased compared to the arrangement in which the longitudinal direction of the transmission antenna 32 is orthogonal to the wheel rotation direction, The drop before and after the peak of the electric field intensity also increases. Therefore, the configuration in which the two transmission antennas 32 are shifted in the wheel rotation direction as in the present embodiment is particularly effective when the longitudinal direction of the transmission antenna 32 is arranged in parallel to the wheel rotation direction.

(Other embodiments)
In the above embodiment, the two transmission antennas 32 are arranged so as to be shifted in the wheel rotation direction. However, the number of the transmission antennas 32 may be plural, and three or more transmission antennas 32 may be arranged so as to be shifted in the wheel rotation direction. May be.

  In the above embodiment, the electric field antenna shown in FIG. 4B is used as the transmission antenna 32. However, the present invention is not limited to this, and the present invention is also applicable to the case of using another type of antenna such as an air-core loop antenna. Can be applied.

It is a figure which shows the block configuration of the tire air pressure detection apparatus of the said embodiment. It is a figure which shows the block configuration of a sensor apparatus. (A) is sectional drawing which looked at the air injection valve with which the sensor apparatus was incorporated from the front, (b) is AA sectional drawing of (a). (A) is a figure which shows the block configuration of a transmitter / receiver, (b) is a figure which shows the cross-sectional structure of the antenna for transmission / reception. It is the figure seen from the vehicle advancing direction which shows the arrangement | positioning relationship between a sensor apparatus and a transmitter / receiver. It is a side view which shows the arrangement | positioning relationship between a sensor apparatus and a transmitter / receiver. It is a figure which shows the electric field strength of the charge electromagnetic wave from the transmitter / receiver in a sensor apparatus.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Vehicle, 2 ... Sensor apparatus, 3 ... Transmitter / receiver, 4 ... Control apparatus, 5 ... Alarm apparatus, 6 ... Wheel, 7 ... Vehicle body, 32 ... Antenna for transmission / reception.

Claims (1)

A sensing unit (21) provided on each of the plurality of wheels (6a to 6d) and outputting a detection signal corresponding to the tire air pressure provided on each of the plurality of wheels (6a to 6d), and the sensing unit A control unit (23a) that performs signal processing on the detection signal of (21), and a transmission / reception unit (23b) that transmits the detection signal that has been signal-processed by the control unit (23a) and that receives radio waves for power charging. ) And a charging unit (22) for charging power with the electric wave for power charging, and a sensor device (2),
A transmission means (3) provided on the vehicle body (7) side and having a transmission antenna (32) for transmitting the electric wave for power charge; a reception means (3) for receiving the detection signal; and the detection A vehicle body side device (3, 4) having a control device (4) for determining the tire air pressure based on a signal,
A plurality of the transmission antennas (32) are arranged in the vicinity of the wheel (6) in the vehicle body (7) and shifted in the rotation direction of the wheel (6),
The transmitting antenna (32) is arranged so that its longitudinal direction is parallel to the rotational direction of the wheel (6) ,
The transmission antenna (32) is a loop type antenna in which a conductive coil (32b) is configured in a loop shape, and the normal direction of the loop surface of the conductive coil (32b) is substantially the rotational direction of the wheel (6). A tire pressure detecting device characterized by matching .

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