JP2008126805A - Tire state detecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tire state detecting device capable of considerably reducing part cost and installation cost with little electric power loss. <P>SOLUTION: The tire state detecting device receives a detection signal transmitted from a transponder 2 mounted to each tire 1 by a vehicle body side antenna 3 and inputs the signal to a control processing circuit (ECU) 4. The vehicle body side antenna 3 and the control processing circuit 4 are integrated and mounted to the approximate center of the bottom surface 6 of the vehicle body. In the vehicle body side antenna 3, monopole antennae 30 for communicating with the transponder 2 are arranged in respective horn-like spaces 34 which are four sections partitioned by first, second, and third metal plates 31-33. As the second metal plate 32 having a cross shape in a plan view operates as a corner reflector, radiation beams 7a-7d having strong directivity are radiated toward side walls 10 of the corresponding tires 1 from openings of the respective horn-like spaces 34. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a tire condition detection device that can receive information on tire air pressure transmitted from a transponder mounted in a tire on the vehicle body side and input it to a control processing means.

  In order to allow drivers to quickly grasp tire pressure and abnormalities while driving a car, in recent years, tire pressure has been reduced at the driver's seat by installing a transponder incorporating a pressure sensor, antenna element, etc. in the tire. Systems that enable monitoring are becoming popular. In such a tire pressure monitoring system (TPMS), a detection signal such as tire pressure transmitted from a transponder in a tire is received by an antenna element mounted on the vehicle body side, and this received signal is transmitted to an ECU (Electronic Control) via a coaxial cable. Unit) or the like. (For example, refer to Patent Document 1).

  Generally, the antenna element on the vehicle body side is attached to a tire house or the like in the vicinity of each tire. Therefore, the detection signals transmitted from the transponders in the four tires are received by the antenna elements on the vehicle body side located in the vicinity, and the received signals are coaxially wired between the antenna elements and the control processing means. It is transmitted individually to the cable. That is, information related to the pneumatic pressure of the four tires is input to the control processing means via the four coaxial cables, and the input information is controlled and processed by the control processing means, so that the driver's seat The tire status is displayed on the display device and a warning sound is emitted.

In addition, since the tire mounted on the metal wheel has a steel belt embedded in the tread side, communication between the transponder in the tire and the antenna element on the vehicle body is a rubber which is a side wall portion of the tire. This is done through a side wall.
Japanese Patent Laying-Open No. 2005-161944 (page 3-5, FIG. 1)

  By the way, as described above, the antenna element on the vehicle body side is conventionally installed in a tire house or the like in the vicinity of the tire, but the shape of the tire house differs depending on the vehicle type, and even in the same vehicle, the tire house on the front wheel side and rear wheel side Since the shapes are different, it is not easy to select and mount a suitable mounting position of the antenna element in each of the four tire houses, and the mounting work may be difficult. Patent Document 1 discloses a technique in which an antenna element on the vehicle body side is embedded in a mud guard at the rear of a tire. However, in this conventional technique, a special mud guard has to be manufactured, so that the cost of parts significantly increases. Resulting in. Furthermore, conventionally, since the antenna elements on the vehicle body side respectively installed in the vicinity of the four tires are connected to the control processing means using the four coaxial cables, the wiring cost and parts cost of the coaxial cable increase. There is also a problem that power loss occurs while signals are transmitted through a coaxial cable of several meters.

  The present invention has been made in view of such a state of the art, and an object of the present invention is to provide a tire state detection device that can greatly reduce the component cost and the installation cost and has little power loss.

  In order to achieve the above object, according to the present invention, a transponder that is mounted in each of a plurality of tires and transmits a detection signal obtained by detecting the state of the tire to an external space, and the transponder in each tire individually A plurality of monopole antennas capable of communicating with each other, and a control that is attached to the bottom of the vehicle body and receives the detection signals via the plurality of monopole antennas, and outputs a required signal based on these detection signals to an external device In a tire condition detection device comprising processing means, a corner reflector is provided in the vicinity of the monopole antenna for reflecting radio waves radiated from the monopole antenna in an undesired direction and directing them in the desired direction. A monopole antenna and a corner reflector are all attached to the center of the vehicle body integrally with the control processing means. The were set as radio waves emitted from the monopole antenna is directed to the corresponding tire sidewall.

  In this way, a plurality of monopole antennas for communication with the transponders in each tire are combined with the corner reflectors and attached to the bottom of the vehicle body integrally with the control processing means, and the radio waves radiated from each monopole antenna are respectively If it is set so as to be directed to the sidewall of the corresponding tire, a complicated operation is not forced at the time of installation as in the case where the antenna element on the vehicle body side is installed in a tire house or the like in the vicinity of the tire. Moreover, since the wiring of the coaxial cable is not required, the component cost and the installation cost can be greatly reduced, and the power loss during transmission can be avoided.

  In the above configuration, a first metal plate extending substantially parallel to the road surface and a second metal plate having a cross shape in plan view that hangs down from the first metal plate are provided at the bottom of the vehicle body. The lower space of the first metal plate is divided into four sections opened radially outward by the second metal plate, and the monopole antenna is disposed in each of the four sections. It is preferable to use the second metal plate as the corner reflector because a radiation beam having strong directivity from the approximate center of the bottom of the vehicle body toward the sidewall of each tire can be realized with a simple and inexpensive structure. In this case, if the distance from each monopole antenna to the center of the cross shape of the second metal plate is set to about one quarter of the free space wavelength corresponding to the resonance frequency of the monopole antenna, Since the radio wave directly traveling in the desired direction from the monopole antenna and the radio wave reflected in the desired direction after being reflected by the corner reflector are likely to have the same phase, the gain can be improved, which is preferable.

  Further, in the configuration in which the first and second metal plates are provided, if a third metal plate extending substantially parallel to the first metal plate is provided below the second metal plate, the vehicle It is preferable because the second metal plate can be easily prevented from being deformed even while traveling, and the communication between the monopole antenna on the vehicle body side and the transponder in the tire is not adversely affected by the metal body on the road surface.

  In the above configuration, it is preferable that a plurality of monopole antennas are mounted on the circuit board of the control processing unit because the configuration can be further simplified.

  Further, in the above configuration, if a plurality of monopole antennas are set to sequentially communicate with corresponding transponders by switching control of the control processing means, the detection signals received by the respective monopole antennas are processed in parallel. Therefore, it is not necessary to provide a complicated circuit mechanism for the control processing circuit unit.

  According to the tire condition detection device of the present invention, a plurality of monopole antennas for communicating with the transponders in each tire are combined with a corner reflector and attached to the bottom of the vehicle body integrally with the control processing means. Since the radio waves radiated from the antenna are set so as to go to the corresponding tire sidewalls, it is difficult to perform complicated work at the time of installation like when installing the antenna element on the vehicle body in a tire house etc. near the tire It will not be done. Moreover, since the wiring of the coaxial cable is not required, the component cost and the installation cost can be greatly reduced, and the power loss during transmission can be avoided.

  An embodiment of the invention will be described with reference to the drawings. FIG. 1 is a bottom view of a vehicle showing the overall configuration of a tire condition detection device according to an embodiment of the present invention, and FIG. 2 is a vehicle body side antenna of the tire condition detection device. FIG. 3 is an explanatory view showing a part of the vehicle body antenna portion, and FIG. 4 is a cross-sectional structure explanatory view corresponding to FIG.

  The tire condition detection apparatus shown in these drawings receives tire information transmitted from the transponder 2 mounted in each tire 1 of the automobile by the vehicle body side antenna unit 3 and inputs it to the control processing circuit unit 4. The air pressure and temperature of each tire 1 can be grasped at the driver's seat. As shown in FIGS. 1 and 2, the vehicle body side antenna unit 3 and the control processing circuit unit 4 are integrated and covered with a radome 5, and this integrated product is mounted at the approximate center of the vehicle body bottom surface 6. Also, four monopole antennas 30 are disposed in the vehicle body side antenna unit 3 to communicate with each transponder 2, and a predetermined frequency (this embodiment) is provided in a space between the vehicle body bottom surface 6 and the road surface. In the case of the example, 2.4 GHz) radio waves are propagated so that communication can be performed between each monopole antenna 30 and each transponder 2.

  The transponder 2 in each tire 1 is configured to incorporate a pressure sensor, a temperature sensor, a transmission / reception circuit, an antenna element, etc. (not shown), and this built-in antenna element is equivalent to the monopole antenna 30 of the vehicle body side antenna unit 3. It is designed to resonate at a frequency of 2.4 GHz. As the built-in antenna element of the transponder 2, for example, an inverted F type antenna is suitable.

  The control processing circuit unit 4 is an ECU, and its circuit board 40 extends substantially parallel to the road surface. The control processing circuit unit 4 is provided with a microcomputer (not shown), an input / output interface, and the like.

  The vehicle body side antenna unit 3 includes a circular first metal plate 31 fixed to the bottom surface of the circuit board 40 of the control processing circuit unit 4 and a cross-shaped first metal plate 31 that hangs down from the first metal plate 31. 2 metal plates 32, a circular third metal plate 33 on which the second metal plate 32 is mounted, and a fan 4 in plan view defined by the first to third metal plates 31 to 33. It is mainly constituted by four monopole antennas 30 that hang down in the horn-shaped space 34 of the partition. The first metal plate 31 and the third metal plate 33 have the same size and extend substantially parallel to the road surface, and the first metal plate 31 operates as a ground plate for each monopole antenna 30. In addition, a space sandwiched between the first metal plate 31 and the third metal plate 33 is divided into four sections by the second metal plate 32, thereby defining a horn-like space 34 having an opening on the radially outer side. It is made. Then, the monopole antenna 30 having a length of about ¼ (about 3 cm) of the free space wavelength λ of the radio wave used for communication is connected to the center of the cross of the second metal plate 32 in each horn-shaped space 34 The second metal plate 32 is made to operate as a corner reflector of each monopole antenna 30 by being disposed downward at a position where the distance is about λ / 4.

  The vehicle body side antenna unit 3 is mounted integrally with the control processing circuit unit 4 at substantially the center of the bottom surface 6 of the vehicle body. At this time, as shown in FIG. It is set so as to face the sidewall 10 of the tire 1. Thereby, radiation beams 7a to 7d having strong directivity from each monopole antenna 30 and its corner reflector (second metal plate 32) toward the sidewall 10 of the desired tire 1 are obtained. That is, by the vehicle body side antenna unit 3, the radiation beam 7a having high directivity to the right front wheel, the radiation beam 7b having strong directivity to the left front wheel, the radiation beam 7c having strong directivity to the right rear wheel, A radiation beam 7d having high directivity toward the rear wheel is generated. Note that all of the four monopole antennas 30 are mounted on the circuit board 40 of the control processing circuit unit 4 using solder 41, as shown in FIG.

  Next, the operation of this embodiment will be described. When a signal requesting tire state detection information is issued from the control processing circuit unit 4, radio waves serving as question signals are transmitted from the monopole antennas 30 of the vehicle body side antenna unit 3. This radio wave is transmitted from the opening of each horn-like space 34 toward the sidewall 10 of the corresponding tire 1 as radiation beams 7a to 7d. Therefore, the built-in antenna element of the transponder 2 in each tire 1 is excited by these radiation beams 7a to 7d to generate a high-frequency current. The transponder 2 responds from the built-in antenna element by supplying a signal current obtained by superimposing the tire pressure information detected by the pressure sensor and the tire temperature information detected by the temperature sensor to the built-in antenna element. Transmit radio waves as signals. However, a power battery may be incorporated in the transponder 2.

  Since the frequency used is 2.4 GHz, which is highly linear, radio waves transmitted from the transponders 2 and passing through the sidewalls 10 are likely to propagate into the horn-like space 34 in which the corresponding monopole antenna 30 is disposed. It is difficult to propagate into the horn-like space 34 of the other three sections. Therefore, detection signals relating to the air pressure and temperature of each tire 1 are efficiently transmitted to the corresponding monopole antennas 30, and these detection signals are input to the control processing circuit unit 4 via each monopole antenna 30. The

  Further, in this embodiment, since the four monopole antennas 30 are set to sequentially communicate with the corresponding transponders 2 by switching control of the control processing circuit unit 4, the detection received by each monopole antenna 30 is detected. There is no need to provide the control processing circuit unit 4 with a complicated circuit mechanism for processing signals in parallel.

  In this way, when detection information related to tire air pressure and tire temperature is input from the transponder 2 in each tire 1 to the control processing circuit unit 4 via the vehicle body side antenna unit 3, these detection information is controlled by the control processing circuit unit 4. After processing, the detection result after processing is displayed on the display device of the driver's seat or a warning sound is emitted.

  Thus, in the present embodiment, the four monopole antennas 30 for communicating with the transponders 2 in the four tires 1 are combined with the second metal plate 32 that operates as a corner reflector. The vehicle body side antenna portion 3 is configured, and the vehicle body side antenna portion 3 is mounted integrally with the control processing circuit portion 4 at the substantially center of the vehicle body bottom portion 6. And since the directivity is strengthened so that the radio wave radiated from each monopole antenna 30 propagates from the opening of the horn-shaped space 34 toward the corresponding sidewall 10 of the tire 1, There is no need to perform complicated work at the time of installation as in the case where the antenna element is installed in a tire house or the like near the tire. In addition, since no coaxial cable wiring is required, the component cost and the installation cost can be greatly reduced, and power loss during transmission can be avoided.

  Further, in the present embodiment example, the four horn-shaped spaces 34 of the vehicle body side antenna unit 3 are defined by the first to third metal plates 31 to 33. The radiation beams 7a to 7d having high directivity toward 10 can be realized with a simple and inexpensive structure. In addition, since the third metal plate 33 extending substantially parallel to the first metal plate 31 is provided below the second metal plate 32, the mechanical strength of the vehicle body side antenna unit 3 is high. Thus, the second metal plate 32 is not easily deformed even while the vehicle is running. Further, the presence of the third metal plate 33 has an advantage that the communication between the monopole antenna 30 and the transponder 2 in the tire 1 is less likely to be adversely affected by a metal body or the like on the road surface. However, the communication performance between the monopole antenna 30 and the transponder 2 can be secured even if the third metal plate 33 is omitted and the lower portion of each horn-shaped space 34 is opened.

  In the above embodiment, the case where the vehicle body side antenna unit 3 is circular in plan view has been described. However, as shown in FIG. May have a triangular shape in plan view.

1 is a vehicle bottom view illustrating an overall configuration of a tire state detection device according to an embodiment of the present invention. It is an external view which shows the vehicle body side antenna part and control processing circuit part of this tire state detection apparatus. It is explanatory drawing which shows a part of this vehicle body side antenna part. FIG. 4 is an explanatory diagram of a cross-sectional structure corresponding to FIG. 3. It is explanatory drawing which shows the modification of this vehicle body side antenna part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Tire 2 Transponder 3 Car body side antenna part 4 Control processing circuit part (ECU)
6 Car body bottom part 7a-7d Radiation beam 10 Side wall 30 Monopole antenna 31 1st metal plate 32 2nd metal plate 33 3rd metal plate 34 Horn-like space 40 Circuit board

Claims (6)

A transponder that is mounted in each of the tires and transmits a detection signal obtained by detecting the state of the tire to the external space, a plurality of monopole antennas that can communicate with the transponder in each tire individually, and a vehicle body The tire condition detection device includes a control processing unit that is mounted on the bottom and receives the detection signals via the plurality of monopole antennas and outputs a required signal based on the detection signals to an external device. And
In the vicinity of the monopole antenna, there is provided a corner reflector for reflecting the radio wave radiated from the monopole antenna in an undesired direction and directing it in the desired direction, and all of the monopole antenna and the corner reflector are controlled by the control processing means. The tire state detection device is configured so that the radio waves radiated from the monopole antennas are directed to the corresponding sidewalls of the tire by being mounted at substantially the center of the bottom of the vehicle body.   2. The first metal plate extending substantially parallel to the road surface at the bottom of the vehicle body, and a second metal plate having a cross shape in plan view that hangs down from the first metal plate. And the space below the first metal plate is divided into four sections opened radially outward by the second metal plate, and the monopole antenna is disposed in each of the four sections. A tire condition detection device, wherein the second metal plate is used as the corner reflector.   3. The distance from the monopole antenna to the center of the cross shape of the second metal plate is set to about one quarter of a free space wavelength corresponding to the resonance frequency of the monopole antenna. A tire condition detection device characterized by the above.   4. The tire condition detection device according to claim 2, wherein a third metal plate extending substantially parallel to the first metal plate is provided below the second metal plate. .   5. The tire state detection device according to claim 1, wherein the plurality of monopole antennas are mounted on a circuit board of the control processing unit.   The tire condition detection device according to any one of claims 1 to 5, wherein the plurality of monopole antennas are sequentially communicated with the corresponding transponders by switching control of the control processing means. .

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