JP2003347811A - Sensor tag for tire pressure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sensor tag for tire pressure which allows proper propagation of stabilized radio waves, containing pressure information indicating the state of the tire internal pressure. <P>SOLUTION: A tire pressure sensor tag 10 has a board 24, a pressure sensor, provided on the board 24, for sensing a tire internal pressure, a processing circuit, provided on the board 24, for generating pressure information for indicating the tire internal pressure sensed by the pressure sensor, and an antenna 20 for transmitting the pressure information generated by the processing circuit as radio waves. The antenna 20 has a radiating portion 20a composed of a band conductor member, which has a curvature of the out-of-plane direction on at least one portion in the longitudinal direction of the band conductor member, is formed into an approximately loop shape, and is provided above the substrate surface of the board 24. <P>COPYRIGHT: (C)2004,JPO

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire pressure sensor tag for detecting tire internal pressure and transmitting pressure information representing the state of tire internal pressure as a radio wave.

[0002]

2. Description of the Related Art In order to make vehicle traveling safer, tire pressure monitoring devices that detect tire internal pressure and notify the driver of the vehicle internal pressure are in practical use today. Such a tire pressure monitoring device includes a pressure sensor that detects a tire internal pressure, a processing circuit that generates pressure information indicating a state of the tire internal pressure detected by the pressure sensor, and pressure information generated by the processing circuit. A transmission antenna that transmits as a radio wave is provided, a tire pressure sensor tag mounted on a wheel, a reception antenna provided on a vehicle that receives a radio wave transmitted from the tire pressure sensor tag, and a reception antenna connected to the reception antenna And a receiving device for notifying the driver in the vehicle of the state of the tire internal pressure based on the pressure information received in step (1).

Here, a voltage corresponding to the strength of the radio wave radiated from the transmitting antenna and arriving at the receiving antenna is excited to the receiving antenna, and when this excited voltage is a predetermined value or more, it is connected to the receiving antenna. The receiving device receives pressure information, and if the excitation voltage is smaller than a predetermined value, no pressure information is received. For this reason, the radiation intensity of the radio wave radiated and propagated from the transmitting antenna must be set so that it is always more than a predetermined value at the position where the receiving antenna is arranged in order to obtain stable reception by the receiving antenna. I must.

[0004]

By the way, since the tire pressure sensor tag is mounted on the wheel surface facing the hollow area of the rotating tire, the tire pressure sensor tag has a transmitting antenna for transmitting pressure information and the pressure information. The relative position of the receiving antenna for receiving changes as the tire rotates. The conventional tire pressure sensor tag is
4 (a) is a perspective view of a conventional tire pressure sensor tag, FIG. 4 (b) is a side view of the conventional tire pressure sensor tag, and FIG. 4 (c) is a plan view of the conventional tire pressure sensor tag (shaded portion). As shown in FIG. 2), a planar antenna in which the antenna 42 is printed on the substrate 44 is generally used in order to simplify the configuration. Therefore, the conventional tire pressure sensor has a maximum radiation intensity in a direction perpendicular to the substrate 44, and radio waves are mainly emitted in the vertical direction. Therefore, in the receiving antenna, with the rotation of the tire, the direction and distance of the radio wave radiated by the transmitting antenna will change repeatedly according to the rotation period,
The strength of the radio wave received by the receiving antenna also varies according to the rotation period of the tire.

For this reason, for example, when a conventional tire pressure sensor tag mounted so that the maximum radiation intensity is in the radial direction of the tire reaches the lowest point as the tire rotates, it is radiated from the transmitting antenna. The direction of the radio wave is mainly the ground direction. In such a case, even if the radio wave radiated in the direction of the ground is reflected by the ground, the intensity of the radio wave at the receiving antenna becomes small, and thus the voltage excited by the receiving antenna becomes smaller than a predetermined value, The device may not receive pressure information stably.

In the radio wave law, there is a limit on the radiation intensity of radio waves that can be radiated. Therefore, such a problem cannot be solved by increasing the radio wave radiation intensity radiated from the transmitting antenna.

The present invention has been made to solve the above-described problems, and provides a tire pressure sensor tag capable of satisfactorily and stably propagating radio waves including pressure information representing the state of tire internal pressure. Is an issue.

[0008]

In order to solve the above-mentioned problems, the present invention provides a substrate, a pressure sensor for detecting the tire internal pressure provided on the substrate, and the state of the tire internal pressure detected by the pressure sensor. A processing circuit provided on the substrate that generates pressure information to represent, and an antenna that transmits the pressure information generated by the processing circuit as a radio wave,
The antenna has a radiating portion composed of a strip-shaped conductor member, and the strip-shaped conductor member has an out-of-plane curvature in at least a part of the longitudinal direction of the strip-shaped conductor member, and is formed in a substantially loop shape. A tire pressure sensor tag is provided above a substrate surface of a substrate.

Here, the angle formed by the normal direction of the conductor surface of the strip-shaped conductor member and the normal direction of the substrate surface of the substrate is 70.
It is preferably not less than 110 degrees and not more than 110 degrees. Moreover, it is preferable that the said board | substrate is attached to the surface which faces the tire cavity area | region of the wheel with which the tire was mounted | worn.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The tire pressure sensor tag of the present invention will be described in detail based on a preferred embodiment shown in the accompanying drawings.

FIG. 1 shows a tire pressure sensor tag 1 according to the present invention.
It is a block diagram showing an example of a schematic configuration of 0. As shown in FIG. 1, the tire pressure sensor tag 10 is sent from the air pressure sensor 12 that detects the tire internal pressure, the analog amplifier 14 that amplifies the electric signal that represents the tire internal pressure detected by the air pressure sensor 12, and the analog amplifier 14. Based on the electrical signal thus generated, pressure information representing the state of the tire internal pressure is generated, a processing circuit 16 that outputs the pressure signal as a pressure signal, and a carrier wave for transporting the pressure signal output from the processing circuit 16 are generated. An oscillator 18 that modulates a signal and oscillates a high-frequency signal, an antenna 20 that radiates a carrier wave modulated by a pressure signal as a radio wave, a battery 22 that supplies power to drive these components, and a substrate on which these components are provided 24.

The air pressure sensor 12 may be a sensor having a diaphragm made of an elastic material such as silicon rubber, and detecting the deformation of the diaphragm due to the tire internal pressure as a change in capacitance and converting the state of the tire internal pressure into an electric signal. And
Other types of sensors may be used. The air pressure sensor 12
Corresponds to the pressure sensor of the present invention. The analog amplifier 14 is a part that amplifies an analog electrical signal sent from the air pressure sensor 12, and is a known one.

Although not shown, the processing circuit 16 includes a storage unit, a CPU, and a pressure signal generation unit, and is a part that generates pressure information. The storage unit is a part that stores pressure information corresponding to the electrical signal output from the air pressure sensor 12.
The CPU is a part that extracts pressure information corresponding to the electrical signal stored in the storage unit based on the electrical signal sent from the analog amplifier 14. The pressure signal generator is a CPU
It is a part which produces | generates the pressure signal showing the pressure information extracted by. The processing circuit 16 may generate a pressure signal representing pressure information generated at a predetermined time interval, or generate a pressure signal based on an instruction input (for example, by a driver in the vehicle). There may be.

The processing circuit 16 may generate a pressure signal representing pressure information for determining whether the tire internal pressure is normal or abnormal. In this case, the CPU
Calculates the tire internal pressure from the electrical signal sent from the analog amplifier 14, and determines that the tire internal pressure is normal if the tire internal pressure is within the allowable internal pressure range stored in the storage unit, and abnormal if not within the allowable range. It is determined that In this case, if the CPU determines that the tire pressure is normal, the pressure signal generator generates a pressure signal indicating that the tire pressure is normal, and the CPU indicates that the tire pressure is abnormal. If it is discriminated, a pressure signal indicating an abnormality is generated.

The oscillator 18 generates a carrier wave, frequency-modulates the carrier wave based on the pressure signal sent from the processing circuit 16, oscillates the modulated carrier wave, and sends it to the antenna 20 for transmission as a radio wave. Part. The modulation method is not limited to frequency modulation, and may be amplitude modulation or the like. Note that the frequency band of the carrier wave is, for example, 315 MHz to 433 MHz, and in this embodiment, the frequency of the carrier wave is 375 MHz.

The antenna 20 is a part that transmits a modulated carrier wave transmitted from the oscillator 18 as a radio wave.
This is a characteristic part of the present invention.

FIGS. 2A to 2C show the shape of the antenna 20 and the positional relationship between the antenna 20 and the substrate 24. FIG. 2A is a perspective view of the tire pressure sensor tag 10,
2B is a side view of the tire pressure sensor tag 10, and FIG.
FIG. 4C is a plan view of the tire pressure sensor tag 10. Here, the air pressure sensor 12, the analog amplifier 14, the processing circuit 16, the oscillator 18, and the battery 22 are provided on the substrate 24, but are omitted in FIGS. 2 (a) to 2 (c).

The antenna 20 shown in FIGS. 2 (a) to 2 (c).
Has a radiation portion 20a composed of a substantially loop-shaped strip-shaped conductor member that radiates radio waves. This strip-shaped conductor member has, for example, a width of 2 mm and a thickness of 100 μm, and a circumferential length (loop length). Is phosphor bronze of 5 cm. Further, the angle formed by the normal direction of the conductor surface of the strip-shaped conductor member and the normal direction of the substrate surface of the substrate 24 is 90 degrees, and is spaced apart by 2 mm above the substrate surface of the substrate 24. . That is,
The radiating portion 20 a is formed in a substantially loop shape above the substrate surface of the substrate 24 so that the conductor surface of the radiating portion 20 a is orthogonal to the substrate surface of the substrate 24. Here, the substantially loop shape does not necessarily circulate, but the radiating portion 20 extends in at least three directions among the four directions surrounding the substrate 24 such as a U-shape and a U-shape.
It is the shape formed so that the conductor surface of a may face.

Note that an antenna 20 is provided at the end of the radiation section 20a.
A supporting portion 20b that supports the radiating portion 20a is connected, and the radiating portion 20a is provided above the substrate 24 by the supporting portion 20b. One of the two support portions 20b includes
A feeding point is formed by being connected to a transmission line from the oscillator 18 provided on the substrate 24.

Thus, by forming the radiating portion 20a with a substantially loop-shaped strip-shaped conductor member, radio waves can be radiated in the direction indicated by the arrow in FIG. 2 (a). Further, since the radiating portion 20a has a substantially loop shape, radio waves can be radiated toward the periphery of the substrate 24. This is different from a radiation pattern in which a conventional antenna radiates radio waves with a maximum radiation intensity in a direction perpendicular to the substrate surface of the substrate. By configuring the antenna 20 in this way, it is possible to radiate radio waves around the substrate 24 in a substantially isotropic direction, and it is possible to efficiently propagate radio waves within the tire cavity region.

The angle formed by the normal direction on the conductor surface of the strip-shaped conductor member of the antenna 20 and the normal direction of the substrate surface of the substrate 24 is not limited to 90 degrees, but is 70 degrees to 110 degrees. Is preferred. In this range, it is possible to efficiently propagate radio waves radiated within the tire cavity region. Also,
Radiation part 20a of antenna 20 shown in Drawing 2 (a)-(c).
The shape is a rectangular loop shape in which the curvature is extremely large at four locations to form corners, but the shape of the radiating portion 20a is not limited to the rectangular loop shape, and is at least a part of the longitudinal direction of the strip-shaped conductor member. Any loop shape having a curvature in the out-of-plane direction may be used. For example, a loop shape of an arc such as a circle or an ellipse may be used. In particular, the radiating portion 20a preferably has a loop shape that radiates radio waves evenly in a direction of 90 degrees (right angle) with respect to the normal direction of the substrate surface of the substrate 24. Also,
The loop shape may be constituted by a twisted strip-shaped conductor member, the width of the strip-shaped conductor member may be partially non-uniform, or the thickness is a partially non-uniform strip-shaped member. Also good.

As the battery 22, a small button type battery or a coin type battery (for example, CR-2032 (coin type lithium manganese dioxide battery)) is used so as to be attached to the substrate 24. The substrate 24 is made of a material such as porcelain, plastic or glass suitable for the purpose of mechanical support and insulation, in addition to a silicon substrate or a gallium arsenide substrate. In addition, unlike the substrate 44 of the conventional tire pressure sensor tag, the antenna 42 does not need to be in close contact with the substrate 44, so that the antenna 42 can be used without being limited to a material having a high relative dielectric constant. There is also an advantage that the degree of freedom of selection is high.

The tire pressure sensor tag 10 of the present invention is configured as described above. In this embodiment, the substrate 24 is attached to the surface facing the tire cavity region of the wheel mounted on the tire.

Next, the tire pressure sensor tag 10 of the present invention.
The operation of will be described. Tire pressure sensor tag 10
Are attached to the surface of the wheel facing the tire cavity region and move in position as the tire rotates. In the air pressure sensor 12, the state of the tire internal pressure is converted into an electric signal, amplified by the analog amplifier 14, and processed by the processing circuit 1.
6 is sent. The processing circuit 16 corresponds to an electrical signal received from the analog amplifier 14 by a CPU (not shown) at a predetermined interval set in advance or according to an instruction transmitted from the receiving device according to an instruction from a driver or the like. Pressure information is extracted, and a pressure signal representing the state of tire internal pressure is generated in the pressure signal generator. The pressure signal generated by the processing circuit 16 is sent to the oscillator 18.

In the oscillator 18, the generated 375 MHz carrier wave is modulated by the pressure signal, and the modulated carrier wave oscillates as a harmonic signal and is sent to the antenna 20 for transmission as a radio wave.

In the antenna 20, the substrate 2 is based on the modulated 375 MHz carrier wave sent from the oscillator 18.
Radio waves are emitted in a radiation pattern having a maximum radiation intensity in a direction of 90 degrees (right angle) with respect to the normal direction of the substrate surface No. 4. Moreover, since the radio waves are radiated in four directions from the radiating portion 20a toward the peripheral portion of the substrate 24, they are propagated into the tire cavity region.

FIG. 3 shows the radio wave radiated from the tire pressure sensor tag 10 of the present embodiment and the conventional tire pressure sensor tag at the same level as the reception level (the radio wave intensity) at the position where the receiving antenna of the vehicle body is attached. It is the figure which measured and compared actually.

As shown in FIG. 3, when the conventional tire pressure sensor tag is used, the reception level of the radio wave at the receiving antenna fluctuates greatly with time, that is, with the rotation cycle of the tire. Therefore, when a radio wave is emitted when the tire pressure sensor tag is located at a position where the reception level becomes weak, only a voltage lower than a predetermined voltage for allowing the receiving device to receive the pressure signal is excited at the receiving antenna. For this reason, there has been a case where the driver cannot be stably notified of the state of the tire internal pressure.

However, as shown in FIG. 3, when the tire pressure sensor tag 10 according to the present invention is used, it is hardly affected by the time, that is, the rotation period of the tire, and the reception antenna receives a substantially constant reception. Radio waves are received at the level. Therefore, by using the tire pressure sensor tag 10, a voltage equal to or higher than a predetermined voltage that allows the receiving device to receive the pressure signal can be obtained regardless of the position of the tire pressure sensor tag 10 that moves as the tire rotates. When excited, the driver in the vehicle is stably notified of the state of the tire internal pressure.

Although the tire pressure sensor tag of the present invention has been described in detail above, the present invention is not limited to the above-described embodiment, and various improvements and modifications may be made without departing from the spirit of the present invention. Of course.

[0031]

As described in detail above, by using the tire pressure sensor tag of the present invention, it is possible to stably and satisfactorily propagate radio waves including pressure information representing the state of tire internal pressure in the tire cavity region. .

[Brief description of the drawings]

FIG. 1 is a block diagram showing an example of a configuration of a tire pressure sensor tag according to the present invention.

2A is a perspective view of an example of a tire pressure sensor tag of the present invention, FIG. 2B is a side view of an example of a tire pressure sensor tag of the present invention, and FIG. 2C is a plan view of an example of a tire pressure sensor tag of the present invention. FIG.

FIG. 3 is a diagram showing an example of fluctuations in reception level obtained with the tire pressure sensor tag shown in FIG. 2 and an example of fluctuations in reception level obtained with a conventional tire pressure sensor tag.

4A is a perspective view of a conventional tire pressure sensor tag, FIG. 4B is a side view of a conventional tire pressure sensor tag,
(C) is a top view of the conventional tire pressure sensor tag.

[Explanation of symbols] 10 Tire pressure sensor tag 12 Air pressure sensor 14 Analog amplifier 16 Processing circuit 18 Oscillator 20, 42 Antenna 20a Radiation part 20b Support part 22 battery 24, 44 substrate

──────────────────────────────────────────────────── ─── Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme code (reference) H04B 5/02 H04B 5/02 F-term (reference) 2F055 AA12 BB19 CC02 DD11 EE25 FF34 GG11 5J046 AA03 AA12 AB11 MA03 MA11 PA07 5J047 AA03 AA12 AB11 EA01 EA06 5K012 AA01 AA05 AC06 BA19

Claims (3)

[Claims] 1. A substrate, a pressure sensor for detecting a tire internal pressure provided on the substrate, and a processing circuit provided on the substrate for generating pressure information representing a state of the tire internal pressure detected by the pressure sensor And an antenna that transmits the pressure information generated by the processing circuit as a radio wave, and the antenna has a radiating portion composed of a strip-shaped conductor member, and the strip-shaped conductor member is a longitudinal direction of the strip-shaped conductor member. A tire pressure sensor tag, wherein at least a part of the tire has a curvature in an out-of-plane direction, is formed in a substantially loop shape, and is provided above the substrate surface of the substrate. 2. The angle formed by the normal direction of the conductor surface of the strip-shaped conductor member and the normal direction of the substrate surface of the substrate is 70 degrees or more.
The tire pressure sensor tag according to claim 1, wherein the tire pressure sensor tag is 10 degrees or less. 3. The tire pressure sensor tag according to claim 1, wherein the substrate is attached to a surface facing a tire cavity region of a wheel mounted on the tire.