JP2003182323A - Tyre pneumatic pressure sensing system, tyre and tyre pneumatic pressure sensor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To perform a high precise sensing of a pneumatic pressure of a tyre installed at a vehicle body irrespective of its running state or parking state. <P>SOLUTION: An IC chip 13 is fixed to a tyre 12 installed at a vehicle body 11. The vehicle body 11 is provided with a tyre pneumatic pressure sensing device 14. The tyre pneumatic pressure sensing device 14 is operated such that an electromagnetic wave is sent by a transmitter 16 and a transmitting antenna 16a toward the IC chip 13 and a responding electromagnetic wave from the IC chip 13 is received by a receiving antenna 17a and a receiver 17. An intensity of the received responding electromagnetic wave is detected and judged at CPU 15 so as to determine whether or not the pneumatic pressure is decreased. In the case that the pneumatic pressure is decreased, any one of lamps 18a to 18d in alarm light 18 corresponding to the tyre 12 showing a decreased pneumatic pressure is turned on or lit to make an alarm against a driver or the like. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to detecting the state of air pressure of tires mounted on a vehicle body, and particularly to a tire air pressure detection system capable of detecting even when the air pressures of all tires decrease at the same time. The present invention relates to a tire and a tire air pressure detection device.

[0002]

2. Description of the Related Art Recently, there are various types of systems for detecting a tire air pressure state. These systems are equipped with a sensor that detects the air pressure state on the wheel in which the tire is fitted or the tire itself, and the signal detected by this sensor is transmitted to the processing device provided on the vehicle side by wire or wirelessly, so that the tire on the vehicle side. There are many things that make it possible to grasp the air pressure state of.

FIG. 8 shows a schematic diagram of a decompression alarm device 1 in a method for detecting a decompressed tire of a vehicle according to Japanese Patent Publication No. 5-55322 as one example of conventional systems. The decompression alarm device 1 is provided with detectors 3A, 3B, 3C, 3D that detect the angular velocities of the tires 2A, 2B, 2C, 2D, and connects these detectors 3A, 3B, 3C, 3D to the central processing unit 4. is doing. The central processing unit 4 is for each detector 3
The air pressure drop is judged based on the detection signals from A, 3B, 3C and 3D, and if there is an abnormality, it corresponds to the abnormal tire among the warning lamps 5A, 5B, 5C and 5D connected to the central processing unit 4. It controls to turn on the ones that do.

The determination of the decrease in air pressure by the central processing unit 4 is based on the change in the angular velocity at the time of rotation due to the reduction of the tire diameter due to the decrease in air pressure. The central processing unit 4 determines that the tires 2A, 2B, 2C are rotating, The 2D angular velocities are compared with each other based on the respective detection signals, and it is determined that a tire whose angular velocity is faster than others has a low air pressure, and the warning lamp is turned on to notify the driver of the low air pressure.

[0005]

The conventional system as described above is capable of coping with the case where only one tire has a decrease in air pressure because the detection signals for the respective tires are compared with each other, but a plurality of tires are used. There is a problem that the abnormality cannot be detected when the air pressures of the two simultaneously decrease. For example, when the vehicle is left unattended for a long period of time, the air pressures of the four tires often drop evenly, so the detection signals for each tire also change, and the relative comparison shows that the tires are different. There is a problem that the decrease in air pressure cannot be grasped because it does not occur.

Further, if there is an excessively inflated tire mounted on the vehicle body, the tire having the excessively high inflation pressure has a tire diameter larger than that of the tire having the normal inflation pressure, so that the detection signal regarding the angular velocity is also generated. Different from other tires. In this case, since the tire diameter of the tire having normal air pressure is smaller than that of the tire having too much air pressure, a tire having normal air pressure may be erroneously determined as a decrease in air pressure in the relative comparison as in the conventional system.

Further, in the conventional system for detecting the change in tire air pressure from the angular velocity of the tire, when the vehicle is running,
That is, there is a problem that it cannot be detected unless the tire is rotating. Therefore, there is a problem in that the risk of starting traveling of the vehicle without noticing the tire whose air pressure has dropped cannot be eliminated.

The present invention has been made in view of the above problems, and it is possible to reliably detect the air pressure state of a tire by judging the air pressure of each tire individually rather than comparing it with other tires. An object is to provide a detection system, a tire, and a tire air pressure detection device. Another object of the present invention is to provide a tire air pressure detection system, a tire, and a tire air pressure detection device that can determine the suitability of air pressure even when the air pressures of all the tires mounted on the vehicle body decrease at the same time. Further, it is an object of the present invention to provide a tire air pressure detection system and a tire which can detect the tire air pressure state in any state regardless of whether the vehicle is running or stopped.

[0009]

A tire air pressure detection system according to a first aspect of the present invention is a tire air pressure detection system for detecting a state of air pressure of a tire mounted on a vehicle body,
A reactant attached to a tire and returning a response to an external input; a detector attached to the vehicle body for outputting to the reactant to detect a response from the reactant; and a detector. And a detection unit that is connected to the detection unit and that detects the intensity of the response due to the variation in the distance between the reactant and the detection unit.

According to the first aspect of the invention, the tire air pressure condition is judged for each tire based on the variation in the distance between the reactant and the detecting means, rather than the relative comparison between the tires. Whether or not the tire pressure is appropriate can be determined regardless of the state. Further, in the present invention, since the angular velocity accompanying the rotation of the tire is not used for detecting the tire air pressure state, the air pressure can be detected regardless of the vehicle state.

Further, it is preferable that the tire air pressure detection system is provided with warning means for outputting a tire air pressure warning in response to the detection, which is connected to the detection means. By providing the warning means in this way, the driver of the vehicle or the like can grasp the state of the tire air pressure by the warning means, and when the air pressure drops, prevent the occurrence of problems due to the air pressure drop and take appropriate measures. It can be carried out.

Further, it is preferable that the reactant is attached to all the tires mounted on the vehicle body, while the detecting means is attached to all the tires mounted on the vehicle body. By doing so, the air pressure state of each tire of the vehicle can be detected even when the air pressures of all the tires mounted on the vehicle body are uniformly reduced. The system of the present invention is not limited to a vehicle having four tires, and various vehicles such as a motorcycle having two tires mounted therein, a truck having four or more tires mounted therein, a special automobile, etc. Applicable to

In the tire pressure detection system according to the second aspect of the present invention, the reaction body includes means for returning a response electromagnetic wave as the response, and the detection means includes a transmission section for transmitting an electromagnetic wave as an output to the reaction body, And a receiver for receiving a response electromagnetic wave. In the second invention, since the tire air pressure detection system uses the type of reactant that responds to electromagnetic waves and returns response electromagnetic waves,
By providing the detection unit with a transmission unit that sends out an electromagnetic wave and a reception unit that receives a response electromagnetic wave, the response electromagnetic wave can be reliably received by a non-contact type wireless, and this system can be easily applied to a rotating tire. it can.

Further, it is possible to surely detect the tire air pressure state from the intensity of the response electromagnetic wave. That is, it is known that the intensity of the response electromagnetic wave is inversely proportional to the square of the distance from the output location to the reception location, and by utilizing this characteristic, the tire pressure change can be detected. Therefore, when the tire air pressure decreases, the tire diameter at least in the vicinity of the ground contact portion is reduced as compared with the case where the air pressure is normal. By judging the strength change, the air pressure state of each tire can be detected without comparing with other tires.

Since the tire rotates, it becomes very difficult to send and receive electromagnetic waves and supply power to the reactants attached to the tires. Therefore, the reactants receive electromagnetic waves without being supplied with power. In this case, it is preferable to use a non-contact type IC chip that returns a response electromagnetic wave. Further, recently, an extremely small type of 0.4 mm square is also provided for such an IC chip. Therefore, if such a small IC chip as described above is used, it can be embedded inside the tread portion or the inner surface side. Various attachment forms can be applied depending on the situation, such as sticking to.

The transmitter and the receiver are preferably attached to the vehicle body from the top of the tire mounted on the vehicle toward the ground contact point of the tire. By such a mounting form, when the tire air pressure is reduced, the electromagnetic wave is sent to the reaction product and the response electromagnetic wave from the reaction product in the vicinity of the ground contact point of the tire at which the ratio of the reduction of the tire diameter becomes the largest. Since it can be received, the detection can be performed with higher accuracy.

Further, in the tire air pressure detection system, the detection means compares the intensity of the response electromagnetic wave with the threshold with a means for setting a threshold value for the intensity of the response electromagnetic wave according to the specified air pressure of the tire. And a means for determining a decrease in tire air pressure when the intensity of the response electromagnetic wave is equal to or more than the threshold value by the comparison.

If the detection means sets a threshold value for the intensity of the response electromagnetic wave as described above, it is possible to reliably detect a decrease in tire air pressure based on this threshold value. For example, while attaching the reactant to the tread portion of the tire, when attached to the transmitter and receiver of the detection means on the top of the tire, the intensity of the response electromagnetic wave detected by the receiver,
It is weakest when the reactant is located at the ground contact point of the tire.
After that, the intensity of the response electromagnetic wave increases with the rotation of the tire, and when the reactant is located at the top of the tire, the intensity of the response electromagnetic wave becomes the strongest and then gradually decreases with the further rotation of the tire. It becomes the weakest at the ground contact point, and then the above cycle is repeated as long as the tire rotates.

Therefore, if the threshold value is set slightly above the value at which the intensity of the response electromagnetic wave is the weakest when the tire is in the inflated pressure state, the intensity of the response electromagnetic wave is such that the reactant is located near the grounding point. In this case, the level is lower than the threshold. When this is determined in the state where the tire continuously rotates, the intensity of the response electromagnetic wave alternately exceeds the threshold and falls below the threshold as the tire rotates. On the other hand, when the tire pressure decreases, the strength of the response electromagnetic wave increases due to the shortening of the tire diameter, and even at the location where the response electromagnetic wave becomes weakest, the threshold value is exceeded, and the response is obtained even when the tire rotates. The electromagnetic wave will always exceed the threshold. As a result, the difference between the threshold value when the air pressure is normal and the threshold value when the air pressure is abnormal becomes clear, and the change in the air pressure can be reliably detected.

Further, the detection means may include means for detecting whether or not the response electromagnetic wave is received, and means for determining a decrease in tire air pressure when the response electromagnetic wave is received. When the output intensity of the response electromagnetic wave of the reactant attached to the tire is small and the distance from the reactant to the receiving section is long, the intensity of the response electromagnetic wave is zero, that is, when the response electromagnetic wave itself cannot be received, as described above. Since it is not appropriate to detect the air pressure state by setting the threshold value, it is possible to detect the air pressure state depending on whether or not the response electromagnetic wave is received.

For example, when the reactant attached to the tread portion of the tire is located at the grounding point of the tire, the detection means of the detecting means is provided at a location at a limit distance where the response electromagnetic wave from the reactant cannot be received when the tire is in a prescribed air pressure state. Attach the receiver. With such a positional relationship, if the tire has a prescribed air pressure, the response electromagnetic wave does not reach the receiving part while the reactant is located at the grounding point due to the rotation of the tire, and the response is generated once during one rotation of the tire. The reception of electromagnetic waves is lost. On the other hand, when the air pressure is reduced, the response electromagnetic wave reaches the receiving portion even when the reactant is in contact with the ground due to the reduction of the tire diameter, which eliminates the time when the response electromagnetic wave is not received.

Therefore, the detection means can determine that the tire air pressure is low if the response electromagnetic wave is always received even if the tire makes one rotation, and the processing of the detection means can be reduced as compared with the case where the threshold value is set. .

In the tire pressure detection system according to the third aspect of the present invention, a plurality of the reactants are attached at intervals in the width direction of the tire, and each reactant returns the response electromagnetic wave containing different identification information. And detecting means,
It is characterized by further comprising means for detecting the intensity of the response electromagnetic wave by distinguishing each reactant by the identification information.

In the third aspect of the invention, since a plurality of reactants are attached in the width direction of the tire, by comparing the intensity of the response electromagnetic wave for each reactant, the accuracy of detecting the change in tire air pressure can be further improved. . That is, when the air pressure of the tire decreases, the tire diameter reduction rate is different between the side portion and the center in the width direction, and the tire diameter reduction rate is higher near the center. Therefore, by mounting the reactants at different positions near the side part in the width direction and near the center,
By mutually compensating for the degree of detection, it is possible to detect a more accurate tire air pressure state.

When a plurality of reactants are used in this way,
By including the identification information for distinguishing each reactant in the response electromagnetic wave, it is possible to distinguish from which reactant a plurality of response electromagnetic waves are output by the detection means. In addition, if the reactant is attached to the inside of the tire in a buried state, the reactant can be attached to the tread portion of the tire, and the tire pressure can be detected for a long period of time without exposing the reactant to tire consumption. It will be possible.

In the tire pressure detection system according to the fourth aspect of the present invention, a plurality of the reactants are attached at intervals in the circumferential direction of the tire, and each reactant returns the response electromagnetic wave containing different identification information. And detecting means,
It is characterized by further comprising means for detecting the intensity of the response electromagnetic wave by distinguishing each reactant by the identification information. In the fourth aspect of the invention, since a plurality of reactants are attached in the circumferential direction, the response electromagnetic waves are detected for each of the reactants and the detection results are averaged to equalize the error and the like, and Even in various cases such as when the vehicle is running, it is possible to perform detection with higher reliability.

Further, by mounting a plurality of reactants as described above, it is possible to detect a change in tire air pressure with high accuracy even when the vehicle is stopped. For example, when the transmitting unit and the receiving unit of the detecting means are attached from the top of the tire toward the grounding point, the intensity of the response electromagnetic wave from the vicinity of the grounding point becomes the weakest, so setting the threshold value or the response electromagnetic wave as described above. It is possible to detect the state of the air pressure by the presence or absence of acceptance of.

The tire according to the fifth aspect of the invention is a tire having a reactant attached thereto, wherein the reactant is provided with means for outputting a response electromagnetic wave when the electromagnetic wave is received from the outside. In the fifth aspect of the invention, since the tire has a reactant that receives an electromagnetic wave and outputs a response electromagnetic wave,
By mounting the tire on a vehicle equipped with an electromagnetic wave output means and a response electromagnetic wave reception means, a system capable of detecting the tire air pressure state on the vehicle side can be configured.

In the tire according to the sixth invention, the reactant is
A plurality of tires are attached at intervals in the width direction of the tire, and each reactant outputs the response electromagnetic wave including different identification information. In the sixth aspect of the invention, since the tire has a plurality of reactants mounted in the width direction, it is possible to detect changes in air pressure with higher accuracy.

In the tire according to the seventh invention, the reactant is
A plurality of tires are attached at intervals in the circumferential direction of the tire, and each reaction body outputs the response electromagnetic wave containing different identification information. In the seventh aspect of the invention, since the plurality of reactants are embedded in the circumferential direction of the tire, it is possible to stably detect the air pressure regardless of the running state or the stopped state of the vehicle.

The tire pressure detecting device according to the eighth invention is
A tire air pressure detection device for detecting a tire air pressure state, comprising: a transmitter that sends out an electromagnetic wave; a receiver that receives a response electromagnetic wave to the electromagnetic wave; and a detection unit that detects the intensity of the response electromagnetic wave. To do. According to the eighth aspect of the present invention, the tire pressure detecting device including the transmitting unit, the receiving unit, and the detecting means is attached to the vehicle body, and the tire to which the reaction body that outputs the response electromagnetic wave is attached is attached to the vehicle body. The air pressure of the mounted tire can be detected by the tire air pressure detection device.

Further, the tire air pressure detection device may further include warning means for outputting a tire air pressure warning in response to the detection. As described above, if the warning means is provided, the result that the tire pressure is detected as abnormal by the detection means can be output in the form of a warning, so that it is possible to reliably inform the driver of the vehicle that the tire pressure is abnormal. Can communicate.

Further, in the tire air pressure detection device, the detection means compares the intensity of the response electromagnetic wave with the threshold value with a means for setting a threshold value for the intensity of the response electromagnetic wave according to the specified air pressure of the tire. And a means for determining a decrease in tire air pressure when the intensity of the response electromagnetic wave is equal to or higher than the threshold value.
When the detection means sets a certain threshold value as described above, the comparison with respect to the response electromagnetic wave becomes clear, and since the threshold value is set corresponding to the specified air pressure of the tire, the accuracy of the judgment of normal or abnormal air pressure is also improved. However, the reliability of the warning can be improved.

Further, in the tire air pressure detecting device, the detecting means detects whether or not the response electromagnetic wave is received, and means for determining a decrease in tire air pressure when the response electromagnetic wave is received. It is preferable to include and. If the detection means determines the decrease in the air pressure depending on the presence or absence of the reception of the response electromagnetic wave, the air pressure state can be reliably determined, the processing load related to the determination can be reduced, and quick processing can be realized.

[0035]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing the embodiments thereof. FIG. 1 is an overall configuration diagram of a tire air pressure detection system 10 according to the first embodiment of the present invention. The tire pressure detection system 10 includes a vehicle body 11
IC chip 13 as a reactant on tire 12 mounted on
Is attached to the outer periphery of the tire 12 in a buried state, while the vehicle body 11 is provided with a tire air pressure detection device 14 for detecting the air pressure state of the tire 12.

The tire air pressure detecting device 14 includes a detecting means 14a for outputting to the IC chip 13 to detect a response from the IC chip 13, and a CPU 15 as a detecting means for detecting the air pressure state of the tire 12 from the intensity of the response. When,
A warning lamp 18 is provided as a warning unit that is connected to the CPU 15 and outputs an air pressure warning when it is determined that the air pressure has dropped.

The detecting means 14a has a transmitter 16 which is a transmitter for transmitting an electromagnetic wave as an output to the IC chip 13 and a transmitting antenna 16a, and a receiver which is a receiver for receiving a response electromagnetic wave which is a response from the IC chip 13. 17
And a receiving antenna 17a. Transmitting antenna 1
6a and the receiving antenna 17a, the tire 12 is the vehicle body 11
Installed on the tire 12 from the top of the tire 12
It is attached so as to face the grounding point 12a.
It should be noted that a total of four detecting means 14a are attached to the entire vehicle body 11 corresponding to each tire attached to the vehicle body 11.

The CPU 15 is connected to the receiver 17 and determines whether or not the air pressure of the tire 12 has dropped from the change in the intensity of the response electromagnetic wave received by the receiver 17. It should be noted that the CPU 15 is also connected to the remaining three receivers 17 not shown in FIG. 1 so that it is possible to determine the decrease in the air pressure of all the tires mounted on the vehicle 11.

Further, the CPU 15 is connected to a warning lamp 18 mounted on an instrument panel of the vehicle 11 and the four lamps 18a to 18d corresponding to the four tires 12 provided on the warning lamp 18 are turned on. Is controlled according to the decrease in air pressure. That is, if the air pressure of the right front tire 12 is abnormal, the lamp 1 is output as an air pressure warning output.
8a is turned on, and similarly, if the air pressure of the left front tire 12 is abnormal, the lamp 18b is used. If the right rear tire 12 has abnormal air pressure, the lamp 18c is used, and the left rear tire 12 is operated.
If the air pressure is abnormal, the lamps 18d are turned on. The warning lamp 18 may be provided with at least one lamp. In the case of one lamp, the lamp is controlled to be turned on if the air pressure of any tire is abnormal.

On the other hand, the IC chip 13 attached to the tire 12 is of a non-contact type and does not need to be fed with electric power. When an electromagnetic wave is received as an input from the outside, a response electromagnetic wave is returned as a response. Since it is embedded in the tire 12 in this embodiment, the IC chip 13 has a high-frequency analog circuit of 2.45 GHz and a 128-bit ROM (Read On).
ly Memory) is applied in a size of 0.4 mm square. The IC chip 13
Is also attached to all the tires 12 mounted on the vehicle body 11.

The intensity of the response electromagnetic wave output from the IC chip 13 is inversely proportional to the square of the distance between the IC chip 13 and the receiving antenna 17a. Specifically, as shown in FIG. 2A, when the tire 12 is defined as a circle for simplification of calculation, and the reception antenna 17a and the IC chip 13 are also defined as points on the circumference, respectively. ,
When the central angle formed by the center 12b of the tire 12 between the receiving antenna 17a and the IC chip 13 is θ, the square of the distance L between the receiving antenna 17a and the IC chip 13 is
It is shown by the following formula.

L ² = R ² × (2−2cos θ) (1) (where R is the radius of the tire 12)

Therefore, the strength of the response electromagnetic wave is 2 at the distance L.
Since it is inversely proportional to the power, it can be shown by a graph as shown in FIG. The horizontal axis represents the central angle θ, and the vertical axis represents the intensity of the response electromagnetic wave.

In FIG. 2 (b), the solid line graph 19a.
Shows a change in the intensity of the response electromagnetic wave when the tire 12 makes one revolution from the state where the IC chip 13 is located at the tire top when the tire 12 has a specified air pressure. That is, since the distance L between the IC chip 13 and the receiving antenna 17a becomes the longest when the IC chip 13 is located at the grounding point (center angle θ = π) as the tire 12 rotates, the strength of the response electromagnetic wave is increased. Is minimum in inverse proportion to the square of the distance L.

On the other hand, the broken line graph 19b shows that the tire 12 is 1 when the air pressure of the tire 12 is reduced as described above.
The change in intensity of the response electromagnetic wave when rotated is shown. In this case, the tire diameter (radius R) of the tire 12 shrinks as the sidewall portion of the tire 12 expands in the width direction and bends as the air pressure decreases, so that when the IC chip 13 is located at the ground contact point (center angle). Even if θ = π), the distance L between the IC chip 13 and the receiving antenna 17a is shorter than that at the specified air pressure.

Therefore, the minimum value of the intensity of the response electromagnetic wave also increases in inverse proportion to the square of the shortened distance L as compared with the case of the specified air pressure, so that when the IC chip 13 is located near the grounding point. By comparing the strength of the response electromagnetic waves, C
The PU 15 can determine whether the air pressure of the tire 12 is normal.

In the present embodiment, the determination of the air pressure is C
A certain threshold value is set by the PU 15, and whether or not the minimum value of the intensity of the response electromagnetic wave is equal to or more than the threshold value is determined. That is, as shown in FIG. 2B, the minimum value 1 of the graph 19a
The CPU 15 sets a constant threshold value 20 that is an intermediate value between 9c and the minimum value 19d of the graph 19b.

By setting the threshold value 20 as described above, when the tire 12 is at the specified air pressure, during one rotation of the tire 12,
There is a period when the intensity of the response electromagnetic wave is below the threshold value 20,
When the air pressure of the tire 12 is low, the intensity of the response electromagnetic wave is always 20 or more during one rotation. Therefore, C
The PU 15 makes a comparative judgment as to whether or not the intensity of the response electromagnetic wave during one rotation becomes equal to or higher than the threshold value 20, and if the intensity of the response electromagnetic wave is continuously equal to or higher than the threshold value 20 during one rotation, the PU 15 determines that the air pressure has decreased. . Based on this determination, the CPU 15 causes the warning light 18
One of the corresponding lamps 18a to 18d is turned on. The number of lamps provided in the warning light 18 is 1
In the case of individual pieces, a single lamp is turned on.

Further, in actual running, the tire 12 continuously rotates, and the intensity of the response electromagnetic wave in this case is, as shown in FIG. 3, a graph 19a in FIG. 2 (b) depending on the tire air pressure. 19b appears in consecutive cycles, CPU1
5 continuously detects the change in the air pressure of the tire 12 by continuously performing the above-described comparison determination while the vehicle body 11 is traveling. The CPU 15 can determine whether or not the tire 12 has made one revolution by connecting a pulse transmitter or the like attached to the axle of the tire 12 to the CPU 15 and making a determination based on the number of detected pulse signals. Possible and applicable vehicle body 11
If the ABS is equipped with an anti-lock brake system, a pulse generator for ABS or the like may be used.

Although the above description has been made with respect to one tire 12, the CPU 15 simultaneously performs the same processing on the other tires 12 of the vehicle body 11 in parallel. Therefore, since the air pressure of the tires 12 is not individually compared with each other as in the conventional case, but is performed individually, even if the air pressures of a plurality of tires 12 are simultaneously decreased, it is possible to reliably detect them. Needless to say, even if the air pressure of any one of the tires 12 drops, it can be detected.

Further, the tire air pressure detection system 10 of the first embodiment can have various forms other than the above, and the tire air pressure detection system 10 detects four or more tires 12 on each vehicle body 11 such as a truck. By providing the means 14a and attaching the IC chips 13 to all the tires, it is possible to detect the decrease in the air pressure in the same manner as above. Further, it can be similarly applied to a two-wheeled vehicle equipped with less than four tires 12. Further, as means for transmitting the decrease in air pressure to the driver or the like, in addition to the warning light 18, a warning sound or visual indication of a decrease in tire air pressure may be displayed by an in-vehicle monitor or the like.

Moreover, the detection of the decrease in air pressure by the CPU 15 is performed by setting the threshold value 20 as shown in FIG.
The determination may be made based on whether or not the response electromagnetic wave from the C chip 13 is received. Specifically, the distance between the IC chip 13 and the receiving antenna 17a is set to be a little less than the limit distance at which the response electromagnetic wave can be received from the IC chip 13 located at the grounding point 12a when the tire 12 has a prescribed air pressure. The receiving antenna 17a so that
Attach to.

As described above, when the tire 12 has the specified air pressure, the intensity of the response electromagnetic wave output from the IC chip 13 located at the grounding point 12a is the same as that of the receiving antenna 1.
It becomes zero at 7a, that is, the reception of the response electromagnetic wave itself disappears.
On the other hand, when the air pressure of the tire 12 is reduced, the tire diameter is reduced, so that the IC chip 13 contacts the grounding portion 12a.
Even if it is located at, the reception electromagnetic wave is accepted by the reception antenna 17a. Therefore, the CPU 15 can determine that the response air pressure is not received during one rotation of the tire 12 when the tire 12 makes one rotation, and can determine that the air pressure is low when the response electromagnetic wave is always received during one rotation. Detecting the air pressure without setting the threshold 20 in this way is suitable when the output intensity of the response electromagnetic wave of the IC chip 13 is weak and it is difficult to set the threshold 20.

On the other hand, since the tire 12 is generally mounted on the vehicle body 11 with a suspension interposed, the tire 12 moves up and down by this suspension, and the distance between the IC chip 13 and the receiving antenna 17a fluctuates. It is also envisaged to interfere with the detection of the air pressure at 12. In such a case, as shown in FIG. 4, a bracket B extending above the tire 12 is provided on the suspension arm S of the suspension system that moves up and down together with the tire 12, and the bracket B receives the receiving antenna 1
By attaching 7a, the receiving antenna 17a follows the vertical movement of the tire 12. Even if the tire 12 moves up and down by such attachment, the set positional relationship between the IC chip 13 and the receiving antenna 17a is maintained, and the change in the air pressure of the tire 12 can be accurately detected.

FIG. 5 shows how reactants are attached to the tire 22 in the tire pressure detection system 20 according to the second embodiment of the present invention. In the second embodiment as well, the same IC chip as in the first embodiment is used as the reactant, but in the second embodiment, a plurality of IC chips 23A to 23A.
23F are attached in a state where they are embedded in the width direction of the tire 22 at intervals. These IC chips 23A-23
F includes the identification information for identifying itself in the response electromagnetic wave that responds when receiving the electromagnetic wave, and the CPU 25 receives the response electromagnetic wave by the identification information received by the receiving antenna 27a attached above the top of the tire 22. The IC chips 23A to 23F can be distinguished from each other.

The tire pressure detection system 10 according to the first embodiment has the same structure except the above-mentioned portions, and the transmitter transmits an electromagnetic wave through the transmitter antenna and the receiver antenna 27a and the receiver 27. The CPU 25 compares and determines the intensity of the response electromagnetic wave received through to determine the decrease in air pressure, and controls to turn on the required lamp of the warning lamp. Also, each I by the CPU 25
The processing for each C chip is basically the same as that of the first embodiment.

As described above, a total of six IC chips 23A ...
By attaching 23F, the air pressure of the tire 22 can be detected more accurately. In other words, when the tire 22 bends due to a decrease in air pressure, the ratio of bending near the side portion in the width direction of the tire 22 is smaller than that in the central portion, so that the IC chip 23A (or 23F) and the receiving antenna 27a. IC chip 23C
The distance between (or 23D) and the receiving antenna 27a becomes smaller than the contraction rate.

Therefore, the CPU 25 detects the response electromagnetic wave from each of the IC chips 23A to 23F as in FIG. 3 of the first embodiment, but the IC chip 2 located near the side portion is detected.
3A (or 23F), IC chip 2 located near the center
3C (or 23D), IC chip 2 located in the middle
In 3B (or 23E), the threshold values are set differently.

That is, since the IC chip 23C (or 23D) near the center has a large difference between the normal air pressure and the low air pressure, the threshold value is set to the highest value.
(Or 23E), the threshold value is set to be slightly lower than the value set above, and the IC chip 23A (or 2
For 3F), the threshold is set to the lowest. By appropriately setting the threshold values in this manner, during one rotation of the tire 22, if there is a period in which the intensity of all the response electromagnetic waves from the IC chips 23A to 23F is below each threshold value as the tire 22 rotates, 22 can be judged to be the prescribed air pressure.

On the other hand, if the intensity of all the response electromagnetic waves of the IC chips 23A to 23F is always above the threshold value, the tire 2
It can be judged that the air pressure of No. 2 has dropped. Also, each IC
Of the chips 23A to 23F, the intensity of the response electromagnetic wave is below the threshold value on one side in the width direction, but the other side is above the threshold value. It can be determined that the tire diameter has been reduced due to the load, and the CPU 25 determines that the tire air pressure has not dropped. Such a state often occurs during traveling on a curve or the like, and since the air pressure itself is a specified value, a plurality of IC chips 23A to 23F are attached to the tire 22 to prevent erroneous recognition of air pressure detection, and have high reliability. You can build a system.

The number of the IC chips 23A to 23F is not limited to six, and may be increased or decreased depending on the type of vehicle to which the tire 22 is attached, the size of the tire 22 itself, and the like. It is possible. Further, instead of setting the threshold value and comparing and judging the strength of the received response electromagnetic wave, the suitability of the air pressure can be judged based on whether the response electromagnetic wave is received or not, as in the first embodiment.

FIG. 6 shows how the reactant is attached to the tire 32 in the tire pressure detection system 30 according to the third embodiment of the present invention. In the third embodiment, the same IC chip as that of the first embodiment is used as the reactant, but in the third embodiment, a plurality of IC chips 33A to
33H are embedded at equal intervals in the circumferential direction of the tire 32. As in the second embodiment, each of the IC chips 33A to 33H includes identification information for identifying itself in the response electromagnetic wave,
Reception antenna 37a mounted above the top of the tire 32
The CPU 35 can distinguish which of the IC chips 33A to 33H has output the response electromagnetic wave through the receiver 37.

The tire pressure detection system 10 according to the first embodiment has the same structure except the above-mentioned portion, and sends electromagnetic waves from the transmitter 36 through the transmitting antenna 36a and receives the receiving antenna 37a and the receiving antenna 37a. The strength of the response electromagnetic wave received by the machine 37 to the CPU 3
5 determines the decrease of the air pressure by comparing and judging, and controls the lighting of the warning light. Further, each IC by the CPU 35
The processing for each chip is similar to that of the first embodiment.

As described above, a total of eight IC chips 33A to
By attaching 33H, it is possible to reliably detect a change in air pressure even when the vehicle 31 is stopped. That is, electromagnetic waves are transmitted from the transmitting antenna 36a to all the IC chips 33A to 33A.
By outputting toward H, the IC chips 33A to 33A
H returns a response electromagnetic wave, but the grounding point 32a of the tire 32
If the intensity of the response electromagnetic wave from the IC chip 33E located in the vicinity is the tire 32 with the specified air pressure, the CPU 3
The threshold set in 5 cannot be exceeded.

Therefore, the CPU 35 makes a judgment by comparing the intensity of the response electromagnetic waves from all the IC chips 33A to 33H with the threshold value. If there is a response electromagnetic wave having an intensity not exceeding the threshold value, the air pressure of the tire 32 is a specified value. I think there is. On the other hand, when the intensity of the response electromagnetic waves from all the IC chips 33A to 33H is equal to or higher than the threshold value by the comparison judgment of the CPU 35, the air pressure of the tire 32 is determined to be low,
The CPU 35 is processing a warning. Note that, in the third embodiment as well, the state of the air pressure can be detected by the presence or absence of reception of the response electromagnetic wave, as in the second embodiment.

Further, the tire air pressure detection system 30 of the third embodiment can further improve the accuracy of air pressure detection when the tire 32 is rotating. In this case, the transmitting antenna 36a is the ground contact point 32a of the tire 32.
Electromagnetic waves are output toward the vicinity, and the CPU 35 can determine whether the tire 32 has made one revolution from a vehicle speed sensor or a pulse transmitter. Further, the CPU 35 is an IC equipped with an internal counter and attached to the tire 32.
The number of chips 33A to 33H can be set and stored (eight in this embodiment).

A series of processes of the CPU 35 for detecting the air pressure of the rotating tire 32 is as shown in the flowchart of FIG. 7. The process for a plurality of IC chips 33A to 33H in the circumferential direction will be described with reference to this flowchart. In the above flow chart, the CPU 35 does not set a threshold value to compare and determine the change in air pressure, but to determine the change in air pressure based on the presence or absence of reception of a response electromagnetic wave. Further, the tire 32 is assumed to rotate from the state in which the first IC chip 33A is located at the ground contact point 32a.

First, similarly to the first embodiment and the like, electromagnetic waves are continuously output from the transmitting antenna 36a (S1). Next, the CPU 35 determines from the identification information whether or not the response electromagnetic wave is received from the first IC chip 33A via the receiving antenna 37a (S2). In this case, if the air pressure of the tire 32 is a specified value, the response electromagnetic wave is not accepted, whereas if the tire 32 has a reduced air pressure, the response electromagnetic wave is accepted. When the response electromagnetic wave is received, the CPU 35 increments the internal counter to count "1" (S3). When the response electromagnetic wave is not received, the above counting is not performed.

Thereafter, from the second IC chip 33B to the eighth IC chip 33H, it is determined whether or not the same response electromagnetic wave is received (S2) and the count when the response electromagnetic wave is received (S3). Are sequentially performed (S4 to S17).
After that, the CPU 35 starts the detection and then the tire 32
It is determined whether or not has rotated once (S18). Tire 32
If is rotated once, the CPU 35 compares whether the number counted by the internal counter is equal to or larger than the set and stored number of IC chips (S19).

According to the above comparison, when the count number in the internal counter is equal to or greater than the IC chip number "8", it is determined that the air pressure of the tire 32 is low, and the CPU 35 outputs a warning (S20). On the other hand, when the count number is smaller than the IC chip number “8”, the air pressure of the tire 32 is determined to be normal, and the process of the first rotation of the tire 32 is ended. Even if it is determined that the tire 32 has not made one rotation by the determination as to whether or not the tire 32 has made one rotation (S18), the process for the first rotation of the tire 32 is terminated because the comparison is impossible. .

When the processing of the first rotation is completed, 1
The step from the step (S2) of judging whether or not the response electromagnetic wave is received from the second IC chip 33A to the end is sequentially repeated for each rotation of the tire to detect the tire air pressure. Even in the process of the above flow chart, it is possible to set the threshold value and determine the suitability of the air pressure. In this case, in each step (S2 etc.) of determining the presence or absence of reception of the response electromagnetic wave from each IC chip, the response Judgment is made based on whether or not the intensity of electromagnetic waves is above a threshold value.

As described above, in the third embodiment, the intensity of the response electromagnetic wave is determined for each of the eight IC chips 33A to 33H on the basis of one rotation of the tire. Therefore, the response electromagnetic wave is extremely high without being influenced by an error or the like. It enables accurate air pressure detection.

For example, when the vehicle is running, the tire 32 itself may momentarily bend due to an impact due to the unevenness of the road surface. In such a case, the response electromagnetic wave is accepted even if the tire 32 has a specified air pressure. Therefore, the CPU 35 may erroneously determine that the air pressure has dropped when the determination is made only once. However, in the tire air pressure detection system 30 of the third embodiment, whether or not the response electromagnetic wave is received is judged eight times per one rotation of the tire, and it is decided whether or not the air pressure is lowered by integrating these judgments. Such an instant tire 32
The state of the air pressure can be detected without being affected by the bending of the.

The number of IC chips is not limited to eight, and may be increased or decreased as appropriate in accordance with the size of the tire 32 or the like.
It is preferable to increase the number of C chips. Further, in order to realize highly accurate detection from all aspects, the IC chip mounting method of the second embodiment is also combined, the IC chips are mounted at intervals in the tire width direction, and the IC chips are spaced in the tire circumferential direction. You may make it attach an IC chip on both sides. The processing of the CPU 35 other than the above is the same as that of the first embodiment.

[0075]

As described above in detail, in the first aspect of the invention, the change in tire air pressure is individually judged from the change in the distance between the IC chip which is the reactant and the receiving antenna of the detecting means. Therefore, it is possible to reliably detect the air pressure state of the tires, and it is possible to detect the air pressure state even when the air pressures of a plurality of tires simultaneously decrease.

According to the second aspect of the invention, since a reaction body such as an IC chip that returns a response electromagnetic wave when receiving an electromagnetic wave is applied, the intensity of the response electromagnetic wave does not affect the surrounding environment. It is possible to reliably detect the tire air pressure state.

In the third aspect of the invention, since a plurality of IC chips are attached in the width direction of the tire, it is possible to improve the detection accuracy with respect to changes in tire air pressure. According to the fourth aspect of the invention, since the plurality of IC chips are attached in the tire circumferential direction, the state of air pressure can be detected even when the vehicle is stopped.

According to the fifth aspect of the present invention, the tire is provided with the IC chip which returns the electromagnetic wave responsive to the electromagnetic wave. Therefore, when the tire is mounted on the vehicle equipped with the tire air pressure detecting device, the decrease of the tire air pressure can be detected. it can.
According to the sixth aspect of the invention, since a plurality of IC chips are attached to the tire in the width direction, highly accurate detection of changes in air pressure can be dealt with. According to the seventh aspect of the invention, since the plurality of IC chips are attached to the tire in the circumferential direction, the air pressure can be detected stably regardless of whether the vehicle is stopped or running.

According to the eighth aspect of the invention, the tire air pressure detecting device for the vehicle body is provided with the transmitting section for transmitting the electromagnetic wave, the receiving section for receiving the response electromagnetic wave, the detecting means, and the like. By simply attaching the to the vehicle body, it is possible to easily detect a decrease in tire air pressure.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram of a tire air pressure detection system according to a first embodiment of the present invention.

FIG. 2A is an explanatory view showing a simplified positional relationship between an IC chip and a receiving antenna, and FIG.
It is a graph which shows the intensity change of the response electromagnetic waves when rotating.

FIG. 3 is a graph showing changes in the intensity of response electromagnetic waves when the tire continuously rotates.

FIG. 4 is a schematic diagram showing an example of mounting a receiving antenna of the tire air pressure detection system of the first embodiment.

FIG. 5 is a schematic configuration diagram of a tire air pressure detection system of a second embodiment.

FIG. 6 is a schematic configuration diagram of a tire air pressure detection system of a third embodiment.

FIG. 7 is a flowchart for air pressure change detection processing of the tire air pressure detection system of the third embodiment.

FIG. 8 is a schematic view of a conventional decompression alarm device.

[Explanation of symbols]

10 Tire pressure detection system 11 car body 12 tires 13 IC chips 14 Tire pressure detection device 15 CPU 16 transmitter 16a transmitting antenna 17 receiver 17a receiving antenna 18 Warning light 19a Graph (at normal air pressure) 19b Graph (when air pressure drops) 20 threshold

Claims (8)

[Claims] 1. A tire pressure detection system for detecting a state of air pressure of a tire mounted on a vehicle body, comprising a reaction body which is attached to the tire and returns a response to an external input, and a reaction body which is attached to the vehicle body. A detection unit that outputs to the reactant and detects a response from the reactant, and is connected to the detection unit, the intensity of the response due to the change in the distance between the reactant and the detection unit. A tire air pressure detection system, comprising: a detection means for detecting. 2. The reaction body includes means for returning a response electromagnetic wave as the response, and the detection means includes a transmission unit for transmitting an electromagnetic wave as an output to the reaction body and a reception unit for receiving the response electromagnetic wave. The tire air pressure detection system according to claim 1. 3. A plurality of the reaction bodies are attached at intervals in the width direction of the tire, each reaction body includes means for returning the response electromagnetic wave containing different identification information, and the detection means: 3. A means for detecting the intensity of a response electromagnetic wave by distinguishing each reactant based on the identification information.
The tire pressure detection system described in 1. 4. A plurality of the reactants are attached at intervals in the circumferential direction of the tire, each reactant includes means for returning the response electromagnetic wave containing different identification information, and the detecting means, 3. A means for detecting the intensity of a response electromagnetic wave by distinguishing each reactant based on the identification information.
Alternatively, the tire air pressure detection system according to claim 3. 5. A tire having a reactant attached thereto, wherein the reactant comprises means for outputting a response electromagnetic wave when an electromagnetic wave is received from the outside. 6. A plurality of the reactants are attached at intervals in the width direction of the tire, and each reactant outputs the response electromagnetic wave containing different identification information. The tire described in. 7. A plurality of the reactants are attached at intervals in the circumferential direction of the tire, and each reactant outputs the response electromagnetic wave including different identification information. Alternatively, the tire according to claim 6. 8. A tire air pressure detection device for detecting a tire air pressure state, comprising: a transmitter that sends out an electromagnetic wave; a receiver that receives a response electromagnetic wave to the electromagnetic wave; and a detection unit that detects the intensity of the response electromagnetic wave. A tire pressure detection device provided.