JPH08244424A - Tire pressure monitoring system - Google Patents

Abstract

PURPOSE: To detect a pressure of a tire when necessary by providing a response unit for radio wave transmitting to a questioning unit the output data of a pressure sensor detecting a pneumatic pressure of a tire and selectively supplying a battery power selected by an identifying code transmitted by a questioning unit and displaying the output data on a display. CONSTITUTION: A modulating unit 10a of a questioning unit 10 provided in a driver's seat modulates a transmitting output of a transmitting unit 12 with a modulating circuit 13 according to an identifying code output by an identifying code generating circuit 11 and transmits the modulated output to response units 20-50 of each wheel via an antenna 14. Among the response units 20-50, only the response unit which detects a signal coincident with the identifying code turns on a switch 27 to supply electric power 28 to a pressure sensor 25 and a transmitting unit 26. The pressure sensor 25 thus becomes under operating conditions and detects a pneumatic pressure of a tire and then transmits the output thereof to the questioning unit 10 as a radio wave by a transmitting unit 26 via an antenna 29. When an antenna 15 of a demodulating assembly 10b receives the output, the output is processed by a band-pass filter 16 and a demodulating circuit 18 to display it on a display 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire pressure monitor system for monitoring the air pressure of automobile tires using radio waves.

[0002]

2. Description of the Related Art It is important for safety to monitor whether or not the air pressure (hereinafter referred to as tire pressure) of an automobile tire is equal to or higher than a specified value. A conceptual diagram of this type of tire pressure monitor system is shown in FIG. In the figure, 1 is a body of an automobile, 2 and 3 are wheels, and 4 is a pressure sensor attached to a wheel 3b of the wheel 3 to detect the pressure of a tire 3a of the wheel. A battery is used as a power source of this pressure sensor, and this battery is also attached to the wheel 3b. The wheel 2 and the other two wheels not shown in the figure are also provided with sensors similar to the pressure sensor 4 having a battery. Reference numeral 5 denotes a display, and the pressure of each tire provided on the driver's side is detected by a pressure sensor 4 attached to each wheel, and the detected value is wirelessly transmitted to the display 5 to display the value. To be done. 6 is a transmitting antenna wound around the wheel 3b, 7
Shows the receiving antennas provided on the display 5, respectively.

In the monitor system having such a structure, batteries mounted on the wheels of the respective wheels are used as the power source of the pressure sensor, but a large capacity is required to keep the batteries for a long time. However, when such a large battery is attached to the wheels of a running car,
The wheels are unbalanced and dangerous. It is possible to turn on the transmission circuit only when the car rotates as a method of avoiding battery drain and keeping a small capacity battery for a long time, but a separate detection circuit for detecting that the car has rotated is required. Further, this method has a problem that it is impossible to detect the tire pressure in the idling state.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its purpose is to save power and to reduce tire pressure over a long time even with a small capacity battery. It is an object of the present invention to provide a pressure monitoring system of this type that can detect the above-mentioned pressure and does not require a rotation detection circuit or the like.

[0005]

SUMMARY OF THE INVENTION The present invention is an interrogator which is provided on the driver's side of an automobile and emits a recognition code as a radio wave.
And output data of a pressure sensor which is attached to each wheel of the automobile and which is selected by the recognition code transmitted from the interrogator and which detects the tire air pressure by being supplied with battery power, is transmitted to the interrogator side as a radio wave. A response device is provided, and the pressure data of the selected tire is displayed by the display device provided on the interrogator side.

[0006]

According to the present invention as described above, the pressure of the desired tire selected is detected only when necessary, thereby preventing the consumption of the battery.

[0007]

The present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a system according to the present invention. In the figure, reference numeral 10 is an interrogator including a modulator 10a and a demodulator 10b, which is provided on the driver's side of the automobile. 20 ~
50 is a transponder including a pressure sensor, and the transponder 20
Is attached to the right front wheel, 30 is the left front wheel, 40 is the right rear wheel, and 50 is the left rear wheel of the vehicle. The interrogator 10 communicates with each of the responders 20-50.

In the modulator 10a of the interrogator 10, 11
Is a recognition code (IDcode) of the transponder to be communicated among the transponders 20 to 50, for example, a code for recognizing front, rear, left and right wheels such as "A" for the right front wheel and "B" for the left front wheel. Recognition code generation circuit, 12 is, for example, 430 MH
It is an oscillator that oscillates a carrier signal that satisfies the z band specific low power standard. No particular power saving is required for the interrogator 10 provided on the driver's side. Therefore, for example, a microprocessor is used for the recognition code generation circuit 11, and even if serial I / O of this processor is used, a serial ROM is used. You may make it use what input the recognition code. Reference numeral 13 is a modulation circuit to which the outputs of the recognition code generation circuit 11 and the oscillator 12 are given, and which modulates the output of the oscillator 12 according to the output signal of the recognition code generation circuit 11, and 14 is an antenna which radiates the output of the modulation circuit. As the modulation circuit 13, either an ASK modulation circuit or an FSK modulation circuit may be used as long as it satisfies the wireless standard. In the demodulation unit 10b, 15 is an antenna that receives radio waves radiated from the responder to be communicated among the responders 20 to 50, and 16 is a bandpass filter that receives a reception signal of the antenna and that passes a frequency in a specific region.
It is a filter. Reference numeral 17 designates an amplifier for amplifying the output of this filter, and 18 designates an antenna 15 for receiving the output of the amplifier 17.
A demodulation circuit that demodulates the data received in step 19 and a display 19 that displays the measured tire pressure value based on the output data of the demodulation circuit 18. Interrogator 10 consisting of such parts
As described above, it is provided on the driver's side of the automobile, in which case the display 19 corresponds to the display 5 in FIG. 5, and the antennas 14 and 15 correspond to the antenna 7 in FIG.

In the responder 20, 21 is the interrogator 1 described above.
An antenna for receiving radio waves accompanying the recognition code radiated from the antenna 14 of 0, 22 is a bandpass filter, and 23
Is a demodulation circuit that demodulates the output of the bandpass filter 22, and 24 is a recognition code determination circuit that determines whether or not the demodulated recognition code and the previously input recognition code match. 25 is a known pressure sensor for detecting the tire pressure, that is, the right front wheel of the automobile in this case, for detecting the tire pressure of the front wheel, and 26 is the pressure sensor 25.
Is a transmitter that outputs a weak signal that is modulated according to the output of. 27 is a switch that is turned on by a recognition code coincidence signal obtained by the recognition code determination circuit 24 and supplies a power supply 28 to the pressure sensor 25 and the transmitter 26; The above-mentioned receiving antenna 21 is wound around the wheel portion of the right front wheel in the embodiment. A battery is used as the power supply 28.

As the demodulation circuit 23, when an FSK modulation circuit is used as the modulation circuit 13 of the interrogator 10, for example, it comprises a frequency-voltage converter 23a and an amplifier 23b for amplifying the output of this converter as shown in FIG. When the FSK demodulation circuit or the ASK modulation circuit is used, the ASK including the detection diode 23c and the amplifier 23d as shown in FIG.
It is conceivable to use a demodulation circuit. On the other hand, as the recognition code discrimination circuit 24, for example, as shown in FIG.
3 is added to the output serially and converted in parallel to be output, a shift register 24a, an EX-OR gate 24b to which the output of this register and a predetermined recognition code are input, and the output of this EX-OR. OR input
It is conceivable to use a circuit composed of the gate 24c.
In the recognition code discrimination circuit 24 having such a configuration, when the data in the shift register 24a and the recognition code match, all the EX-OR gates become "L". Each EX-
By ORing the output of the OR gate with the OR gate 24c, a pattern mismatch occurs when the output of the OR gate 24c is "H", and a pattern match occurs when the output of the OR gate 24c is "L".

The transponders 30 to 50 are the same as the transponder 20 except for the recognition code which is input in advance to the respective recognition code discriminating circuit 24. They are only given and their re-explanation is omitted.

As described above, the power source 28 is a battery. This battery power is supplied to the pressure sensor 25 and the transmitter 26 among the circuits constituting the transponder 20 via the switch 27 as necessary, but other circuits constituting the transponder, for example, Demodulation circuit 23 or discrimination circuit 24
Etc. are always added. In this case, the power consumption of the demodulation circuit 23 or the discrimination circuit 24 is extremely smaller than that of the pressure sensor 25 and the transmitter 26, and even if the demodulation circuit 23 or the discrimination circuit 24 or the like is always supplied with electric power, it is particularly advantageous for power saving. There is no problem.

The operation of the system according to the present invention having such a configuration will be described below. The modulation circuit 13 in the modulation unit 10a of the interrogator 10 modulates the transmission output of the transmitter 12 according to the recognition code of the transponder that needs to be accessed and output by the recognition code generation circuit 11, and the modulated output is output from each antenna 1
4 to the responders 20 to 50, and the receiving antenna 21 of each responder receives the radio wave. The recognition code discriminating circuit 24 of each of the transponders 20 to 50 preliminarily inputs the recognition code obtained by demodulating the signal received by the receiving antenna 21 through the bandpass filter 22 and the demodulation circuit 23 to the recognition code discriminating circuit. It is determined whether or not they match the respective recognition codes, and only the transponder that has detected the matched signal turns on the switch 27 and the pressure sensor 2
5 and the transmitter 26 are supplied with a power supply 28. This allows
The pressure sensor 25 is in an operating state and detects the pressure of the tire to which the pressure sensor is attached, and its output is transmitted as a radio wave from the antenna 29 via the transmitter 26 to the responder 1.
It is radiated to the 0 side. The antenna 15 of the demodulator 10b in the transponder 10 receives this, and its output is a bandpass signal.
The tire pressure value of the accessed desired wheel is displayed on the display 19 via the filter 16, the amplifier 17, and the demodulation circuit 18. The tire you want to select is
The modulator 10a of the interrogator 10 can be freely accessed by changing the recognition code.

In the above-described embodiment, the output of the oscillator 12 in the interrogator 10 has been described as satisfying the specific low power standard, but the output of the oscillator 12 is not limited to this, and any radio wave standard is applicable. You may make it use the electric wave or the weak electric wave which corresponded to. Further, in the embodiment, the output of the oscillator 12 is modulated by the modulation circuit 13 outside this oscillator, but an oscillator built in the modulation circuit 13 may be used.

[0015]

According to the present invention, the battery power is supplied to the transponder including the sensor for detecting the tire pressure to operate the transponder only when the recognition codes match. Therefore, power saving can be achieved. , Even if the battery is used as the power source, the battery with a small capacity is sufficient. Therefore, it is possible to detect the tire pressure for a long time even with a small capacity battery. Further, according to the present invention, it is possible to monitor even during parking, but when the monitor is not needed, the power of the transponder is turned off, and the output signal of the transponder uses weak radio waves. The interrogator from the responder does not cause interference and does not need to be retransmitted. However, even in these points, power saving is achieved. Moreover, a rotation detection circuit for detecting the rotation of the wheels is not necessary, and there is an effect that it is possible to realize a tire pressure monitoring system having a simplified structure as a whole.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram of an example of a demodulation circuit used in the system of FIG.

3 is a circuit diagram of an example of a demodulation circuit used in the system of FIG.

FIG. 4 is a circuit diagram of an example of a recognition code determination circuit used in the system of FIG.

FIG. 5 is a conceptual diagram of a tire pressure monitoring system.

[Explanation of Codes] 10 Interrogator 11 Recognition Code Generation Circuit 14, 15, 21, 29 Antenna 19 Display 20-50 Responder 24 Recognition Code Discrimination Circuit 25 Pressure Sensor 26 Transmitter 27 Switch 28 Battery Power Supply

Front page continuation (72) Inventor Kiyoshi Takai 2-9-32 Nakamachi, Musashino City, Tokyo Yokogawa Electric Co., Ltd.

Claims (1)

[Claims] 1. An interrogator provided on the driver's seat side of an automobile that emits a recognition code as a radio wave, and a battery power source provided by being selected by an identification code attached to each wheel of the automobile and transmitted from the interrogator. By including a responder that transmits the output data of the pressure sensor that detects the tire air pressure to the interrogator side as a radio wave, and displays the pressure data of the selected tire on the indicator provided on the interrogator side. A tire pressure monitor system consisting of.