JP2645937B2 - Tire pressure warning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alarm display circuit used as a device for automatically detecting tire pressure while a vehicle is running and sending an alarm to a driver's seat when the detected tire pressure is abnormal. .

[0002]

2. Description of the Related Art A pressure switch for detecting tire pressure and an electromagnetic resonance circuit which is changed by the pressure switch are provided on the tire side, and the resonance state of the resonance circuit is wirelessly detected from a device provided on the vehicle body. A tire pressure detecting device is disclosed in Japanese Utility Model Laid-Open No. 61-81396, Japanese Utility Model Application Laid-Open No. 1-14.
No. 7,706, and Japanese Utility Model Laid-Open No. 2-116395.

[0003] These prior arts are all excellent ideas that can monitor the tire pressure during traveling by a radio signal, detect the decrease in tire pressure early, and send an alarm to the driver's seat.

[0004]

However, the technology using the above-mentioned principle has a considerably high reliability mounted on a normal automobile even though much research has been carried out. Because they cannot be offered at affordable prices, they are not actually installed in commercial vehicles. The main cause is that the transmitter including the sensor mounted on the tire and the electromagnetic resonance circuit is subjected to severe vibrations as the vehicle travels. For this reason, it is necessary to change the structure of the wheel and the like, and it becomes impossible to use a wheel that is conventionally mass-produced. A small car has two axles and the number of tires is four. There are three tires and ten tires, and a reasonable control circuit for centrally controlling these tires cannot be obtained at a low cost so that it can be easily used in a practical vehicle.

Although a device for automatically detecting and alarming the tire air pressure during running is useful for safe driving, the fact that a driver needs a special operation for the tire air pressure alarm device requires a special operation. It is not appropriate that the alarm output becomes complicated, and that the alarm output becomes annoying to the driver.

That is, the present invention solves this problem.
It is an object of the present invention to provide a tire pressure alarm device that does not require a special operation by a driver, does not bother the display of a driver's seat, and can be rationally used in a practical vehicle.

[0007]

SUMMARY OF THE INVENTION The present invention comprises a pressure sensor,
A transmitter whose resonance frequency changes in accordance with the output of the pressure sensor is mounted on the tire side, an antenna facing the transmitter, a control circuit for transmitting and receiving signals to and from the antenna, and an alarm output of the control circuit are displayed. An indicator is mounted on the vehicle body side, the control circuit includes a transmission circuit that transmits a short pulse signal to the antenna, and a reception circuit that receives a resonance signal transmitted by the transmitter in response to the transmission of the pulse signal. A tire pressure alarm device including a frequency discriminating circuit for discriminating the frequency of the resonance signal, and a program control circuit for sending out the alarm output based on the output of the frequency discriminating circuit. Alarm lamps, and the program control circuit includes the order of states of the pressure sensors for a plurality of wheels. Control means for executing an operation test of the apparatus itself by continuously performing detection by a spontaneous and periodic start signal, and continuously turning on the lamp when power supply to the program control circuit is started, Turning off the lamp when all the detected values of the pressure sensors for a plurality of wheels are normal values, and turning on the lamp when at least one detected value of the pressure sensors is abnormal; Alarm logic means for flashing the lamp when the result of the test is abnormal.

[0008]

According to the device of the present invention, only one alarm lamp is provided in the driver's seat to indicate the alarm output, and has almost no effect on the arrangement of the dashboard, and the driver needs extra attention. Nor.

When driving an automobile equipped with the device of the present invention, when the driver first starts the engine, the power supply current is also supplied to the tire pressure alarm device to start the operation. At that time, the alarm lamp of this device is continuously turned on, so it can be confirmed that the alarm lamp has not been cut off. When the automobile starts running, detection of tire pressure is sequentially performed. If all tire pressures are normal, the warning lamp goes off. In the normal case, since everything is normal, there is no need for the driver to be conscious in this state. If any abnormality is detected in the tire pressure, the alarm lamp is turned on. Thus, the driver stops the vehicle, goes out of the vehicle, and checks which tire is abnormal with an air gauge or the like. If there is an abnormality in the tire pressure warning device itself, the warning lamp flashes, so that the wiring of the device can be checked according to the service manual to repair the faulty part.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic structure of the apparatus according to the embodiment of the present invention and its operating principle will be described first. FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention. Each tire is provided with a pressure sensor 1 for detecting its air pressure. The pressure sensor 1 is a pressure switch that closes a contact when the tire air pressure is equal to or higher than a predetermined value and opens a contact when the tire air pressure is lower than the predetermined value. The transmitter 2 is electrically connected to the pressure switch. This transmitter 2 is a resonance circuit. O of pressure switch of pressure sensor 1
By N and OFF, the capacitance of the capacitor of this resonance circuit changes and the resonance frequency changes.

FIG. 2 is a diagram for explaining the operation principle of the apparatus of this embodiment. On the vehicle side, an antenna 3 is installed facing each transmitter 2. The antennas 3 are provided at both ends of each axle, and are connected to the control circuit 4 by electric wiring. The output of the control circuit 4 is connected to an alarm lamp 6 provided in the driver's seat. The sensor 1 is a pressure switch, and when the tire air pressure is equal to or higher than a predetermined value, the contact 7 is closed.
When the tire pressure falls below a predetermined value, the contact 7 opens. The transmitter 2 includes one coil L1 and capacitors C1 and C2 connected in parallel to the coil L1, of which the capacitor C1 is connected via the contact 7 of the pressure switch. . Therefore, when the tire pressure is sufficiently high, the two capacitors C1 and C2 are connected in parallel, but when the tire pressure decreases, the capacitor C1 is disconnected and only the capacitor C2 is connected to the coil L1.

As described above, the resonance frequency of the transmitter 2 changes according to the opening and closing of the contact 7. Incidentally, when the contact 7 is closed and the two capacitors are in parallel, the resonance frequency is about 87 KHz, and when the capacitor C1 is disconnected, the resonance frequency becomes about 140 KHz.

FIG. 3 is a block diagram of the control circuit 4. The antenna 3 is connected to the antenna terminal 10. A pulse having a short width is oscillated by the oscillator 11 (in this embodiment, the pulse width is several μS, the repetition time is several tens μS), amplified by the transmission circuit 12, and transmitted from the antenna 3 as an electromagnetic wave. When this electromagnetic wave is sensed by the coil L1 of the transmitter 2, the resonance circuit including the coil and the capacitor is stimulated to sustain the damped oscillation at the resonance frequency. This resonance frequency is captured by the antenna 3 as an electromagnetic wave, and is input from the receiving circuit 13 to the frequency discriminating circuit 14. This operation is sequentially performed for each wheel under the control of the program control circuit 15, and if at least one of the tire pressure drops is detected, the display terminal 19 is displayed.
An alarm output is sent to the driver to turn on the alarm lamp 6 in the driver's seat.

Here, in the apparatus according to the embodiment of the present invention, the indicator 5 is one alarm lamp 6 provided in the driver's seat, and the program control circuit 15 sequentially detects the states of the pressure sensors 1 for a plurality of wheels. By a spontaneous and periodic start signal, and subsequently, a control means for executing an operation test of the own device, and continuously turning on the alarm lamp 6 when power supply to the program control circuit 15 is started. When all the detected values of the pressure sensors 1 for the plurality of wheels are normal values, the alarm lamp 6 is turned off. When at least one of the detected values of the pressure sensors 1 is abnormal, the alarm lamp 6 is turned off. Alarm logic means for turning on the light and blinking the alarm lamp 6 when the result of the operation test is abnormal.

Next, the operation of the alarm lamp 6 of the embodiment of the present invention will be described with reference to FIG. FIG. 4 is a time chart for explaining the operation of the alarm lamp 6 of the embodiment of the present invention.

The driver turns the starter switch on at the driver's seat.
When N, power is supplied to the control circuit 4. Further operation of the starter switch rotates the starter and starts the engine. At this time, there is no tire rotation yet,
Since each antenna 3 cannot obtain a resonance signal from each transmitter 2, the control circuit 4 indicates a tire pressure abnormal state as shown in FIG. 4A, and the alarm lamp 6 remains lit. If lighting is not confirmed at this point, the burnout and disconnection of the wiring must be checked.

When the driver operates the clutch to start the vehicle as shown in FIG. 4b, the tires start to rotate, but the alarm lamp 6 has not yet been turned off. The antenna 3 and the transmitter 2 start transmitting and receiving the pulse signal and the resonance signal corresponding thereto. When this state starts steadily continuing, the control circuit 4 releases the alarm and the alarm lamp 6 is turned off. In the example, the light was turned off after traveling about 30 m.

When the control circuit 4 detects an abnormality in tire pressure while the vehicle is running, the alarm lamp 6, which has been turned off while the vehicle is running, is turned on as shown in FIG. 4d. The driver must stop the vehicle and check and adjust the tire pressure as shown in FIG. 4e. Thereafter, as shown in FIG. 4f, if the alarm lamp 6 is turned off immediately after departure, it can be confirmed that the adjustment has been performed normally.

As shown in FIG. 4g, when the alarm lamp 6 starts blinking, it is an abnormality of the control circuit 4. This does not immediately impede the running of the vehicle, but since an alarm cannot be obtained when the tire pressure is abnormal, it must be repaired as soon as possible as shown in FIG. 4h.

[0020]

The present invention has only one alarm lamp for displaying the alarm output on the display, and can reduce the influence on other instruments and the visibility of the driver's seat.

Since the self-diagnosis function of the own device is added, it is possible to prevent an abnormality in the tire pressure from being overlooked due to a failure of the device.

[Brief description of the drawings]

FIG. 1 is a block diagram of an apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of the operation principle of the device according to the embodiment of the present invention.

FIG. 3 is a configuration diagram of a control circuit of the device according to the embodiment of the present invention.

FIG. 4 is a time chart for explaining the operation of the alarm lamp of the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pressure sensor 2 Transmitter 3 Antenna 4 Control circuit 5 Display 6 Alarm lamp 10 Antenna terminal 11 Oscillator 12 Transmitting circuit 13 Receiving circuit 14 Frequency discriminating circuit 15 Program control circuit 16 Storage circuit 17, 18 I / O circuit 19 Display terminal 20 Bit terminal 21 bit wire 22 connector 23 harness wire

Claims (1)

(57) [Claims] 1. A pressure sensor, a transmitter whose resonance frequency changes according to the output of the pressure sensor is mounted on a tire side, an antenna facing the transmitter, a control circuit for transmitting and receiving signals to and from the antenna, An indicator for displaying an alarm output of the control circuit is attached to the vehicle body. The control circuit includes a transmission circuit that transmits a short pulse signal to the antenna, and the transmitter that transmits the pulse signal in response to the transmission of the pulse signal. A tire pressure alarm device comprising: a receiving circuit that receives a resonance signal to be transmitted; a frequency discrimination circuit that discriminates the frequency of the resonance signal; and a program control circuit that sends out the alarm output based on the output of the frequency discrimination circuit. Is a warning lamp provided in the driver's seat, and the program control circuit includes a plurality of wheels. Control means for sequentially executing the detection of the state of the pressure sensor by a spontaneous and periodic start signal, and then executing an operation test of the apparatus; and the lamp when the power supply to the program control circuit is started. Is turned on continuously, the lamp is turned off when all the detected values of the pressure sensors for the plurality of wheels are normal values, and when at least one detected value of the pressure sensor is an abnormal value, Alarm logic means for illuminating the lamp and blinking the lamp when the result of the operation test is abnormal.