JPH071928A - Tire pressure sensing device - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To provide a tire internal pressure sensing device having a simple structure, capable of reducing manufacturing cost, and improving durability. [Structure] A magnet 14 and a magnetic sensor 18 are fixedly provided on a vehicle body 4, and a resistance value fluctuates according to an internal pressure of a tire 2 and a power generation unit 20 that generates an electromotive force due to fluctuations in a magnetic field between the magnet 14 and the magnet 14. Pressure-sensitive member 22, coil 24, magnet 1
And a power generation unit 20 that generates an electromotive force due to a change in the magnetic field between the tire 4 and the tire 4. The coil 24, the pressure sensitive member 22, and the power generation unit 20 are connected in series.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire internal pressure sensing device for sensing the internal pressure of a tire mounted on a vehicle body such as an automobile.

[0002]

2. Description of the Related Art A conventional tire internal pressure sensing device of this type is equipped with a pressure sensor for each wheel, and the internal pressure of the tire is directly detected by this pressure sensor. A transmitter that transmits the output of the pressure sensor is provided on the rotating tire side, while an antenna or the like that receives a signal from the transmitter is provided on the vehicle body side to transmit the signal.
For this reason, the conventional tire internal pressure sensing device has a problem that a transmitter, an antenna and the like for signal transmission are required, the structure is complicated, and the manufacturing cost is high. The present invention has been made in view of the above circumstances, and an object thereof is to provide a tire internal pressure sensing device that has a simple structure, can reduce manufacturing cost, and can improve durability.

[0003]

SUMMARY OF THE INVENTION The present invention is a tire internal pressure sensing device for sensing the internal pressure of a tire rotatably attached to a vehicle body, comprising a magnet fixed to the vehicle body and a tire. A power generation unit that is fixedly provided and that generates an electromotive force due to fluctuations in the magnetic field between the magnet, and a pressure-sensitive member that is fixedly provided to the tire and that changes the resistance value according to the internal pressure of the tire, and the tire. A coil fixedly mounted on the vehicle body and connected in series to both the power generation unit and the pressure-sensitive member; and a magnetic sensor fixedly mounted on the vehicle body for detecting fluctuations in the magnetic field generated in the coil. It is characterized by becoming.

[0004]

In the tire internal pressure sensing device having the above structure, the rotation of the tire itself causes an electromotive force in the power generation portion, and the electromotive force causes a magnetic field in the coil. Then, the magnetic field generated in this coil fluctuates due to the change in the resistance value of the pressure-sensitive member according to the fluctuation in the tire internal pressure, and this fluctuation is detected by the magnetic sensor, and the tire internal pressure is detected.

[0005]

Embodiments of the present invention will be described below with reference to the accompanying drawings. In FIG. 1, reference numeral 2 is a tire, which is attached to the vehicle body 4 so as to be rotatable about its axis.
Further, the vehicle body 4 has a support portion 6 having a built-in bearing,
It is fixedly connected integrally via an arm (trailing arm) 8. The tire internal pressure sensing device according to the present embodiment,
The magnet 1 integrally provided on the support portion 6 via the arm 12.
4, a magnetic sensor 18 also provided via the arm 16, a power generation unit 20 fixedly provided on the rim 10 side of the tire 2, a pressure sensitive member 22 and a coil 24.

As shown in FIG. 2, the power generation section 20 comprises a coil 26 and a magnet 28 which produces a magnetic field passing through the coil 26. Then, the coil 2 of the power generation unit 20
6 is arranged so as to pass through a space close to the magnet 14 as the tire 2 rotates, and
4, an induced electromotive force is generated in the coil 26 with a change in the magnetic field passing through the coil 26, and the capacitor 32 is charged by this intermittent power generation. The pressure-sensitive member 22 is composed of a film-shaped sensor, and its resistance value decreases as the pressure applied to its active area increases. The pressure sensitive member 22 is arranged inside the tire 2 and converts a change in internal pressure of the tire 2 into a change in resistance value.

The coil 24 is fixedly arranged on the tire 2 so as to pass through a space close to the magnetic sensor 18. The coil 24, the pressure sensitive member 22, and the power generation unit 20 are connected in series with each other as shown in FIG. The magnetic sensor 18 includes a Hall element using the Hall effect or an MR element using the magnetoresistive effect in which the resistance of the magnetically sensitive portion changes according to the strength of a magnetic field applied from the outside. It is connected to an output section (not shown) provided on the vehicle body 4 side.

In the tire internal pressure sensing device having the above structure, the power generation section 2 is rotated as described above as the tire 2 rotates.
The zero capacitor 32 is charged, and current is supplied to the pressure sensitive member 22 and the coil 24 connected to the power generation unit. A magnetic field passing through the coil 24 is generated by this current and is detected by the magnetic sensor 18. When the internal pressure of the tire 2 changes, the resistance value of the pressure sensitive member 22 changes, so the coil 24
The current that flows through also changes. That is, when the internal pressure of the tire 2 increases, the resistance value of the pressure sensitive member 22 decreases and the coil 2
4 increases and the internal pressure decreases, the resistance value of the pressure sensitive member 22 increases and the current flowing through the coil 24 decreases. The change in the magnetic field of the coil 24 thus generated is detected through the magnetic sensor 18 to sense the internal pressure of the tire 2.

An example of the output from the magnetic sensor 18 is shown in FIG. The output from the magnetic sensor 18 is amplified by the amplifier 40, converted into a digital signal by the converter 42, and then guided to the comparison means 44, 46, 48. If the output value is within the range of the lower limit value UN and the upper limit value UP, the display means 52 displays the proper pressure, and if the output value is less than the lower limit value UN, the display means 50 displays the insufficient pressure.
If the upper limit value is equal to or higher than the upper limit value UP, the display unit 54 displays an excessive pressure.

The tire internal pressure sensing device as described above has a simple structure which does not require a transmitter, an antenna or the like for signal transmission as in the prior art, and can reduce the manufacturing cost and improve the durability. . Further, since the power source of the pressure sensitive member 22 is secured on the tire 2 side, labor such as battery replacement is unnecessary, and the economy and operability are also good. Further, the magnetic sensor is resistant to dirt, mechanical strength, and environmental resistance.

[0011]

As described above, the tire internal pressure sensing device according to the present invention is provided by a magnet fixedly mounted on the vehicle body and a magnet fixedly mounted on the tire, and is caused by a change in the magnetic field between the magnet and the magnet. A power generation unit that generates electric power, a pressure-sensitive member that is fixedly provided on the tire and that changes the resistance value according to the internal pressure of the tire, and a pressure-sensitive member that is fixedly provided on the tire and is connected in series to both the power generation unit and the pressure-sensitive member. It has a simple structure that includes a coil connected to the vehicle and a magnetic sensor that is fixedly provided on the vehicle body and that detects changes in the magnetic field generated in the coil. Can be improved.

[Brief description of drawings]

FIG. 1 is a front sectional view showing a tire internal pressure detection device according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing a power generation unit.

FIG. 3 is a diagram showing an example of an output of a magnetic sensor.

[Explanation of symbols]

 2 tire 4 vehicle body 14 magnet 18 magnetic sensor 20 power generation unit 22 pressure-sensitive member 24 coil

Claims (1)

[Claims] 1. A tire internal pressure sensing device for sensing the internal pressure of a tire (2) rotatably attached to a vehicle body (4), comprising a magnet (1) fixed to the vehicle body (4).
4) and a tire (2), and a power generation unit (20) fixed to the tire (2) and a power generation unit (20) that generates an electromotive force due to a change in magnetic field between the magnet (14). ,
A pressure-sensitive member (22) that varies its resistance value according to the internal pressure of the tire (2) and a pressure-sensitive member fixed to the tire (2) and provided to both the power generation unit (20) and the pressure-sensitive member (22). A coil (24) connected in series, and a magnetic sensor (18) fixedly provided on the vehicle body (4) for detecting fluctuations of a magnetic field generated in the coil (24). Tire pressure sensing device.