JP2002264618A - Tire air pressure sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tire air pressure sensor equipped with a travel sensor with such high reliability that it prevents imperfect contact, as compared with conventional switch contact types, by detecting the travel of a vehicle not by a conventional mechanical contact opening/closing method, but by a highly reliable method of detecting it from changes in electrostatic capacity. SOLUTION: The tire air pressure sensor comprises a pressure sensor 1 for detecting the pneumatic pressure of a tire, a travel sensor 2 for detecting the travel of the vehicle, an electronic circuit part 3 for transmitting the detected pressure to a receiver on the vehicle body by means of electric waves, and a battery 4 or the like for actuating the electronic circuit part 3. The travel sensor 2 is formed of a fixed electrode 5 and an opposite movable electrode 6 and determines that the vehicle is traveling when the electronic circuit part 3 detects a change in electrostatic capacity between the fixed electrode 5 and the movable electrode 6 caused by the displacement of the movable electrode 6 due to either a centrifugal force or acceleration produced by the rotation of the tire.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tire pressure sensor capable of confirming the state of air pressure in an automobile tire at a vehicle compartment side.

[0002]

2. Description of the Related Art In a conventional tire pressure sensor, FIG.
As shown in the figure, the centrifugal switch 7 is connected to the battery 4 and the electronic circuit 3.
When the traveling speed becomes, for example, 20 km / h,
The centrifugal force switch 7 is turned on, the power of the electronic circuit unit 3 is turned on, and the operation as the tire pressure sensor starts.

FIG. 4 shows an example of the centrifugal switch 7.
The moving element 8 is configured to move by overcoming the force of the spring 9 by the centrifugal force caused by the traveling, and to make the contact points 10 and 11 conductive. In such a configuration, the normal consumption current of the electronic circuit is as small as several μA, so that it is necessary to make the contacts 10 and 11 extremely reliable. There are problems such as the necessity of increasing the size of the tire pressure sensor itself, and the increase in cost due to the structure that eliminates vibration and impact in the tire.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems. The present invention is not limited to a conventional mechanical contact opening / closing method, but a highly reliable static state. It is an object of the present invention to provide a tire pressure sensor adopting a method of detecting a change in electric capacity.

[0005]

SUMMARY OF THE INVENTION An air pressure sensor according to the present invention comprises a pressure sensor for detecting a tire air pressure, a travel sensor for detecting travel, an arithmetic and processing of the sensor signal, and a transmission of the tire air pressure to the vehicle by radio waves. An electronic circuit unit for transmitting to the receiver, and a battery or the like for operating the electronic circuit unit, the traveling sensor is formed of a movable electrode facing the fixed electrode, and the centrifugal force due to the rotation of the tire or The electronic circuit unit detects that the capacitance between the fixed electrode and the movable electrode changes due to the bending displacement generated in the movable electrode due to the acceleration, and determines that the vehicle is in the traveling state.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a configuration diagram of a tire pressure sensor according to the present invention. The tire pressure sensor 1 detects a tire pressure, a traveling sensor 2 composed of a fixed electrode 5 and a movable electrode 6 detects traveling, and a static sensor based on the traveling sensor 2. The electronic circuit unit 3 processes the change in electric capacity to determine whether to start or stop running, calculates and processes the signal of the pressure sensor 1 according to the result, and transmits the signal to the receiver on the vehicle body side by radio waves.
And a battery 4 for operating the electronic circuit section 3.

FIG. 2 is a sectional view of the structure of the travel sensor 2, which is composed of a fixed electrode 5 and a movable electrode 6 which generates a bending displacement due to centrifugal force or acceleration due to rotation of the tire.

According to the pneumatic sensor of the present invention, the movable electrode bends due to the centrifugal force or acceleration caused by the rotation of the tire, and as a result, the capacitance between the movable electrode and the fixed electrode changes, By detecting this by an electronic circuit, it is possible to detect the running start of the vehicle.

[0008]

As described above, the tire pressure sensor of the present invention has a structure in which a change in capacitance between a movable electrode and a fixed electrode caused by centrifugal force or acceleration due to rotation of a tire is detected by an electronic circuit. In addition, there is no trouble due to poor contact of the contacts such as the switch contact type, and a highly reliable tire pressure sensor with a traveling sensor can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram of a tire pressure sensor according to the present invention.

FIG. 2 is a structural sectional view of a travel sensor constituting a tire pressure sensor according to the present invention.

FIG. 3 is a block diagram of a tire pressure sensor when a conventional centrifugal switch is used.

FIG. 4 is a structural sectional view of a conventional centrifugal switch.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Pressure sensor 2 Running sensor 3 Electronic circuit part 4 Battery 5 Fixed electrode 6 Movable electrode 7 Centrifugal force switch 8 Movement 9 Spring 10 Contact 11 Contact

Claims (1)

[Claims] 1. A pressure sensor 1 for detecting tire pressure.
A travel sensor 2 for detecting travel of the vehicle, and an electronic circuit unit 3 for transmitting the detected pressure to a receiver on the vehicle body by radio waves.
And a tire pressure sensor including a battery 4 and the like for operating the electronic circuit unit 3, wherein the running sensor 2 is formed by a fixed electrode 5 and a movable electrode 6 opposed to each other, and a centrifugal force caused by rotation of the tire is generated. Alternatively, a tire pressure sensor configured to detect a change in the capacitance between the fixed electrode 5 and the movable electrode 6 due to a displacement generated in the movable electrode 6 due to acceleration by the electronic circuit unit 3 and determine the traveling state.