JPS60131306A - Monitor for tire inflation pressure - Google Patents

Abstract

PURPOSE:To monitor whether tire internal pressure is right or not, by transmitting a tire internal pressure variation to a bellows pipe via a fine pipe from a central groove part on the circumference of a wheel, while constituting it so as to be displayed as a magnetic variation through a permanent magnet. CONSTITUTION:A pipe 3 is attached to a circumferential part of a steel wheel 2 and bent to the side of a brake drum 4 at the central vicinity of the wheel 2, connecting it to a bellows pipe 5, then a permanent magnet 6 of 1kG or so is locked thereto. And, a magnetic field variation detecting device 12 is set up in position opposed to the permanent magnet 6. In this constitution, when tire inflation pressure is normal, the bellows pipe 5 expands, coming close to the magnetic field variation detecting element 12 whereby a constant output is generated but when the tire inflation pressure decreases, the bellows pipe 5 is contracted, therefore output in the magnetic field variation detecting element 12 drops, thus a display or the like takes place via a car control circuit (unillustrated herein). With this constitution, anything unusual in the tire inflation pressure is detected, thus safety is well improvable.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a device for detecting a decrease in tire air pressure. - [Background of the invention] It has already been 75 years since pneumatic tires were installed on automobiles, but nothing better than this has yet to be invented, and the number of such tires is likely to increase in the future.

One problem with this pneumatic tire is that the air pressure decreases due to tire damage or the like.

To deal with this, various studies have been conducted on devices that detect air pressure and notify whether it is normal or abnormal, but very few have been put into practical use.

On the contrary, safety measures for automobiles have made significant progress in recent years due to rapid advances in various sensors and electronic circuits. . □Among these, the development of automatic tire pressure monitoring devices, which determine the safety of driving, has been delayed and its practical application is awaited.

Tire pressure monitoring devices are divided into an air pressure sensor installed on the tire side and a transmission means that transmits the sensor output from the wheel to the inside of the car.Means for checking air pressure include mechanical ones such as pressure switches, changes in tire width, There have been reports of devices that measure temperature changes, changes in vehicle height, etc.

On the other hand, methods for introducing the obtained information into the vehicle are being considered either mechanically or electrically.

Recently, optical transmission methods have been considered,
None of these methods have been put into practical use as they are still at the IDITCH stage, and the realization of a highly practical method is awaited.

Further, a tire pressure warning device using a reed switch using a bellows and a magnet is known from Japanese Patent Laid-Open No. 55-39801.

[Purpose of the invention]

An object of the present invention is to detect the air pressure in a tire by a pressure detection unit and a magnetic field change detection element provided in a tire wheel,
This is to display information on whether it is normal or abnormal and notify the driver.

[Summary of the invention]

A pipe is pulled out from the outer periphery of the metal wheel that holds the tire, fixed to the center of the wheel, and connected to its tip with a bellows tube that expands and contracts using air pressure and is closed at one end.

If a permanent magnet is fixed to the end face of the bellows tube in the expansion/contraction direction, and a magnetic field change detection element is provided on the bearing side of the wheel so as to face and approach this permanent magnet, the length of the bellows tube will change as the tire air pressure changes. changes, and as a result, the distance between the permanent magnet and the magnetic field change detection element changes, and the output of the magnetic field change detection element changes.

This output is obtained once per rotation of the wheel, and its level decreases as the air pressure decreases. This device correlates the decrease in the output level with the vehicle speed and issues an alarm to indicate an abnormal condition if preset conditions are not met.

[Embodiments of the invention]

Hereinafter, the present invention will be described in detail with reference to embodiments.

FIG. 1 shows an example in which a general steel wheel is equipped with the tire air pressure detection section of the present invention, and a tire 1 is supported by a steel wheel 2.

A metal pull-out pipe 3 protrudes from the outer periphery of the steel wheel 2, and its tip is bent toward the brake drum 4 near the center of the steel wheel 2, and the pipe is fixed to a certain size at the normal air pressure of the tire. A bellows tube 5 that expands and contracts in size when the pressure is reduced is connected. The tip of the bellows tube 5 is flat, and a permanent magnet 6 of about 1 kilogaum is fixed thereto.

The bellows tube 5 and permanent magnet 6 are made of non-magnetic material (
For example, the bearing side that supports the axle 8 contained in the protective case 7 made of material (aluminum, brass, copper, etc.) is bearing 9 and bearing 1.
The magnetic field change detection element 12 is fixed to the drum case 11 at a position facing the bellows tube 5 and the permanent magnet 6 of the brake drum 4. The magnetic field change detection element 12 can be any element capable of detecting changes in the magnetic field, such as a magnetoresistive element or a Hall element.

The input and output of the magnetic field change detection element 12 are connected to the cable 13.
is connected to the control circuit inside the vehicle.

The fixing screw 14 is a screw that fixes the steel wheel 2 to the brake drum 4.

FIG. 2 is an enlarged view of the air pressure detection section explained in FIG. 1, and when the tire air pressure is normal, the bellows tube 5 of the permanent magnet 6 extends and approaches the magnetic field change detection element 12. Therefore, the output of the magnetic field change detection element 12 can have a constant value.

One output is obtained each time the wheel rotates, and when the tire air pressure is reduced, the bellows tube 5 becomes denser and the output level decreases.

The connecting pipe 15 is a pipe that connects the drawer pipe 3 and the bellows pipe.

In FIG. 3, the direction of the bellows tube 5 is changed by the connecting tube 15,
The direction of the magnetic field change detection element 12 is changed accordingly.

Figure 4 shows an example in which the air pressure detection unit of the present invention is mounted on a wheel equipped with a disc brake.The bellows tube 5 and permanent magnet 6 are mounted with through holes provided in the disc 16, and the operation is exactly the same. It is.

FIG. 5 shows an example in which a magnetoresistive element is used as the magnetic field change detection element 12. The magnetoresistive element 17 is driven by a DC power supply 18, and R1 and R2 change in response to changes in the external magnetic field, and the midpoint of both resistances is voltage changes.

This change in voltage results in output characteristics 23 and 24 shown in FIG.

The output characteristic 23 corresponds to the case where the permanent magnet 6 approaches the magnetic field change detection element 12, and the output characteristic 24 corresponds to the case when the permanent magnet 6 moves away from the magnetic field change detection element 12.

When the tab has normal air pressure, the output characteristic is as shown in 23, and when the air pressure is abnormal, the output characteristic is as shown in 24.

Since the level at which the tire air pressure should drop to be displayed or warned varies depending on whether the vehicle is driving at high speeds or normal driving, a method is used in which the vehicle speed signal is taken in to make a determination.

In FIG. 5, a comparison circuit 19 determines whether the air pressure information obtained by the magnetoresistive element 17 exceeds a set air pressure. The vehicle speed sensor 22 always receives vehicle speed information, which corresponds to the vehicle speed, and a set air pressure value prepared in advance becomes the threshold value of the comparison circuit.

This means that the threshold value of the comparison circuit changes when the vehicle is not dangerous during normal driving (for example, 4 okm/hr) but becomes dangerous when driving at high speed (for example, xooxm/hr).

The processing circuit 20 determines whether the condition is normal or abnormal based on the signals from the comparison circuit 19 and the vehicle speed sensor 22, and issues a display and an alarm. The display and alarm 21 are installed on the instrument panel in front of the driver's seat.

In Fig. 6, the threshold values 25 and 26 have the relationship as shown in the figure with respect to the output characteristic 23 at normal air pressure and the output characteristic 24 at abnormal air pressure, and the threshold value 25 is the example during normal driving. The value 26 is an example when the vehicle is running at high speed.

As described above, according to the present invention, it is possible to detect tire air pressure and determine whether it is impossible to drive or at what speed the vehicle can be driven without danger, which is effective in improving safety when driving. .

〔Effect of the invention〕

As explained above, according to the present invention, by using a bellows tube and a permanent magnet as the tire pressure detection means and a magnetic resistance element as the signal transmission means, the tire pressure can be detected relatively easily, and the vehicle speed can be detected relatively easily. It is clear that the use of a method of varying the safety set point of the air pressure in combination with the information significantly improves driving safety.

This method is not foolproof and can be easily applied to tires of both passenger cars and cargo vehicles.Even if you change tires, you only need to make the initial settings, and signal transmission is done without contact, so it wears out. It can be used for a long time since there is no place to put it.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the configuration of the present invention, FIGS. 2 and 3 are enlarged views of the pressure detection section of the present invention, FIG. 4 is a diagram showing an application example, and FIG. 5 is a system block diagram of the present invention. , FIG. 6 is an explanatory diagram of the air pressure signal. 1... Tires, 2... Steel wheels, 3...
・Bow 1 pipe, 4... Brake drum, 5...
Bellows tube, 6... permanent magnet, 8... axle, 11...
・Drum case, 12...Magnetic field change detection element, 13.
... Cable, 17... Magnetoresistive element, 19...
Comparison circuit, 20...Processing circuit, 21...Display and alarm, 22...Vehicle speed sensor, Fig. 1, Fig. 2, Fig. 4, Fig. 5, Fig. 6, time direction -

Claims (1)

[Claims] 1. In a pneumatic tire used for wheels of automobiles, etc., a thin pipe that transmits the air pressure inside the tire from the central groove on the outer periphery of the metal wheel that holds the tire is installed in the center of the wheel. The tip is expanded and contracted by air pressure,
The feature is that one end of the Perot tube is closed, a permanent magnet is fixed to the end face of the Perot tube in the direction of expansion and contraction, and a magnetic field change detection element is provided on the bearing side of the wheel, facing and approaching this permanent magnet. Tire pressure monitoring device. 2. In claim 1, a signal from a magnetic field change detection element on the bearing side, which is provided opposite to and close to a permanent magnet fixed to the end face of a Perot tube, is compared and determined by a circuit to determine whether the tire air pressure is normal or not. A tire pressure monitoring device characterized by displaying abnormalities on a part of the instrument panel in front of the driver's seat. 3. In claim 1, the tire air pressure information and the vehicle speed information from the vehicle speed sensor are made to correspond to each other, and it is determined whether the air pressure is appropriate for the driving condition, and if it is inappropriate, it is configured to display or issue a warning. A tire pressure monitoring device characterized by: