JPS58160833A - Measuring device of tire air tressure - Google Patents

Abstract

PURPOSE:To find variation in air pressure, not to mention an abnormal state in its early stage and to prevent an accident caused by abnormal air pressure by using a magnetic detecting means to detect variation in magnetic field corresponding to the displacement of a magnetism generating body and measuring the air pressure of a tire, and measuring and displaying the air pressure during a vehicle run successively all the time. CONSTITUTION:While a vehicle runs, a permanent magnet 18 rotates together with the tire 14, but a magnetic sensor 21 does not rotates. When the permanent magnet 18 moves from the center point of the magnetic sensor 21, an AC output is obtained from the magnetic sensor 21. The AC output obtained from the magnetic sensor 21 and amplified by an amplifying circuit 22 is outputted to a display meter 25, where the tire air pressure is displayed. In this state, if the tire air pressure drops, bellows 15 contract to increase the clearance between the permanent magnet 18 and magnetic sensor 21 gradually. As the clearance l is increased, the output of the magnetic sensor 21 decreases. Consequently, the tire air pressure value on the display meter 25 decreases with the output.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tire air pressure measuring device, and more particularly to a measuring device that can continuously measure tire air pressure and display the current tire air pressure.

Pneumatic tires used in general automobiles have a specified air pressure during use, and if this air pressure is not appropriate, it will adversely affect the tire and be dangerous. In other words, if the air pressure is too high, the ride quality will be poor and it will be easy to slip, and if the air pressure is too low, it will not be able to support the specified load, and the heat generated by the dust cocoon will peel off, shortening the life of the tire. This can also cause accidents. Therefore, it goes without saying that the driver knows the tire air pressure before driving, but it is also desirable for traffic safety to be able to know the tire air pressure while driving.

From this point of view, a system has already been proposed (Japanese Unexamined Patent Publication No. 52-6576) that detects when the air pressure of an automobile tire has decreased and issues a warning to the driver.

Briefly explaining this conventional device based on No. 1111, the inside and outside of the tire 1 are communicated with each other so that the cylinders 2 and 3 are connected to each other, and the tire internal pressure received by the tire inner cylinder 2 is transferred to the tire outer cylinder through an incompressible fluid. The reed switch 4t placed near the cylinder 3 is activated by moving the magnet via the plunger provided in the cylinder 3 outside the tire in accordance with the pressure of the inner tire, and when the tire internal pressure falls below the set value. At 9 o'clock, the reed switch was set to 4t off to emit an alarm. In addition, 5 in the figure is a caliper, 6
is the tire rim.

However, this conventional device is configured to detect tire pressure not continuously but on and off based on the alarm generation pressure, so if the alarm generation pressure is also higher than the above alarm generation pressure, for example, the tire pressure is decreasing while driving. 4 The driver doesn't notice. In such a case, it is dangerous, especially in places such as expressways where parking is not possible freely. Furthermore, it is possible that by 9:00 a.m. when a warning is issued, the situation will be close to dangerous, and it may be too late to respond.

The present invention has been made in view of the above-mentioned circumstances, and is designed to continuously detect and display tire pressure sounds, particularly in order to promptly notify occupants of abnormal tire conditions such as punctures while the vehicle is running, and to improve safety. This allows passengers to know the tire pressure even while driving.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings from FIG. 2 onwards.

In FIG. 2, reference numeral 10 denotes an axle shaft to which a wheel disk 11 is fixed with bolts 12. 13 is a tire rim, and 14 is a tire.

The tire rim 13, which rotates together with the tire 14, has an extendable shaft substantially parallel to the axle shaft 10.
15 is fixed. As shown in Figure 3, this bellows 1s is surrounded by a cylindrical guide 16 so that it can expand and contract approximately parallel to the axle shirt 1G, and the inside of the bellows 15 is formed in the tire rim 1s and has a through hole 17. It is configured to communicate with the inside of the tire 14 via the tire and expand and contract depending on the tire air pressure. The relationship between the tire air pressure and the bellows 1s is as shown in Figure 4, when the air pressure is 1.0~2.0~/
It is set so that the displacement is about θ to 3− in the − range. A permanent magnet 1- as a magnetizing body is fixed integrally with the tip 11111iiKti of the bellows 15. Also, a bracket 20 fixed to the axle housing 19
, .

In K, a magnetic sensor 21 as a magnetic detection means is fixed so as to face the permanent magnet 1@. The magnetic sensor? 2
1 is a permanent magnet 1840 based on the expansion and contraction movement of bellows 1s
The magnetic field strength for the magnetic sensor 21 that changes according to the displacement is detected, and the output changes continuously according to the change in the magnetic field strength. Patterned nine ferromagnetic thin film elements are used.

The output from the magnetic center t21 is amplified by an amplifier circuit 22, as shown in FIG. The tire air pressure is displayed by operating the air pressure display meter 25.

Next, the action will be explained.

When the vehicle is running, the permanent magnets 18 rotate together with the tires 14, but the magnetic sensor 1 does not rotate. Therefore, the permanent magnet 18 is connected to the magnetic sensor 21 in FIG. 6 (4).
) Move as shown by the arrow inside. When a ferromagnetic thin film Takako is magnetized, its resistance value changes depending on the angle formed between the direction of magnetization and the direction of current.When one permanent magnet is moved from the center point of the magnetic sensor 21 in the 61st prisoner, as shown in Figure 6. of)
An output like this is obtained from the magnetic sensor 1. Furthermore, the 6th
The output voltage in FIG. 6 is the one amplified by the amplifier circuit 22. The AC output (permanent magnet 18
is being rotated) is hand-rectified by the half-wave rectifier circuit 23 and then output to the display meter 2s via the filter 24t to display the tire air pressure.

When the tire air pressure decreases from this state, the bellows 15 contracts as shown in FIG.
(indicated by t in the figure) gradually expands. Here, there is a relationship between the clearance L and the output of the magnetic sensor 21 as shown in FIG. 7, and as the clearance t increases, the output of the magnetic sensor 21 decreases. Therefore, the output waveform rectified by the half-wave rectifier circuit 2s has its peak value gradually decreased as shown in FIG. 8, and the output waveform from the filter 24 also decreases as shown in FIG. So,
The tire air pressure value displayed on the display meter 2s also decreases in accordance with this output. Therefore, by looking at the display meter 25, the occupant can notice a decrease in tire air pressure at an early stage while the vehicle is running, and can quickly take action to deal with the problem, thereby greatly improving safety. Also, this magnetic sensor? 21
In the case of , it is possible to detect minute displacements of several square meters and has high stability, and unlike reed switches, it is a non-contact type, so it has a long life and is extremely advantageous in terms of cost.

Note that a Hall element may be used in addition to a ferromagnetic thin film element as a magnetic sensor. When a Hall element is used, only the magnetic field perpendicular to the element is effective, so only positive output waveforms appear. There is no need for a half-wave rectifier circuit.

As described above, according to the present invention, the generator body is displaced according to the tire air pressure, and the change in the magnetic field corresponding to the displacement of the magnetizer is detected using the magnetic detection means whose output continuously changes according to the change in the magnetic field. Since the system is configured to measure tire air pressure, tire air pressure can be displayed continuously while the vehicle is running, so not only tire abnormalities such as punctures, but also slight changes in tire air pressure can be detected at an early stage. It greatly improves safety when riding, and is extremely effective in preventing accidents caused by abnormal tire pressure.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an example of a conventional device, Fig. 2 is a sectional view of a tire pressure check ttIm according to an embodiment of the present invention, the third wheel is an enlarged sectional view of the magnet attachment part, and Fig. 4 is a graph showing the relationship between tire air pressure and bellows displacement, Fig. 5 is a block diagram of a processing circuit for magnetic top/output, and Figs. 11L6 and 7 respectively show the characteristics of the magnetic sensor. Figure 8 shows the direction of movement of the magnetic sensor, and Figure 8 shows the output characteristics of the magnetic sensor corresponding to the direction of movement of
The output waveform diagram of the E1 path, No. 911 shows the output waveform diagram of the filter. 14... Tire 1s... Be Q-'s 11...
・Communication hole 1@...Magnetic element 21...Magnetic sensor 25...Display meter Patent applicant Nissan Motor Co., Ltd. agent Patent attorney Tomio Sasashima Figure 1 Figure 2 Ton 1 Figure 3 Figure 41t1 020 Kuima air pressure (g/cm2) Figure 5 Figure 7 (A) Clearance (mm)

Claims (1)

[Claims] A telescopic member is provided on the tire support part that rotates together with the tire and expands and contracts according to the tire air pressure, a magnetizing member is fixed to the tip of the telescopic S wing and forms a magnetic field, and the above is fixed to the non-rotating part on the vehicle body side. A magnetic detection section whose output changes continuously in accordance with changes in the magnetic field of the fixed section caused by displacement of the magnetizing body based on the expansion and contraction movement of the elastic member; and a display section that displays tire air pressure corresponding to the output from the magnetic detection section. A tire pressure measuring device characterized by comprising: