JPS5917127A - Display device for air pressure in tire - Google Patents

Abstract

PURPOSE:To convert the change in the resonance frequency of a surface acoustic wave element to a change in air pressure with an arithmetic circuit and to display said change by detecting the change in the air pressure in a tire as a change in said resonance frequency. CONSTITUTION:The signal from a sweep oscillation means 15 is transmitted by a signal from a controller 23 via a transmission means 9 to the 1st and the 2nd surface acoustic wave elements 5, 7. When the elements 5, 7 resonate, energy consumption is induced by a resonance system constituted of said elements and a reception antenna 11, by which the signal level at the antenna 13 is decreased. The resonance point of the decrease in the level is detected with a detection means 17 and is fed to a controller 23. A counter 25 counts the frequency of the means 15 and inputs the same to memories 27, 29. The outputs of the memories are inputted to a subtractor and are fed to a pressure converter 33, by which the outputs are converted to the pressure value signal corresponding to the input frequency. As a result, a display means 21 receives the pressure value signal as the calculated result from an arithmetic means 19 and displays the prescribed air pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tire air pressure display device that displays air pressure in wheel tires installed on a vehicle such as an automobile.

As a conventional tire pressure display device, there is one shown in FIG. 1, for example. In other words, tie A7 (not shown)
A crystal oscillator 105, an open/close switch 103, and a tire side reception antenna 111 are installed on the side, and a transmitter 115, a receiver 117, and a transmission/reception switch 12 are installed on the vehicle body side (not shown).
3 and a vehicle body side transmitting antenna 113 are provided. If the transmitter 115 is activated by the transmitter/receiver switch 123, an oscillation signal (1 = oscillation signal) is transmitted intermittently to the crystal oscillator 105 via the vehicle body side transmitting antenna 113 and the tire side receiving antenna 111, and the tire air pressure is set to a predetermined value. When the value falls below the value, the open/close switch 103 is closed and the crystal resonator 105 on the tie A7 side resonates. At this time, the receiver 117 is activated by switching the transmitter/receiver switch 123, and the resonance energy emitted from the crystal oscillator 105 is received. It is to be displayed.

However, such tire pressure display devices only display whether the tire pressure is a specified tire pressure or a small raft. It is not possible to know exactly what position it is in. However, as the speed of the vehicle increases, a correspondingly higher air pressure is required.Dangerous air pressure in tires while driving changes depending on the speed of the vehicle, so it is important for safety to know exactly what the tire pressure is currently. This is extremely important.

Therefore, it is conceivable to provide a plurality of crystal oscillators to sequentially detect the level of the air pressure in the tie A7, each detecting a different predetermined pressure value. However, in this case, there is a problem that a crystal resonator must be provided corresponding to the number of pressure values, which causes a start-up.

The present invention was devised in view of the above-mentioned problems, and provides a tire pressure display device that can sequentially display changes in tire pressure using a compact structure.

To achieve this object, the present invention provides a surface acoustic wave element that is provided with a resonant frequency that changes at least in response to tire air pressure, and a surface acoustic wave element that is provided with a resonant frequency that changes at least in response to changes in tire air pressure. - a sweep oscillation means whose frequency changes sequentially and continuously over a range of numbers; a signal transmission means which transmits the oscillation signal of the sweep oscillation means to the surface acoustic wave element in a non-contact manner; a detection means for detecting the resonance frequency of the surface acoustic wave element when the surface acoustic wave element is changing; a calculation means for calculating the air pressure of the tie 17 from the resonance frequency detected by the detection means; and a display for displaying the calculation result by the calculation means. It is characterized by having a means.

Hereinafter, a first embodiment of the present invention will be described in detail based on FIGS. 2 to 6.

As shown in FIG. 2, a bellows 3 is provided on the tire 1 side, which expands and contracts in response to increases and decreases in tie V air pressure. One end of the first surface acoustic wave element 5 is fixed to the expansion/contraction surface of the bellows 3, and the other end of the first surface acoustic wave element 5 (not shown) is fixed so as not to move as the bellows 3 expands/contracts. . Therefore, the first surface acoustic wave element 5 moves g5 due to changes in tire air D- and tire temperature. A second surface acoustic wave element 7 is provided adjacent to the first surface acoustic wave element 5.

This second surface acoustic wave element 7 does not contact the l\L1-z 3 and responds only to tire temperature changes, and this response is caused by the same temperature change as that to which the first surface acoustic wave element 5 responds. ,
It is something that First surface acoustic wave element 5 and second surface acoustic wave ↑
(The F-wave element 7 is as shown in Figure N53, with a pair of fouling devices on the base 5a (7a) with a constant thickness)
+1 (71)>, and has a comb-shaped electrode 5C (70) between the reflectors 5b (7b) and interdigitated interdigitated comb-like electrodes. 1st. The second surface acoustic wave element 5.7, shown in FIG. 4, has the characteristic that the resonant frequency changes as the temperature (7) changes, and its use range is within the temperature range. ℃ or below. Also, number 1. When stress is applied in the traveling direction of the second surface acoustic wave element 5.7, the propagation velocity of the surface acoustic wave changes as the elastic coefficient changes, as shown in Figure 5, and the resonance frequency changes. -i L/
Therefore, the first surface acoustic wave element 5 changes its resonance frequency C in response to changes in the air pressure P and temperature t of the tie A7, and the second surface acoustic wave element 7 changes its resonance frequency in response only to changes in temperature. The first and second surface acoustic wave elements 5 and 7 are connected in parallel to the tie (7 side receiving unlaner 11) of the signal transmission means 9 for transmitting signals in a non-contact manner as shown in FIG. There is.

On the other hand, on the vehicle body side (not shown), a vehicle body side transmission antenna 13 of the signal transmission means 9, a sweep signal means 15, a detection means 17,
A calculation means 19 and a display means 21 are provided.

The vehicle body-side transmitting antenna 13 extends from a sweep transmitting means 15, and the sweep transmitting means 15 receives a signal from the L-L-L-RA 23. Due to the temperature change, the frequency of the second surface acoustic wave element 7 changes sequentially and continuously over the range of resonance frequencies that each change due to the temperature change.

The detection means 17 detects the resonance frequency of the first and second surface acoustic wave elements 5.7 when the oscillation signal of the sweep oscillation means 15 is sequentially and continuously changing, and detects the resonance frequency of the first and second surface acoustic wave elements 5.7. [''-ra23'\enter.

One of the note means includes a frequency counter 25 and a first memory 2.
7. Second mechanism 29, subtractor 31, and pressure transducer 33
I'm right. The frequency counter 25 is the sweep oscillation means 15
The frequency of 1 to 27.29 is input to the first and second memories.
Enter. The resonant frequency of the second surface acoustic wave element 7 among the resonant frequencies of the first and second surface acoustic wave elements 5 and 7 input to the controllers 1 to 23 is input to the first memory 27, and the second memory The resonant frequency of the first surface acoustic wave element 5 is input to 29. First memory 27. The outputs of the second memory 29 are both input to the subtracter 31 and subjected to C subtraction processing. The output of the subtracter 31 is input to the FF force converter 33, where it is converted into a pressure value signal corresponding to the input frequency.

The display means 21 receives a pressure value signal as a calculation result outputted from the calculation means 19 and displays the pressure value at a predetermined value using [).
:JfK is mine.

Next, regarding the operation of the above embodiment, Cjlf>Vero.

Upon receiving the signal from the controller 23, the LSI-U sweep oscillation means 15 outputs a signal, and the signal is outputted via the signal transmission means 9 at °C.
1st. It is transmitted to the second surface acoustic wave element 5.7. In this case, the frequency of the signal fed to the vehicle body side transmitting antenna 13 and the output signal of the sweep oscillation means 15 is as shown in FIG. 6(a).
Changes in the amplitude level are shown in FIG. 6(b), and changes in the amplitude level of the signal generated at the tire-side receiving antenna 11 are shown in FIG. 6(C).
1st. Changes in the resonance current flowing through the second surface acoustic wave element 5.7 are shown in FIGS. 6(d) and 6(e).

Here, the first signal is supplied with power. Second surface acoustic wave element5.
7 resonates. Figure 6(a) r415. is the frequency at which the second surface acoustic wave element 7 resonates, where fo is the natural resonance frequency at a temperature of 0°C (aH) and Δft is the change in frequency when the temperature reaches T°C, then f, = IO + △fr. can be expressed. The same <f2 is the frequency at which the first surface acoustic wave element 5 resonates. Let To (see Fig. 4) be the natural resonance frequency at a temperature of 1°C and a pressure of 1 atmosphere, and the change in frequency at a temperature of 1°C ( By substituting Δ[D and the frequency change multiplied by 15 times the tire air pressure P as Δ[P, it can be expressed as r2=r, +Δf T 11\[P.

1st. When the second surface acoustic wave elements 5 and 7 resonate, L energy consumption occurs in the resonance system consisting of the elements 5 and 7 and the tire side receiving antenna 3, and the signal level at the vehicle body side transmitting antenna 3 occurs. A phenomenon occurs in which the amount of water decreases. The detection means 17 detects the resonance point where the signal level decreases and outputs a signal. This output signal is shown in FIG. 6(f). The output signal of the detection means 17 in FIG. 6 ([) is distributed by the controller 23 into signals as shown in FIG. 6 (2), FIG. The ICC word count signal is proportional to the adapted frequency, respectively in FIG. 6(g),
The signal shown in FIG. 6 (11) is stored in the first memory 27 and the second memory as 1-trigger. That is, the resonant frequency r of the second surface acoustic wave element 7 is sent to the first memory 27.
h proportional to +! A numerical signal 81 proportional to the resonant frequency r2 of the first surface acoustic wave element 5 is also sent to the second memory 29.
A numerical signal is recorded. The signal f2 outputted from the second memory 29 is subtracted by the temperature-induced frequency change numerator 1 outputted from the first memory 29 in the subtracter 31, and only the frequency change °Δ[P due to the tire air pressure is extracted. This frequency change Δfp is converted into pressure by the pressure converter 33, and upon receiving this pressure value signal, the display means 21 displays a predetermined pressure. Therefore, when the tire air pressure decreases, the bellows 3 bends, C, the stress applied to the first surface acoustic wave element 5 changes, and the resonance frequency [2 changes, so the display means 21 sequentially displays the tie A) air R'. be done.

FIG. 7 shows a second embodiment, in which a temperature converter 35 and a temperature indicator 37 are added to the first embodiment. In other words, the temperature converter 35 converts the signal @fI output from the first memory 27 by the frequency change △ due to temperature.
[Take out only ■ and display the tire temperature on the temperature display 37.

Therefore, with just one pair of elements 5.7, for example, if the tire air pressure decreases and the running resistance causes the tire A7 temperature to rise, in addition to displaying the tire air pressure, it will also display the upper part of the C tie temperature. This has the effect of double safety, increased reliability, and low cost. Components that are the same as those in the first embodiment are designated by the same reference numerals and their description will be omitted.

41. However, the present invention is not limited to the first embodiment. For example, in the first embodiment, the first. Second surface press 11
A pair of wave elements 5.7 is provided, but if a surface acoustic wave element is used that has a small resonance frequency change due to temperature, the temperature coefficient will always be small due to changes in tire air pressure. If the frequency change caused by the temperature change can be ignored compared to the frequency change, the second surface acoustic wave element 7 can be omitted, and the first mechanism 27 and the reduction device 31b can be omitted.
It can be abbreviated.

According to the configuration of the present invention, changes in tire air pressure can be tracked as changes in the resonance frequency of the surface acoustic wave element, and changes in this resonance frequency can be displayed as tire air pressure. There is no need to prepare this element for the number of detected pressure values, and although the structure is simple and inexpensive, it can display the tire air pressure sequentially. Since the tire pressure can be displayed continuously at all times, it is possible to give the driver a warning of abnormal tire wear and damage due to a drop in tire pressure, improving safety and extending the life of the Tie A7. .

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a conventional tie A7 air pressure display device, FIGS. 2 to 6 relate to a first practical example of the present invention, and FIG. 2 is a block diagram of a tie A7 air pressure display device. Figure 3 is a perspective view of the surface acoustic wave element, Figure 4 is a temperature characteristic diagram of the surface acoustic wave element, Figure 55 is a pressure characteristic diagram of the same, and Figure 6 (a).
) to FIG. 6(11) are operational waveform diagrams, and FIG. 7 is a block diagram of a tie 7 air pressure display device according to a second embodiment of the present invention. 1... Tie (7 5... First surface acoustic wave element 7...: Second surface acoustic wave element 9... Signal transmission means 15... (Hanging and installation means 1
7...Detection means 19...Calculation means 21...
・Display means

Claims (1)

[Claims] A surface acoustic wave element provided with a resonant frequency that changes in response to at least tire air pressure, and a sweep in which the surface acoustic wave element sequentially and continuously changes frequency over a range of resonant frequencies that change in response to at least changes in tire air pressure. oscillation means; signal transmission means for transmitting the oscillation signal of the sweep oscillation means to the surface acoustic wave element in a non-contact manner; It is characterized by having a detection means for detecting a resonant frequency, a display means for calculating the tire air pressure from the resonance frequency detected by the detection means, and a display means for displaying the result of calculation by the calculation means. - Tire pressure display device.