RU2149105C1 - Automobile tyre pressure drop indicator - Google Patents

Abstract

FIELD: automotive industry; controls and instruments. SUBSTANCE: device is designed for putting out warning signals if pressure in automobile tyre drops below tolerable value. Oscillatory circuit is installed on vehicle wheel. This circuit is shunted by change-over switch in case of inadmissible pressure drop and is inductively coupled with coupling coil installed on vehicle body. Coupling coil is connected with generator through current amplifier and, through comparator, with one of inputs of logic phase detector whose other input is connected to generator output. Detector reveals change in phase of signal on coil at shunting of oscillatory circuit and switches on pressure drop indicator. EFFECT: enhanced operation reliability owing to use of phase principle of detection. 3 dwg

Description

 The device is designed to signal a decrease in tire pressure in a vehicle below a set level.

 A device for recording tire pressure in a car is described in Japanese application N 1-52799, MKI 5 G 08 C 19/00 (Invention of the world, 1990, N 7). The device comprises a signal generator that excites an oscillating circuit through a communication coil, which has several resonators, which are connected to it by a switch depending on the pressure in the tire. A similar switch with a set of resonators is also available in the generator. The device contains a sensor for the presence, absence of resonance in the circuit and an indicator that estimates and displays the pressure value using the sensor output signal. The disadvantage of this device is its low reliability due to the use of the amplitude sign of a signal change on the communication coil. Since the resonant circuit with the coupling coil is mounted on the vehicle wheel, the influence of the metal parts of the wheel becomes decisive. The parts close to the coils greatly weaken the connection between them, as a result, the difference in the amplitude of the signals on the fixed coupling coil (i.e., at the input of the resonance sensor) during resonance and during detuning relative to the resonance will be small, which leads to low reliability of the device. In addition, for a simple signaling about the decrease in tire pressure below a certain acceptable level, the considered device is complex.

 Closest to the claimed is a device for signaling a decrease in tire pressure, which is implemented according to the application of Japan N 61-61158, MKI 4 G 08 C 10/00 (Invention of the world, 1987, N 11) / prototype /. The device comprises a generator with a communication coil mounted on the vehicle body; a resonant circuit with a coil and a capacitor mounted on a wheel near the coil and tuned to the frequency of its electromagnetic radiation and closed / opened in accordance with the pressure in the tire by switching, and a circuit with a sensor for recording the state of the circuit. The latter detects a change in the amplitude of the signal on the communication coil when the loop is closed / opened and gives an alarm signal, accompanied by a light signal, when the pressure in the vehicle tire decreases. The disadvantage of the prototype is the low reliability due to the use of the amplitude sign of a signal change on the communication coil.

 The inventive device for the alleged invention is implemented to eliminate this drawback.

 Since the known device described above has low reliability, we offer a device containing an oscillating circuit on a vehicle wheel, shunted by a switch when the tire pressure is below acceptable and connected inductively with a coupling coil fixed relative to the wheel; the generator, which excites the oscillating circuit through the communication coil, and the signaling device, additionally introduce a current amplifier connected between the generator and the communication coil, a comparator connected to the communication coil, a logical phase detector that compares the phases of the signals from the comparator and generator outputs and controls the switching on of the signaling device.

 The essence of the invention is to use a phase feature to detect the fact of shunting the oscillatory circuit by a switch, for which new elements and connections have been introduced, due to which the device becomes more reliable.

 In FIG. 1 shows a functional electrical diagram of the inventive alarm device. In FIG. 2 shows diagrams of signals explaining the principle of operation of the device. In FIG. Figure 3 presents one of the possible implementations of a logical phase detector.

 The inventive device (Fig. 1) contains a generator 1, a current amplifier 2, a communication coil 3, an oscillating circuit 4, a switch 5, a comparator 6, a logic phase detector 7 and a signaling device 8. The oscillatory circuit 4 shunted by a switch 5 is inductively connected to the communication coil 3, which is connected to the output of the current amplifier and to the input of the comparator 6. The output of the latter is connected to the second input of the logical phase detector, the first input of which is connected to the output of the generator 1 and the input of the current amplifier 2. The output of the logical phase detector is connected to gnalizatorom 8.

 The device operates as follows. The generator 1 generates signals (Fig. 2a), which are fed to the input 1 of the logic phase detector 7 and the input of the current amplifier 2. The output of the current amplifier 2 is loaded on the communication coil 3. If the tire pressure exceeds the minimum acceptable level, then switch 5 is open, and the signal on the coupling coil 3, and hence the output of the comparator 6 (Fig. 2b, left plot), lags in phase from the signal of the generator. When the pressure drops below the permissible value, switch 5 closes and shunts circuit 4, as a result of which the signal at the output of comparator 6 changes (Fig. 2b, right diagram), outpacing the signal of generator 1 in phase. The phase change of the signal at communication coil 3 (at the output of comparator 6 ) is detected using a logical phase detector 7. Comparator 6 generates signals suitable for processing on digital microcircuits. In FIG. 3 shows a variant of constructing a logical phase detector, which is implemented by known methods. The generator signal is used as a reference signal in the detector, from which two sequences of pulses corresponding to the edges of the generator signal are distinguished. This is carried out on logic elements 9 to 14. At the output of element 13, pulses corresponding to the leading edge (Fig. 2c) are allocated, and at the output of element 14, to the trailing edge (Fig. 2d). If the bus is intact (the pressure in it exceeds the minimum allowable), then the signal at the output of the comparator 6 allows the passage of pulses 17 corresponding to the trailing edge of the generator signals to the R-input of the trigger (Fig. 2e). The trigger is set to zero by them, i.e. at the output 3 of the logical phase detector, the excitation signal of the detector 8 is absent. In the event of a bus malfunction (puncture), pulses (Fig. 2e) of setting it to a single state pass through element 15 to the S-input of trigger 17. At the output of the logical phase detector 7, a signal appears, exciting the detector 8.

Claims (1)

 A device for signaling a decrease in pressure in a car tire, comprising an oscillating circuit on the vehicle wheel, shunted when the pressure drops below the permissible value by a switch and connected inductively with a communication coil located together with a generator and an indicator on the vehicle body, characterized in that an amplifier is inserted into the device current, a comparator and a logical phase detector, the output of the latter being connected to the detector, its first input connected to the output of the generator and the input of the amplifier I of current, the second input is to the output of the comparator, the input of which is connected to the output of the current amplifier and to the communication coil.

Images