JPS6060505A - Vehicle height detector - Google Patents

Abstract

PURPOSE:To prevent an error in vehicle height detection due to noise by interrupting the detection when an ultrasonic signal which exceeds a specific level is received within a certain time except an expected propagation delay time. CONSTITUTION:An ultrasonic wave from a transmitter 3 which is driven by the output of an oscillator 1 is projected upon the ground surface 7 and its reflected wave is received by a receiver 5. The output of this receiver 5 is detected and smoothed 11, and then compared with a reference voltage Vr by a comparing circuit 15. The output of the comparing circuit 15 is supplied to an AND circuit 29, and the output of the oscillator 1 is also inputted to the AND circuit 29 through a delay circuit 27 with a delay time tau'. If a noise larger than the reference voltage Vr is mixed through the receiver 5 at this time, the AND circuit 29 generates an output. A latch circuit 31 is reset with its output to interrupt the detection of vehicle height H. Thus, an error in the detection due to a noise is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a vehicle height detection device that prevents false detection due to noise.

[Technical background of the invention and its problems] Conventional vehicle height detection devices are, for example,
As shown in No. 57-18254/I, an ultrasonic transmitter is used, and the ultrasonic waves emitted from the ultrasonic transmitter are emitted toward the ground, and the reflected waves reflected from the ground are detected. The vehicle height distance is detected based on the intercostal difference between the time when the reflected wave is received by the ultrasonic wave receiver and the time when the ultrasonic wave is directed toward the ground by the ultrasonic wave transmitter. However, in such conventional devices,
All the signals received by the ultrasonic transmitter are treated as counter-waves, and there is no consideration of external noise, which causes the problem of false detection. .

``Purpose of the Invention (a) and Overview This invention has been made in view of the above, and includes a transmitter arranged so as to be able to transmit ultrasonic waves toward the earth's surface, and a reciprocal wave of the ultrasonic waves from the earth's surface. In a device that detects vehicle height from the propagation delay time difference of the reflected waves of ultrasonic waves, the device detects the vehicle height from the difference in propagation delay time of reflected waves of ultrasonic waves.In order to prevent false detection due to noise, the expected propagation delay is When an ultrasonic signal exceeding a predetermined level is received within a time period excluding hours, it is marked as dark blue (i
It is designed to interrupt width height detection.

[Embodiments of the invention] Hereinafter, the present invention will be explained with reference to the illustrated embodiments.

FIG. 1 shows an embodiment of the invention. The vehicle has a wave transmitter 3 and a wave receiver 5 provided at a suitable immovable part of the vehicle body, such as the lowest end of the vehicle body, and the resonant frequency of the wave transmitter 3 and the wave receiver 5 is A transmission wave P1 having a frequency [0] is periodically generated from the oscillator 1 for a time t1 as shown in <a> in FIG. 2, and this transmission wave P1 is supplied to the transmitter 3. The transmitter 3 transmits an ultrasonic signal 37 toward the ground 7 at a distance of 111 h.

The transmitted ultrasonic signal 37 is received by the receiver 5 as a reflected wave 39 reflected by the ground 7.

As shown in FIG. 2(b), the signal P9 amplified by the amplifier 9 is supplied to the detection/smoothing circuit 11, and an envelope-shaped output signal P11 of the output signal 9 of the amplifier 9 is output. This output signal P11 is supplied to one input terminal of the comparison circuit 15. The other input terminal of the comparison circuit 15 is supplied with the base iF-voltage ■r from the reference voltage generation circuit 13, and this reference voltage Vr is compared with the output signal pH from the detection/smoothing circuit 11, and the output signal P11 The comparator circuit 15 outputs the output signal P15 only when the reference voltage Vr is greater than the reference voltage Vr.

The transmitted wave 1]1 from the oscillator 1 is supplied to the counter 21, which activates the 7J counter 21, and the counter 21 starts counting clock pulses from the clock generator 23. Further, the output signal P1 of the oscillator 1 is supplied to delay circuits 17 and 27 having delay times τ, J and τ-, respectively. The ultrasonic signal transmitted from the transmitter 3 and received by the -C receiver 5 is
As shown in FIG. 1, there is not only a counter-wave 39 reflected by the ground 7, but also a wrap-around wave 41 that directly enters the receiver 5 from the transmitter 3. This is because the directivity of the wave transmitter 3 and the wave receiver 5 exists not only in the front but also directly to the side.

This wraparound wave 41 exists as a wraparound signal P9-41 in front of the output signal P9-39 corresponding to the reflected wave constantly reflected by the ground 7, as shown in FIG. 2(b). This loop signal P9-41 exists.
The timing is determined by the fixed distance J: between the transmitter 3 and the receiver 5, and is always constant without being influenced by the vehicle height distance 11 from the ground 7. More specifically, as shown in FIG. 3, the foul wave output P11-1-39
Time ta to tc until pH-3-39 appears
changes depending on the distance mh, whereas the wraparound signal P1
1-1-41 to P11-3-41 are always at the same position and do not change.

Therefore, in order to remove this loop signal, the delay circuit 17 has a delay time τ larger than the timing at which the loop signal is generated, as shown in (e) in FIG. After the output signal P1 of oscillator 1 is output, time τ
The delayed lζ output signal 17 is generated, and this output signal 1
7 is supplied to one input terminal of the AND circuit 19.

The other input terminal of the AND circuit 19 is connected to the comparison circuit 1
This output signal P15 and the output signal 1)17 of the delay circuit 17 are supplied with the output signal P15 of the delay circuit 17, which AND output is output from the AND circuit 19 as shown in FIG. 2(f). , this output J signal P19 is supplied to another delay circuit 25 and latch circuit 31.

The output signal P19 of the AND circuit 19 drives the latch circuit 31 to latch the counting result of the counter 21 at that point in time and output it. counter 2
1] ~ Depending on the value -C There is a counter that can measure the vehicle height distance 1h.

Further, the delay circuit 25 which is C-driven by the output signal of the AND circuit 19 is configured to generate an output signal and reset the -C counter 21 after a predetermined time after the latch operation is performed. be.

Furthermore, the extension circuit 27 having a delay time τ' removes noise that enters the receiver 5 etc. during vehicle height distance detection, and resets the detection result when noise is detected. This is to temporarily stop the vehicle height detection operation, and as shown in FIG. 4(e), the time J when the reflected wave signal appears.
, the output signal 1 rises after an even longer delay time τ- and is reset by the output signal P1 of the oscillator 1.
] 27 and sends this output signal P27 to an AND circuit 29.
The output signal P of the comparison circuit 15 is supplied to one input terminal of the AND circuit 29 and the other input terminal of the AND circuit 29.
15, and the latch circuit 31 is reset by the output signal of the AND circuit 29. That is, the time point at which the output signal P27 of the delay circuit 27 is generated is between the reflected signal and the output signal of the oscillator 1, and the output signal P15 of the comparison circuit 15 generated during this period is due to external noise. Since this can be determined, the AND circuit 29 detects this and resets the latch circuit 31, thereby stopping vehicle height detection. Sources of this noise include sounds generated by chains, hitting sounds caused by water splashes, and the like.

Next, the operation of this embodiment will be explained.

Ma! First, a normal case where no external noise is mixed into the signal will be described. Ultrasonic signal 37 from transmitter 3
is transmitted toward the ground 7, and the reflected wave 39 reflected by the ground 7 is received by the receiver 5, and after being amplified by the amplifier 9, the output signal P1 of the detection/smoothing circuit 11 is
It is supplied to the comparator circuit 15 as 1. In the comparison circuit 15, it is compared with the reference voltage Vr from the standard voltage generation circuit 13, and an output signal 1]15 is generated from the comparison circuit 15 for an output signal P11 which is larger than the reference voltage Vr.

On the other hand, the output signal 1 of the oscillator 1]1t drives the counter 21 to start counting clock pulses from the clock generator 23, and at the same time drives the delay circuits 17 and 27,
Time τ and τ from each delay circuit 17 and 27, respectively
- generate delayed output signals P17 and 27; The output signal P17 of the delay circuit 17 is supplied to the AND circuit 19 and ANDed with the output signal P15 of the comparison circuit 15, and the latch circuit 31 is driven by the output signal P19 of the AND circuit 19, and the output signal P17 at this time is The count result of the counter 21 is latched and output.

Further, the delay circuit 25 is driven by the output signal P19 from the AND circuit 19, and resets the counter 21 after a predetermined time after the latch operation is performed, thereby starting the next detection wait period. .

Roughly speaking, the output signal P27 of the delay circuit 27 having a delay time τ- is supplied to two AND circuits, where it is ANDed with the output signal P15 of the comparison circuit 15.
When external noise occurs and C does not exist, the output signal 1) of the delay circuit 27 is generated.Since there is no noise while 27 is generated,
Since no output signal is generated from the AND circuit 29, the latch circuit 31 is not reset, and the vehicle height detection operation is not stopped and operates normally.

Next, a description will be given of a platform in which external noise is generated and this external noise is mixed into the vehicle height detection device via the receiver 5.

When external noise is mixed through the receiver 5,
If this external noise is sporadic, it is possible to eliminate the sporadic noise and remove the influence of the noise by averaging or integrating.However, for stationary noise, the average Noise cannot be easily removed even if

That is, such steady external noise is transmitted through the receiver 5.
C, the output signal P is amplified by the amplifier 9, and then detected and smoothed by the detection/smoothing circuit 11.
11- corresponds to (11) in Fig. 4, the wraparound signal P
11'-4, 1, and in addition to the anti-OA wave signal 11-39, if it contains many stationary noises such as external noise PnO-Pn4, the comparison circuit 15 outputs the output signal P11- containing this noise. Compared with the reference voltage Vr, -C
The output signal P15 is generated ((C) in FIG. 4). Therefore, in this case, the noise exceeding the reference voltage Vr is generated as the output node j of the comparison circuit 15, and this output signal 1
) 15 are supplied to one and two AND circuits, respectively.

As a result, in the AND circuit 19 a'3, the output signal P17 of the delay circuit 17 causes the loop signal Pi5-
41 is removed, but the other external fill M is not removed, and the output signal P''19 of the AND circuit 19 is shown in FIG. 4(C). The latch circuit 31 is driven by one external noise 'Ai [including the sound and the output signal 1 of one AND circuit], and the counting result of the counter 21 reaches the point A. In other words, in this case, the output signal 19 due to the normal reflected wave
As shown in FIG. 4(C), an error may occur where C is at time t2, but it is at time t3 due to the influence of external noise P19-no.

Therefore, if such external noise is mixed in, in order to notify such an error and stop the vehicle height detection operation,
As described above, the output signal 1 of the oscillator 1 drives the delay circuit 27 to generate an output signal P27 delayed by 1.1 τ, and the output signal P27 and the comparison circuit 1
5 output signal 15 to AND circuit 29 -C
The output signal JP29 is generated.

Then, the output signal P29 of the AND circuit 29 due to the steady external noise extracted in this way is supplied to the latch circuit 31, and J is reset to reset the latch circuit 31 and eliminate the above-mentioned error. In addition to erasing the result of the numerical value, the detection of the vehicle height distance is also stopped.

In the above embodiment, the output of the comparator circuit 15 is supplied to the other input terminal of the AND circuit 29, but instead of the output signal of the comparator circuit 15, the output signal of the AND circuit 19 is supplied. Of course, it may be supplied to the other input terminal of the AND circuit 29.

FIG. 5 is a block diagram showing another embodiment of the present invention, and in this embodiment, the reflected wave signal behind the external noise shown in (d) of FIG. It is characterized by being able to detect previously generated external noises 19-110. Therefore, the configuration shown in FIG. 5 differs only in that a delay circuit 33 having a short delay time τ9 and an inverter 35 are provided in place of the delay circuit 27 in the configuration shown in FIG. The configuration is the same as that in FIG. Therefore, the same components are denoted by the same reference numerals H1, , T, and their explanations will be omitted.

That is, the delay circuit 33 has a short delay time τ' as shown in FIG.
9 or Pl 9-39 is generated, and this output signal is inverted via an inverter 35 and then supplied to one input terminal of an AND circuit 29. So-C1 This AND circuit 20
The input terminal of the other H is the output signal n of the AND circuit 19;
The output signal P29 of the AND circuit 29 is supplied with P29, and the output signal P29 of the AND circuit 29, which is supplied with P29, is outputted by ANDing the two input signals, and this output signal P29 is supplied to the latch circuit 31. As mentioned above, there is a mechanism that is erroneously latched by the latch circuit 31 described in the embodiment of FIG.

[Effects of the Invention] As explained above, according to this issue 11, the transmitter is arranged to restart transmitting ultrasonic waves toward the earth's surface, and the transmitter is arranged to be able to receive reflected waves of the ultrasonic waves from the earth's surface. 4-- Dish Wr.
nLL L f-4rr l in fL around + +
'71 F; I'L (kb mountain);” taken: la I
A device that detects the vehicle height from the difference between +18 and 18 receives an ultrasonic signal that exceeds a predetermined level within a time excluding the expected propagation delay time. Since the detection is interrupted, it is possible to prevent the vehicle height from being erroneously detected due to noise.

[Brief explanation of the drawing]

Fig. 1 is a configuration diagram of an embodiment of the present invention, Fig. 2 is a waveform diagram showing the operating waveforms of Fig. 1, and Fig. 3 is a waveform diagram showing the operating waveforms of Fig. FIG. 4 is a waveform diagram showing operating waveforms when external noise is present in FIG. 1. FIG.
The figure is a waveform diagram corresponding to the operating waveform of FIG. 5. 1... Oscillator 3... Transmitter 5... Receiver 7... Ground 21... Counter 27.33... Delay circuit 29... AND circuit 31... Latch circuit 39・・・
・Inverter patent applicant Nissan Motor Co., Ltd.

Claims (1)

[Claims] The ultrasonic wave is directed toward the earth's surface, and a transmitter placed at the transmission angle (1) and a receiver placed so as to be able to receive the reflected waves of the ultrasonic wave from the earth's surface are set. In a device that detects vehicle height from the propagation delay time difference of reflected waves, a means is installed to interrupt mid-height detection when an ultrasonic signal exceeding a predetermined level is received within a time excluding the expected propagation delay time. Vehicle height detection device featuring