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DESCRIPTION JPH05232242

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DESCRIPTION JPH05232242
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an
ultrasonic sensor for detecting an object present in front of an ultrasonic transducer.
[0002]
2. Description of the Related Art As shown in FIG. 8, a conventional ultrasonic sensor
intermittently transmits ultrasonic waves to ultrasonic transducers 1 and 2, and ultrasonic
transducers 1 intermittently at a predetermined frequency. A transmission signal circuit 2 for
outputting a sound wave pulse, and a reception amplification circuit 3a for amplifying a
reception signal received by the ultrasonic transducer 1 between the transmission and the next
transmission, and the reception amplification circuit 3a Reception signal processing circuit 3 for
detecting an object by comparing the reception signal amplified in the above-mentioned manner
with a predetermined threshold value, and a notification indicating the presence or absence of an
object by receiving an output signal from the reception signal processing circuit 3 Means 4 and.
The ultrasonic transducer 1 is of an integrated transmission-reception type, and receives a
transmission signal from the transmission signal circuit 2 to transmit an ultrasonic pulse signal
and receives a reflected wave from an object. . The notification means 4 comprises a display or a
speaker for display.
[0003]
This reports the presence of an object when the level of the reflected wave from the object
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appearing between the transmission and the next transmission is above a predetermined
threshold.
[0004]
When the ultrasonic sensor as described above is provided on the side of a car, such as a
bumper, it malfunctions to detect and notify the road even if there is no obstacle. Therefore, in
order to prevent this malfunction, the detection area is narrowed by lowering the gain of the
reception amplification circuit of the reception signal processing circuit.
As a result, it is not possible to detect an obstacle present at a short distance in front of and
under the bumper or the like.
[0005]
The present invention has been made in view of such a reason, and the purpose of the present
invention is to detect the road surface and to detect the road surface, even if the vehicle is
provided at a low place of the vehicle or the like. Providing an ultrasonic sensor capable of
detecting an obstacle present in the
[0006]
SUMMARY OF THE INVENTION In order to achieve the above object, an ultrasonic sensor
according to the present invention comprises an ultrasonic transducer for transmitting and
receiving ultrasonic pulses, and an ultrasonic transducer at a predetermined frequency. A
transmission signal circuit for intermittently outputting ultrasonic pulses, and a reception
amplification circuit for amplifying a reception signal received by the ultrasonic transmitterreceiver between the transmission and the next transmission, Reception signal processing circuit
for detecting an object by comparing the reception signal amplified in step with a predetermined
threshold, and notification means for receiving an output signal from the reception signal
processing circuit and notifying the presence or absence of an object An ultrasonic sensor having
a signal processing circuit, and a gain control signal circuit for reducing the gain of the wave
receiving amplification circuit between transmission and transmission timing by a predetermined
level according to the passage of time. Is provided.
[0007]
According to this configuration, when the gain of the receiving amplifier is lowered with the
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passage of time, the detection area changes from a substantially conical shape to a substantially
bell shape along with this, so the receiving amplification is performed. By appropriately
controlling the level of gain of the circuit as time passes, the desired bell-shaped detection area is
obtained.
[0008]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A first embodiment of the present
invention will be described below with reference to FIGS.
[0009]
1
The ultrasonic transducer is an integrated transmitter-receiver type having an ultrasonic
transducer (not shown) using a piezoelectric element etc. Connected to each.
The ultrasonic transducer 1 transmits an ultrasonic wave when an ultrasonic pulse signal created
intermittently by the transmission signal circuit is input, and the ultrasonic transducer 1
transmits the ultrasonic wave before the next transmission. Receives an ultrasonic wave reflected
on the object and inputs a received signal to the received signal processing circuit.
[0010]
2
A transmission signal circuit is composed of a periodic oscillation circuit 2a, an oscillation circuit
2b, and a transmission amplification circuit 2c.
The periodic oscillation circuit 2a generates a pulse signal S1 of a constant period, and outputs
the pulse signal S1 to the oscillation circuit 2b and a detection signal processing circuit and a
gain control signal circuit described later.
The oscillation circuit 2b converts a pulse signal S1 of a fixed cycle from the periodic oscillation
circuit 2a into an ultrasonic pulse signal S2 of a predetermined frequency and outputs the
ultrasonic pulse signal S2 to the transmission amplification circuit 2c.
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The transmission amplification circuit 2 c amplifies the ultrasonic pulse signal S 2 from the
oscillation circuit 2 b which is intermittently input, and outputs the amplified signal to the
ultrasonic transducer 1.
[0011]
3
Reference numeral denotes a wave receiving signal processing circuit, which comprises a wave
receiving amplification circuit 3a, a detection / waveform shaping circuit 3b, a comparator 3c, a
detection signal processing circuit 3d, and a gain control signal circuit 3e. The wave receiving
amplifier circuit 3a receives a wave receiving signal from the ultrasonic transducer 1, amplifies it
to a predetermined level by the signal from the gain control signal circuit 3e, and outputs the
amplified signal to the detection and waveform shaping circuit 3b. The detection and waveform
shaping circuit 3b receives the signal S4 from the wave receiving amplification circuit 3a,
removes the high frequency component of the signal S4, extracts only the envelope of the signal,
shapes the waveform, and outputs the waveform to the comparator 3c. The comparator 3c
detects the received wave signal output from the detection and waveform shaping circuit 3b with
a threshold and outputs a High signal to the detection signal processing circuit 3d. The detection
signal processing circuit 3d has a detection gate generation circuit and outputs a High signal
when the output S5 from the comparator 3c inputted between the detection gates is a High
signal, and outputs a Low signal to notification means described later when the output S5 is a
Low signal. . The gain control signal circuit 3e receives a pulse signal of a fixed cycle from the
periodic oscillation circuit 2a, and the gain of the reception amplification circuit 3a is set
between the transmission and the next transmission according to the passage of time from a
predetermined level. A gain control signal S3 for decreasing a predetermined level is output. The
gain control signal S3 is appropriately controlled to change the gain of the reception
amplification circuit 3a stepwise or continuously.
[0012]
4 The alarming means comprises an LED, a buzzer and the like, operates in response to the High
signal from the detection signal processing circuit 3d, and stops in response to the Low signal.
[0013]
This system changes the gain of the wave receiving amplification circuit 3a so that the detection
area A is formed at a predetermined distance away from the road surface over a predetermined
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distance which can be detected from the proximity of the ultrasonic transducer 1. .
[0014]
Next, a second embodiment of the present invention will be described based on FIG. 3 to FIG.
This main part is in the detection area expanding means 5 provided in the reception signal
processing circuit 3.
The members other than the main part are the same as those of the first embodiment described
above, and therefore, substantially the same members are denoted by the same reference
numerals and detailed description thereof will be omitted.
[0015]
The detection area enlarging means 5 comprises a second gain control signal circuit 5a and a
timer 5b. The second gain control signal circuit 5a is connected in parallel to the first gain
control signal circuit 3e, that is, the gain control signal circuit 3e of the first embodiment, and the
first gain control signal circuit 5a outputs the first signal while the timer 5b outputs a high
signal. A gain control signal S3 is output in which the gain of the wave receiving amplifier circuit
3a controlled by the gain control signal S4 from the gain control signal circuit 3e is uniformly
increased. The timer 5b receives an external trigger signal, turns on for a predetermined time,
and outputs a High signal to the second gain control signal circuit 5a. The ON operation time is
set to several times the time from transmission to the next transmission.
[0016]
In this embodiment, when the timer 5b is ON, the detection area A of the first embodiment is
uniformly expanded by the gain control signal S3 from the second gain control signal circuit 5a,
and the timer 5b detects the road surface. At the time of the OFF operation, the road surface is
not detected in the detection area A of the first embodiment. Then, when the timer 5b is operated
at an arbitrary timing when it is desired to diagnose the detection operation state, there is no
obstacle object in the detection area, and the ultrasonic transmitter / receiver 1 operates with
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normal sensitivity. Sometimes, the notification means 4 is turned on when using an operation
such as an LED, and is not turned on when operating at an abnormal sensitivity.
[0017]
As shown in FIGS. 5 and 6, in the second gain control signal circuit 5a of the second embodiment,
when the timer 5b is ON, the gain of the wave receiving amplifier circuit 3a has elapsed from a
predetermined level over time. The circuit may be configured to output a gain control signal S3
obtained by uniformly delaying the timing of outputting the gain control signal S4 that lowers
the predetermined level in accordance with the above.
[0018]
Further, as shown in FIG. 7, the detection area expanding means 6 controls the frequency by
outputting it to the oscillation circuit 2b of the transmission signal circuit 2 instead of the second
gain control signal circuit 5a of the second embodiment. As the control signal circuit 6a, the
frequency may be controlled in the direction in which the detection area A is expanded in
accordance with the structure of the ultrasonic transducer 1.
[0019]
According to the ultrasonic sensor of the present invention, a desired bell-shaped detection area
can be formed by appropriately controlling the gain level of the receiving amplifier circuit as
time passes, according to the above-described configuration. Even if provided at a low position of
the vehicle body of the vehicle, it is possible to detect an obstacle present in a short distance in
front of the lower front of a bumper or the like without detecting the road surface.
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