JPH09145836A - Detecting device using ultrasonic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the presence of a detected object even in an undetectable area near a sensor. SOLUTION: In a control circuit 13 of a detecting device 10 using an ultrasonic sensor, a transmit signal generated by a microcomputer 22 is amplified by an amplifier 24 and supplied to the ultrasonic sensor 12. When the transmit signal is supplied, an ultrasonic signal is radiated to a detected object from the ultrasonic sensor 12. An amplifier 32 is disposed near the ultrasonic sensor 12, and the received signal is amplified by the amplifier 32, further amplified by an amplifier 34 and inputted to a comparator 36. An output signal from the comparator 36 is inputted to the microcomputer 22, and the microcomputer measures the arrival time difference between the transmit time and a reflection signal, that is, the reciprocating time of ultrasonic wave and judges the presence of the detected object from the time change of received reverberation waveform to the reference time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detection device using an ultrasonic sensor, and more particularly to a detection device using an ultrasonic sensor that also serves as a transmitter and a receiver.

[0002]

2. Description of the Related Art Conventionally, as a detection device using an ultrasonic sensor, a device for detecting the position of an occupant seated in a passenger seat of an automobile has been known, one example of which is disclosed in JP-A-7-1960.
No. 06 publication.

As shown in FIG. 8, in this device 70, an airbag device 74 provided in front of the passenger seat 72 in the vehicle is actuated at the time of sudden deceleration of the vehicle to deploy an airbag bag. An occupant detection device for determining whether or not the device needs to be operated, the distance sensors 76, 7 including ultrasonic sensors.
8 is used to detect the distance to the occupant 80 as the detection object existing in the space from the airbag device 74 to the passenger seat 72, and the airbag device 74 is detected based on the signals from the distance sensors 76 and 78. The necessity of operation is determined.

[0004]

However, when an ultrasonic sensor having both a transmitting function and a receiving function is used as the distance sensor of such a device, the oscillator itself is generated due to signal generation at the time of transmission. Due to the influence of reverberation that oscillates for a certain period of time, it becomes difficult to distinguish between a signal due to the vibration of the sensor itself at the time of transmission and a reflected signal (echo) returned from a detection target object in a short distance from the sensor. Further, when a horn is mounted to control the beam divergence angle (beam width) of ultrasonic waves, this reverberation time tends to be long. Therefore, considering the application of such an ultrasonic sensor to, for example, occupant detection, it is not possible to determine whether or not there is an occupant in the vicinity of the sensor because the distance cannot be measured in the non-detection region near the sensor.

In view of the above facts, an object of the present invention is to obtain a detection device using an ultrasonic sensor capable of detecting the presence or absence of an object to be detected even in a non-detection region near the sensor.

[0006]

According to a first aspect of the present invention, in a detection device using an ultrasonic sensor that also functions as a transmitter / receiver, a reverberant waveform received based on a transmission signal from the ultrasonic sensor is detected. The feature is that the presence or absence of the detection target is determined from the change with time with respect to the reference time.

Therefore, when the distance between the object to be detected and the sensor approaches within a certain distance, the reverberation waveform and the reverberation waveform based on the echo overlap at the time of transmission, and the apparent reverberation time becomes long. The presence or absence of the detection target is determined from the change with time.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a detection device using an ultrasonic sensor according to the present invention will be described with reference to FIGS.

As shown in FIG. 3, the detection device 10 using the ultrasonic sensor of the present embodiment is provided with an ultrasonic sensor 12 that also functions as a transmitter and a receiver.
The control circuit 13 detects the situation on the passenger seat 16 of the automobile 14 (presence or absence of the occupant 18, proximity of the occupant 18 to the airbag device 20, mounting direction of a child seat (not shown), etc.) to detect the airbag device. The operation of 20 is optimally controlled.

As shown in FIG. 1, in the control circuit 13,
The ultrasonic sensor 1 amplifies the transmission signal (5 Vp-p) created by the microcomputer 22 to 20 Vp-p by the amplifier 24.
It is supposed to be added to 2. Amplified transmission signal (2
0 Vp-p), the ultrasonic sensor 12 irradiates an ultrasonic signal to an object to be detected such as the occupant 18.

As shown in FIG. 3, the ultrasonic sensor 12 is mounted in the dash panel 26, and the detection surface (signal emission surface) 12A of the ultrasonic sensor 12 is directed toward the windshield 28 (upward). ). Therefore, the ultrasonic signal emitted from the ultrasonic sensor 12 is reflected by the windshield 2
It is reflected by 8 and emitted toward the occupant 18.

A horn 30 is mounted on the detection surface 12A. Above the upper opening of the horn 30, the wire mesh 3
1 is disposed so as not to protrude from the upper surface of the dash panel 26, and prevents relatively large dust from entering the horn 30. Further, in the horn 30, a filter 33 made of porous polyurethane sponge, which has a small attenuation of ultrasonic waves and does not greatly affect the directivity, is arranged, so that fine dust or the like that passes through the wire net 31 may be generated. It is prevented from entering the ultrasonic sensor 12. Furthermore, a drain hole 30A is formed in the lower part of the horn 30,
The liquid foreign matter that has entered the horn 30 is caused to flow out from the water drain hole 30A to prevent the liquid foreign matter from accumulating in the horn 30.

The ultrasonic signal reflected by the object to be detected is reflected by the windshield 28 and the ultrasonic sensor 12
To be received by.

As shown in FIG. 1, an amplifier 32 is arranged near the ultrasonic sensor 12, and the ultrasonic sensor 1
The signal received at 2 is amplified. The output signal of the amplifier 32 is further amplified by the amplifier 34, and the comparator 36 performs the processing described later.
The output signal of the comparator 36 is input to the microcomputer 22, and the microcomputer 22 measures the difference between the transmission time and the arrival time of the reflected signal, that is, the round-trip time of ultrasonic waves,
It is designed to measure the distance to the object to be detected.

Next, the operation of this embodiment will be described with reference to the flowcharts of FIGS. 6 and 7.

As shown in FIG. 6, in the detection device 10 using the ultrasonic sensor of this embodiment, the microcomputer 22 causes the output signal of the comparator 36 (see the comparator output A in FIG. 2) to rise or fall. When the edge interrupt is performed, it is determined in step (hereinafter referred to as S) 100 whether or not the interrupt is the first interrupt. First, when it is determined that the interrupt is the first interrupt due to the rising edge of the output signal of the comparator 36 due to the start of the output of the transmission signal emitted from the ultrasonic sensor, the transmission start time is stored in S102. On the other hand, if it is determined in S100 that it is not the first interrupt, in S104,
It is determined whether or not it is the second interruption due to the falling edge of the output signal of the comparator 36 due to the end of the output of the transmission signal emitted from the ultrasonic sensor. When it is determined that the interruption is the second interruption, the reverberation time Tz is calculated in S106. If it is determined in S108 that the interrupt is not the second interrupt but the third interrupt due to the rising edge of the output signal of the comparator 36 due to the start of the reception signal due to the reflection echo from the detection target, in S108, The ultrasonic round-trip time Tt is calculated.

In this case, as shown in FIG. 2, the reverberation waveform W1 is contained in the reception signal A and the time corresponding to the distance between the detection object and the output of the transmission signal emitted from the ultrasonic sensor 12 at substantially the same timing. After a delay, the echo W2 reflected from the detection target appears. Therefore, the waveform of the received signal A and the reference signal of the comparator 36 (Vref1 for the reverberation signal and Vref for the echo)
By performing a comparison process with ref2), a waveform-shaped comparator output A (comparator output A) is obtained. Here, Tz1 is a reverberation time at a normal time, and Tt is a time including the distance information to the detection target.

This reverberation time Tz1 usually shows a constant value, but when the distance between the object to be detected and the sensor is closer than a certain distance (for example, 200 to 400 mm), the received signal B has a reverberation waveform W1 and an echo W2. Becomes difficult to distinguish, and the reverberation time is apparently extended to Tz2 as shown in the comparator output B (comparator output B).

Therefore, as shown in FIG. 7, the microcomputer 22 determines in S200 whether or not the reverberation time Tz is greater than the reverberation time threshold TZth (corresponding to TZ1) as the reference time, and the reverberation time is calculated. When it is determined that the time Tz is larger than the reverberation time threshold TZth, in S202, the distance R to the detection target is set to the minimum distance (RMIN), for example, 30 to 50 cm when the horn 30 is present, and the horn 30 is not present. In case of 20cm. From this result, it is detected that the occupant 18 has entered the proximity area, and the airbag device 20 is deployed and operated according to the proximity state.

On the other hand, when it is determined in S200 that the reverberation time Tz is not larger than the reverberation time threshold TZth, the distance R = 1 from the detection object is detected in S204.
/ 2 · Tt · C (Tt is the round trip time of ultrasonic waves, C is the speed of sound)
And the airbag device 20 according to the calculated distance R
To deploy. If the occupant is not detected in S202 and S204, the operation of the airbag device 20 is unnecessary.

Therefore, in the detection device 10 using the ultrasonic sensor of this embodiment, the presence or absence of the detection target can be detected even in the non-detection region near the sensor.

Further, in the detection device 10 using the ultrasonic sensor of the present embodiment, the wire net 31 can prevent a relatively large dust from entering the horn 30, and the filter 33 allows the fine dust to pass through the wire net 31. Etc. can be prevented from entering the ultrasonic sensor 12, and the drain hole 30
The liquid foreign matter that has entered the horn 30 can be discharged by A. Therefore, due to dust and dirt entering and adhering to the detection surface of the ultrasonic sensor 12 (in the horn when the horn is attached), the intensity of the signal irradiated to the object to be detected is reduced or the transmission signal is output. Therefore, it is possible to prevent a decrease in the detection range and a malfunction of the sensor itself.

On the other hand, the object to be detected by the occupant 18 should be one that easily absorbs ultrasonic waves (for example, a thick sweater) or one that has a smooth surface and is less likely to scatter ultrasonic waves (such as a leather jumper). In such a case, a sufficient signal level (S / N ratio) may not be obtained from the received reflected signal, and if this situation continues, no signal appears at the output of the comparator 36, and thus the distance measurement is performed. Can not.

However, in an actual situation, such a situation rarely occurs continuously while the vehicle is running,
As long as the occupant is present, changes in the surface shape (wrinkles) of the clothes due to changes in posture (including movement due to breathing) appear, which improves the scattered state of ultrasonic waves, and the received signal C in FIG. As shown, the reception signal C1 that can be temporarily measured appears within a certain measurement period Tc, and the detection signal P appears at the output of the comparator 36. After that, when the received signal level becomes insufficient again, the detection signal P does not appear in the output of the comparator 36.

Therefore, in the detection device 10 using the ultrasonic sensor of this embodiment, as shown in FIG.
In the case of being undetectable, that is, when there is no raw data of the sensor, 2 uses the previous valid data (D1) and stores it as the sensor output after signal processing. Further, if this non-detection state continues for a certain period (N times), the (N + 1) th data is the data indicating the non-detection state (D
X), it is determined that there is no object to be detected, and it is set as “absence of occupant”. In this state, if effective distance data (D2) is detected even once in the N + 3th raw data, for example, that data is adopted and stored as the sensor output after signal processing.

Therefore, in the detection device 10 using the ultrasonic sensor of the present embodiment, if the received signal level is not sufficient and the detection result varies, the period when the received signal level is not sufficient is within the predetermined period. By using the previous valid data, the presence or absence of the detection target can be reliably detected.

In the above, the present invention has been described in detail with respect to specific embodiments, but the present invention is not limited to such embodiments, and various other embodiments within the scope of the present invention. It is obvious to a person skilled in the art that For example, the detection device using the ultrasonic sensor of the present invention can be applied to a passenger detection device in the rear seat, a corner sensor, etc., in addition to the passenger detection device in the passenger seat.

[0028]

According to the present invention as set forth in claim 1, in a detection device using an ultrasonic sensor which also functions as a transmitter and a receiver, a time change of a received reverberation waveform with respect to a reference time based on a transmission signal from the ultrasonic sensor. Since the presence or absence of the detection object is determined from the above, there is an excellent effect that the presence or absence of the detection object can be detected even in the non-detection region near the sensor.

[Brief description of the drawings]

FIG. 1 is a block diagram showing main members of a detection device using an ultrasonic sensor according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a relationship between respective signals of the detection device using the ultrasonic sensor according to the embodiment of the present invention.

FIG. 3 is a schematic side view showing an occupant detection device to which a detection device using an ultrasonic sensor according to an embodiment of the present invention is applied.

FIG. 4 is an explanatory diagram showing a relationship of each signal of the detection device using the ultrasonic sensor according to the embodiment of the present invention.

FIG. 5 is an explanatory diagram showing sensor output data of the detection device using the ultrasonic sensor according to the embodiment of the present invention.

FIG. 6 is a flowchart showing control by interruption of the detection device using the ultrasonic sensor according to the embodiment of the present invention.

FIG. 7 is a flowchart showing distance calculation control of the detection device using the ultrasonic sensor according to the embodiment of the present invention.

FIG. 8 is a schematic side view showing an occupant detection device to which a detection device using an ultrasonic sensor according to a conventional embodiment is applied.

[Explanation of symbols]

 10 Detection Device Using Ultrasonic Sensor 12 Ultrasonic Sensor 13 Control Circuit 22 Microcomputer 30 Horn 31 Wire Mesh 33 Filter 36 Comparator

Claims (1)

[Claims] 1. A detection device using an ultrasonic sensor that also serves as a transmitter and a receiver, and based on a transmission signal from the ultrasonic sensor, the presence or absence of an object to be detected is determined from a time change of a received reverberation waveform with respect to a reference time. A detection device using an ultrasonic sensor.