JPS59116074A - Object detector of reflection type - Google Patents

Abstract

PURPOSE:To obtain an object detector of a reflection type which is simple in constitution, is easily attachable to a vehicle, etc. and makes sure detection operation by energizing an ultrasonic vibrator and detecting the reflected wave of an ultrasonic wave upon lapse of a prescribed period so that the vibrator is used commonly for transmitting and receiving the ultrasonic wave without problem. CONSTITUTION:A selecting circuit 25 is controlled by a microcomputer 90 and one of a driving circuit 50 which energizes an ultrasonic vibrator 20 for transmitting an ultrasonic wave and a discriminating circuit 60 which detects and discriminates the reception of the reflected ultrasonic wave by the vibrator 20 is selected at a prescribed timing. Therefore, the vibrator 20 is selected after the residual oscillation of the vibrator 20 attenuates upon lapse of a prescribed time since the vibrator 20 is energized, and the vibrator is commonly used for transmitting and receiving the ultrasonic wave without false detection of the reflected ultrasonic wave due to a residual oscillation and any problem. As a result, an object detector of a reflection type which is simple in constitution, is easily attachable to a vehicle, etc., and makes sure detection operation is obtd. The intensity of the ultrasonic wave, the sensitivity in wave reception, etc. are set according to the distance range and the objects at different distances are detectable satisfactorily.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reflection-type object detection device that uses ultrasonic waves to detect objects such as obstacles located at a distance from a vehicle or the like.

For example, in a vehicle, it is a device that detects obstacles that are out of the driver's field of vision and guides the driver.
Object detection devices are known. This type of object detection device generally uses ultrasonic waves. In this type of device, ultrasonic waves of a predetermined intensity are emitted from an ultrasonic transmitter in a predetermined direction, and the ultrasonic transmitter emits ultrasonic waves at a predetermined distance of 1 iJ.
The presence or absence of a reflected wave reaching an ultrasonic receiver placed at a position ffl away is detected, and if there is a reflected wave, the distance between the detection device and the obstacle is determined from the reception timing.

By the way, when this type of device is installed in a vehicle, for example, at least the transmitting and receiving ends of the ultrasonic transmitter and the ultrasonic receiver must be exposed outside the vehicle. therefore,
To install this device on a vehicle, make at least two holes (or one large hole) in the vehicle, install an ultrasonic transmitter and an ultrasonic receiver on the vehicle body, and install the ultrasonic transmitter and ultrasonic receiver on the vehicle body side or This means that the ultrasonic receiver will be waterproofed.

However, such processing increases the cost and
The cost 1- of the ultrasound transmitter and ultrasound receiver itself is also relatively high. Particularly in the case of vehicles, it is desirable to install an ultrasonic oscillator and an ultrasonic receiver on at least the right and left sides of the vehicle body, so this type of cost accounts for a fairly high proportion of the total cost of the device. .

The first object of the present invention is to provide a reflection type object detection device that is easy to process for device installation and is inexpensive, and the second purpose is to provide a reflection type object detection device with reliable detection operation.
The purpose of

In order to achieve the above object, in the present invention, one ultrasonic transducer is used for both transmission and reception.

Then, reflected wave detection is started after a predetermined time ΔT has elapsed after transmission is stopped so that residual vibration of the ultrasonic transducer immediately after transmission is stopped is not detected as reflected wave reception. In other words, immediately after switching the ultrasonic transducer from energized to de-energized, the ultrasonic transducer does not immediately stop imaging, and if the presence or absence of an object is determined from the electrical output of the ultrasonic transducer at this time, the ”
False detections may occur due to residual components of the ultrasonic transducer's vibrations, but since these vibrations attenuate over time, such false detections will not occur after a predetermined period of time has elapsed after the ultrasonic transducer was deenergized. do not have.

According to this, the number of ultrasonic transducers for transmission or reception can be reduced by at least -1 compared to the conventional method. In other words, this reduces the exposed area.

Installation, waterproofing, and other processing become easier, and considerable cost reductions can be achieved, including the cost of the ultrasonic transducer itself.

The time from when the energization is stopped until the residual vibration caused by the energization of the ultrasonic transducer no longer affects erroneous detection during reception is determined by the following parameters.

a) Energization level (Ve) of ultrasonic vibrator: The higher the energization voltage, the larger (longer) the residual vibration will be.

b) energizing time (t) of ultrasonic vibrator: When the energizing time is relatively short, as the energizing time becomes longer, the energizing energy increases and the residual vibration becomes larger (longer).

C) Performance of the ultrasonic transducer (S) Changes depending on the characteristics of the transducer itself, such as the difference in resonance frequency due to dual use as a transmitter and receiver, allowable input voltage, reception sensitivity, etc.

(1) Receiving side amplification (Gs): amplifier gain, etc.
) Threshold level (Vc): Comparison value for determining the presence or absence of a reflected wave. Therefore, the predetermined time Δ1' is determined by the following function.

△T=f (Ve, t, S, G3.Vc) -----(
1) In one preferred embodiment of the present invention, the detection distance range is divided into a plurality of regions, different detection sensitivities and/or transmission strengths are set for each range, and the reception waiting time from transmission to reception determination is Set long. The intensity of the reflected wave changes depending on the distance between the ultrasonic transducer and the object, so by setting the detection sensitivity or transmission intensity according to the distance 181, object detection accuracy can be increased and reception waiting time can be reduced. Because it is long, it does not pick up the lingering sound of the transmission,
Erroneous detection is eliminated and detection operation becomes reliable. That is,
As the detection position is sequentially shifted from a short distance to a long distance, the reception level in the presence of an object decreases, so in order to compensate for this, the transmission energy and/or reception sensitivity are sequentially increased. If you increase the value, the lingering sound of the transmission will be longer, and if you increase the receiving sensitivity, there is a possibility that a weak lingering sound or a weak reflection outside the detection range may be mistakenly detected as an object. Since the delay time ΔT from transmission to reception determination is lengthened accordingly, such erroneous detection does not occur. As the detection distance increases, the transmission energy and/or reception sensitivity increases, so if an object is within the detection distance, it will take a long time for the reflected wave to reach the ultrasonic transducer, so the delay time will increase. Increasing the length of T does not impede object detection. In this way, the detection position is sequentially shifted further away, and the transmitted energy and/or
Alternatively, increasing the reception sensitivity and sequentially delaying the reception discrimination timing (sequentially increasing ΔT) are perfectly compatible, and the detection accuracy becomes significantly higher.

Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

Figure 1 shows the exterior of a car equipped with an obstacle detection device. Referring to FIG. 1, in this embodiment, ultrasonic transducers 20 and 30 are attached to both ends of a rear bumper 2 of an automobile 1, respectively. The ultrasonic transducers 20 and 30 used in this example are ultrasonic ceramic microphones EFR-RS 84 manufactured by Matsushita Electric.
0K2.

FIG. 2 shows a block diagram of the electric circuit of the obstacle detection device mounted on the vehicle shown in FIG. 1. This will be explained with reference to FIG. The ultrasonic transducers 20 and 30 are connected to selection circuits 25 and 35, respectively. The selection circuits 25 and 35 change the electrical connection of the ultrasonic transducer, as will be described later.
(or 30). The selection control is performed by the microcomputer 90.

Selection circuits 25 and 35. Drive circuits 50 and 70 and discrimination circuits 60 and 80 are connected to microcomputer 90, respectively. The microcomputer 90 used in this embodiment is an 8-bit single-chip microcomputer 8748 manufactured by Intel Corporation. 90a
is a crystal oscillator that generates clock pulses that are the basis of microcomputer operation. Reference numeral 40 denotes a starting circuit, which is composed of a starting switch 41 and a waveform shaping circuit 42. The starting switch 41 is of a self-resetting type and has normally open contacts. The start switch 41 is arranged on the operation panel of the driver's seat. 100
is a buzzer circuit, and the buzzer 102 that constitutes it is
Microcomputer 9 via buzzer drive circuit 101
0 output port. 110 is a distance display circuit that displays the distance between the vehicle body and an obstacle. Distance display port! The PJ 110 includes a 7-segment display 111 with 3 digits. display], 1.1 is segment drive circuit 1
12 and a finger drive circuit 113 for dynamic display driving.

FIG. 3 shows a specific configuration of the drive circuit 50 shown in FIG. 2.

Note that, in FIG. 2, the drive circuits 50 and 70 have the same configuration, so a description of the configuration of the drive circuit 70 will be omitted. This will be explained with reference to FIG. 51 is a pulse oscillator constructed using an integrated circuit, and the duty is always 50%.
A pulse signal with a frequency of 40KIIz is output. The output signal of the pulse oscillator 51 is applied via the NAND gate 1-52 and the inverter 53 to a power amplification port 1i'f 154 composed of two transistors. One input end of the Nando game 1-52 is connected to the microcomputer 90.
When the output level of the port is at a high level H, a pulse signal from the pulse oscillator 51 is generated at the output terminal of the NAND game 1-52. A voltage vb of 12V from the battery is applied to the power amplifier circuit 54, and a pulse signal having an amplitude of 12V appears at the output terminal of the power amplifier circuit 54.

The output terminal of the power amplifier circuit 54 is connected to the primary side of the step-up transformer T, and when a pulse signal is applied to the primary side of the transformer T, a signal with an amplitude of about 100 V is generated on the secondary side. . This boosted 40Ktlz signal is
It is applied to the ultrasonic transducer 20 via the selection circuit 25.

FIG. 4 shows a specific configuration of the discrimination circuit 60 shown in FIG. 2.

Note that since the discrimination circuits 60 and 80 have the same configuration, a description of the discrimination circuit 80 will be omitted. This will be explained with reference to FIG. The ultrasonic transducer 20 is connected to an amplification circuit 61 of a discrimination circuit 60 via a selection circuit 25. The amplifier circuit 61 includes three stages of cascade-connected narrowband amplifiers AI and A2.
and A3. Each of the amplifiers Al, A2, and A3 is an inverting amplifier composed of an operational amplifier, and has a 4.0 KII 7.
A parallel resonant circuit consisting of a resonant capacitor and an electric coil is connected.

62 is a variable gain amplifier. This variable gain amplifier 62 is composed of an operational amplifier 62a, an analog switch (analog multiplexer) AS, and a large number of resistors. The analog switch AS used here is CMO5MSIMC14051 manufactured by Motorola. To briefly explain the variable gain amplifier 62, this circuit is as follows.
Control input terminal Co of the analog switch AS (3 pins)
Microcomputer 90 applied to C1 and C2
The resistor selected according to the signal from the operational amplifier 6
2a as a feedback resistor, and amplifies the signal with an amplification degree determined by the resistor and the input resistor rin. In other words,
The amplification degree G of this circuit 62 is determined by the combined resistance of the feedback resistors connected between the inverting input terminal and the output terminal of the operational amplifier 62a.
If t, it is expressed by the following formula.

G= rt/rin (1) Analog switch AS has its ports xo, xi.

A2. A3. ..., A7 is selected by the 3-bit gain setting signal applied to the control input terminals Co, CI and C2, and the port and the common board 1-YO are selected.
Connect electrically. For example, if the data of the gain setting signal is different for the input terminals GO, CI and C2,
In the case of L and "o" which becomes L, po hXO is selected and the combined resistance rt becomes rO, so the gain G becomes -ro/rin. Similarly, the data of the gain setting signal are rl'', r2''.

r, l, r4'', r5'', r6'' and ``7'', respectively, the ports XI, A2. A3. A4
゜A5. A6 and A7 are selected and the combined resistances rt are rO, rO+rl, rO'+rl+r2, respectively.
ro+rl+r2+r3. ro+rl+r2+r3+r
4. ro+rl+r2+r3+r4+r5. rO+
rl+r2+r3+r4-1-r5+r6 and ro+
'rl+r2+t-3+r4+rS+r6+r7. Therefore, the gain G of the variable gain amplifier 62 can be set in eight stages by the gain setting signal. In this embodiment, the maximum gain when the data of the gain setting signal is "7" is set to about 128 times the minimum gain when the gain setting signal data is rOJ.

63 is an inverting amplifier, 64 is a rectifying and smoothing circuit, and 65 is a comparator. A reference voltage Vr obtained by dividing the voltage vb by a resistor is applied to one input terminal of the comparator 65, and a DC voltage Vs obtained by the rectifying and smoothing circuit 64 is applied to the other input terminal of the comparator 65. has been done. 66 is a level conversion circuit, ie, an interface circuit, the output end of which is connected to the microcomputer 90. Voltage Vcc is 5
It is V.

FIG. 5 shows the configuration of the selection circuit 25. Note that selection circuit 2
5 and 35 are of the same 4Ff configuration. See Figure 5! 4tt
and explain. Ash,, AS2. AS3 and AS4
14016 is an analog switch made by Molola Co., Ltd., terminals a and b are input/output terminals, and terminals 7-c are control input terminals. Analog switch ΔSJ and A, S
The control input C1 of AS2 and the control input C of AS4 are connected to inverters IN1 and IN2, respectively. The input end of the inverter (2) N2 is connected to the microcomputer 9o.

When the input terminal of the inverter IN2 becomes a high level I, the analog switches ASI and AS2 are turned on, and AS3 and AS4 are turned off. Therefore, the drive circuit 50
An ultrasonic transducer is connected to the output of (or 70) and becomes the transmission mode. Furthermore, when the input terminal of IN2 becomes a low level L, analog switches AS1 and AS2 are turned off and AS3 and AS4 are turned on, so that the terminal of the ultrasonic transducer is connected to the discrimination circuit 60 (or 80) and the reception mode is set. Become.

The general operation of the obstacle detection device will be explained. This device is the 6th
As shown in the figure, since ultrasonic waves are generated from both ends of the rear bumper 2 of the automobile 1, if an obstacle 3 exists, the ultrasonic waves reflected by the obstacle 3 reach the ultrasonic transducer, and this The presence of an obstacle is detected by detecting it in an electrical circuit.

In reflective obstacle detection using ultrasonic waves, the intensity of reflected waves varies greatly depending on the location of the obstacle, and if the detection sensitivity is too high, even objects that are not obstacles may be detected as obstacles. Furthermore, there are reflected waves that reach the receiver after being reflected multiple times, and if the distance is calculated by detecting these reflected waves, a large error will occur. Therefore, in this embodiment, the area to be detected is divided into a number of areas according to distance, different sensitivities are set for each area, and a time window is set to determine the time required to detect obstacles. We have achieved high reliability by regulating the Specifically, the sensitivity is set by changing the data of the gain setting signal that sets the analog switch AS. Furthermore, the time is determined by changing the reference data to be compared with the data counted by the interval timer inside the microcomputer 90.

The following Table 1 shows the gain setting signal data D2 in each region, the reflected wave detection inhibition period data ΔT, the sampling end time data Tgmax, and the sampling period data T.
This shows the relationship between n. In Table 1, the numerical values shown with alphanumeric characters 1-11 are shown in hexadecimal notation. Values within 0 are decimal numbers. The data in Table 1 is stored in a ROM (read-only memory) in the microcomputer 90 in advance as a data table. The value 1 in the time data ΔT + T g max etc. shown in Table 1 corresponds to a time of 60 μs in this example.

Table 1, FIG. 7 shows a schematic operation of the microcomputer 90, and FIG. 8 shows a schematic operation timing.

This will be explained with reference to FIGS. 7 and 8.

When the power is turned on, the output capacitors 1 to 1 are set to the initial level, the contents of the memory (RAM) are cleared, and the system waits for the start switch 41 to be turned on. When the start switch 41 is turned on, the next step is to start measurement.

First, the gain G is set to an initial value of 0.

Output the signal ``G'' to the inverter IN2 and set it to the transmission mode. The ultrasonic transducers 20 and 30 are now connected to the output ends of the drive circuits 50 and 70, respectively.

A predetermined value is output to the analog switch AS according to the gain G to set the gain. Next, drive circuits 50 and 70
11 for a predetermined period of time (80μ5 in this example). Now, the oscillator 51 generates a period of 25 μs (
That is, a voltage of 40 Kl+z) is applied to the driver 54, and this signal energizes the ultrasonic transducers 20 and 30 via the transformer T and the selection circuit.

When the output of the ultrasonic wave is finished, start the internal timer and wait for Δt to elapse. No reception is performed during this period. As shown in Table 1 above, the time ΔT varies depending on the gain G, but in order to eliminate the influence of residual imaging of the ultrasonic transducer, the time ΔT is at least 2011, that is, 1.92 m5.
It is set to .

When ΔT has elapsed, L is output to the selection ports 'i, Pi 25 and 35, and the receiving mode is set. The output levels of the discrimination circuits 60 and 8C- are checked to see if the reflected wave detection level is output to either one. This process reads the state of the input port connected to the output end of the level conversion circuit 66 and checks whether it is at the ultrasonic detection level, that is, whether V 1 , s > V r.

The period during which this determination is made, ie, the sampling period, is from after ΔT has elapsed until TgmaX has elapsed, as shown in FIG. As shown in Table 1, the sampling period (Tgmax-8T) is constant (840 μs) except when the gain G is 7.

If no reflected wave is detected even after T g max has elapsed, the gain G is increased by +1, and if G is less than or equal to G max (7), the measurement is performed again after waiting for the sampling period Tn to elapse. When the gain G changes, Δ
Tgmax and Tgmax change, and the timing of sampling in each sampling period changes.

If no reflected wave is detected until G > G max, a buzzer is activated for one second to notify the driver that there is no obstacle. When a reflected wave is detected, the distance between the ultrasonic transducer and the obstacle is calculated based on the timer value at that time, and the result is displayed on the display 110.

The velocity V of the ultrasonic wave is as follows, where θ is the temperature.

V=331-. 50.61 θ, I: m/s) If the temperature θ is 15°C, V-” is 59.7 μs/2 cm, so the distance between the object and the ultrasonic transducer and the time after emitting the ultrasonic wave are The relationship with the time until the reflected wave is detected is as follows.

60 μs/c [ In the example, the numerical value 1 corresponds to 60 μs, so this numerical value l corresponds to the distance (cm) between the ultrasonic transducer and the obstacle. That is, in each sampling of gain G=O to 7, the number is 32 to 46 (less than: the same applies hereinafter).
, 46-60. 60-74, 74-88. 88-10
2. 102~116°116-1.30, 130~1
Reflected waves from a range of 92 [crn] will be detected.

In this example, the distance I from the ultrasound transducer is less than 32 cm.
The reflected wave from the object located at 1 is not detected because it may cause false detection due to residual vibration during ultrasonic transmission. As the gain G becomes larger, the sensitivity to residual vibration becomes higher and false detection is more likely to occur. However, in this embodiment, as the gain becomes higher, the period △T during which detection is prohibited from stopping the ultrasonic waves becomes longer. Since the gain is set to , false detection will not occur even if the gain becomes large.

In the above embodiment, the sensitivity of the obstacle detection device is changed by changing the amplification degree of the amplifier on the receiving device side, but the sensitivity can also be changed by changing the reference voltage Vr of the comparator 65.
Conversely, the sensitivity can also be changed by changing the ultrasonic transmission intensity on the transmitting device side.

FIG. 9 shows an embodiment in which the reference voltage vr of the comparator is changed. This will be explained with reference to FIG. In this embodiment, the variable gain amplifier 62 shown in FIG. 4 is omitted, and instead, the common baud 1-YO of the analog switch AS is connected to one end of the comparator 65. Each baud 1-Xo-X7 of the analog switch AS is connected to a resistor rx, r
Different voltages obtained by dividing the voltage Vb at o=r7 are applied. Therefore, the control input capo-1-GO, CI
If a microcomputer is connected to C2 and C2, the reference voltage Vr will be changed by changing the data output to these bauds 1 to 1. Therefore, the reflected wave received by the ultrasonic transducer 20 or 30 will be judged as having a reflected wave. The detection level, or sensitivity, changes.

FIG. 10 shows an embodiment in which the ultrasonic transmission intensity on the transmitting device side is changed. This will be explained with reference to FIG. In this embodiment, the intensity of the transmitted ultrasonic waves is changed by changing the voltage applied to the power amplification port 2854. In this embodiment, the voltage is generated by the power supply PW. This power supply PW is a modification of a commonly used series control type constant voltage power supply. That is, 1-
The analog switch AS switches the voltage applied to the transistor Q1, that is, the error amplifier, thereby changing the output voltage of the power supply. In other words, analog switch AS
Since different voltages obtained by dividing the output voltage of the power supply PW by a number of resistors are applied to each port X0-X7 of the analog switch AS, the control input capos-1-Co,
Changing the data output to CI and C2 changes the voltage applied to the error amplifier and changes the output voltage. If the output voltage of 1 W changes, the amplitude of the output pulse of the power amplifier circuit 54 will change, so the intensity of the emitted ultrasonic wave will change, and this will change the intensity of the ultrasonic wave that reaches the ultrasonic transducer. Obstacle detection sensitivity changes.

In the embodiment described in item 1, two ultrasonic transducers are provided at the rear of the vehicle, but the ultrasonic transducers may also be provided on the side of the vehicle. It may be provided on the fork of the rack to detect cargo.

Note that the number of ultrasonic transducers may be one or three or more.

Further, in the above embodiment, each ultrasonic transducer is provided with a drive circuit and a discrimination circuit, but the number of these drive circuits and discrimination circuits may be at least 1. If multiple ultrasonic receivers (three receivers are connected to one discrimination circuit g7f, use an analog switch, for example, to switch the signal from each ultrasonic receiver and select one of them)
The configuration may be such that one is connected to the discrimination circuit.

In the above embodiment, the selection circuit is used to switch the electrical connection of the ultrasonic vibration r in the transmission mode and the reception mode, but this circuit r (1 is not necessarily required. For example, the selection circuit and the Connect the sonic wave transducer, the discrimination circuit and the ultrasonic transducer through a resistor, and
If a protection circuit such as an ode is connected to the input side of the discrimination circuit, no problems such as failure will occur even if the ultrasonic transducer, drive circuit, and discrimination circuit are connected.

As described above, according to the present invention, one ultrasonic transducer is used for both transmission and reception, so at least one ultrasonic transducer can be omitted and removed (=J injury is simplified, and
The cost of the device itself can be lowered.

Moreover, since the detection is performed after a sufficient period of time has elapsed since the transmission was stopped, malfunctions due to residual vibrations of the ultrasonic transducer do not occur.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of an automobile equipped with an embodiment of a reflective object detection device. FIG. 2 is a block diagram of the electric circuit of the apparatus according to the embodiment installed in the automobile of FIG. FIG. 3 is a block diagram showing one drive circuit 50 of FIG. FIG. 4 is a block diagram showing one discrimination circuit 60 of FIG. 2. FIG. 5 is a block diagram showing one selection circuit 25. 6 is a plan view schematically showing the operation of the apparatus shown in FIG. 2. FIG. 7 is a flowchart 1 to 1 showing a schematic operation of the microcomputer 90 shown in FIG. 2, and FIG. 8 is a timing chart showing an example of the operation of the reflective object detection device. FIG. 9 and FIG. 10 are block diagrams showing a part of the electric circuit of the object detection device of other embodiments, respectively. 1: Car 2: Rear bumper 3: Obstacle 20.30: Ultrasonic transducer 25 +
35: Selection circuit (selection means) 40: Starting circuit 50.70: Drive circuit (energizing means) 130.80: Discrimination circuit 51: Pulse oscillation circuit 61
:-shaped band amplifier (amplifier 12) 62: Variable gain amplifier (level change means) 64: Rectification and smoothing circuit 65: Comparator 66 Two-level conversion circuit 90: Microcomputer (electronic control unit) J02:
Buzzer AS, Ash, AS2. ΔS3. ΔS4: Analog switch

Claims (6)

[Claims] (1) An ultrasonic transducer that performs electrical signal-mechanical vibration conversion and mechanical vibration-electric signal conversion; Ultrasonic transducer biasing means that applies a predetermined electrical signal to the ultrasonic transducer; From the ultrasonic transducer amplifying means for amplifying the electrical signal;
and an electronic control device that energizes the ultrasonic transducer and determines the presence or absence of an object according to the received output of the amplification means after a predetermined period of time has elapsed since the end of the energization. (2) The electronic control device divides the distance range in which an object is detected into a plurality of parts, and sets different ultrasound transmission intensities or ultrasound reception sensitivities for each range. Reflective object detection device as described in Section 1. (3) The electronic control unit starts object detection from the shortest distance range, notifies you when an object is detected, and updates the detection distance range to the next shortest distance if no object is detected within that range. , the reflective object detection device according to claim 2, wherein this operation is repeated until the maximum distance range is reached. (4) The electronic control device determines the distance between the detector and the object by 1iJIu according to the time from energizing the ultrasonic transducer to receiving the ultrasonic wave.
The reflective object detection device according to claim 3, which calculates the following. (5) Claims (1) and (2) above, wherein the ultrasonic transducer is connected to the biasing means and the amplification means via a selection means that is switched and controlled by an electronic control device; 3rd (3rd
) or (4). (6) If there is no object during the transmission energization and reception determination of the ultrasonic transducer, the electronic control device next increases at least one of the ultrasonic transmission intensity and reception sensitivity than the previous time, and then activates the ultrasonic transducer. The reflective object detection device according to claim 1, wherein the predetermined time is set to be longer than the previous value.