JPH08166451A - Obstacle detector for vehicle - Google Patents

Abstract

PURPOSE: To detect an obstacle accurately over a wide range, from a short distance to a long distance, by computing distance data to an obstacle based on a receiving signal, processing the operation results according to a predetermined system and alarming the obstacle. CONSTITUTION: A switching circuit 2 switches individual sensors constituting a sensor array 1, and a transmission circuit 3 drives a sensor selected by the switching circuit 2 to transmit an ultrasonic wave. A short distance receiving circuit 4a has low sensitivity and suppresses after tremor of transmitting wave well thus detecting a reflected waved from a short distance obstacle. A long distance receiving circuit 4b has high sensitivity and a receiving signal of a faint reflected wave from long distance is amplified to be identified. A control operation section 5 measure the time elapsed after transmission of ultrasonic wave before reception of reflected wave and computes the distance to the obstacle. Detected information related to the obstacle is imaged and presented at a display section 7 and an alarm sound corresponding to the detected distance of obstacle is delivered from a buzzer circuit 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vehicle obstacle detection device for detecting obstacles near a vehicle by utilizing the reflection of ultrasonic waves.

[0002]

2. Description of the Related Art In recent years, as one of the techniques for improving the convenience of a vehicle, there is a device that detects an obstacle in front of and behind the driver that is difficult to recognize from the driver's seat and informs the driver. This type of device detects an obstacle in the vicinity of a vehicle using ultrasonic waves, lasers, radio waves, infrared rays, and the like, and in many cases, an ultrasonic sensor is attached to a bumper.

Such obstacle detecting devices using ultrasonic waves include corner sensors which mainly detect obstacles near the front, rear, left and right corners of the vehicle, a backsonner which mainly detects obstacles near the bumper, or There is a clearance sonar.

[0004]

However, in the above-described conventional obstacle detection device, in many cases, the reception sensitivity is set so as to be able to distinguish between the after vibration of the transmitted wave and the received signal of the reflected wave. Although it is set low, it is effective for detecting relatively short distances (hereinafter 0 to 1 m), but the amplitude of reflected waves from long distances (hereinafter 1 to 3 m) is small, so Detection of long distances is difficult. On the other hand, when the receiving sensitivity is increased to detect a long distance, the weak after vibration of the transmitted wave is amplified and the after vibration becomes long, so that the after vibration of the transmitted wave and the received signal of the reflected wave are separated. This makes it impossible to identify them, which in turn makes it difficult to detect short distances. Therefore, in the conventional obstacle detection device, it is effective only for one of the short distance and the long distance in setting the receiving sensitivity, and it is extremely difficult to detect accurately from the short distance to the long distance.

The present invention has been made in view of the above problems of the prior art, and provides an obstacle detection device for a vehicle capable of accurately detecting an obstacle over a wide range from a short distance to a long distance. With the goal.

[0006]

In order to achieve the above object, a vehicle obstacle detection device according to a first aspect of the present invention detects an obstacle in the vicinity of a vehicle by utilizing reflection of ultrasonic waves. In an obstacle detection device for a vehicle, a sensor for transmitting and receiving ultrasonic waves, a transmitting means for driving the sensor to transmit ultrasonic waves, and a reception signal of a reflected wave received by the sensor driven by the transmitting means are provided. A plurality of receiving means connected in parallel having different receiving sensitivities, a computing means for computing a distance data to an obstacle by inputting a received signal detected by at least one of the plurality of receiving means; And a notifying unit for processing the calculation result of the unit into a predetermined format and notifying the result.

According to a second aspect of the present invention, there is provided a vehicle obstacle detection device according to the first aspect, wherein the plurality of receiving means are short-distance receiving circuits suitable for short-distance detection. And a long-distance receiving circuit suitable for long-distance detection. The vehicle obstacle detection device according to a third aspect is the vehicle obstacle detection device according to the second aspect, characterized in that the short-distance receiving circuit has low reception sensitivity.

According to a fourth aspect of the present invention, there is provided the vehicle obstacle detection device according to the second aspect, wherein the long-distance receiving circuit has high reception sensitivity.

[0009]

In the vehicle obstacle detection device according to the first aspect of the present invention configured as described above, the transmitting means drives the sensor to transmit ultrasonic waves. The transmitted ultrasonic wave hits the obstacle and returns, but the reflected wave is received by the sensor. The received signal of the reflected wave received by the sensor is simultaneously input to a plurality of receiving means having different receiving sensitivities, and is compared with a reference signal for detecting a received signal which is appropriately set in advance in accordance with the receiving sensitivity.
The reception sensitivity of each sensor is set appropriately in advance according to the target detection distance. As a result of the comparison, the received signal of the reflected wave is detected by at least one receiving unit. The detected reception signal is input to the calculation means, where the time difference from the transmission of the ultrasonic wave to the reception of the reflected wave is measured, and the distance data to the obstacle is calculated.
The notifying means processes the calculation result of the calculating means into a predetermined format (for example, imaging an obstacle, displaying a numerical value of the distance to the obstacle, an alarm sound corresponding to the distance to the obstacle, and the like) and displaying (displaying). , Alarm). That is, since a plurality of receiving means having different reception sensitivities are provided depending on the target detection distance, it is possible to accurately detect an obstacle over a wide range from a short distance to a long distance by one transmission.

According to another aspect of the vehicle obstacle detection device of the present invention, the received signal of the reflected wave received by the sensor is simultaneously input to the short-distance receiving circuit and the long-distance receiving circuit, thereby The received signal of the reflected wave from is detected by the short distance receiving circuit, and the received signal of the reflected wave from the long distance is detected by the long distance receiving circuit. That is, since the two-system receiving circuits for short-distance detection and long-distance detection are provided, it is possible to accurately detect an obstacle over a wide range from short-distance to long-distance by one transmission.

Further, in the vehicle obstacle detection device according to the third aspect of the invention, since the short-distance receiving circuit has a low receiving sensitivity, the surplus of the transmitted wave can be suppressed to be small, and therefore the surplus of the transmitted wave can be suppressed. It is possible to distinguish between the vibration and the received signal of the reflected wave. Therefore, it is possible to detect a short distance by appropriately setting the threshold waveform.

Further, in the obstacle detecting device for a vehicle according to the fourth aspect, since the receiving circuit for a long distance has a high receiving sensitivity, the received signal of the weak reflected wave from a long distance is amplified,
It becomes possible to identify this. Therefore, it is possible to detect a long distance by appropriately setting the threshold waveform.

[0013]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an embodiment of a vehicle obstacle detection device of the present invention. As shown in FIG. 1, this obstacle detection device sequentially switches between an array-type sensor 1 that detects an obstacle near a vehicle by utilizing reflection of ultrasonic waves, and individual sensors that form the array-type sensor 1. The switching circuit 2, the transmission circuit 3 as a transmission unit for driving the sensor selected by the switching circuit 2 to transmit ultrasonic waves, and the reflection from the short distance received by the sensor selected by the switching circuit 2. For short-distance receiving circuit 4a as a receiving means for detecting a received signal of a wave, and for long-distance receiving means as a receiving means for detecting a received signal of a reflected wave from a long distance received by a sensor selected by switching circuit 2. Time for controlling the receiving circuit 4b, the switching circuit 2, the transmitting circuit 3, the short-distance receiving circuit 4a, and the long-distance receiving circuit 4b, and transmitting ultrasonic waves and receiving reflected waves. Measured, and a control arithmetic unit 5 of the distance to the obstacle as a calculating means for calculating according to a predetermined equation. The short-distance receiving circuit 4a and the long-distance receiving circuit 4b are connected in parallel, and the reception signal of the sensor is input to both the circuits 4a and 4b at the same time. The control calculation unit 5 has a built-in memory 6, and the obtained distance data to the obstacle is related to the sensor that detected it (for example, together with the sensor number or its mounting position). It is stored in the memory 6. The control calculation unit 5 outputs, for example, a display unit 7 as an informing unit for displaying information on the screen of the obstacle detected by the array type sensor 1 and an alarm sound corresponding to the detected distance of the obstacle. A buzzer circuit 8 as a notification means is connected to each. The display unit 7 also has a function of numerically displaying the detected distance to the obstacle. The display unit 7 is integrated with various operation switches 9.

2A and 2B are views showing an example of the array type sensor 1. FIG. 2A is a plan view and FIG. 2B is a front view. As shown in the figure, the array type sensor 1 includes a plurality (17 here) of sensors Sn (n = 1, 2, ..., 17).
Are arranged adjacent to each other in a line. Each sensor Sn is preferably of the same type and has the same structure and directional characteristics. When driving the array type sensor 1,
The individual sensors Sn constituting it are transmitted / received while being sequentially switched by the switching circuit 2.

FIG. 3 is a schematic configuration diagram of each sensor Sn which constitutes the array type sensor 1. As shown in the figure, each sensor Sn emits an ultrasonic wave of that frequency when an AC voltage is applied, and generates an AC voltage of that frequency when a reflected wave is received. The directivity angle of the sound wave emitted from
A conical member 11 that is limited to (for example, about 8 °) is housed in a case 12. By using the array type sensor 1 as described above, it is possible to detect an obstacle with no blind spot and good azimuth resolution. Therefore, the detected obstacle is imaged by considering its direction data and measured distance data. You can

In this embodiment, as described above, the short distance (0
˜1 m) Short range receiving circuit 4a for detection and long range (1 to 1 m)
3m) A long-distance receiving circuit 4b for detection, which is a two-system receiving circuit is provided. These two receiving circuits 4a,
4b has different reception sensitivity settings, as will be described later, and has sensitivity settings suitable for detection of a short distance and a long distance, respectively.

FIG. 4 is a block diagram showing a schematic configuration of each of the receiving circuits 4a and 4b. Since the short-distance receiving circuit 4a and the long-distance receiving circuit 4b have the same configuration,
Here, it will be simply called the receiving circuit 4. As shown in FIG. 4, the receiving circuit 4 includes an amplifier 13 for amplifying output signals from the individual sensors Sn forming the array type sensor 1 with a predetermined gain, and a signal amplified by the amplifier 13 with a predetermined reference voltage. And a reference voltage generator 15 for generating a reference voltage input to the comparator 14. The amplifier 13 includes a gain adjuster 16 (for example, a knob of a variable resistor) for adjusting the gain of the amplifier 13.
Is connected. The gain is adjusted, for example, by rotating the knob 16 to change the resistance value of a predetermined variable resistor in the amplifier 13 to change the amplification factor. The output signal of each sensor Sn in the array-type sensor 1 contains a mixture of the after-effect of the transmitted wave and the received signal of the reflected wave, and the comparator 14 uses the array signal as described in detail later. The (amplified) output signal of each sensor Sn in the sensor 1 is compared with the reference voltage output from the reference voltage generator 15, and the output signal from the sensor Sn is used as a threshold voltage with the reference voltage as a threshold value. When it exceeds, the detection signal indicating that the received signal of the reflected wave is detected is output (FIGS. 7 and 8).
reference). A level adjuster 17 (for example, a knob of a variable resistor) for adjusting the level of the reference voltage is connected to the reference voltage generator 15. Reference voltage generator 15
Is external (for example, the control calculation unit 5) as described later.
When a pulse signal is input from, a reference voltage having a predetermined waveform with respect to time is generated (see FIG. 6).

FIG. 5 is a circuit diagram of the reference voltage generator 15. As shown in FIG. 5, the reference voltage generator 15 has two variable resistors R1 and R2 connected in series, and one variable resistor R2 and a capacitor C connected in parallel, One end of the variable resistor R1 is connected to the power source Vcc, and one end of the variable resistor R2 is grounded. Capacitor C
One end of is also grounded. In this circuit, for example, when a predetermined pulse signal is input from the control calculation unit 5 via the diode 18 (see FIG. 6A), the voltage of the level of the pulse signal is input to the comparator 14 and pulse When there is no signal, the reference voltage is a variable resistor R1, R with a time constant determined by the variable resistor R2 and the capacitor C.
Voltage divided by 2, ie, {R2 / (R1 + R2)}
The voltage is attenuated to the level of Vcc. That is, the reference voltage generated when the pulse signal is input has, for example, a waveform as shown in FIG.

The level of the reference voltage is adjusted, for example, by turning the knob 17 to change the resistance values of the variable resistors R1 and R2. Further, the slope portion 20 of the reference voltage that attenuates after the end of the pulse signal (see FIG. 6B).
The adjustment of (see) is performed by previously determining the time constant in relation to the variable resistor R2 and the capacitor C.

The above-described gain adjustment, reference voltage level adjustment, and reference voltage slope portion 20 adjustment are performed as follows.
The short-distance receiving circuit 4a is adjusted in advance to an optimum state so that it is suitable for short-distance detection, and the long-distance receiving circuit 4b is suitable for long-distance detection.

More specifically, in the short-distance receiving circuit 4a, as shown in FIG. 7 (A), the after vibration 21 of the transmission wave forming the output signal d of the sensor Sn, the short-distance receiving signal a,
And the received signal b of the long distance, the received signal a of the short distance
Is sufficiently larger than the size (amplitude) of the received signal b at a long distance, the lowering of the gain of the amplifier 13 in the receiving circuit 4a reduces the amplitude of the transmitted wave 21.
Is kept small (minimization of after vibration), so that the after vibration of the transmitted wave 2
1 and the short-distance received signal a can be distinguished. Further, the reference voltage c, which is a threshold value for detecting the short-distance received signal a, is set to the short-distance received signal a.
The waveform is adjusted in advance so that only the signal is detected. In other words, the level of the reference voltage c is 2
It is set to be sufficiently higher than 1, the slope portion 20 of the reference voltage c is adjusted so as to approach the after vibration 21 of the transmitted wave, and the received signal a at a short distance can be detected. It is set higher than the received signal b at a long distance.
Therefore, the comparator 14 in the receiving circuit 4a detects the short-distance receiving signal a by comparing the output signal d of the sensor Sn with the reference voltage c set as described above, and a detection pulse to that effect. The signal e (see FIG. 7B) is output to the control calculator 5. In this embodiment, in order to reliably detect the received signal of the reflected wave, the reference voltage c is set to a predetermined time t (for example, about 1.6) from the start point of the ultrasonic wave transmission.
ms) so that it starts up early.

In the long distance receiving circuit 4b,
As shown in FIG. 8A, the amplifier 13 in the receiving circuit 4a is
By increasing the gain of, the weak received signal b at a long distance is greatly amplified and the received signal b at a long distance can be identified. Further, the reference voltage c, which is a threshold value for detecting the long-distance received signal b, is appropriately adjusted in advance to a waveform such that only the long-distance received signal b is detected. That is, the level of the reference voltage c is set sufficiently higher than the after-vibration of the transmitted wave and the received signal at a short distance (the two are mixed and indistinguishable as shown in the figure), and the reference voltage c is set to them. And the low level of the reference voltage c is set lower than that of the reception signal b at a long distance. Therefore, the comparator 14 in the receiving circuit 4b detects the long-distance receiving signal b by comparing the output signal d of the sensor Sn with the reference voltage c set as described above, and a detection pulse to that effect. The signal e (see FIG. 8B) is output to the control calculation unit 5. It should be noted that, in order to reliably detect the received signal of the reflected wave, the reference voltage c is set to rise earlier by a predetermined time t (for example, about 1.6 ms) than the time when the transmission of the ultrasonic wave is started. This is similar to the case of the distance receiving circuit 4a.

Next, the operation of the vehicle obstacle detection device configured as described above will be described with reference to the flowchart of FIG. When the power is turned on and the program starts,
The control calculation unit 5 resets the value of the parameter n for counting the order of the sensors Sn in the array type sensor 1 to 1 (step S1), and, for example, the measurement start switch 9 of the display unit 7 is turned on and a measurement start command is issued. It is determined whether or not the data is input to the control calculation unit 5 (step S2). As a result of this determination, if the measurement start command is not input, the standby state is entered, and if it is input, the process proceeds to the next step S3.

In step S3, the control calculation section 5 outputs a pulse signal to the reference voltage generator 15 in each of the receiving circuits 4a and 4b, and after the elapse of a predetermined time t (for example, about 1.6 ms), the switching circuit 2 outputs the pulse signal. The sensor switching command is output and the transmission command is output to the transmission circuit 3. The switching circuit 2 that has input the sensor switching command switches the sensor Sn to select the sensor Sn corresponding to the current value of the parameter n, and the transmission circuit 3 that has input the transmission command sets the sensor Sn selected by the switching circuit 2 to the predetermined value. An alternating voltage is applied to drive this, and ultrasonic waves are transmitted. The reference voltage generator 15 in each of the receiving circuits 4a and 4b that receives the pulse signal generates the reference voltage c and outputs it to the comparator 14 (see FIGS. 6A and 6B).

The ultrasonic wave transmitted in step S3 hits an obstacle and is reflected, and the reflected wave is received by the same sensor Sn selected by the switching circuit 2 as transmitted. This received signal is simultaneously input to the short-distance receiving circuit 4a and the long-distance receiving circuit 4b together with the after-effect of the transmitted wave, amplified in the respective circuits 4a and 4b, and then compared with a predetermined reference voltage. After that, it is detected in the form of a detection signal.

That is, in the short-distance receiving circuit 4a, as described above, the gain of the amplifier 13 in the circuit 4a is made small to minimize the after vibration 21 of the transmitted wave, and thereby the after vibration 21 of the transmitted wave is close. The reference signal c for comparison generated by the reference voltage generator 15 is adjusted in advance so that it can be discriminated from the reception signal a at a distance, and the waveform is such that only the reception signal a at a short distance is detected. Therefore, the reception signal a at a short distance can be detected via the comparator 14, and the detected pulse signal e is output to the control calculation unit 5 (FIG. 7).
(See (A) and (B)). In the long distance receiving circuit 4b, the long distance receiving signal b is identified by increasing the gain of the amplifier 13 in the receiving circuit 4a to greatly amplify the weak long distance receiving signal b, as described above. The reference voltage c for comparison generated by the reference voltage generator 15 is adjusted in advance so that only the reception signal b at a long distance can be detected. A long-distance received signal b can be detected, and the detected pulse signal e is output to the control calculation unit 5 (FIG. 7).
(See (A) and (B)) (above, step S4). By using these two-system receiving circuits 4a and 4b for short distance and long distance, an obstacle can be detected accurately from a short distance to a long distance.

When an obstacle is detected in at least one of the short-distance receiving circuit 4a and the long-distance receiving circuit 4b, the control calculation unit 5 determines the time until the ultrasonic wave is transmitted and the reflected wave is received. The time difference between the measurement and, more specifically, the output of the transmission command to the transmission circuit 3 to the input of the detection pulse signal e from the reception circuits 4a and 4b is counted, and the distance to the obstacle is calculated by a predetermined formula. And the result is stored in the internal memory 6 in a form having a relationship with the sensor at that time (for example, together with the sensor number n) (step S5), and the process proceeds to the next step S6. If the reflected wave is not received within a predetermined time (for example, a time sufficient for the ultrasonic wave to reciprocate over the effective detection distance) after the ultrasonic wave is transmitted, the above-mentioned time elapses immediately and step S6 is immediately performed. Proceed to.

In step S6, the value of the parameter n is a predetermined value N (the total number of sensors forming the array type sensor 1,
Here, it is determined whether N = 17) or more.
If n <N as a result of this determination, the value of the parameter n is incremented by 1 (step S7), and the process returns to step S3. That is, the switching circuit 2 sequentially detects the obstacles while sequentially switching the individual sensors Sn constituting the array type sensor 1, and stores the distance data for one screen.

If n ≧ N as a result of the determination in step S6, it is determined that the driving of the sensor Sn in the array type sensor 1 has completed one cycle, and the display unit 7 causes the memory 6 in the control arithmetic unit 5 to operate. The distance data for one screen is read from the screen, the obstacles detected by pre-programmed image display software are imaged, and the images of the detected obstacles are displayed on the screen. The distance to an obstacle is displayed numerically (step S8). Further, the buzzer circuit 8 outputs an alarm sound according to the detected distance to the obstacle (step S9). Then, for example, unless the measurement end switch 9 of the display unit 7 is turned on and the measurement end command is input to the control calculation unit 5 (step S10), the process returns to step S1 to repeat the above series of operations.

Therefore, according to the present embodiment, since the two-system receiving circuits 4a and 4b for short distance and long distance are provided, the accuracy of obstacles can be improved over a wide range from short distance to long distance by one transmission. To be able to detect well,
The detection area in an obstacle detection device for a vehicle such as an automobile can be expanded.

In this embodiment, the array type sensor 1 composed of a plurality of sensors Sn is taken as an example of the sensor, but the present invention is not limited to this. It is needless to say that the present invention can be applied to a device including only one sensor.

Further, in the present embodiment, the two-system receiving circuits 4a and 4b for short distance and long distance are provided, but the number of receiving circuits is not limited to this. In order to further expand the detection range and improve the detection accuracy, it is possible to provide three or more receiving circuits.

Further, it goes without saying that the configurations shown in FIGS. 1, 4, and 5 are merely examples, and the present invention is not limited to these. For example, in FIG. 1, the display unit 7 and the buzzer circuit 8 are provided as the notification means, but either one may be provided. Further, the display unit 7 has a function of imaging an obstacle, but when the array type sensor 1 is not used, it may have only a function of displaying a distance to the obstacle by a numerical value or an LED.

[0034]

As described above, according to the vehicle obstacle detection device of the first aspect of the present invention, a plurality of receiving means having different reception sensitivities are provided according to the target detection distance. By transmitting once, obstacles can be accurately detected over a wide range from short distance to long distance.

Further, according to the vehicle obstacle detection device of the second aspect, since the two-system receiving circuits for short-distance detection and long-distance detection are provided, it is possible to transmit from a short-distance to a long-distance by one transmission. It is possible to detect obstacles with high accuracy over a wide range.

Further, according to the vehicle obstacle detection device of the third aspect, since the receiving sensitivity of the short-distance receiving circuit is reduced, it becomes possible to distinguish between the after-vibration of the transmitted wave and the received signal of the reflected wave. , Can detect short distances.

According to the vehicle obstacle detection device of the fourth aspect, since the reception sensitivity of the long-distance receiving circuit is increased, the long-distance received signal can be identified and the long-distance detection can be performed. be able to.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an embodiment of a vehicle obstacle detection device of the present invention.

FIG. 2 is a diagram showing an example of an array type sensor.

FIG. 3 is a schematic configuration diagram of individual sensors forming an array type sensor.

FIG. 4 is a block diagram showing a schematic configuration of each receiving circuit.

FIG. 5: Circuit diagram of reference voltage generator

FIG. 6 is a waveform diagram showing the input and output of the reference voltage generator.

[Fig. 7] Waveform diagram of each signal at short distance detection

[Fig. 8] Waveform diagram of each signal during long-distance detection

9 is a flowchart showing the operation of the apparatus of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Array type sensor (sensor) 2 ... Switching circuit 3 ... Transmission circuit (transmission means) 4a ... Short-distance reception circuit (reception means) 4b ... Long-distance reception circuit (reception means) 5 ... Control operation part (operation means) ) 7 ... Display unit (informing means) 8 ... Buzzer circuit (informing means)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location G08G 1/16 C (72) Inventor Norihiro Nishio 2-10-19 Step-in, Ueda City, Nagano Prefecture Ueda Nihon Radio Co., Ltd. (72) Inventor Takao Yamakoshi 2-10-19, Ueda City, Nagano Prefecture Ueda Nihon Radio Co., Ltd. (72) Inventor Akihiko Okabe 2-10, Ueda City, Nagano Prefecture No. 19 Ueda Nihon Radio Co., Ltd.

Claims (4)

[Claims] 1. A vehicle obstacle detection device for detecting an obstacle in the vicinity of a vehicle by utilizing the reflection of ultrasonic waves, and a sensor (1) for transmitting and receiving ultrasonic waves, and driving the sensor (1). Transmitting means (3) for transmitting an ultrasonic wave, and a plurality of receiving means connected in parallel and having different receiving sensitivities for detecting a received signal of a reflected wave received by the sensor (1) driven by the transmitting means (3) (4a, 4b)
And a calculation means (5) for calculating distance data to an obstacle by inputting a reception signal detected by at least one of the plurality of reception means (4a, 4b), and calculation of the calculation means (5) An obstacle detection device for a vehicle, comprising: an informing means (7, 8) for processing and informing the result in a predetermined format. 2. A plurality of receiving means comprises a short-distance receiving circuit (4a) suitable for short-distance detection and a long-distance receiving circuit (4b) suitable for long-distance detection. The obstacle detection device for a vehicle according to claim 1. 3. The obstacle detecting device for a vehicle according to claim 2, wherein the short-distance receiving circuit (4a) has a low receiving sensitivity. 4. The obstacle detecting device for a vehicle according to claim 2, wherein the long-distance receiving circuit (4b) has a high receiving sensitivity.