JPH0763845A - Obstacle detector of vehicle - Google Patents

Abstract

PURPOSE:To make it possible to prevent lowering of the performance of detection of an obstacle at the time of high-speed running) even when a reception signal of an ultrasonic wave is attenuated by a running-caused air stream, by enlarging a transmission output of a pressure wave as a vehicle speed becomes high. CONSTITUTION:A sensor 2 transmits an ultrasonic wave toward the right rear side of its own vehicle and receives a reflected wave from an obstacle which is present on the right rear side of the vehicle. A system control part 6 measures the time of start of transmission of the ultrasonic wave and the time of start of reception of the reflected wave of a signal strength exceeding a threshold thereof, by a clock, and calculates time required for reflection of the ultrasonic wave, calculating a distance from the vehicle to the obstacle from this time. Besides, the system control part 6 controls a transmission circuit 3 so that a transmission output of the ultrasonic wave be enlarged as a vehicle speed becomes high. Thereby the strength of a reception signal of the ultrasonic wave can be increased as a whole and also the reflected wave can hold the signal strength sufficient for making determination of the obstacle possible even when the reception signal of the ultrasonic wave is attenuated by a running-caused air stream.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an obstacle detecting device for a vehicle which detects the presence or absence of an obstacle around the vehicle by an ultrasonic sensor using ultrasonic waves as a detecting medium.

[0002]

2. Description of the Related Art Conventionally, an obstacle detection device for a vehicle has been
For example, there is one that detects an obstacle around the vehicle by a laser sensor using a laser beam as a detection medium. Since this laser sensor is expensive, there is a problem in that the manufacturing cost of the obstacle detection device for a vehicle is high.

Therefore, for example, Japanese Patent Laid-Open No. 3-16631 discloses a vehicle obstacle detection device for detecting an obstacle around a vehicle by an ultrasonic sensor using ultrasonic waves instead of a laser beam as a detection medium. ing. Since the ultrasonic sensor is cheaper than the laser sensor, it is possible to reduce the cost for manufacturing the obstacle detection device for the vehicle.

[0004]

However, since the ultrasonic waves are pressure waves and use air as a medium, the ultrasonic waves are disturbed by the turbulent flow (hereinafter, referred to as running wind) generated when the vehicle is running, and the received signal of the ultrasonic waves. Is attenuated. Therefore, as the speed of the vehicle increases, the influence of the traveling wind of the ultrasonic waves increases, which increases the attenuation rate of the reception signal of the ultrasonic waves and reduces the signal strength of the reflected waves. Therefore, as the vehicle speed increases, the obstacle detectable distance becomes shorter, and the obstacle detectable area becomes smaller. As a result, there arises a problem that the obstacle detection performance at the time of high speed traveling is deteriorated.

The present invention has been made in view of the above problems, and an object of the present invention is to reduce the obstacle detection performance during high-speed traveling even when the ultrasonic reception signal is attenuated by traveling wind. The present invention provides an obstacle detection device for a vehicle that can prevent the above.

[0006]

An obstacle detection device for a vehicle according to claim 1, wherein a pressure wave is transmitted from the vehicle in a predetermined direction and a reflected wave is received by the transmitting / receiving element and the transmitting / receiving element receives the pressure wave. Based on the reflected wave, the obstacle determination means for determining the presence or absence of obstacles around the vehicle, the vehicle speed detection means for detecting the speed of the own vehicle, the vehicle speed detected by the vehicle speed detection means, depending on the pressure, And a transmission output changing means for changing the transmission output of the wave.

An obstacle detecting device for a vehicle according to claim 2 is
A transmitting / receiving element that transmits a pressure wave in a predetermined direction from the vehicle and receives the reflected wave, and an obstacle determining means that determines the presence or absence of an obstacle around the vehicle based on the reflected wave received by the transmitting / receiving element. And a vehicle speed detecting means for detecting the speed of the host vehicle, and in accordance with the vehicle speed detected by the vehicle speed detecting means, the obstacle determining means receives an amplification degree with respect to the signal intensity of the reflected wave received by the transmitting / receiving element. It is characterized by changing.

An obstacle detection device for a vehicle according to claim 3 is
A transmitting / receiving element that transmits a pressure wave in a predetermined direction from the vehicle and receives the reflected wave, and an obstacle determining means that determines the presence or absence of an obstacle around the vehicle based on the reflected wave received by the transmitting / receiving element. And a vehicle speed detecting means for detecting the speed of the own vehicle, and the obstacle determining means, in accordance with the vehicle speed detected by the vehicle speed detecting means, is an obstacle against the signal strength of the reflected wave received by the transmitting and receiving element. The feature is that the threshold value for judgment is changed.

[0009]

According to the structure of claim 1, by increasing the transmission output of the pressure wave as the vehicle speed increases,
The strength of the received signal of the pressure wave can be increased overall. As a result, even if the received signal of the pressure wave is attenuated by the traveling wind, it is possible to obtain a signal strength that is large enough to determine an obstacle. Therefore, the detectable distance and the detectable area of the obstacle from the low speed to the high speed can be kept substantially constant without being affected by the attenuation of the pressure wave reception signal due to the traveling wind. It is possible to prevent the detection performance of the obstacle from being deteriorated.

According to the second aspect of the invention, the intensity of the received signal of the reflected wave can be improved by increasing the amplification degree of the reflected wave of the pressure wave as the vehicle speed increases, for example. As a result, even if the received signal of the pressure wave is attenuated by the traveling wind, it is possible to obtain a signal strength that is large enough to determine an obstacle. Therefore, the detectable distance and the detectable area of the obstacle from the low speed to the high speed can be kept substantially constant without being affected by the attenuation of the pressure wave reception signal due to the traveling wind. It is possible to prevent the detection performance of the obstacle from being deteriorated.

Further, according to the third aspect of the present invention, the threshold value for obstacle determination with respect to the signal intensity of the reflected wave of the pressure wave becomes smaller as the vehicle speed increases, so that the traveling wind can change the threshold value. The presence or absence of an obstacle can also be determined by the signal intensity of the attenuated reflected wave. As a result, the detectable distance and the detectable area of the obstacle can be kept almost constant from low speed to high speed without being affected by the attenuation of the pressure wave reception signal due to the running wind. It is possible to prevent the detection performance of the obstacle from being deteriorated.

[0012]

【Example】

[Embodiment 1] FIG. 1 to FIG.
The explanation is based on the following.

The obstacle detection device for a vehicle according to this embodiment is
As shown in FIG. 1, as a detection medium, a sensor 2 as a transmission / reception element that transmits an ultrasonic wave that is a kind of pressure wave and receives the reflected wave, and a transmission output of the ultrasonic wave transmitted from this sensor 2 are used. Transmitting circuit 3 to be set, the sensor 2
An amplifier circuit 4 for amplifying the received signal of the reflected wave received by
An amplification degree setting unit 8 that sets an amplification rate (hereinafter, referred to as amplification degree) of an output signal with respect to an input signal in the amplification circuit 4, a detection circuit 5 that demodulates the signal amplified by the amplification circuit 4, and at least the above A system control unit 6 including a transmission output changing unit that changes the transmission output of a sound wave and an obstacle determining unit that determines the presence or absence of an obstacle based on the signal strength of the received signal from the sensor 2, and the speed of the host vehicle. The vehicle speed sensor 7 serves as a vehicle speed detecting means for detecting

As shown in FIG. 2, for example, the sensor 2 is provided on the right rear end side with respect to the traveling direction of the host vehicle 1, transmits ultrasonic waves to the right rear side of the host vehicle 1, and sends the host vehicle 1 It receives the reflected waves from the obstacles on the right rear side. At this time, the detectable distance by the sensor 2 is L and the detectable area is A. These L and A are, for example, signals of the reflected wave set in advance in the signal received by the system controller 6 by the sensor 2. It is formed by an ultrasonic wave corresponding to a signal that exceeds a threshold value for obstacle judgment with respect to signal strength, and within this detectable area A, the presence or absence of obstacles can be accurately judged. There is.

Further, the sensor 2 transmits an ultrasonic wave by a transmission output preset by the transmission circuit 3 based on a control signal from the system control section 6, while receiving a reflected wave reflected by an obstacle. To do. The reflected wave of the ultrasonic wave is amplified by the amplification circuit 4 by the amplification degree preset by the amplification degree setting unit 5 and input to the system control unit 6 via the detection circuit 9.

In the system control section 6, based on the signal intensity of the input reflected wave, for example, as shown in FIG.
An obstacle determination threshold value S _T for the signal intensity of the reflected wave is set, and when the signal intensity of the reflected wave exceeds the threshold value S _T , it is determined that an obstacle exists. .

At this time, at the same time as the start of transmission of ultrasonic waves, for example, at time T ₁ according to the clock provided in the system control section 6, ultrasonic waves are output and reflected by hitting an obstacle, and the signal intensity of the reflected wave is reduced. When the threshold value S _T is exceeded, the ultrasonic wave output from the sensor 2 is stopped at time T ₂ , and the distance from the vehicle 1 to the obstacle is measured from T ₁ and T ₂ described above. .

That is, the transmission start time T _{1 of the} ultrasonic wave having the signal strength S ₁ and the reception start time T ₂ of the reflected wave having the signal strength S ₂ exceeding the threshold value S _T are measured by the clock, such calculates the time (T ₂ -T ₁₎ to the reflection of sound waves, and calculates the distance from the vehicle 1 to the obstacle from the time.

On the basis of the distance from the own vehicle 1 to the obstacle calculated in this way, for example, the system control section 6 issues an alarm or the like to notify the driver and controls to take avoidance measures by automatic braking or the like.

The above-mentioned threshold value S _T is a reference for determining whether the received signal is an obstacle or noise, and is preset to a value capable of accurately discriminating the obstacle. Has been done.

However, since the ultrasonic wave is a kind of pressure wave using air as a medium, the ultrasonic wave is disturbed and attenuated in the air by the traveling wind generated while the host vehicle 1 is running, whereby the signal of the reflected wave is generated. Strength is reduced. Therefore, as shown in FIG. 3, even in the ultrasonic wave transmitted with the same signal strength S ₁ , the reception strength S ₂ of the reflected wave is equal to the threshold value S ₂ at low speed running.
_Although it exceeds _T , the signal intensity S ₂ 'of the reflected wave becomes lower than the above-mentioned threshold value S _T at high speed traveling.

Therefore, even if the signal strength is the same, as the vehicle speed increases, the distance at which the obstacle can be detected becomes shorter, and the detection area also shrinks accordingly. As a result, the ability to detect obstacles in high-speed traveling is lower than in low-speed traveling.

Therefore, in the present embodiment, the system control unit 6 as the transmission output changing means for changing the transmission output of the ultrasonic wave changes the transmission output of the ultrasonic wave according to the vehicle speed.

As shown in FIG. 4, for example, the system control section 6 controls the transmission circuit 3 so that the transmission output P of ultrasonic waves increases as the vehicle speed V increases.

[0025] That is, the system controller 6, the transmission output P ₁ with respect to the vehicle speed V _1, the transmission output P ₂ with respect to the vehicle speed V _2,
By setting (V ₁ <V ₂ , P ₁ <P ₂ ), as shown in FIG. 5, in the case of X ₁ (V ₁ , P ₁ ), the ultrasonic wave of signal strength S ₃ is transmitted at the start time T. When transmitted at ₃ , the reflected wave having the signal strength S ₄ exceeding the threshold value S _T is received at the reception start time T ₄ , while at the time of X ₂ (V ₂ , P ₂ ), the signal strength S ₃ '( S ₃ '> S ₃ ) ultrasonic waves are transmitted at the transmission start time T ₃ , control is performed so that a reflected wave having a signal strength S ₄ exceeding the threshold S _T is received at the reception start time T _4. There is.

Therefore, the system control unit 6 controls so that the intensities of the received signals at the same detection distance are substantially the same and the transmission output of ultrasonic waves increases as the vehicle speed increases.

As described above, by changing the transmission output of ultrasonic waves to increase as the vehicle speed increases, it is possible to increase the intensity of the reception signal of ultrasonic waves as a whole. As a result, even if the received signal of the ultrasonic wave is attenuated by the traveling wind, the reflected wave can hold the signal strength sufficient to determine the obstacle. Therefore, the detectable distance and the detectable area of the obstacle can be kept almost constant from low speed to high speed without being affected by the attenuation of the ultrasonic reception signal due to the running wind, and as a result, the It is possible to prevent the detection performance of the obstacle on the rear side from being deteriorated.

In this embodiment, the vehicle obstacle detecting device provided with only one sensor 2 is shown, but the present invention is not limited to this, and two or more sensors detect different directions. May be provided as follows. In this case, the detectable area can be expanded in proportion to the number of installed sensors, and as a result, the obstacle detection accuracy can be improved and the vehicle traveling safety can be improved.

The sensor 2 is turned on / off at a rate of, for example, 10 times per second, and a detection signal is input to the system control section 6 each time, so that the system control section 6 is Based on the detection data of this time and the previous time, the size of the distance to the obstacle this time is judged compared to the previous time, and if the distance to the obstacle is within the predetermined range based on this judgment result, drive with an alarm etc. It may be configured to control so as to notify the person.

Further, the ON / OFF of the sensor 2 is
It is also possible to use it in conjunction with a turn signal. In this case, the sensor 2 is turned on in association with the operation of the turn signal indicator when the driver changes lanes while the vehicle is traveling, and is in the detection state of an obstacle around the vehicle, that is, an approaching vehicle.
Then, when an approaching vehicle is detected, the system control unit 6 issues an alarm or the like to notify the driver based on the detection signal. Further, after the lane change is completed without the approaching vehicle, the sensor 2 in the ON state is turned OFF in association with the stop of the turn signal indicator.

By controlling ON / OFF of the sensor 2 so as to interlock with the turn signal in this way, the sensor 2 can be operated only when necessary, so that the output energy of the sensor can be saved. It is possible to improve the energy efficiency of the entire obstacle detection device of the vehicle.

[Embodiment 2] The following description will discuss another embodiment of the present invention with reference to FIGS. 6 and 7. The members having the same functions as those in the above-described embodiment are designated by the same reference numerals, and the description thereof will be omitted. The same applies to other embodiments described later.

In the first embodiment, the system controller 6
Although the control is performed so as to change the ultrasonic wave transmission output according to the vehicle speed, in the present embodiment, the system control unit 6 increases as the obstacle detection distance L increases as shown in FIG. 6, for example. The amplification signal Z that sets the amplification degree of the reflected wave is increased by the amplification degree setting unit 8 so that the amplification signal Z is increased for the same detection distance L so that the reception signal increases and the vehicle speed V increases. It is controlled so that the received signal becomes larger by increasing the signal.

That is, the system controller 6 detects the detection distance L ₁
Then, when the vehicle speed V is up to 30 km / h, the amplified signal is Z
_When the vehicle speed is V = 80 km / h or more so that the amplified signal becomes Z ₂ , as shown in FIG. 7, X ₃ (L ₁ , Z ₁ ), X ₄ ( L ₂ , Z ₂ )
In any case, when the ultrasonic wave having the same signal strength S ₅ is transmitted at the transmission start time T ₅ , the reflected wave having the signal strength S ₆ exceeding the threshold value S _T for both X ₃ and X ₄ is received at the start time T 5. It is controlled to receive at ₆ .

Therefore, the system control unit 6 controls the received signal strength at the same detection distance to be substantially the same by increasing the amplification degree of the reflected wave as the vehicle speed increases.

As described above, by changing the amplification degree of the reflected wave of the ultrasonic wave to increase as the vehicle speed increases, the intensity of the received signal of the reflected wave is a signal sufficient to judge an obstacle. It can be increased to strength. As a result, even if the received signal of the reflected wave of the ultrasonic wave is attenuated by the traveling wind, it is possible to obtain a signal strength that is large enough to determine the obstacle. Therefore, the detectable distance and the detectable area of the obstacle can be kept almost constant from low speed to high speed without being affected by the attenuation of the ultrasonic reception signal due to the running wind, and as a result, the It is possible to prevent the detection performance of the obstacle from being deteriorated.

Further, in this embodiment, instead of changing the transmission output of ultrasonic waves as in the first embodiment, the amplification degree of the received signal is changed to improve the obstacle detection performance during high speed running. It prevents the decline. Therefore, compared to changing the output of ultrasonic waves, changing the amplification of the received signal requires less energy for the entire vehicle obstacle detection device and improves the energy efficiency of the entire device. You can

[Embodiment 3] The following description will explain still another embodiment of the present invention with reference to FIGS. 8 and 9.

In the first and second embodiments, the system control section 6 controls the ultrasonic transmission output or the amplification degree of the received signal of the reflected wave according to the vehicle speed. In the present embodiment, the system control unit 6 controls so as to change a threshold value (hereinafter, simply referred to as a threshold value) for obstacle determination with respect to a received signal of a reflected wave of ultrasonic waves according to a vehicle speed. .

That is, as shown in FIG. 8, the system control unit 6 reduces the threshold value as the vehicle speed increases, so that the vehicle speed V ₃ is set to the threshold value S _T0 and the vehicle speed V ₄ (V _4,> V _3), the threshold _{S T1 (S T1 <S T0} )
By setting the following, as shown in FIG. 9, X ₅ (V ₃ , S
_{When an} ultrasonic wave having the same signal strength S ₇ is transmitted at the transmission start time T ₇ for both _{T 0} ), X ₆ (V ₄ , S _T1 ), at X ₅ ,
While receiving a reflected wave of the signal strength S ₈ exceeding the threshold S _T0 at the receiving start time T _8, the X _6, the reception start time a reflected wave of the signal strength S ₈ 'exceeds the threshold value S _T1 T ₈ It is controlled to receive at.

Therefore, the system control unit 6 can accurately perform obstacle determination during high-speed running by setting a lower threshold value in accordance with the received signal that decreases as the vehicle speed increases. .

As described above, as the vehicle speed increases, the threshold value for obstacle determination with respect to the signal intensity of the reflected wave of the ultrasonic wave is changed so that the signal intensity of the reflected wave attenuated by the traveling wind. The presence / absence of an obstacle can also be determined by. As a result, the detectable distance and the detectable area of the obstacle can be kept almost constant from low speed to high speed without being affected by the attenuation of the ultrasonic wave reception signal due to the running wind. It is possible to prevent deterioration of the detection performance of the obstacle.

Further, in the present embodiment, the threshold value for obstacle judgment with respect to the received signal is changed according to the vehicle speed.
Compared to the case where the transmission power of ultrasonic waves is changed or the amplification degree of reflected waves of ultrasonic waves is changed as in the first and second embodiments, only the threshold value is changed. Therefore, the energy efficiency of the entire vehicle obstacle detection device can be improved.

In each of the first, second and third embodiments described above, the change of the ultrasonic wave transmission output, the change of the reflected wave amplification degree, and the change of the threshold value are described as independent forms according to the vehicle speed. However, it is also possible to combine the change of the ultrasonic wave transmission output, the change of the reflected wave amplification degree, and the change of the threshold value. In this case, it is possible not only to prevent the obstacle detection performance from deteriorating during high-speed traveling, but also to improve the obstacle detection performance.

[0045]

As described above, the obstacle detecting device for a vehicle according to the present invention transmits the pressure wave from the vehicle in a predetermined direction and receives the reflected wave, and the transmitting / receiving element. On the basis of the reflected wave received in, the obstacle determination means for determining the presence or absence of obstacles around the vehicle, vehicle speed detection means for detecting the speed of the own vehicle, depending on the vehicle speed detected by the vehicle speed detection means , And a transmission output changing means for changing the transmission output of the pressure wave.

As a result, even if the received signal of the pressure wave is attenuated by the traveling wind, the reflected wave can obtain a sufficient signal strength for determining the obstacle. Therefore, the detectable distance and the detectable area of the obstacle from the low speed to the high speed can be kept substantially constant without being affected by the attenuation of the pressure wave reception signal due to the traveling wind. It is possible to prevent the detection performance of the obstacle from being lowered.

As described above, the obstacle detecting device for a vehicle according to the invention of claim 2 transmits and receives the pressure wave from the vehicle in a predetermined direction, and the transmitting and receiving element which receives the reflected wave.
Based on the reflected wave received by the transmission / reception element, an obstacle determination means for determining the presence or absence of an obstacle around the vehicle, and a vehicle speed detection means for detecting the speed of the host vehicle are provided, and the vehicle speed detection means detects the vehicle speed. The obstacle determining means changes the amplification degree with respect to the signal intensity of the reflected wave received by the transmitting / receiving element according to the vehicle speed.

As a result, even if the received signal of the pressure wave is attenuated by the traveling wind, it is possible to obtain a signal strength that is large enough to determine an obstacle. Therefore, the detectable distance and the detectable area of the obstacle from the low speed to the high speed can be kept substantially constant without being affected by the attenuation of the pressure wave reception signal due to the traveling wind. It is possible to prevent the detection performance of the obstacle from being lowered.

Further, as described above, the obstacle detection device for a vehicle according to a third aspect of the present invention transmits and receives the pressure wave from the vehicle in a predetermined direction and receives the reflected wave, and the transmission and reception element. On the basis of the reflected wave received by the vehicle, obstacle judgment means for judging the presence or absence of obstacles around the vehicle, and vehicle speed detection means for detecting the speed of the host vehicle are provided, and the vehicle speed detected by the vehicle speed detection means is provided. According to the above, the obstacle determining means changes the threshold value for obstacle determination with respect to the signal intensity of the reflected wave received by the transmitting / receiving element.

Thus, the presence or absence of an obstacle can be determined based on the signal intensity of the reflected wave attenuated by the traveling wind, so that from low speed to high speed without being affected by the attenuation of the received signal of the pressure wave due to the traveling wind. It is possible to keep the detectable distance and the detectable area of the obstacle substantially constant, and as a result, it is possible to prevent deterioration of the obstacle detection performance at high speed.

[Brief description of drawings]

FIG. 1 is a control block diagram of an obstacle detection device for a vehicle according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a detectable distance and a detectable area of an obstacle in a vehicle equipped with the vehicle obstacle detection device.

FIG. 3 is a graph showing the relationship between the ultrasonic signal strength and the reflection time of the vehicle obstacle detection device.

FIG. 4 is a graph showing the relationship between the ultrasonic wave transmission output of the vehicle obstacle detection device and the vehicle speed.

FIG. 5 is a graph showing the relationship between the ultrasonic wave signal intensity and the reflection time when the transmission output of the output wave is changed according to the vehicle speed.

FIG. 6 is a graph showing another embodiment of the present invention and showing a relationship between an amplified signal for amplifying a received signal of a reflected wave in an obstacle detection device for a vehicle and an obstacle detection distance.

FIG. 7 is a graph showing the relationship between the ultrasonic signal intensity and the reflection time when the amplified signal is changed according to the vehicle speed.

FIG. 8 shows still another embodiment of the present invention, and is a graph showing a relationship between an obstacle determination threshold value and a vehicle speed for a received signal of a reflected wave in an obstacle detection device for a vehicle.

FIG. 9 is a graph showing the relationship between the ultrasonic signal intensity and the reflection time when the threshold value is changed according to the vehicle speed.

[Explanation of symbols]

1 own vehicle 2 sensor (transmission / reception element) 6 system control unit (obstacle determination means, transmission output change means) 7 vehicle speed sensor (vehicle speed detection means)

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Hideki Nishitake, No. 3 Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda Co., Ltd. (72) No. 3-1, Shinchi, Fuchu-cho, Aki-gun, Hiroshima Prefecture Mazda shares In the company

Claims (3)

[Claims] 1. A transmission / reception element that transmits a pressure wave in a predetermined direction from a vehicle and receives the reflected wave, and the presence / absence of an obstacle around the vehicle is determined based on the reflected wave received by the transmission / reception element. There is provided an obstacle determining means, a vehicle speed detecting means for detecting the speed of the own vehicle, and a transmission output changing means for changing the transmission output of the pressure wave according to the vehicle speed detected by the vehicle speed detecting means. An obstacle detection device for a vehicle characterized by the above. 2. A transmission / reception element that transmits a pressure wave from a vehicle in a predetermined direction and receives the reflected wave, and the presence / absence of an obstacle around the vehicle is determined based on the reflected wave received by the transmission / reception element. The obstacle determining means and the vehicle speed detecting means for detecting the speed of the own vehicle are provided, and the obstacle determining means detects the reflected wave received by the transmitting / receiving element according to the vehicle speed detected by the vehicle speed detecting means. An obstacle detection device for a vehicle, wherein an amplification degree with respect to a signal strength is changed. 3. A transmission / reception element that transmits a pressure wave in a predetermined direction from a vehicle and receives the reflected wave, and the presence / absence of an obstacle around the vehicle is determined based on the reflected wave received by the transmission / reception element. The obstacle determining means and the vehicle speed detecting means for detecting the speed of the own vehicle are provided, and the obstacle determining means detects the reflected wave received by the transmitting / receiving element according to the vehicle speed detected by the vehicle speed detecting means. An obstacle detection device for a vehicle, wherein a threshold value for obstacle judgment with respect to signal strength is changed.