JPS623688A - Object detector - Google Patents

Abstract

PURPOSE:To make the sensitivity distribution of a sensor uniform by providing an earthing conductor so that it faces a part where the object detection sensitivity in the sensor is high. CONSTITUTION:Sensors 11 and 12 are arranged in parallel in the part of a bumper 10 of an automobile 9, and an earthing conductor 13 facing sensors 11 and 12 is provided in the center part where the object detection sensitivity is high. The effect that sensor parts facing each other are shielded electrostatically by the earthing conductor 13 appears, and a distance (d) between sensors 11 and 12 and the earthing conductor 13 is adjusted properly to determine the strength of the shield effect in this case, and a length l of the earthing conductor 13 facing sensors 11 and 12 is adjusted properly to determine the range of the shield effect; and thereby, the sensitivity in the center part where the object detection sensitivity is high is reduced as prescribed to make the sensitivity distribution approximately uniform.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an object detection device that detects the approach of an object such as an obstacle.

Recently, as an object detection device used for detecting obstacles when a car is running, for example, as shown in FIG. A sensor has been developed that is installed in a line along the inside of a bumper 10 made of urethane foam or the like, and detects the approaching state of an object based on the change in stray capacitance between the sensor 1 and the obstacle. (See Japanese Patent Application No. 58-220412).

Figure 6 is a circuit diagram showing the basic principle of object detection. When an AC signal is applied to a series circuit of electrode member 1 and resistor R, the stray capacitance C between sensor 1 and object ○ changes depending on the distance between the sensor 1 and the object ○. Focusing on the change in AC output voltage at which voltage dividing point of sensor 1 and resistor R changes, sensor 1 detects the falling state of the output voltage when object O approaches it, and determines the approaching state of object ○. We are trying to detect this.

Figure 7 shows an object detection device constructed based on this basic principle, which consists of an oscillator 2 that generates an alternating current signal of a constant frequency, and a resistor divider installed in parallel on the output side of the oscillator 2. A network 3 consisting of a circuit, a sensor 1 connected to a dividing point of the network 3, a band filtering amplifier 4 that performs noise removal and amplification of the AC output voltage from the network 3, and a band filter amplifier 4 of the amplified output signal. A detector 5 that performs wave detection, and a voltage fluctuation detection circuit 6 that detects the approaching state of object ○ from the falling state of the detected voltage signal and detects if there is a voltage drop that exceeds a preset condition. , and a driver 7 that controls the operation of the alarm device 8 according to the detection signal.

With this configuration, when an AC signal with a constant frequency Fo is applied from the oscillator 2 to the network 3, the AC signal is appropriately attenuated in proportion to the proximity of the object O facing the sensor 1. The signal is sent to a bandpass filtering amplifier 4, where noise induced in the sensor 1 and the like is removed and only the alternating current component of the frequency Fo is amplified. Then, the predetermined amplified AC signal is detected by a wave detector 5, and a DC voltage signal corresponding to the amplitude of the AC signal is sent to a voltage fluctuation detection circuit 6. The voltage fluctuation detection circuit 6 is
The falling state of the given DC voltage signal is detected, and when the degree of voltage drop becomes less than a preset reference value, an alarm command is issued to the driver 7, indicating that the object O has entered the dangerous area. give. Thereby, the alarm device 8 is configured to issue an alarm to that effect, such as by sounding or being driven to turn on.

When using the above object detection means, the object detection sensitivity of the sensor (electrode member) 1 is approximately proportional to the distance of the object to the sensor 1 and the area of the object facing the sensor 1. As shown in Figure 5, when the sensor 1 is installed in a line along the bumper 10 of a car 9, objects cannot be detected in the central part of the sensor 1, as shown by the sensitivity distribution curve S1 in the figure. The sensitivity is the highest, and the closer you go to the end of the sensor 1, the lower the object detection sensitivity becomes.

The present invention has been made in consideration of the above points, and when detecting the approaching state of an object according to the change in stray capacitance between the sensor and the object facing the sensor, the present invention has a high object detection sensitivity in the sensor. An object detection device is provided in which the apparent sensitivity distribution in the sensor is made uniform by lowering the sensitivity in the sensor.

Sentence 11 In order to achieve the object, the present invention provides a grounding member having an electrostatic shielding effect opposite the part of the sensor where the object detection sensitivity is high, thereby partially reducing the object detection sensitivity of the sensor. There is.

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

In the object detection device according to the present invention, for example, as shown in FIG.
, 12 are arranged in parallel, and a ground wire 13 facing each sensor 11, 12 is provided in the central portion where the object detection sensitivity is high.

Therefore, the ground wire 13 has the effect of electrostatically shielding the sensor portions facing each other, and in this case, as shown in FIG. 2, the distance d between each sensor 11, 12 and the ground wire 13 is adjusted as appropriate. By determining the strength of the shielding effect, and determining the range of the shielding effect by appropriately adjusting the length Q of the grounding wire 13 facing each sensor 11, 12, it is possible to detect objects as shown in Fig. 3. In the figure, S2 indicates a uniform sensitivity distribution curve by lowering the sensitivity in the central portion where the sensitivity is high to a predetermined value to make the sensitivity distribution substantially uniform.

As shown in FIG. 1, the sensors 11 and 12 are arranged in parallel on the bumper 10 of the automobile 9 by utilizing the difference in object detection sensitivity of each sensor 11 and 12. A multi-sensor system is used in which objects in the direction are excluded from detection targets and only objects in front can be detected with directionality. In this case, an object detection system consisting of the sensor 1 to the voltage fluctuation detection circuit 6 shown in FIG. After processing, the AND-processed signal may be given to the driver 7 to cause the alarm device 8 to perform an alarm operation as appropriate.

FIG. 4 shows another embodiment of the present invention, in which a pair of sensors IIA and IIB are installed on both sides of the bumper 10 so that obstacles on both sides of the front of the vehicle can be detected well. The sensor 12 is arranged in parallel with the sensor 12, and the grounding wire 13 is provided in the same manner as described above. In addition, when providing a grounding wire, a single sensor may be used, and various measures can be taken, such as placing a grounding member appropriate for the shape of the sensor, not limited to a linear sensor, facing the sensor. Needless to say.

Above the peritoneum, the object detection device according to the present invention includes a means for replacing a change in stray capacitance between a sensor consisting of an electrode member and an object with a change in a frequency signal, and a means for replacing a change in stray capacitance between a sensor consisting of an electrode member and an object, and a means for replacing a change in a stray capacitance between a sensor consisting of an electrode member and an object, and a means for replacing a change in a stray capacitance with a change in a frequency signal, A means for detecting an approaching state, in which a grounding member is provided opposite the part of the sensor where the object detection sensitivity is high, and the sensitivity of the part of the sensor where the object detection sensitivity is high is lowered. This has the excellent advantage that the apparent sensitivity distribution in the sensor can be made uniform, and objects facing the sensor can be detected satisfactorily.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of how a part consisting of a sensor and a grounding member used in an object detection device according to the present invention is installed in a car, and FIG. 2 is a front view showing details of the part consisting of the sensor and grounding member. Fig. 3 is a plan view showing the uniform sensitivity distribution state of the sensor, Fig. 4 is a perspective view showing another example of how the part consisting of the sensor and the grounding member is installed in the automobile, and Fig. 5 6 is a plan view showing the sensitivity distribution state of a conventional sensor, FIG. 6 is a circuit configuration diagram showing the basic principle of object detection according to the present invention, and FIG. 7 is a block diagram showing a specific example of the configuration of the object detection device. It is.

Claims (1)

[Claims] In a sensor comprising means for replacing a change in stray capacitance between a sensor made of an electrode member and an object with a change in a frequency signal, and a means for detecting an approaching state of an object according to attenuation of the frequency signal, An object detection device characterized in that a grounding member is provided opposite a portion with high object detection sensitivity.